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    • 专利摘要:
    CELLS DEFICIENT IN CMP-N-ACETYLNEURAMINIC ACID HYDROXYLASE AND/OR GLYCOPROTEIN ALPHA-1,3-GALACTOSYLTRANSFERASE. The present invention provides non-human mammalian cell lines that are deficient in CMP-Neu5Ac hydroxylase (Cmah) and/or glycoprotein alpha-1,3-galactosyltransferase (Ggta1). Methods for using the cells disclosed herein to produce recombinant proteins with human-like glycosylation patterns are also provided. 20116591v1
    公开号:BR112013033448B1
    申请号:R112013033448-7
    申请日:2012-06-29
    公开日:2022-01-25
    发明作者:Nan Lin；Henry J. George；Joaquina Mascarenhas；Trevor N. Collingwood；Kevin J. Kayser；Katherine Achtien
    申请人:Sigma-Aldrich Co. Llc；
    IPC主号:
    专利说明:

    FIELD OF THE INVENTION
    [0001] The present disclosure relates generally to cells useful for the production of proteins, and especially therapeutic proteins. More specifically, the present disclosure relates to cells deficient in certain N-glycan processing enzymes, methods of producing the cells, and methods of using the cells to produce proteins having certain glycosylation patterns. FUNDAMENTALS OF THE INVENTION
    [0002] Approximately 70% of therapeutic proteins, such as antibodies, growth factors, cytokines, hormones, and clotting factors, are glycoproteins, which are post-translationally modified proteins by glycan attachment. Most recombinant therapeutic glycoproteins are produced in mammalian expression systems because the location, number, and structure of N-glycans have been shown to affect the bioactivity, solubility, stability, pharmacokinetics, immunogenicity, and release rate of therapeutic glycoproteins. Two differences in the glycosylation machinery of humans and other mammals explain the differences in the glycosylation patterns of glycoproteins produced by human cells and glycoproteins produced by other mammalian cells such as rodent cells.
    [0003] First, humans cannot synthesize a terminal fraction of galactose alpha-1,3 galactosyltransferase (also known as alpha-Gal or α-Gal) in N-glycans. The enzyme glycoprotein alpha-1,3-galactosyltransferase (Ggta1) forms the α-Gal moiety by linking a galactose residue via an α-1,3 glycosidic bond to a terminal galactose of the N-glycan. Humans apparently have a GGTA1 gene, but it is an expressed pseudogene that encodes a nonfunctional truncated protein containing the first four translated exons but missing the two catalytic exons. Although humans do not express a functional Ggta1 enzyme and therefore do not synthesize α-Gal fractions, many humans produce antibodies against this structure.
    [0004] Second, humans cannot synthesize sialic acid, N-glycolylneuraminic acid (Neu5Gc). Neu5Gc is produced by the hydroxylation of CMP-N-acetylneuraminic acid (Neu5Ac) to CMP-Neu5Gc by the enzyme CMP-Neu5Ac hydroxylase (Cmah). Although the human Cmah gene is irreversibly mutated, preventing Neu5Ac expression, traces of Neu5Gc were detected in human serum. It appears that non-human Neu5Gc can be metabolically incorporated into human tissues from certain mammalian-derived foods, so essentially all humans have antibodies specific to Neu5Gc, sometimes at high levels.
    [0005] Chinese hamster ovary (CHO) cells are widely used for the production of therapeutic proteins, in part, because it has been assumed that they produce proteins with human-like glycosylation patterns. For example, it was generally accepted that CHO cells lacked the biosynthetic machinery to produce glycoproteins with α-Gal moieties. Furthermore, although CHO cells express Cmah and produce proteins containing Neu5Gc units, the proportion of Neu5Gc and Neu5Ac units can be reduced by modifying CHO cell culture conditions. Despite the general acceptance that CHO cells were not able to synthesize α-Gal fractions, CHO ortholog of Ggta1 was recently identified (Bosques et al. Nature Biotechnol. 2010, 28(11): 1153-1156). Due to the potential for hypersensitivity reactions to recombinant therapeutic glycoproteins, there is a need for CHO cell lines and other non-human mammalian cell lines that produce the glycoproteins devoid of α-Gal and/or Neu5Gc residues. SUMMARY OF THE INVENTION
    [0006] Briefly, therefore, one aspect of the present disclosure provides a non-human mammalian cell line deficient in cytidine-monophosphate-N-acetylneuraminic acid (Cmah) hydroxylase. In one embodiment, the cell line comprises an inactivated chromosomal coding sequence that encodes Cmah. In certain embodiments, the inactivated chromosomal sequence encoding Cmah comprises a deletion of at least one nucleotide, an insertion of at least one nucleotide, a substitution of at least one nucleotide, or combinations thereof. In one embodiment, the inactivated chromosomal sequence encoding Cmah does not comprise any exogenously introduced sequence. In another embodiment, the inactivated chromosomal sequence encoding Cmah is monoallelic and the cell line produces a reduced amount of Cmah. In yet another embodiment, the inactivated chromosomal sequence encoding Cmah is biallelic and the cell line does not produce Cmah. In one embodiment, the chromosomal sequence is inactivated with a tagging endonuclease, for example, a meganuclease, a TALEN, a site-specific endonuclease, or a zinc finger nuclease. In either of these embodiments, the cell line can produce proteins devoid of N-glycolylneuraminic acid (Neu5Gc) residues.
    [0007] In another aspect of the present disclosure, the Cmah-deficient cell line is also Ggta1-deficient. In one embodiment of this cell line, the cell line comprises an inactivated chromosomal sequence encoding Ggta1. In certain embodiments, the inactivated chromosomal sequence encoding Ggta1 comprises a deletion of at least one nucleotide, an insertion of at least one nucleotide, a substitution of at least one nucleotide, or combinations thereof. In one embodiment, the inactivated chromosomal sequence encoding Ggta1 does not comprise any exogenously introduced sequence. In one embodiment, the inactivated chromosomal sequence encoding Ggta1 is monoallelic and the cell line produces a reduced amount of Ggta1. In another embodiment, the inactivated chromosomal sequence encoding Ggta1 is biallelic and the cell line does not produce Ggta1. In another embodiment, the chromosomal sequence is inactivated with a tagging endonuclease, for example, a meganuclease, a TALEN, a site-specific endonuclease, or a zinc finger nuclease. In either of these embodiments, the non-human mammalian cell line can produce proteins that additionally lack alpha-1,3-galactose (alpha-Gal) galactose residues.
    [0008] In one embodiment, the cell line comprises a monoallelic inactivation of the chromosomal sequence encoding Cmah and a monoallelic inactivation of the chromosomal sequence encoding Ggta1, and the cell line produces a reduced amount of Cmah and a reduced amount of Ggta1. In another embodiment, the cell line comprises a biallelic inactivation of the chromosomal sequence encoding Cmah and a biallelic inactivation of the chromosomal sequence encoding Ggta1, and the cell line does not produce Cmah or Ggta1. In a particular embodiment, the non-human mammalian cell line produces proteins devoid of N-glycolylneuraminic acid (Neu5Gc) residues and alpha-1,3-galactose (alpha-Gal) galactose residues.
    [0009] In a particular embodiment of the invention, the cell line is a Chinese hamster ovary (CHO) cell line. In one embodiment, the CHO cell line comprises a monoallelic inactivation of the chromosomal sequence encoding Cmah and producing a reduced amount of Cmah. In another embodiment, the CHO cell line comprises a biallelic inactivation of the chromosomal sequence encoding Cmah, and does not produce Cmah. In another embodiment, the CHO cell line comprises a monoallelic inactivation of the chromosomal sequence encoding Cmah and a monoallelic inactivation of the chromosomal sequence encoding Ggta1, and produces a reduced amount of Cmah and a reduced amount of Ggta1. In yet another embodiment, the CHO cell line comprises a biallelic inactivation of the chromosomal sequence encoding Cmah and a biallelic inactivation of the chromosomal sequence encoding Ggta1, and does not produce Cmah or Ggta1. In one embodiment, the CHO cell line produces proteins devoid of N-glycolylneuraminic acid residues (Neu5Gc) and alpha-1,3-galactose (alpha-Gal) galactose residues.
    [00010] In another aspect, the disclosure includes methods for producing a cell line deficient in Cmah and/or Ggta1. In one embodiment, the method comprises introducing into the cell line a target endonuclease or a nucleic acid encoding a marker endonuclease targeted to a chromosomal sequence encoding Cmah. In another embodiment, the method comprises introducing into a cell line that is Cmah deficient, a target endonuclease or a nucleic acid encoding a target endonuclease targeted to a chromosomal sequence encoding Ggta1. In another embodiment, the method comprises introducing into a cell line a target endonuclease or a nucleic acid encoding a target endonuclease targeted to a chromosomal sequence encoding Cmah and a target endonuclease or a nucleic acid encoding a target endonuclease. targeted to a chromosomal sequence encoding Ggta1.
    [00011] Another aspect of the disclosure includes a method for producing a recombinant protein having a human-like glycosylation pattern. The method comprises expressing the protein in a non-human mammalian cell line deficient in Cmah and/or Ggta1. In a specific embodiment, the cell line is a Chinese hamster ovary (CHO) cell line. In one embodiment, the cell lineage comprises an inactivated chromosomal sequence encoding Cmah and/or an inactivated chromosomal sequence encoding Ggta1. In one embodiment, the inactivated chromosomal sequence encoding Cmah and/or Ggta1 is monoallelic and the cell line produces a reduced amount of Cmah and/or Ggta1. In another embodiment, the inactivated chromosomal sequence encoding Cmah and/or Ggta1 is biallelic, and the cell line does not produce Cmah and/or Ggta1. In another embodiment, the recombinant protein is devoid of N-glycolylneuraminic acid (Neu5Gc) residues and/or galactose-alpha-1,3-galactose (alpha-Gal) residues. In one embodiment, the recombinant protein contains at least one property that is improved over a similar recombinant protein produced by a comparable cell line not deficient in Cmah and/or Ggta1, e.g., reduced immunogenicity, increased bioavailability, efficacy increased stability, increased solubility, improved half-life, improved clearance, improved pharmacokinetics and combinations thereof. The recombinant protein can be any protein, including a therapeutic protein. Examples of proteins include those selected from an antibody, an antibody fragment, a growth factor, a cytokine, a hormone, a clotting factor, and a functional fragment or variants thereof.
    [00012] Other aspects and iterations of the reveal are described in more detail below. DESCRIPTION OF THE FIGURES
    [00013] FIG. 1 illustrates the ZFN-mediated cleavage of the Ggta1 locus in CHO cells. Results of a Cel-1 surveyor nuclease assay are shown. Arrows indicate 215 bp and 100 bp cleavage products in CHO cells transfected with ZFN mRNA (1) or ZFN DNA (2). No cleavage products were detected in mock-transfected cells (3).
    [00014] FIG. 2 documents ZFN-mediated cleavage of the Cmah locus in CHO cells, as detected by a Cel-1 surveyor nuclease assay. The arrow indicates a cleavage product.
    [00015] FIG. 3 illustrates ZFN-mediated cleavage of the Ggta1 locus in Cmah (-/-) cells, as detected by a Cel-1surveyor nuclease assay. Cells transfected with ZFN (marked "#1" and "#2"), but not mock-transfected cells contained 215 bp and 100 bp cleavage fragments. DETAILED DESCRIPTION OF THE INVENTION
    [00016] The present disclosure provides non-human mammalian cell lines deficient in Cmah and/or Ggta1. In one embodiment, the cell lines comprise inactivated chromosomal sequences encoding Cmah and/or Ggta1 such that the cell lines produce reduced amounts of Cmah and/or Ggta1. In another embodiment, the cell lines comprise inactivated chromosomal sequences that encode Cmah and/or Ggta1 such that the cell lines do not produce Cmah and/or Ggta1. Also provided herein are methods for producing the cell lines disclosed herein and methods for using the cell lines disclosed herein to produce recombinant proteins with human-like glycosylation patterns. Due to the fact that the cell lines are deficient in Cmah and/or Ggta1, the cell lines produce recombinant glycoproteins with reduced content of Neu5Gc and/or α-Gal or glycoproteins devoid of Neu5Gc and/or α-Gal. (1) Cell Lines Deficient in Cmah and/or Ggtal
    [00017] One aspect of the present disclosure provides a non-human mammalian cell line deficient in cytidine-monophosphate-N-acetylneuraminic acid hydroxylase (Cmah) and/or glycoprotein alpha-1,3-galactosyltransferase (Ggta1). (a) Cmah and Ggtal
    [00018] Cmah and Ggta1 are enzymes involved in the generation of N-glycans in glycoproteins. Cmah catalyzes the conversion of sialic acid Neu5Ac to its hydroxylated derivative Neu5Gc. Ggta1 links a galactose residue via an α-1,3 glycosidic bond to a galactose on N-glycan to form a terminal Gal-α-1,3-Gal (ie α-Gal) moiety. In one embodiment, the cell line is Cmah deficient. In another embodiment, the cell line is deficient in Ggta1. In yet another embodiment, the cell line is deficient in both Cmah and Ggta1.
    [00019] In some cases, the cell line deficient in Cmah and/or Ggta1 may have reduced levels of Cmah and/or Ggta1 relative to the parental cell line. For example, levels of Cmah and/or Ggta1 can be reduced by about 5% to about 10%, by about 10% to about 20%, by about 20% to about 30%, by about 30% to about 40%, from about 40% to about 50%, from about 50% to about 60%, from about 60% to about 70%, from about 70% to about 80 %, by about 80% to about 90%, or from about 90% to about 99.9% relative to the parental cell line that is not deficient in Cmah and/or Ggta1. Cell lines containing reduced levels of Cmah and/or Ggta1 generally produce proteins with reduced content of Neu5Gc and/or α-Gal relative to proteins produced by comparable cells that are not deficient in Cmah and/or Ggta1.
    [00020] In other cases, the cell line deficient in Cmah and/or Ggta1 may produce essentially no Cmah and/or Ggta1. As used herein, the term "essentially no Cmah and/or Ggta1" means that no mRNA or protein from Cmah and/or Ggta1 can be detected in the deficient cells or lysates derived using procedures well known in the art. Non-limiting examples of suitable procedures for determining the level of mRNA or protein include PCR, qPCR, Western blotting and ELISA assays. Thus, the level of Cmah and/or Ggta1 mRNA and/or protein detected in the deficient or lysed cells is essentially the same as background levels. The cell line lacking Cmah and/or Ggta1 generally produces proteins lacking Neu5Gc and/or α-Gal residues.
    [00021] In some embodiments, the genome of the cell line deficient in Cmah and/or Ggta1 may be edited so that the chromosomal sequence encoding Cmah and/or the chromosomal sequence encoding Ggta1 are inactivated. As used herein, the term "inactivated chromosomal sequence" refers to a chromosomal sequence that is not capable of generating a functional gene product. In an embodiment in which the cell lineage comprises euploid cells, the inactivated chromosomal sequence may be monoallelic such that the cell produces reduced levels of Cmah and/or Ggta1. In another embodiment in which the cell lineage is euploid, the inactivated chromosomal sequence may be biallelic so that the cell produces essentially no Cmah and/or Ggta1 and the cell may be termed a "knock-out" cell. Alternatively, in other embodiments where the cell lineage is aneuploid, one or more copies of the chromosomal sequences encoding Cmah and/or Ggta1 is/are inactivated, resulting in a reduced amount of Cmah and/or Ggta1. In another embodiment in which the cell lineage is aneuploid, all copies of the chromosomal sequences encoding Cmah and/or Ggta1 are inactivated, resulting in a complete loss of Cmah and/or Ggta1 gene expression.
    [00022] The inactivated chromosomal sequence encoding Cmah and/or Ggta1 may comprise a deletion of at least one nucleotide, an insertion of at least one nucleotide, or a substitution of at least one nucleotide. The chromosomal sequence encoding Cmah and/or Ggta1 can be inactivated using target endonuclease-mediated genome editing technology, as detailed below in section (II). In various embodiments, the chromosomal sequence encoding Cmah and/or Ggta1 can be inactivated by deleting all or part of the exonic coding region, deleting all or part of a control region, and/or deleting a DNA processing site. such that the cell line is unable to produce Cmah and/or Ggta1. In other embodiments, the chromosomal sequence encoding Cmah and/or Ggta1 can be inactivated through deletions, insertions, and/or nucleotide substitutions to introduce a premature stop codon, new splicing site, and/or SNPs into the chromosomal sequence of such that the cell line is unable to produce Cmah and/or Ggta1.
    [00023] In one embodiment, the cell lineage may comprise an inactivated chromosomal sequence encoding Cmah due to a deletion, insertion and/or substitution of at least one nucleotide within the chromosomal sequence encoding Cmah. For example, the chromosomal sequence encoding Cmah may be inactivated due to a deletion, insertion and/or substitution of at least one nucleotide within exon 5 of the chromosomal sequence encoding Cmah. In another embodiment, the cell line may comprise an inactivated chromosomal sequence encoding Ggta1 due to a deletion, insertion and/or substitution of at least one nucleotide within the chromosomal sequence encoding Ggta1. For example, the chromosomal sequence encoding Ggta1 can be inactivated due to a deletion, insertion and/or substitution of at least one nucleotide within exon 9 of the chromosomal sequence encoding Ggta1.
    [00024] In some embodiments, the cell line deficient in Cmah and/or Ggta1 may also be deficient in glutamine synthetase (GS), dihydrofolate reductase (DHFR), hypoxanthine-guanine phosphoribosyltransferase (HPRT), or combinations thereof. The cell line further comprising deficiencies in GS, DHFR, and/or HPRT may be deficient in GS, DHFR and/or HPRT due to inactivated chromosomal sequences encoding GS, DHFR and/or HPRT. (b) cell types
    [00025] The cell lineage type that is deficient in Cmah and/or Ggta1 can be any of a number of appropriate cell types. In general, the cell line is a non-human mammalian cell line. Suitable non-human mammalian cell lines include, but are not limited to, Chinese hamster ovary (CHO) cells, baby hamster kidney (BHK) cells, NS0 mouse myeloma cells, mouse embryonic fibroblast 3T3 cells, A20 cells of mouse B lymphoma; mouse melanoma B16 cells, mouse myoblast C2C12 cells; mouse myeloma SP2/0 cells, mouse embryonic mesenchymal C3H-10T1/2 cells, mouse carcinoma CT26 cells, mouse prostate DuCuP cells, mouse breast EMT6 cells, mouse hepatoma Hepa1c1c7 cells, J5582 cells mouse myeloma, mouse epithelial MTD-1A cells, mouse myocardium MyEnd cells; mouse renal RenCa cells; mouse pancreatic RIN-5F cells; mouse melanoma X64 cells, mouse lymphoma YAC-1 cells, mouse glioblastoma 9L cells, mouse B lymphoma RBL cells, mouse neuroblastoma B35 cells; rat hepatoma cells (HTC), buffalo rat liver BRL 3A cells, canine kidney cells (MDCK), canine mammary cells (CMT), rat osteosarcoma D17 cells, rat monocyte/macrophage DH82 cells, SV-40 monkey kidney transformed fibroblast (COS7); monkey kidney CVI-76 cells; and African green monkey kidney cells (VERO-76). An extensive list of non-human mammalian cell lines can be found in the catalog of the American Type Culture Collection (ATCC, Mamassas, VA). In one embodiment, the cell line that is deficient in Cmah and/or Ggta1 is other than a murine cell line. In yet another embodiment, the cell line that is deficient in Cmah and/or Ggta1 is other than a porcine cell line.
    [00026] In some embodiments, the cell line is of a type that is widely used for the production of recombinant glycol proteins. In an exemplary embodiment, the cell line is a CHO cell line. Several CHO cell lines are available through ATCC and commercial suppliers. Suitable CHO cell lines include, but are not limited to, CHO-K1 cells and derivatives thereof, CHO-K1SV cells, CHO DG44 cells, CHO-S cells, CHO P12 cells, CHO pro3- cells, CHO/DHFR- cells, CHO/GS- and CHO DXB11 cells. c) optional nucleic acid
    [00027] In some embodiments, the non-human mammalian cell line disclosed herein may further comprise at least one nucleic acid sequence encoding a recombinant protein. The recombinant protein can be, among others, an antibody, a fragment of an antibody, a monoclonal antibody, a humanized antibody, a humanized monoclonal antibody, a chimeric antibody, an IgG molecule, an IgG heavy chain, a light chain of IgG, an IgA molecule, an IgD molecule, an IgE molecule, an IgM molecule, a glycoprotein, a growth factor, a cytokine, an interferon, an interleukin, a hormone, a clotting (or clotting) factor , a blood component, an enzyme, a therapeutic protein, a nutraceutical protein, a vaccine, a functional fragment or a functional variant of any of the aforementioned, or a fusion protein comprising any of the foregoing proteins and/or fragments thereof functional or variants thereof.
    [00028] In some embodiments, the nucleic acid sequence encoding the recombinant protein may be linked to a nucleic acid sequence encoding hypoxanthine-guanine phosphoribosyltransferase (HPRT), dihydrofolate reductase (DHFR), and/or glutamine synthetase (GS ), so that HPRT, DHFR, and/or GS can be used as an amplifiable selectable marker.
    [00029] In some embodiments, the nucleic acid sequence encoding the recombinant protein may be extrachromosomal. That is, the nucleic acid encoding the recombinant protein can be transiently expressed from a plasmid, a cosmid, an artificial chromosome, a minichromosome, and the like. Those skilled in the art are familiar with appropriate expression constructs, appropriate expression control sequences, and methods of introducing such constructs into cells.
    [00030] In other embodiments, the nucleic acid sequence encoding the recombinant protein may be chromosomally integrated into the genome of the cell so that the recombinant protein is stably expressed. In some iterations of this embodiment, the nucleic acid sequence encoding the recombinant protein may be operably linked to a suitable heterologous expression control sequence (i.e., the promoter). In other interactions, the nucleic acid sequence encoding the recombinant protein can be placed under the control of an endogenous expression control sequence. The nucleic acid sequence encoding the recombinant protein can be integrated into the genome of the cell line using techniques well known in the art.
    [00031] Methods, cloning vectors, and techniques for preparing and introducing exogenous nucleic acid sequences (e.g., those encoding a recombinant protein), are well known in the art (see, for example, "Current Protocols in Molecular Biology" Ausubel et al., John Wiley & Sons, New York, 2003 or "Molecular Cloning: A Laboratory Manual" Sambrook & Russell, Cold Spring Harbor Press, Cold Spring Harbor, NY, 3rd edition, 2001). (d) exemplary modalities
    [00032] In a specific embodiment, the cell line is a CHO cell line that comprises a monoallelic or biallelic inactivation of the chromosomal sequence encoding Cmah. In another specific embodiment, the cell line is a CHO cell line that comprises either a monoallelic or biallelic inactivation of the chromosomal sequence encoding Ggta1. In yet another embodiment, the cell line is a CHO cell line that comprises a monoallelic or biallelic inactivation of the chromosomal sequence encoding Cmah and a monoallelic or biallelic inactivation of the chromosomal sequence encoding Ggta1. (II) Methods to Prepare Cell Lines Deficient in Cmah and/or Ggtal
    [00033] The cell line deficient in Cmah and/or Ggta1 can be prepared by a variety of methods. In certain embodiments, the Cmah and/or Ggta1-deficient cell line can be prepared by a target endonuclease-mediated genome editing process. In other embodiments, the Cmah and/or Ggta1 deficient cell line can be prepared by RNAi methods, random mutagenesis, site-specific recombination systems, or other methods known in the art. (a) target endonuclease-mediated genome editing
    [00034] Restriction endonucleases can be used to edit (ie, inactivate or modify) a specific chromosomal sequence. A specific chromosomal sequence can be inactivated by introducing into a cell a target endonuclease or a nucleic acid encoding the target endonuclease, which is designed to target a specific chromosomal sequence. In one embodiment, the target endonuclease recognizes and binds to the specific chromosomal sequence and introduces a double strand break that is repaired by a non-homologous end-joint (NHEJ) repair process. Because NHEJ is error-prone, a deletion, insertion, or substitution of at least one nucleotide can occur, thus disrupting the reading region of the chromosomal sequence so that no protein product is produced. In another embodiment, target endonucleases can also be used to modify a chromosomal sequence through a homologous recombination reaction by co-introducing a polynucleotide sequence having substantial identity with a portion of the target chromosomal sequence. The double strand break introduced by the target endonuclease is repaired by a homology-driven repair process such that the chromosomal sequence is exchanged with the polynucleotide in a manner that results in the chromosomal sequence to be edited. (i) target endonucleases
    [00035] A variety of targeting endonucleases can be used to modify the chromosomal sequence. The target endonuclease can be a naturally occurring protein or an engineered protein. In one embodiment, the target endonuclease can be a meganuclease. Endodeoxyribonuclease meganucleases are characterized by long recognition sequences, that is, the recognition sequence generally ranges from about 12 base pairs to about 40 base pairs. As a consequence of this requirement, sequence recognition generally occurs only once in a given genome. Among meganucleases, the family of homing endonucleases named LAGLIDADG has become a valuable tool for the study of genomes and genome design. Meganuclease can be targeted to a specific chromosomal sequence by altering its recognition sequence using techniques well known to those skilled in the art.
    [00036] In another embodiment, the target endonuclease may be a transcriptional activator-type effector nuclease (TALE). TALE are transcription factors from plant pathogens Xanthomonas that can be easily engineered to bind new DNA targets. TALE or truncated versions thereof can be associated with the catalytic domain of endonucleases such as FokI to create target endonucleases called TALE nucleases or TALENs.
    [00037] In yet another embodiment, the target endonuclease may be a site-specific endonuclease. In particular, the site-specific endonuclease may be a "rare cutter" endonuclease whose recognition sequence rarely occurs in a genome. Preferably, the site-specific endonuclease recognition sequence occurs only once in a genome. In an alternative embodiment, the targeting endonuclease may be an artificially targeted DNA double-strand breaking agent.
    [00038] In other embodiments, the targeting endonuclease may be a zinc finger nuclease (ZFN). Typically, a zinc finger nuclease comprises a DNA binding domain (i.e., the zinc finger) and a cleavage domain (i.e., nuclease), both of which are described below.
    [00039] Zinc finger binding domains. Zinc finger binding domains can be designed to recognize and bind to any nucleic acid sequence of choice. See, for example, Beerli et al. (2002) Nat. Biotechnol. 20:135-141; Pabo et al. (2001) Ann. Rev. Biochem. 70:313-340; Isalan et al. (2001) Nat. Biotechnol. 19:656-660; Segal et al. (2001) Curr. opinion Biotechnol. 12:632-637; Choo et al. (2000) Curr. opinion Struct. Biol. 10:411-416; Zhang et al. (2000) J. Biol. Chem. 275(43):33850-33860; Doyon et al. (2008) Nat. Biotechnol. 26:702-708; and Santiago et al. (2008) Proc. natl. academy Sci. USA 105:5809-5814. A designed zinc finger binding domain may have binding specificity compared to a naturally occurring zinc finger protein. Engineering methods include, among others, rational design and various types of selection. Rational design includes, for example, using databases that comprise doublet, triplet, and/or quadruplet nucleotide sequences and the individual zinc finger amino acid sequences, in which each doublet, triplet, or quadruplet nucleotide sequence is associated with a or more zinc finger amino acid sequences linking the particular triplet or quadruplet sequence. See, for example, US Patents 6,453,242 and 6,534,261, the disclosures of which are incorporated herein by reference in their entirety. As an example, the algorithm described in US Patent 6,453,242 can be used to design a zinc finger binding domain to target a preselected sequence. Alternative methods such as rational design using a non-degenerate code recognition table can also be used to design a zinc finger binding domain to target a specific sequence ( Sera et al. (2002) Biochemistry 41:7074-7081 ) . Publicly available web-based tools for identifying potential target sites in DNA sequences as well as designing zinc finger binding domains are known in the art. For example, tools for identifying potential target sites in DNA sequences can be found at http://www.zinfingertools.org. Tools for creating zinc finger binding domains can be found at http://bindr.gdcb.iastate.edu/ZiFiT/. (See also, Mandell et al (2006) Nuc. Acid Res. 34: W516-W523, Sander et al (2007) Nuc. Acid Res. 35: W599-W605 )
    [00040] A zinc finger binding domain can be designed to recognize and bind a DNA sequence ranging from about 3 nucleotides to about 21 nucleotides in length, or, preferably, between about 9 to about 18 nucleotides in length. . In general, the zinc finger binding domains of the zinc finger nucleases disclosed herein comprise at least three zinc finger (i.e., zinc finger) recognition regions. In one embodiment, the zinc finger binding domain comprises four zinc finger recognition regions. In another embodiment, the zinc finger binding domain comprises five zinc finger recognition regions. In yet another embodiment, the zinc finger binding domain comprises six zinc finger recognition regions. A zinc finger binding domain can be designed to bind to any appropriate target DNA sequence. See, for example, US Patents 6,607,882; 6,534,261 and 6,453,242, the disclosures of which are incorporated herein by reference in their entirety.
    [00041] Exemplary methods for selecting a zinc finger recognition region may include the phage display and two-hybrid systems, which are described in US Patents 5,789,538; 5,925,523; 6,007,988, 6,013,453, 6,410,248, 6,140,466, 6,200,759, and 6,242,568, as well as in WO 98/37186, WO 98/53057, WO 00/27878, WO 01/88197 and GB 2338 237, each of which is incorporated herein by reference in its entirety. Furthermore, increased binding specificity for zinc finger binding domains has been described, for example, in WO 02/077227, the entire disclosure of which is incorporated herein by reference.
    [00042] Zinc finger domains and methods for designing and constructing fusion proteins (and polynucleotides encoding the same) are known to those skilled in the art and are described in detail in, for example, US Patent 7,888,121, which is incorporated herein as a reference in its entirety. Zinc finger recognition regions and/or zinc finger proteins from multiple fingers can be joined using appropriate linker sequences, including, for example, linkers of five or more amino acids in length. See, US Patents 6,479,626; 6,903,185 and 7,153,949, the disclosures of which are incorporated herein by reference in their entirety, for non-limiting examples of linker sequences six or more amino acids in length. The zinc finger binding domains described herein may include a combination of suitable linkers between the individual zinc fingers of the protein.
    [00043] In some embodiments, the zinc finger nuclease further comprises a signal or nuclear localization sequence (NLS). An NLS is an amino acid sequence that facilitates the targeting of the zinc finger nuclease protein in the nucleus to introduce a double strand break in the target sequence on the chromosome. Nuclear localization signals are known in the art. See, for example, Makkerh et al. (1996) Current Biology 6:1025-1027.
    [00044] Cleavage domain. A zinc finger nuclease also includes a cleavage domain. The cleavage portion of the zinc finger nuclease domain can be obtained from any endonuclease or exonuclease. Non-limiting examples of endonucleases from which a cleavage domain can be derived include, but are not limited to, restriction enzymes and homing endonucleases. See, for example, New England Biolabs Catalog or Belfort et al. (1997) Nucleic Acids Res. 25:3379-3388. Additional enzymes that cleave DNA are known (eg, S1 Nuclease; bean sprout nuclease; pancreatic DNase I; micrococcal nuclease; yeast HO endonuclease). See also Linn et al. (eds.) Nucleases, Cold Spring Harbor Laboratory Press, 1993. One or more of these enzymes (or functional fragments thereof) can be used as a source of cleavage domains
    [00045] A cleavage domain can also be derived from an enzyme, or portion thereof, as described above, which requires dimerization for cleavage activity. Two zinc finger nucleases may be required for cleavage, as each nuclease comprises a monomer of the dimer of the active enzyme. Alternatively, a single zinc finger nuclease can comprise both monomers to create an active enzyme dimer. As used herein, an "active enzyme dimer" is an enzyme dimer capable of cleaving a nucleic acid molecule. The two cleavage monomers may be derived from the same endonuclease (or functional fragments thereof), or each monomer may be derived from a different endonuclease (or functional fragments thereof).
    [00046] When two cleavage monomers are used to form an active enzyme dimer, the recognition sites for the two zinc finger nucleases are preferentially arranged so that the binding of the two zinc finger nucleases to the respective zinc finger recognition sites cleavage places the monomers in a spatial orientation relative to each other that allows the cleavage monomers to form an active enzyme dimer, for example, by dimerization. As a result, the ends of the next recognition sites can be about 5 to about 18 nucleotides apart. For example, near ends can be separated by about 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 nucleotides. It will, however, be understood that any integer number of nucleotides or nucleotide pairs may intervene between two recognition sites (e.g., from about 2 to about 50 or more nucleotide pairs). The ends near the zinc finger nuclease recognition sites, such as those described in detail here, can be separated by six nucleotides. In general, the cleavage site is between the recognition sites.
    [00047] Targeting endonucleases (restriction enzymes) are present in many species and are capable of binding to specific DNA sequences (at a recognition site) and of cleaving DNA at or near the binding site. Certain restriction enzymes (eg, type IIS) cleave DNA at sites taken from the recognition site and have separable binding and cleavage domains. For example, the FokI Type IIS enzyme catalyzes the double-stranded cleavage of DNA, 9 nucleotides from its recognition site on one strand and 13 nucleotides from its recognition site on the other. See, for example, US Patents 5,356,802; 5,436,150 and 5,487,994; as well as Li et al. (1992) Proc. natl. academy Sci. USA 89:4275-4279; Li et al. (1993) Proc. natl. academy Sci. USA 90:2764-2768; Kim et al. (1994a) Proc. natl. academy Sci. USA 91:883887; Kim et al. (1994b) J. Biol. Chem. 269:31978-31982. Thus, a zinc finger nuclease may comprise the cleavage domain of at least one type of IIS restriction enzyme and one or more zinc finger binding domains, which may or may not be engineered. Examples of Type IIS restriction enzymes are described, for example, in International Publication WO 07/014, 275, the disclosure of which is incorporated herein by reference in its entirety. Additional restriction enzymes also contain dissociable binding and cleavage domains, and these are also contemplated by the present disclosure. See, for example, Roberts et al. (2003) Nucleic Acids Res. 31:418-420.
    [00048] An example of a Type IIS restriction enzyme, whose cleavage domain is dissociable from the binding domain, is FokI. This particular enzyme is active as a dimer (Bitinaite et al (1998) Proc Natl Acad Sci USA 95. 10, 570-10, 575). Thus, for the purposes of the present disclosure, the portion of the FokI enzyme used in a zinc finger nuclease is considered a cleavage monomer. Thus, for target double-stranded cleavage using a FokI cleavage domain, two zinc finger nucleases, each comprising a FokI cleavage monomer, can be used to reconstitute an active enzyme dimer. Alternatively, a single polypeptide molecule containing a zinc finger binding domain and two FokI cleavage monomers can also be used.
    [00049] In certain embodiments, the cleavage domain includes one or more engineered cleavage monomers that minimize or prevent homodimerization. By way of non-limiting examples, amino acid residues at positions 446, 447, 479, 483, 484, 486, 487, 490, 491, 496, 498, 499, 500, 531, 534, 537, and 538 of FokI are all targets to influence dimerization of FokI cleavage half-domains. Examples of engineered FokI cleavage monomers that form obligate heterodimers include a pair in which a first cleavage monomer includes mutations at amino acid residue positions 490 and 538 of FokI and a second cleavage monomer that includes mutations at amino acid residue positions of FokI. amino acids 486 and 499.
    [00050] Thus, in one embodiment, a mutation at amino acid position 490 replaces Glu (E) with Lys (K), a mutation at amino acid residue 538 replaces Iso (I) with Lys (K), a mutation at residue of amino acid 486 replaces Gln (Q) with Glu (E) and a mutation at position 499 replaces Iso (I) with Lys (K). Specifically, engineered cleavage monomers can be prepared by mutating position 490 from E to K and 538 from I to K in a cleavage monomer to produce an engineered cleavage monomer designated "E490K:I538K" and by mutating positions 486 from Q to E and 499 from I to L into another cleavage monomer to produce a designed cleavage monomer designated "Q486E:I499L". The engineered cleavage monomers described above are obligate mutant heterodimers in which abnormal cleavage is minimized or abolished. Engineered cleavage monomers can be prepared using an appropriate method, for example, by wild-type cleavage site-directed mutagenesis (FokI) as described in US Patent 7,888,121, which is incorporated herein in its entirety. (ii) optional polynucleotide
    [00051] The method for editing the target genome may further comprise introducing into the cell at least one polynucleotide comprising a sequence having substantial sequence identity with a sequence on at least one side of the target cleavage site. For example, the polynucleotide may comprise a first sequence having substantial sequence identity with sequence on one side of the target cleavage site and a second sequence having substantial sequence identity with sequences on the other side of the target cleavage site. Alternatively, the polynucleotide may comprise a first sequence having substantial sequence identity with the sequence on one side of the target cleavage site and a second sequence having substantial sequence identity with a sequence located away from the target cleavage site. The sequence located away from the target cleavage site may be tens, hundreds or thousands of nucleotides upstream or downstream of the target cleavage site.
    [00052] The lengths of the first and second sequences in the polynucleotide that contain substantial sequence identity to the sequences in the chromosomal sequence can and will vary. In general, each of the first and second sequences of the polynucleotide is at least about 10 nucleotides in length. In various embodiments, polynucleotide sequences having substantial sequence identity to chromosomal sequences are about 15 nucleotides, about 20 nucleotides, about 25 nucleotides, about 30 nucleotides, about 40 nucleotides, about 50 nucleotides, about 100 nucleotides, or more than 100 nucleotides in length.
    [00053] The term "substantial sequence identity" means that the sequences in the polynucleotide contain at least about 75% sequence identity to the chromosomal sequences of interest. In some embodiments, the sequences in the polynucleotide contain about 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% sequence identity to the chromosomal sequence of interest.
    [00054] The length of the polynucleotide can and will vary. For example, the polynucleotide can range from about 20 nucleotides in length to about 200,000 nucleotides in length. In various embodiments, the e polynucleotides range from about 20 nucleotides to about 100 nucleotides in length, from about 100 nucleotides to about 1000 nucleotides in length, from about 1000 nucleotides to about 10,000 nucleotides in length, from about 10,000 nucleotides to about 100,000 nucleotides in length, or from about 100,000 to about 200,000 nucleotides in length.
    [00055] Typically, the polynucleotide will be DNA. DNA can be single-stranded or double-stranded. The donor polynucleotide can be a DNA plasmid, a bacterial artificial chromosome (BAC), a yeast artificial chromosome (YAC), a viral vector, a piece of linear DNA, a PCR fragment, a naked nucleic acid, or a nucleic acid complexed with a delivery vehicle such as a liposome or poloxamer.
    [00056] In some embodiments, the polynucleotide may further comprise a tag. Non-limiting examples of suitable labels include restriction sites, fluorescent proteins or selectable labels. These markers make it possible to screen target integrations. (iii) introduction into the cell
    [00057] The target endonuclease can be introduced into the cell, either as a protein, or as a nucleic acid encoding the target endonuclease. The nucleic acid encoding the target endonuclease can be either DNA or RNA (ie, mRNA). In embodiments where the nucleic acid encoding is mRNA, the mRNA may be 5'-capped and/or 3' polyadenylated. In embodiments where the nucleic acid encodes DNA, the DNA may be linear or circular. The DNA may be part of a vector, wherein the DNA it encodes is optionally operably linked to a suitable promoter. Those skilled in the art are familiar with appropriate vectors, promoters, other control elements, and means of introducing the vector into the cell of interest.
    [00058] The target endonuclease or nucleic acid encoding the target endonuclease and the optional polynucleotide described above can be introduced into the cell through a variety of means. Suitable delivery means include microinjection, electroporation, sonoporation, bioballistics, calcium phosphate-mediated transfection, cationic transfection, liposome transfection, dendrimer transfection, heat shock transfection, nucleofection transfection, magnetofection, lipofection, impalefection, optical transfection, agent proprietary method of promoting nucleic acid uptake, and release via liposomes, immunoliposomes, virosomes, or artificial virions. In certain embodiments, the target endonuclease molecule and optional polynucleotides are introduced into a cell by nucleofection or electroporation.
    [00059] In embodiments where more than one target endonuclease molecule and more than one polynucleotide are introduced into a cell, the molecules may be introduced simultaneously or sequentially. For example, target endonuclease molecules, each specific for a targeted restriction site (and optional polynucleotides) can be introduced at the same time. Alternatively, each target endonuclease molecule as well as optional polynucleotides can be introduced sequentially.
    [00060] The ratio of the target endonuclease molecule (or nucleic acid encoding the optional polynucleotide can and will vary. In general, the ratio of the target endonuclease molecule to the polynucleotide can vary from about 1:10 to about of 10:1. In various embodiments, the ratio of the target endonuclease molecule to the polynucleotide is about 1:10, 1:9, 1:8, 1:7, 1:6, 1:5, 1 :4, 1:3, 1:2, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, or 10: 1. In one embodiment, the ratio is about 1:1. (b) RNA interference
    [00061] In another embodiment, the cell line deficient in Cmah and/or Ggta1 can be prepared using an RNA interference agent (RNAi), which inhibits the expression of a target mRNA or transcript. The RNAi agent can lead to cleavage of the target or transcript mRNA. Alternatively, the RNAi agent can prevent or stop the translation of target mRNA into protein.
    [00062] In some embodiments, the RNAi agent may be a short interfering RNA (siRNA). In general, a siRNA comprises a double-stranded RNA molecule that ranges from about 15 to about 29 nucleotides in length. The siRNA can be about 16-18, 17-19, 21-23, 24-27, or 27-29 nucleotides in length. In a specific embodiment, the siRNA is about 21 nucleotides in length. The siRNA may optionally further comprise single or double stranded overhangs, for example a 3' overhang at one or both ends. The siRNA can be formed from two RNA molecules that hybridize together or, alternatively, can be generated from a short hairpin RNA (shRNA) (see below). In some embodiments, the two strands of the siRNA are fully complementary, so that there are no mismatches or overhangs in the duplex formed between the two sequences. In other embodiments, the two strands of the siRNA are substantially complementary, such that one or more mismatches or overhangs may exist in the duplex formed between the two sequences. In certain embodiments, one or both of the 5' ends of the siRNA contain a phosphate group, while in other embodiments, one or both of the 5' ends do not contain a phosphate group. In other embodiments, one or both of the 3' ends of the siRNA contain a hydroxyl group, while in other embodiments one or both of the 5' ends do not contain a hydroxyl group.
    [00063] A siRNA strand, which is referred to as the "antisense strand" or "guide strand", includes a portion that hybridizes to the target transcript. In certain embodiments, the antisense strand of the siRNA is completely complementary to a region of the target transcript, i.e., it hybridizes to the transcript of a single target, without mismatches or overhangs along a target region of about 15 and about 29 nucleotides. in length, preferably at least 16 nucleotides in length, and more preferably about 18-20 nucleotides in length. In other embodiments, the antisense strand is substantially complementary to the target region, that is, one or more mismatches and/or overhangs may exist in the duplex formed by the antisense strand and the target transcript. Normally, siRNAs are targeted to the exonic sequences of the target transcript. Those skilled in the art are familiar with the programs, algorithms, and/or commercial services that design siRNAs to target transcripts. One example is the Rosetta siRNA Algorithm Design (Rosetta Inpharmatics, North Seattle, WA) and MISSION® siRNA (Sigma-Aldrich, St. Louis, MO). SiRNAs can be synthesized enzymatically in vitro using methods well known to those skilled in the art. Alternatively, the siRNA can be chemically synthesized using oligonucleotide synthesis techniques, which are well known in the art.
    [00064] In other embodiments, the RNAi agent may be a short hairpin RNA (shRNA). In general, an shRNA is an RNA molecule that comprises at least two complementary portions that hybridize or are capable of hybridizing to form a double-stranded structure of sufficient length to mediate RNA interference (as described above), and at least , a single-stranded portion that forms a loop of ligation of the regions of the shRNA that form the duplex. The structure can also be called a rod-handle structure, with the rod being the part of the duplex. In some embodiments, the portion of the duplex structure is completely complementary, so that there are no mismatches or overhangs in the duplex region of the shRNA. In other embodiments, the portion of the duplex structure is substantially complementary, such that one or more mismatches/or overhangs exist in the portion of the shRNA duplex. The loop of the structure can be from about 1 to about 20 nucleotides in length, preferably from about 4 to about 10 nucleotides in length, and more preferably from about 6 to about 9 nucleotides in length. The loop may be located at the 5' or 3' end of the region that is complementary to the target transcript (ie, the portion of the antisense shRNA).
    [00065] The shRNA may further comprise an overhang at the 5' or 3' end. The optional overhang can be from about 1 to about 20 nucleotides in length, and more preferably from about 2 to about 15 nucleotides in length. In some embodiments, the overhang comprises one or more U residues, for example, between about 1 and about 5 U residues. In some embodiments, the 5' end of the shRNA contains a phosphate group, while in other embodiments it does not. In other embodiments, the 3' end of the shRNA contains a hydroxyl group, while in other embodiments it does not. In general, shRNAs are processed into siRNAs by RNAi conserved cellular machinery. Thus, shRNAs are precursors of siRNAs and are equally capable of inhibiting the expression of a target transcript that is complementary to a portion of the shRNA (ie, the portion of the antisense shRNA). Those skilled in the art are familiar with the resources available (as detailed above) for the design and synthesis of shRNAs. An example is MISSION® shRNAs (Sigma-Aldrich).
    [00066] In still other embodiments, the RNAi agent may be an RNAi expression vector. Typically, an expression vector is used for intracellular (in vivo) RNAi synthesis of RNAi agents such as siRNAs or shRNAs. In one embodiment, two separate complementary siRNA strands are transcribed using a single vector containing two promoters, each of which directs the transcription of a single siRNA strand (i.e., each promoter is operably linked to a template for the siRNA so that transcription can take place). The two promoters may be in the same orientation, in which case each is operably linked to a template for one of the complementary strands of siRNA. Alternatively, the two promoters may be in opposite orientations, flanking a single template such that transcription of the promoters results in the synthesis of two complementary strands of siRNA. In another embodiment, the RNAi expression vector may contain a promoter that directs the transcription of an RNA molecule comprising two complementary regions, such that the transcripts form an shRNA.
    [00067] Those skilled in the art will appreciate that it is preferred for the siRNA and shRNA agents to be produced in vivo, via transcription of more than one transcriptional unit. In general, promoters used to direct the in vivo expression of one or more siRNA or shRNA transcriptional units can be promoters for RNA polymerase III (Pol III). Some Pol III promoters, such as U6 or H1 promoters, do not require cis-acting regulatory elements in the transcribed region, and thus are preferred in certain embodiments. In other embodiments, Pol II promoters can be used to direct the expression of one or more siRNA or shRNA transcriptional units. In some embodiments, tissue-specific, cell-specific, or inducible Pol II promoters may be used.
    [00068] A construct that provides a template for the synthesis of siRNA or shRNA can be produced using standard recombinant DNA methods and inserted into any of a wide variety of different vectors suitable for expression in eukaryotic cells. Recombinant DNA techniques are described in Ausubel et al, supra and Sambrook & Russell, supra. Those skilled in the art will also appreciate that vectors may comprise additional regulatory sequences (e.g., termination sequence, translational control sequence, etc.), as well as selectable marker sequences. DNA plasmids are known in the art, including those based on pBR322, PUC, and so on. Since many expression vectors already contain a suitable promoter or promoters, it may only be necessary to insert the nucleic acid sequence encoding the RNAi agent of interest into a suitable location with respect to the promoters. Viral vectors can also be used to provide intracellular expression of RNAi agents. Suitable viral vectors include retroviral vectors, lentiviral vectors, adenoviral vectors, adeno-associated virus vectors, herpes virus vectors, and so on. In a specific embodiment, the RNAi expression vector is a lentiviral shRNA or lentiviral particle-based vector such as that provided by MISSION® TRC shRNA products (Sigma-Aldrich).
    [00069] RNAi agents or RNAi expression vectors can be introduced into the cell by methods well known to those skilled in the art. Said techniques are described in Ausubel et al. supra, or Sambrook & Russell, supra, for example. In certain embodiments, the RNAi expression vector, eg a viral vector, is stably integrated into the cell genome, such that expression of Cmah and/or Ggta1 is disrupted over subsequent cell generations. (c) random mutagenesis
    [00070] In yet other embodiments, the cell line deficient in Cmah and/or Ggta1 can be prepared using random mutagenesis. In one embodiment, a random mutation is generated by exposing the cell to a chemical, such as N-ethyl-N-nitrosourea (ENU), N-ethyl-N-nitrosourea (NMU), ethyl methanesulfonate (EMS), nitrous acid ( NA), or another mutagenic chemical. In another embodiment, a random mutation is generated using a transposon-based system to introduce short sequences randomly into the genome, thereby disrupting expression of the chromosomal sequence into which a sequence is inserted. In another embodiment, a random mutation is generated using ionizing radiation. (d) site-specific recombination
    [00071] In alternative embodiments, the cell line deficient in Cmah and/or Ggta1 can be prepared using site-specific recombination techniques. For example, site-specific recombination techniques can be used to exclude all or part of a chromosomal sequence of interest, or to introduce single nucleotide polymorphisms (SNPs) into the chromosomal sequence of interest. In one embodiment, the chromosomal sequence of interest is targeted via a Cre-loxP site-specific recombination system, an FLP-FRT site-specific recombination system, or variants thereof. Said recombination systems are commercially available, and additional studies for these techniques are found in Ausubel et al. above, for example. (III) Methods for Producing Recombinant Proteins
    [00072] Another aspect of the present disclosure includes a method for producing a recombination protein having a human-like glycosylation pattern. In general, a glycoprotein with a human-like glycosylation pattern is devoid of α-Gal and/or Neu5Gc residues. The method comprises expressing the recombination protein in a non-human mammalian cell line deficient in Cmah and/or Ggta1. Cmah and/or Ggta1 deficient cell lines are described above in section (I).
    [00073] In an exemplary embodiment, the cell line may comprise a biallelic inactivation of the chromosomal sequence encoding Cmah such that the cell line does not produce any Cmah and the recombinant protein produced by the cell line is devoid of α-Gal fractions. In another exemplary embodiment, the cell line may comprise a biallelic inactivation of the chromosomal sequence encoding Ggta1 such that the cell line does not produce any Ggta1 and the recombinant protein produced by the cell line is devoid of Neu5Gc residues. In another exemplary embodiment, the cell line may comprise biallelic inactivations of the chromosomal sequences encoding Cmah and Ggta1 and such that the cell line does not produce no Cmah or Ggta1 and the recombinant protein produced by the cell is devoid of α-Gal and Ggta1 residues. Neu5Gc. In another embodiment, in which the cell line is aneuploid, all copies of the chromosomal sequence encoding Cmah are inactivated so that the cell line does not produce any Cmah and the recombinant protein produced by the cell line is devoid of α-Gal fractions. In another exemplary embodiment, in which the cell line is aneuploid, all copies of the chromosomal sequence encoding Ggta1 are inactivated so that the cell line does not produce any Ggta1 and the recombinant protein produced by the cell line is devoid of Neu5Gc residues. In another exemplary embodiment, in which the cell line is aneuploid, all copies of the chromosomal sequence encoding Cmah and all copies of the chromosomal sequence encoding Ggta1 are inactivated so that the cell line does not produce any Cmah or Ggta1 and the recombinant protein. produced by the cell is devoid of α-Gal and Neu5Gc residues.
    [00074] In general, the recombinant protein produced by the cell line deficient in Cmah and/or Ggta1 contains at least one property that is improved over the same protein produced by a comparable cell line that is not deficient in Cmah and/or Mgt1. Non-limiting examples of improved properties include reduced immunogenicity, increased bioavailability, increased efficacy, increased stability, increased solubility, improved half-life, improved clearance, improved pharmacokinetics, and combinations thereof. For example, because the recombinant protein was produced by the method disclosed herein and was devoid of α-Gal and/or Neu5Gc residues, the recombinant protein produced showed reduced immunogenicity and reduced potential to induce hypersensitivity reactions in humans, than is a comparable protein containing α-Gal and/or Neu5Gc residues.
    [00075] The recombinant protein produced in the Cmah and/or Ggta1 deficient cell line can be any suitable protein, including therapeutic proteins and biological products of the protein. For example, the recombinant protein can be, among others, an antibody, a fragment of an antibody, a monoclonal antibody, a humanized antibody, a humanized monoclonal antibody, a chimeric antibody, an IgG molecule, a heavy chain IgG, a light chain IgG, an IgA molecule, an IgD molecule, an IgE molecule, an IgM molecule, a glycoprotein, a growth factor, a cytokine, an interferon, an interleukin, a hormone, a clotting factor ( or clotting), a blood component, an enzyme, a nutraceutical protein, a vaccine, a functional fragment or a functional variant of any of the foregoing, or a fusion protein comprising any of the foregoing proteins and/or functional fragments thereof, or variants thereof.
    [00076] Methods for producing recombinant proteins are well known in the art, and further studies can be provided by Ausubel et al. above. In general, the recombinant protein is expressed from an exogenously introduced nucleic acid. As detailed in the above section (I)(a), the nucleic acid encoding the recombinant protein may be extrachromosomal or the nucleic acid encoding the recombinant protein may be integrated into the genome.
    [00077] Methods for culturing the cell line so that the recombinant protein is expressed are well known in the art. Appropriate media and culture systems are known in the art and are commercially available. In one embodiment, the recombinant protein is produced by the cell lines described herein through serum-free suspension culture. DEFINITIONS
    [00078] Unless defined otherwise, all technical and scientific terms used herein have the meaning commonly understood by one skilled in the art to which this invention pertains. The following references provide the skilled artisan with a general definition of many of the terms used in the present invention: Singleton et al., Dictionary of Microbiology and Molecular Biology (2nd ed. 1994); The Cambridge Dictionary of Science and Technology (Walker ed., 1988); The Glossary of Genetics, 5th Ed., R. Rieger et al. (eds.), Springer Verlag (1991); and Hale & Marham, The Harper Collins Dictionary of Biology (1991). As used herein, the following terms have the meanings ascribed to them, unless otherwise specified.
    [00079] When the elements of the present disclosure or the preferred embodiments thereof are presented, the articles "a", "an", "the" and "said" are intended to mean that there is one or more of the elements. The terms "comprising", "including" and "containing" are intended to be inclusive and mean that there may be elements in addition to the elements listed.
    [00080] As used herein, the term "endogenous sequence" refers to a chromosomal sequence that is native to the cell.
    [00081] The term "exogenous sequence" refers to a chromosomal sequence that is not native to the cell, or to a sequence whose native location is in a different chromosomal location.
    [00082] The terms "edit", "genome editing", or "chromosomal editing" refer to a process by which a specific chromosomal sequence is altered. The edited chromosomal sequence may comprise an insertion of at least one nucleotide, a deletion of at least one nucleotide, and/or a substitution of at least one nucleotide.
    [00083] A "gene", as used herein, refers to a region of DNA (including exons and introns) of the gene that encodes a product, as well as all regions of DNA that regulate the production of the gene product, whether such regulatory sequences adjacent or not to the coding and/or transcribed sequences. Thus, a gene includes, but is not necessarily limited to, promoter sequences, terminators, translational regulatory sequences such as ribosome binding sites and internal ribosome entry sites, enhancers, silencers, insulators, binding elements, origins of replication , matrix binding sites and locus control regions.
    [00084] The term "heterologous" refers to an entity that is not native to the cell or species of interest.
    [00085] The terms "nucleic acid" and "polynucleotide" refer to a deoxyribonucleotide or ribonucleotide polymer, in linear or circular conformation, and in either single- or double-stranded form. For purposes of the present disclosure, these terms are not to be construed as limiting with respect to the length of a polymer. The terms may include known analogs of natural nucleotides, as well as of nucleotides that are modified in base, sugar and/or phosphate moieties (eg, phosphorothioate backbones). In general, an analog of a particular nucleotide has the same base-pairing specificity, that is, an analog of A will pair with T.
    [00086] The term "nucleotide" refers to deoxyribonucleotides or ribonucleotides. The nucleotides can be standard nucleotides (ie, adenosine, guanosine, cytidine, thymidine, and uridine) or nucleotide analogues. A nucleotide analogue refers to a nucleotide that has a modified purine or pyrimidine base or a modified ribose moiety. A nucleotide analog can be a naturally occurring nucleotide (eg, inosine) or a non-naturally occurring nucleotide. Non-limiting examples of modifications to the sugar or base moieties of a nucleotide include the addition (or removal) of acetyl groups, amino groups, carboxyl groups, carboxymethyl groups, hydroxyl groups, methyl groups, phosphoryl groups, and thiol groups, as well as the replacement of the carbon and nitrogen atoms of the bases with other atoms (eg, 7-deaza purines). Nucleotide analogs include dideoxy nucleotides, 2-O-methylnucleotides, blocked nucleic acids (LNA), peptide nucleic acids (PNA), and morpholinos.
    [00087] The terms "polypeptide" and "protein" are used interchangeably to refer to a polymer of amino acid residues.
    [00088] The term "recombination" refers to a process of exchanging genetic information between two polynucleotides. For purposes of this disclosure, "homologous recombination" refers to the specialized form of said exchange that occurs, for example, during the repair of double-strand breaks in cells. This process requires sequence similarity between the two polynucleotides, using a "donor" or "swap" molecule to model the repair of a "target" molecule (i.e., the one that has experienced the double-strand break), and is also known as "non-crossover gene conversion" or "short tract gene conversion", because it leads to the transfer of genetic information from the donor to the target. Without being bound by any particular theory, the transfer may involve correction of heteroduplex DNA mismatches that form between the broken target and the donor, and/or the "annealing-dependent chain of synthesis", in which the donor is used to resynthesize the genetic information that will become part of the target, and/or related processes. Such specialized homologous recombination often results in a change in the sequence of the target molecule such that part or all of the donor polynucleotide sequence is incorporated into the target polynucleotide.
    [00089] As used herein, the terms "target site" or "target sequence" refer to a nucleic acid sequence that defines a portion of a chromosomal sequence to be edited and which a target endonuclease is designed to recognise, link and cleave.
    [00090] The terms "upstream" and "downstream" refer to sites in the nucleic acid sequence relative to a fixed position. Upstream refers to the region that is 5' (i.e. near the 5' end of the strand) to the position and downstream refers to the region that is 3' (i.e. near the 3' end of the strand) to the position.
    [00091] Techniques for determining nucleic acid and amino acid sequence identity are known in the art. Typically, these techniques include determining the mRNA nucleotide sequence for a gene and/or determining the amino acid sequence encoded by it and comparing these sequences to a second nucleotide or amino acid sequence. Genomic sequences can also be determined and compared in this way. In general, identity refers to an exact nucleotide-to-nucleotide and amino acid-to-amino acid correspondence of two polynucleotides or polypeptide sequences, respectively. Two or more sequences (polynucleotide or amino acid) can be compared to determine their percent identity. The percent identity of two nucleic acid or amino acid sequences is the number of exact matches between two aligned sequences divided by the length of the shorter sequences and multiplied by 100. An approximate alignment for the nucleic acid sequences is provided by the homology algorithm Smith and Waterman site, Advances in Applied Mathematics 2:482-489 (1981). This algorithm can be applied to amino acid sequences using the scoring matrix developed by Dayhoff, Atlas of Protein Sequences and Structure, M.O. Dayhoff ed., 5 suppl. 3:353-358, National Biomedical Research Foundation, Washington, D.C., USA, and standardized by Gribskov, Nucl. Acids Res.14(6):6745-6763 (1986). An example implementation of this algorithm to determine the percent identity of a sequence is provided by the Genetics Computer Group (Madison, Wisconsin) in the "BestFit" utility application. Other programs suitable for calculating percent identity or similarity between sequences are generally known in the art, for example another alignment program is BLAST, can be used with default parameters. For example, BLASTN and BLASTP can be used with the following default parameters: genetic code = default; filter = none; ribbons = both; cut = 60; expected = 10; Matrix = BLOSUM62; Descriptions = 50 sequences; sort by = HIGH SCORE, Databases = non-redundant, GenBank + EMBL + DDBJ + PDB+ GenBank CDS translations + Swiss protein+ Spupdate + PIR. Details of these programs can be found on the GenBank website. With respect to the sequences described herein, the range of desired degrees of sequence identity is approximately 80% to 100% and any integer value in between. Typically the percentages of sequence identities are at least 70-75%, preferably 80-82%, more preferably 85-90%, even more preferably 92%, even more preferably 95%, and most preferably 98% sequence identity.
    [00092] As various changes could be made to the cells and methods described above without departing from the scope of the invention, it is intended that the entire object contained in the above description and in the examples presented below, should be interpreted as illustrative and not in a limiting sense. EXAMPLES
    [00093] The following examples illustrate certain aspects of the invention. Example 1: CHO cells contain Ggtal Gene
    [00094] To confirm the presence of the Ggta1 gene in CHO K1 cells, primers were designed to amplify the regions of exons 8 and 9 of the Ggta1 gene. Murine DNA and NS0 and CHO K1 myeloma cells were PCR amplified using a pair of primers. A band of the expected size of approximately 300 bp was detected in both CHO and NS0 cells. PCR fragments isolated from CHO cells were sequenced and aligned with the mouse Ggta1 gene (UniProtKB/Swiss-Prot Accession No.: P23336). Sequence identity was about 85%.
    [00095] Quantitative PCR was used to assess mRNA expression in CHO cells versus mouse cells. After normalization using actin, a comparison of threshold cycle values (Ct) between NS0 mouse cells and CHO cells suggested that Ggta1 expression was significantly lower in CHO cells than in NS0 cells. Example 2: Generation of CHO Cells Comprising an Inactivated Ggtal Locus
    [00096] A pair of ZFNs was designed to target a region within exon 9 of the Ggta1 gene in CHO cells. Ggta1 sequences were obtained from a proprietary transcriptome sequence and verified by RT-PCR. Gene-targeting ZFNs were designed using a proprietary algorithm and subsequently tested. In vitro transcription and mRNA polyadenylation and capping were produced from ZFN plasmid DNA as described in the CompoZr® Knockout Zinc Finger Nucleases (ZFN) product information. Briefly, the ZFN plasmid DNA was linearized, and purified by phenol/chloroform DNA extraction. MessageMaxTM T7 ARCA-Capped Message Transcription Kit (Cell Script Inc.) was used to cover linear DNA. A Poly(A) Polymerase Tailing Kit (EpiCenter) was used to add a poly(A) tail. ZFN mRNA was purified using the MEGAclearTM kit (Ambion).
    [00097] The CHOZN cell line (gs-/-) expressing recombinant human anti-rabies IgG was used. All cell culture media, supplements and other reagents used were purchased from Sigma-Aldrich unless otherwise specified. Prior to transfection, cells were maintained as suspension cultures in Ex-Cell ® CHO CD Fusion (Sigma-Aldrich) supplemented with 6 mM L-glutamine. Cells were seeded at 0.5 □ 10 6 cells/ml in bioreactor tubes one day before transfection. For each transfection, 1 □ 10 6 cells in 150 µL of growth medium 5g of each ZFN mRNA were used. Transfections were performed by electroporation at 140 V and 950 DF in 0.2 cm cuvettes. Electroporated cells were placed in 2 mL of growth medium in a 6-well static culture plate. Control cells were transfected in simulation.
    [00098] On days 3 and 10 after transfection, cells were removed from culture and genomic DNA was isolated using Sigma-Aldrich GeneElute Mammalian Genomic DNA Miniprep Kit. Induced cleavage of ZFN was verified using a Cel-1 nuclease assay as described in the CompoZr® Knockout ZFN product information. This assay is performed to determine the efficiency of the ZFN-mediated gene mutation as previously described ( Miller, JC et al., Nat. Biotechnol.2007, 25:778-785 ). The assay detects alleles of the target locus that deviate from wild-type as a result of the non-homologous splicing effect (NHEJ) mediated by imperfect repair of ZFN DNA induced double-strand breaks. PCR amplification of the target region from a pool of treated ZFN cells generates a mixture of wild-type (WT) and mutant amplicons. Fusion and reannealing of this mixture results in the formation of mismatches formed between heteroduplexes of the WT and mutant alleles. A DNA "bubble" formed at the site of mismatch is cleaved by surveyor nuclease Cel -1, and the cleavage products can be resolved by gel electrophoresis. As shown in FIG. 1, two fragments of about 215 bp and 100 bp were seen in the transfected ZFN cells (lanes 1 and 2), but absent in the mock-transfected control cells Example 3: Single Cell Cloning and Cell Genotyping Ggta1 Knockout
    [00099] After confirmation of ZFN activity using the Cel 1 assay, the transfected ZFN Ggta1 cells were cloned to obtain single cells using limiting dilution. For this, cells were plated at 0.5 cells/well using a mixture of 80% CHO and serum-free cloning media, 20% conditioned media, and 4 mM L-glutamine. Clone formation and growth were verified microscopically on days 7 and 14 post plating, respectively. Growing clones were expanded and genotyped by PCR and sequencing. One Ggta1 (-/-) clone and four Ggta1 (+/-) clones carrying deletions of various lengths were isolated, as detailed in Table 1 below. All cell lines exhibited growth characteristics similar to the parental cell line from which they were derived. Table 1. Genotypic characterization of Ggtal knock-out clones
    Example 4: CHO Cell Generation Comprising an Inactivated Cmah Locus
    [000100] A pair of ZFNs was designed to target a region within exon 5 of the Cmah locus in CHO cells (UniProtKB/Swiss-Prot Accession No: Q9WV23; Chinese hamster); The CHO K1 cell line was transfected with 20 µg of RNA encoding the ZFNs using standard procedures and methods analogous to those described in Example 2. Control cells were transfected with RNA encoding GFP.
    [000101] The efficiency of double stranded chromosome breaks induced by ZFN was determined using the Cel-1 nuclease assay. As shown in FIG. 2 , Cmah ZFNs cleaved target Cmah in CHO cells. The frequency of ZFN-mediated cleavage can be estimated by comparing the relative intensity of the cleavage products with the relative intensity of the parental band. Cleavage frequency was calculated by ImageJ software to be about 11%. Example 5: Single Cell Cloning and Cmah Knockout Cell Genotyping
    [000102] ZFN Cmah transfected cells were cloned as a single cell using limiting dilution (as described above), or fluorescence activated cell sorting (FACS). Growing clones were expanded and genotyped by PCR and sequencing. Genotyping revealed that all 20 clones in this working cycle were Cmah (+/-) carrying deletions and insertions of various lengths. Subsequently, seven Cmah (+/-) clones were pooled, and retransfected with ZFN Cmah RNA, and cloned as a cell using limiting dilution. Six clones from the second round of work were verified by PCR and sequenced as Cmah (-/-). Inactivated Cmah loci carried deletions and insertions of various lengths (see Table 2). The biallelic genotypes of these Cmah knockout cell lines are listed in Table 2. All cell lines exhibited growth characteristics that were similar to the parental cell line from which they were derived. Table 2. Genotypic characterization of Cmah clones (-/-)

    Example 6: Generation of Cmah/Ggta1 Double Knockout Cells
    [000103] A Cmah (-/-) clonal cell line with a confirmed genotype (i.e. AB2) was transfected with Ggta1 restriction ZFNs essentially as described above in Example 2. ZFN activity was confirmed using the nuclease assay Cell-1. As shown in FIG. 3, cleavage products were detected, in which ZFN transfected the cells, but not the mock-transfected cells.
    [000104] Cells were cloned using single cell by limiting dilution, essentially as described above in Example 3. Nested PCR was performed on 192 clones, and 26 clones were identified as potential double knockout clones based on the size of the PCR product. Genomic DNA was isolated from potential double knockout clones, amplified by PCR and sequenced. Four clones had 2x sequence coverage confirming the biallelic deletion of Ggta1 in the background Cmah knockout. Table 3 shows the genotypes of Cmah (-/-) /Ggta1(-/-) double knockout clones Table 3. Genotypic characterization of Cmah/Ggta1 double knockout clones
    权利要求:
    Claims (11)
    [0001]
    1. Method for producing a recombinant protein with a human-like glycosylation pattern, characterized in that it comprises expressing the recombinant protein in a Chinese hamster ovary (CHO) cell line deficient in cytidine-monophosphate-N-acid hydroxylase -acetylneuraminic (Cmah) and glycoprotein alpha-1,3-galactosyltransferase-1 (Ggta1).
    [0002]
    2. Method according to claim 1, characterized in that the cell line comprises an inactivated chromosomal sequence that encodes Cmah and an inactivated chromosomal sequence that encodes Ggta1, and the cell produces a reduced amount of Cmah and/or Ggta1.
    [0003]
    3. Method according to claim 2, characterized in that the recombinant protein has a reduced content of N-glycolylneuraminic acid residues (Neu5Gc) and galactose-alpha-1,3-galactose (alpha-Gal) residues compared to the same recombinant protein produced by a comparable cell line not deficient in Cmah and/or Ggta1.
    [0004]
    4. Method according to claim 2, characterized in that all copies of the chromosomal sequence encoding Cmah and/or Ggta1 are inactivated, and the cell line does not produce Cmah and/or Ggta1.
    [0005]
    5. Method according to claim 4, characterized in that the recombinant protein lacks residues of N-glycolylneuraminic acid (Neu5Gc) and residues of galactose-alpha-1,3-galactose (alpha-Gal).
    [0006]
    Method according to claim 1, characterized in that the recombinant protein has at least one property that is improved compared to the same recombinant protein produced by a comparable cell line not deficient in Cmah and/or Ggta1.
    [0007]
    7. Method according to claim 6, characterized in that the property that is improved is chosen from among reduced immunogenicity, increased bioavailability, increased efficacy, increased stability, increased solubility, improved half-life, improved clearance and improved pharmacokinetics.
    [0008]
    8. Method according to claim 1, characterized in that the recombinant protein is chosen from among an antibody, an antibody fragment, a growth factor, a cytokine, a hormone and a clotting factor.
    [0009]
    9. Method according to claim 1, characterized in that all copies of the chromosomal sequence encoding Cmah are inactivated, the cell line does not produce Cmah and the recombinant protein is devoid of Neu5Gc residues.
    [0010]
    10. Method according to claim 1, characterized in that all copies of the chromosomal sequence encoding Ggta1 are inactivated, the cell line does not produce Ggta1 and the recombinant protein is devoid of alpha-Gal residues.
    [0011]
    11. Method according to claim 1, characterized in that the cell line is a CHO cell line, all copies of the chromosomal sequence encoding Cmah and all copies of the chromosomal sequence encoding Ggta1 are inactivated, the cell line does not produce Cmah or Ggta1 and the recombinant protein is devoid of Neu5Gc and alpha-Gal residues.
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    同族专利:
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    法律状态:
    2018-04-03| B06F| Objections, documents and/or translations needed after an examination request according [chapter 6.6 patent gazette]|
    2019-07-09| B06T| Formal requirements before examination [chapter 6.20 patent gazette]|
    2020-05-12| B07D| Technical examination (opinion) related to article 229 of industrial property law [chapter 7.4 patent gazette]|Free format text: DE ACORDO COM O ARTIGO 229-C DA LEI NO 10196/2001, QUE MODIFICOU A LEI NO 9279/96, A CONCESSAO DA PATENTE ESTA CONDICIONADA A ANUENCIA PREVIA DA ANVISA. CONSIDERANDO A APROVACAO DOS TERMOS DO PARECER NO 337/PGF/EA/2010, BEM COMO A PORTARIA INTERMINISTERIAL NO 1065 DE 24/05/2012, ENCAMINHA-SE O PRESENTE PEDIDO PARA AS PROVIDENCIAS CABIVEIS. |
    2020-09-08| B07E| Notification of approval relating to section 229 industrial property law [chapter 7.5 patent gazette]|
    2021-03-30| B06G| Technical and formal requirements: other requirements [chapter 6.7 patent gazette]|
    2021-07-20| B06A| Patent application procedure suspended [chapter 6.1 patent gazette]|
    2021-11-03| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|
    2022-01-11| B09W| Correction of the decision to grant [chapter 9.1.4 patent gazette]|Free format text: A NOTIFICACAO DE DEFERIMENTO FOI EFETUADA COM INCORRECAO NO QUADRO 1 . |
    2022-01-25| B16A| Patent or certificate of addition of invention granted [chapter 16.1 patent gazette]|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 29/06/2012, OBSERVADAS AS CONDICOES LEGAIS. |
    优先权:
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    US201161503436P| true| 2011-06-30|2011-06-30|
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