Abstract: Disclosed herein are non-human animals (e.g., rodents, e.g., mice or rats) genetically engineered to express a humanized or human T cell receptor (TCR) comprising a variable domain encoded by (a) at least one human TCR variable region ? gene segment and a (human) TCR ? constant region gene sequence and/or (b) or at least one human TCR variable region ? gene segment and a (human) TCR ? constant region gene sequence. Also provided are embryos, tissues, and cells expressing the same. Methods for making a genetically engineered animal that expresses the humanized or human ? and/or ? TCR are also provided. Methods for using the genetically engineered animals that mount a substantially humanized T cell immune response for developing human therapeutics are also provided.

Abstract: Compositions and methods are provided for creating and promoting biallelic targeted modifications to genomes within cells and for producing non-human animals comprising the modified genomes. Also provided are compositions and methods for modifying a genome within a cell that is heterozygous for an allele to become homozygous for that allele. The methods make use of Cas proteins and two or more guide RNAs that target different locations within the same genomic target locus. Also provided are methods of identifying cells with modified genomes.

Abstract: Provided herein are methods and compositions related to the in vivo testing of therapeutic agents comprising a human Fc in genetically modified rodents (e.g., the testing of the pharmacokinetic and/or pharmacodynamic properties of such a therapeutic agent in genetically modified rodents). In some embodiments the genetically modified rodents express antibodies comprising a human Fc (e.g., a human IgG1 Fc, a human IgG4 Fc). In some embodiments, the rodents express fully human antibodies (i.e., antibodies having human heavy chains and human light (? or ?) chains). In certain embodiments the genetically modified rodents comprise one or more Fc receptors with a human extracellular domain (e.g., a Neonatal Fc Receptor (FcRn), a ?-2-microglobulin polypeptide (?2M), a Fc ? receptor 1 ? (Fc?R1?), a Fc ? receptor 1 alpha (Fc?R1a), a Fc gamma receptor 2a (Fc?R2a), a Fc gamma receptor 2b (Fc?R2b), a Fc gamma receptor 3a (Fc?R3a), a Fc gamma receptor 3b (Fc?R3b), a Fc gamma receptor 2c (Fc?R2c)).

Abstract: Compositions and methods are provided for creating and promoting biallelic targeted modifications to genomes within cells and for producing non-human animals comprising the modified genomes. Also provided are compositions and methods for modifying a genome within a cell that is heterozygous for an allele to become homozygous for that allele. The methods make use of Cas proteins and two or more guide RNAs that target different locations within the same genomic target locus. Also provided are methods of identifying cells with modified genomes.

Abstract: Provided herein are methods and compositions related to the in vivo testing of therapeutic agents comprising a human Fc in genetically modified rodents (e.g., the testing of the pharmacokinetic and/or pharmacodynamic properties of such a therapeutic agent in genetically modified rodents). In some embodiments the genetically modified rodents express antibodies comprising a human Fc (e.g., a human IgG1 Fc, a human IgG4 Fc). In some embodiments, the rodents express fully human antibodies (i.e., antibodies having human heavy chains and human light (? or ?) chains). In certain embodiments the genetically modified rodents comprise one or more Fc receptors with a human extracellular domain (e.g., a Neonatal Fc Receptor (FcRn), a ?-2-microglobulin polypeptide (?2M), a Fc ? receptor 1? (Fc?R1?), a Fc ? receptor 1 alpha (Fc?R1a), a Fc gamma receptor 2a (Fc?R2a), a Fc gamma receptor 2b (Fc?R2b), a Fc gamma receptor 3a (Fc?R3a), a Fc gamma receptor 3b (Fc?R3b), a Fc gamma receptor 2c (Fc?R2c)).

Abstract: The invention provides a genetically modified non-human animal that comprises in its genome unrearranged T cell receptor variable gene loci, as well as embryos, cells, and tissues comprising the same. Also provided are constructs for making said genetically modified non-human animal and methods of making the same. Various methods of using the genetically modified non-human animal are also provided.

Abstract: The invention provides a genetically modified non-human animal that comprises in its genome unrearranged T cell receptor variable gene loci, as well as embryos, cells, and tissues comprising the same. Also provided are constructs for making said genetically modified non-human animal and methods of making the same. Various methods of using the genetically modified non-human animal are also provided.

Abstract: Methods and compositions are provided for making one or more targeted genetic modifications at a target genomic locus within a cell and for producing non-human animals comprising the modified genomic locus. The methods employ two or more large targeting vectors which are capable of recombining with each other and with the target genomic locus in a single genomic targeting step. The methods may also be employed in combination with a nuclease agent. Methods and compositions are also provided for enhancing homologous recombination at a target genomic locus in a cell. The methods employ two or more nucleic acids comprising one or more overlapping sequences. The methods may be employed in combination with a nuclease agent or without a nuclease agent.

Abstract: The invention provides genetically modified non-human animals that express chimeric human/non-human MHC I and MHC II polypeptides and/or human or humanized ?2 microglobulin polypeptide, as well as embryos, cells, and tissues comprising the same. Also provided are constructs for making said genetically modified animals and methods of making the same. Methods of using the genetically modified animals to study various aspects of human immune system are provided.

Abstract: Described herein are anchor-modified immunoglobulin polypeptides, wherein the anchor moors the immunoglobulin polypeptide to a receptor of interest. The anchor-modified immunoglobulin polypeptides are generally characterized at the N-terminus with an anchor, e.g., the receptor binding portion of a ligand that binds a receptor. Non-human animals genetically modified with recombinant immunoglobulin segments that encode the anchor-modified immunoglobulin polypeptides are capable of making the anchor-modified immunoglobulin polypeptides. Such non-human animals also provided, along with methods and compositions for making and using the non-human animals. Methods for producing anchor-modified immunoglobulins from non-human animals are also provided, as well as anchor-modified immunoglobulins generated therefrom.

Abstract: Methods and compositions are provided for generating antigen-binding proteins against a foreign antigen of interest.

Abstract: Methods and compositions are provided for making one or more targeted genetic modifications at a target genomic locus within a cell and for producing non-human animals comprising the modified genomic locus. The methods employ two or more large targeting vectors which are capable of recombining with each other and with the target genomic locus in a single genomic targeting step. The methods may also be employed in combination with a nuclease agent. Methods and compositions are also provided for enhancing homologous recombination at a target genomic locus in a cell. The methods employ two or more nucleic acids comprising one or more overlapping sequences. The methods may be employed in combination with a nuclease agent or without a nuclease agent.

Abstract: Disclosed herein are genetically modified rodent animals comprising in their genome a nucleic acid which comprises a nucleotide sequence encoding a human CR1 polypeptide, wherein the rodent animals display a human-like expression of the human CR1 polypeptide. Also disclosed herein are isolated rodent cells including rodent embryonic stem cells, and rodent tissues. Further disclosed are nucleic acid vectors and methods for making the genetically modified rodent animals, as well as methods of using such genetically modified rodent animals for screening and testing candidate compounds.

Abstract: The invention provides genetically modified non-human animals that express chimeric human/non-human MHC I and MHC II polypeptides and/or human or humanized ?2 microglobulin polypeptide, as well as embryos, cells, and tissues comprising the same. Also provided are constructs for making said genetically modified animals and methods of making the same. Methods of using the genetically modified animals to study various aspects of human immune system are provided.

Abstract: The invention provides genetically modified non-human animals that express a humanized MHC II protein (humanized MHC II ? and ? polypeptides), as well as embryos, cells, and tissues comprising the same. Also provided are constructs for making said genetically modified animals and methods of making the same. Methods of using the genetically modified animals to study various aspects of human immune system are provided.

Abstract: Non-human animals and methods and compositions for making and using them are provided, which non-human animals have a genome comprising an engineered or recombinant diversity cluster within an immunoglobulin heavy chain variable region, which engineered or recombinant diversity cluster comprises an insertion of one or more DH segments that are each operably linked to a 23-mer recombination signal sequence. Methods for producing antibodies from non-human animals are also provided, which antibodies optionally contain human variable regions and rodent, e.g., constant regions.

Abstract: The invention provides genetically modified non-human animals that express a humanized MHC II protein (humanized MHC II ? and ? polypeptides), as well as embryos, cells, and tissues comprising the same. Also provided are constructs for making said genetically modified animals and methods of making the same. Methods of using the genetically modified animals to study various aspects of human immune system are provided.

Abstract: Provided herein are methods and compositions related to non-human animals that express exogenous Terminal Deoxynucleotidyltransferase (TdT).

Abstract: The invention provides genetically modified non-human animals that express a humanized MHC II protein (humanized MHC II ? and ? polypeptides), as well as embryos, cells, and tissues comprising the same. Also provided are constructs for making said genetically modified animals and methods of making the same. Methods of using the genetically modified animals to study various aspects of human immune system are provided.

Abstract: Provided herein are methods and compositions related to non-human animals that express exogenous Terminal Deoxynucleotidyltransferase (TdT).