Mice, embryos, cells, and tissues having a restricted immunoglobulin heavy chain locus and an ectopic sequence encoding one or more ADAM6 proteins are provided. In various embodiments, mice are described that have humanized endogenous immunoglobulin heavy chain loci and are capable of expressing an ADAM6 protein or ortholog or homolog or functional fragment thereof that is functional in a male mouse. Mice, embryos, cells, and tissues having an immunoglobulin heavy chain locus characterized by a single human V.sub.H gene segment, a plurality of human D.sub.H gene segments and a plurality of human J.sub.H gene segments and capable expressing an ADAM6 protein or ortholog or homolog or functional fragment thereof are also provided.

The invention discloses methods for the generation of chimaeric human-non-human antibodies and chimaeric antibody chains, antibodies and antibody chains so produced, and derivatives thereof including fully humanized antibodies; compositions comprising the antibodies, antibody chains and derivatives, as well as cells, non-human mammals and vectors, suitable for use in the methods.

The invention relates to the provision of antibody therapeutics and prophylactics that are tailored specifically for human use. The present invention provides libraries, vertebrates and cells, such as transgenic mice or rats or transgenic mouse or rat cells. Furthermore, the invention relates to methods of using the vertebrates to isolate antibodies or nucleotide sequences encoding antibodies. Antibodies, heavy chains, polypeptides, nucleotide sequences, pharmaceutical compositions and uses are also provided by the invention.

The present invention relates to a novel method for identifying pairs of receptors/ligands, transgenic animals useful for carrying out said method, and the use of ligands and/or modulators of the interaction between a ligand and its receptor in the food industry, fragrance industry, and health industry, for instance.

A human artificial chromosome vector comprising a gene encoding a human antibody heavy chain, a gene encoding a human antibody light chain, and a gene encoding an IgM heavy chain constant region derived from a nonhuman animal.

Disclosed is a mouse artificial chromosome vector, comprising: a natural centromere derived from a mouse chromosome; a mouse-chromosome-derived long-arm fragment formed by deleting a long-arm distal region at a mouse chromosome long-arm site proximal to the centromere; and a telomere sequence, wherein the vector is stably retained in a cell and/or tissue of a mammal. In addition, disclosed are cells or non-human animals comprising the vector, and use of the cells or non-human animals.

The invention relates to an approach for introducing one or more desired insertions and/or deletions of known sizes into one or more predefined locations in a nucleic acid (e.g., in a cell or organism genome). They developed techniques to do this either in a sequential fashion or by inserting a discrete DNA fragment of defined size into the genome precisely in a predefined location or carrying out a discrete deletion of a defined size at a precise location. The technique is based on the observation that DNA single-stranded breaks are preferentially repaired through the HDR pathway, and this reduces the chances of indels (e.g., produced by NHEJ) in the present invention and thus is more efficient than prior art techniques. The invention also provides sequential insertion and/or deletions using single- or double-stranded DNA cutting.

Non-human animals, and methods and compositions for making and using the same, are provided, wherein said non-human animals comprise a humanization of an Angiopoietin-like protein 8 (ANGPTL8) gene. Said non-human animals may be described, in some embodiments, as having a genetic modification to an endogenous ANGPTL8 locus so that said non-human animals express a human ANGPTL8 polypeptide.

A genetically modified non-human animal comprising a genome containing an endogenous non-human ACE2 locus genetically modified to encode a complete human ACE2 gene. According to a further embodiment the genome is genetically modified to encode a second, a third, and a fourth complete human ACE2 gene, the human ACE2 gene is at least 85 percent identical to SEQ ID No: 1, the animal of is a mouse, the human ACE2 gene encodes six protein variants, an endogenous Tmprss2 gene is unmodified, a LoxP gene flanks each of a 5′ and a 3′ end of a nucleic acid sequence of the human ACE2 gene, and the human ACE2 gene is expressed in a lung, kidney, spleen, stomach, liver, intestine, heart, and skeletal muscle of the animal, and a cortex, striatum, middle brain, hippocampus, olfactory bulb, and cerebellum of a brain of the animal.

Non-human animals, methods and compositions for making and using the same, are provided, wherein said non-human animals comprise a mutant L-kynurenine hydrolase (or kynureninase) gene. Said non-human animals may be described, in some embodiments, as having a genetic modification in an endogenous kynureninase gene so that said non-human animals express a kynureninase polypeptide that includes an amino acid substitution that results in the elimination of an epitope in said kynureninase polypeptide that is present in the membrane proximal external region of human immunodeficiency virus-1 gp41.