Non-human animals and methods and compositions for making and using them are provided, wherein said 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 coding sequences of a non-immunoglobulin polypeptide of interest. Non-human animals described herein express antibodies characterized by complementary determining regions (CDRs), in particular, CDR3s having diversity that directs binding to particular antigens. Methods for producing antibodies from non-human animals are also provided, which antibodies contain human variable regions and mouse constant regions.
