Abstract: A method for engineering and utilizing large DNA vectors to target, via homologous recombination, and modify, in any desirable fashion, endogenous genes and chromosomal loci in eukaryotic cells. These large DNA targeting vectors for eukaryotic cells, termed LTVECs, are derived from fragments of cloned genomic DNA larger than those typically used by other approaches intended to perform homologous targeting in eukaryotic cells. Also provided is a rapid and convenient method of detecting eukaryotic cells in which the LTVEC has correctly targeted and modified the desired endogenous gene(s) or chromosomal locus (loci) as well as the use of these cells to generate organisms bearing the genetic modification.

Abstract: The invention provides a method of making and secreting a non-secreted protein. The method includes expressing the protein from a nucleic acid construct which includes: (a) a mammary epithelial specific promoter; (b) a milk protein specific signal sequence which can direct the secretion of a protein; (c) optionally, a sequence which encodes a sufficient portion of the amino terminal coding region of a secreted protein to allow secretion in the milk of a transgenic mammal, of the non-secreted protein; and (d) a sequence which encodes a non-secreted protein, wherein elements (a), (b), optionally (c), and (d) are preferably operatively linked in the order recited. Both glutamic acid decarboxylase (GAD) and myelin basic protein (MBP), which are cytoplasmic proteins, have been produced by the methods of the present invention. The invention also provides methods for treating diabetes and multiple sclerosis using proteins produced by the methods of the present invention.