A genomic region encompassing exons 2 through 6, encoding the extracellular domain, the transmembrane domain, and most of the intracellular domain, was deleted via cre-mediated recombination of single loxP sites following exon 1b and exon 6. Protein was undetected by Western blot analysis of liver homogenates obtained from homozygous mutant mice. (J:89758)