Exon 1, encoding the first 45 amino acids, and surrounding intronic sequence were replaced using a vector containing lacZ and neo. Transcript was undetected by RT-PCR analysis of homozygous mutant mice. Western blot analysis, using an antibody raised against the carboxy-terminal, showed an absence of protein in homozygous mutant mice. A lack of immunoreactivity was observed in sections of the vas deferens obtained from homozygous mutant mice. (J:59336)