Exons 4 and 5 were replaced with a PGK-puro cassette via homologous recombination resulting in protein truncation. Northern blot analysis of tissues from homozygous mutant animals did not detect gene transcript although a transcript with deleted exons 4 and 5, presumed to be unstable, was detected by RT-PCR. Western blot of irradiated testes from homozygous mutants did not detect protein product. (J:74284)