Retroviral gene trap insertion occurred between exons 8 and 9. The insertion truncated the protein after amino acid 215, removing half of the protein including the predicted active site. RT-PCR analysis of P0 mutants confirmed elimination of wild-type mRNA. No truncated protein was detected by Western blot analysis; however, a small amount of normal protein was detected in both homozygous and heterozygous mutants, probably due to a small amount of splicing around the gene trap. (J:103485, J:249381)