The transient expression of cre recombinase within ES cells resulted in the excision of a floxed region containing a neomycin gene and the exon containing nucleotides 681-837 of the published mouse cDNA sequence deposited in GenBank as X57111. The deletion introduced a frameshift mutation. RT-PCR analysis of total RNA extracts from homozygous mutant mice showed an absence of normal transcript. Western analysis using an antibody raised against the C-terminal failed to detect protein in homozygous mutant mice. (J:51666)