A gene trap vector inserted in the intron between non-coding exon 1ac and the first coding exon, exon 2. The construct contains a splice acceptor site upstream of a promoter-less beta-galactosidase and neomycin gene fusion (beta-geo) and a polyadenylation sequence. Beta-geo expression in this line is under the control of endogenous regulatory elements for this gene. Loss of both enndogenous protein and messenger RNA was observed. (J:229930)