The gene was disrupted by replacement of a portion of exon 2 encoding 5 N-terminal zinc fingers with a neomycin resistance cassette via homologous recombination. Northern blot analysis of mRNA from homozygous mutant mice did not detect wild-type transcript. However, hybridization with a C-terminal probe revealed a shortened transcript containing the neo cassette. The mutant transcript contains multiple stop codons as assessed by sequence analysis and most likely does not encode a functional protein.