The gene was disrupted by insertion of a PGK-neo cassette into exon 4 via homologous recombination. RT-PCR analysis of homozygous mutants detected a mutant transcript, and sequencing of the product revealed splicing of part of the PGK-neo cassette into the message resulting in a stop codon 30 bp downstream of exon 3. Northern blot analysis of E13.5 homozygous mutant embryos using cDNA probes to the 5' and 3' regions of the gene revealed a transcript similar in size to the wild-type transcript. Western blot analysis using a monoclonal antibody directed to the N-terminal region of the protein showed that no protein product was made from the mutant transcript.