The gene was disrupted by replacement of the end of intron 3 and the first 60 codons of the cytoplasmic catalytic domain containing exon 4 with a PGK-neo cassette via homologous recombination. Homozygous mutant embryos were observed at days E9.5-E11.5 and RT-PCR analysis of embryonic mRNA detected truncated mutant transcripts. (J:63748)