The gene was disrupted by replacement of exons 4-6 with a neomycin resistance cassette via homologous recombination. The targeted mutation results in the loss of a conserved DNA-binding motif called the Walker box, and also causes a frameshift. Homozygous mutant embryos were detected by PCR genotype analysis up to day E10.5. The targeted allele was confirmed by RT-PCR analysis of E8.5 embryos using primers flanking the deleted region. No RT-PCR products were detected. (J:61460)