Nhej1^tm1Fwa

A floxed neomycin selection cassette replaced exons 4 and 5 on allele of the gene locus. Cre recombinase was transiently expressed to remove the neomycin cassette. The same targeting vector was used to target the other allele in this ES cell line and again, cre recombinase was transiently expressed to remove the neo cassette. This targeting strategy could allow for an in-frame splicing event from exon 3 to exon 6 to generate a truncated protein. An antibody to the C-terminal end of the gene product sometimes detected very low levels of the truncated protein in homozygous ES cells. Serial dilution analysis suggests that the level of truncated protein is less than 1% of endogenous levels. Recombinant protein lacking exons 4 and 5 was found to be non-functional in rescuing sensitivity to irradiation. (J:120145, J:138774)