A floxed neomycin cassette replaced the segment of exon 7 that lies between SalI and XbaI restriction sites. This mutation deleted sequences that encode the C-terminal zinc finger domains. The locus produced truncated mRNA as determined by RT-PCR. No protein was detected in immunoblot analysis of homozygote thymus extracts using an antibody specific to the N-terminal of the protein. (J:151553)