A targeting vector replaced exon 3. RT-PCR of brain tissue from E13.5 homozygous mutant embryos did not detect 368 bp wild-type product but did detect a 268-bp product. Western analyses using polyclonal antibodies to either N-terminal or mid-protein sequences did not detect protein in brain tissue from homozygous mutant E13.5 embryos.
The exon 3 deletion is an in-frame deletion causing only the major isoform of Trp53bp2 to be deleted completely; low levels of shorter forms of Trp53bp2 can be expressed. Therefore Trp53bp23 acts as a hypomorphic allele.