Pronuclear-stage embryos were targeted with a zinc finger nuclease pair designed to target exon 3. A founder mouse was identified carrying a 19-bp deletion at the targeted site (CTCGGGatggcactgggtacactggCTGGGCAG -> CTCGGGCTGGGCAG), which causes a reading frame shift resulting in a premature stop codon. Absence of the protein in brain, heart and liver of homozygous mutant mice was confirmed by immunoblot analysis.