Homologous recombination inserted a loxP site before exon 4, a FRT-flanked neo cassette in intron 5 and followed by another loxP sequence. Cre-mediated recombination removed exons 4 and 5, resulting a frameshift and termination in exon 6. Western blot analysis confirms the absence of protein expression in brain lysates from homozygous mice. (J:203414)