Generation of Stk25 conditional mice. A) Exons 4 and 5 were floxed by homologous recombination, which introduced a PGK-EM7 neo drug-selectable marker. The Frt-flanked marker was removed by FLP-mediated recombination. Cre-mediated recombination removes exons 4 and 5, resulting in a frameshift and termination in exon 6. The product of homologous recombination (homologous), FLP-mediated recombination (FLP) and Cre-mediated recombination (Cre) are shown. B) Stk25 protein levels were measured by western blotting (anti-Stk25; ) in brain lysates of P0 mice with the indicated genotype. The Stk25fl/fl (fl/fl) allele is fully functional for Stk25 expression and the germline expression of Cre generated a null allele with no detectable Stk25 expression in the homozygous state (−/−). C) The positions of Satb2-positive layer II-IV and Ctip2-positive layer V-VI neurons are evident in the neocortex of two-month-old wild-type mice. D) An indistinguishable pattern of lamination was observed in the Stk25−/− mice. Cortical layers are indicated to the left of the images (Bar 50 μm).