Fig. 4. Generation of Hes1 cKO mice. (A) Strategy for generation of Hes1 cKO mice. (B) Genomic DNA from drug-resistant cells was digested with HindIII and analyzed by Southern blot using a 0.6-kb HindIII-BamHI fragment as a 5'-probe, which detected wild-type and floxed fragments (6.0 kb), floxed-neo (7.8 kb) and deleted fragments (3.8 kb). (C-E) β-Galactosidase activity in the forebrain of Emx1-Cre;R26R mice at E10.5-E12.5. (F-O) Hes1 and Hes5 were expressed in the dorsal telencephalon of the control (Bmp4⁺, F,L) at E10.5 and E11.5 (G,H,M). In Hes1 cKO mice, Hes1 expression was downregulated around E10.5 (J, asterisk) and was lost by E11.5 (O, asterisk). Insets of M and O show immunohistochemistry for Hes1. Hes1 protein expression was lost in Hes1 cKO mice by E11.5. Hes5 expression was upregulated in Hes1 cKO mice (K). di, diencephalon; tel, telencephalon; hem, cortical hem. Scale bars: 100 µm in C,D,F-O; 200 µm in E.