Fig. 1.

Conditional inactivation of the Sox9 gene by using the Wnt1-Cre transgene. (A) Gross appearance of newborn mice. (B) Skeletons of newborn mice stained by alcian blue followed by alizarin red. (C) Southern blot analysis of fetal genomic DNA and PCR genotyping of Cre transgenes and floxdel alleles. Genomic DNA isolated from the skin or the yolk sac of WT, Sox9^flox/WT; Wnt1-Cre, and Sox9^flox/flox; Wnt1-Cre was digested with BamHI and then hybridized with a 3′ probe (11). The WT and floxed alleles were detected as 13-kb and 7.2-kb fragments, respectively. (D) Expression of Sox9 mRNA in the dorsal neural tube and neural crest of E9.5 WT and mutant embryos. Sox9 mRNA was not detected in mutants. The arrow indicates the dorsal neural tube and neural crest.