Fig. 2. Absence of Bapx1 expression in the sclerotome of Pax1;Pax9-deficient embryos. In situ hybridization for Bapx1 on sagittal (A,C) and transverse (B,D) sections of wild type (w.t.; A,B) or Pax1^-/-, Pax9^-/- (C,D) E11.5 mouse embryos at the lumbar level. The arrows indicate the notochord (n). Note that in the mutant embryo (C,D) loose mesenchyme of sclerotomal cells around the notochord lack Bapx1 expression.