Fig. 3. Signals from the dorsal spinal cord are not sufficient to induce nephrogenesis in Fgf8-deficient metanephric mesenchyme. (A,B) Metanephric mesenchyme (MM) was isolated from E11.5 (A) Fgf8^flox/null (control) or (B) Pax3-cre;Fgf8^flox/null (Fgf8-MM-KO) littermates and cultured in the presence of dorsal spinal cord. After 48 hours of culture, the samples were processed for immunohistochemistry to detect phospho-Histone H3, which marks cells in mitosis (blue) and E-Cadherin, which marks epithelia (red). The arrowhead in A indicates a region where the tubular nature of the E-CAD-positive structures is particularly evident.