Fig. 3. The metanephric mesenchyme fails to form in Odd1^-/- embryos. (A,B) Sections through the metanephric region of E11.5 heterozygous and homozygous null embryos stained with hematoxylin and eosin. In heterozygotes (A), a nephric duct, ureteric bud and condensed metanephric mesenchyme are seen. Homozygous null embryos (B) completely lack a ureteric bud and condensed mesenchyme (arrow). A duct is often present (on right side but not left in B), but smaller than normal. The region between the aorta and nephric duct is also significantly smaller in the Odd1 null embryos. (C-J) Sections through the metanephric region of mouse embryos stained by in situ whole-mount hybridization (C-F) or immunofluorescence (G-J) for the indicated gene products (Dapi nuclear stains in G and I correspond to sections in H and J, respectively). At E10.5, the metanephric mesenchyme of Odd1 heterozygous embryos expresses Six2 (C), Eya1 (E) and Pax2 (H). All three gene products are absent from the metanephric mesenchyme region of Odd1 null mutants (D,F,J). The mutant nephric duct does express Pax2 (J). The duct in mutant embryos is outlined with a dotted line (D,F,I). The fluorescence in the upper right corner in J is autofluoresc;ence from blood cells in the aorta. a, aorta; d, nephric duct; mm, metanephric mesenchyme; u, ureteric bud.