Fig. 1. Histology of paraffin wax-embedded sections of wild-type and Foxd1-null kidneys. At E11.5 (A,B), ureters in Foxd1^+/+ (A) and Foxd1^lacZ/lacZ (B) embryos extend dorsally into the kidney blastemas. At E12.5, wild-type kidneys (C) have rotated and separated (only the right kidney is pictured). A gap (yellow arrowheads) separating the kidney from the body wall occurs. In the Foxd1 null (D), the kidneys have failed to separate and are surrounded by a thick layer of mesenchyme (yellow arrowheads). At E14.5, the wild-type (E) is almost fully detached (yellow arrowheads), while the Foxd1-null kidneys (F) continue to remain attached to the dorsal body wall (yellow arrowheads). da, dorsal aorta; ub, ureteric bud; cm, condensed mesenchyme. Scale bar: 75 µm for A,B; 150 µm for C,D; 200 µm for E,F.