Fig. 1. Generation and characterization of the Bmp7^cre/+ and HoxB7cre kidney deleter strains. (A) Targeting strategy used to generate Bmp7^cre/+. (B,C,D) Bmp7^cre/+ activates the ROSA26^R reporter in Wolffian duct, ureteric bud and the collecting duct system. Mesenchyme excision is scattered through the metanephric blastema at E11.5 (B), and by E12.0 (C), is uniform throughout the mesenchyme condensates surrounding collecting duct tips. A population of cells surrounding the collecting duct trunk is devoid of excision at this stage. At E13.5 (D), excision is limited to the collecting ducts, nephrogenic mesenchyme, renal vesicles, comma- and s-shaped bodies and podocytes. No excision can be seen within stromal cell populations. Bmp7^+/lacZ is expressed in nephrogenic mesenchyme (E), the prospective distal end of the comma-shaped body (H), and podocytes and distal tubules of maturing nephrons (I). Proximal tubules and Bowman's capsules do not express Bmp7^+/lacZ. Staining in Bmp7^cre/+;Rosa26^R kidneys is seen throughout the nephron (F,G). HoxB7cre activity marks the Wolffian duct, ureteric bud and collecting ducts at E11.75 (J) and E13.5 (K). The red line in K denotes the border between the collecting duct and nephron. CB, comma-shaped body; CD, collecting duct; dist, distal tubule; Mes, metanephric mesenchyme; neph, nephron; NM, nephrogenic mesenchyme; pod, podocytes; prox, proximal tubule; PS, peripheral stroma; UB, ureteric bud; WD, Wolffian duct; B, BamHI; Na, NaeI; Nc, NcoI; R, EcoRI.