Fig. 2. Pod1 expression during gonad development. Illustrated are wholemounts (A,B,E,F) and longitudinal sections (C,D,G,H) of Pod1^+/– gonads (go) stained for expression of the lacZ reporter gene. At 11.5 dpc, lacZ staining was observed in gonads from both XY (A) and XX (B) genital ridges. Strong expression was observed in the coelomic epithelium (ce) in male embryos and in mesonephric stromal cells at the boundary between the gonad and the mesonephros (m) (arrowheads) in both XY (C) and XX embryos (D). At 12.5 dpc, lacZ again was expressed in both XY (E) and XX (F) gonads, but higher levels of expression were observed in the male. Again, expression was primarily limited to the coelomic epithelium and some underlying cells (G,H). At 18.5 dpc, high levels of lacZ expression were observed in the interstitial cells of the testis (I,K) both in fetal Leydig cells (le) and in the peritubular myoid cells (pm) surrounding the testicular cords (tc). lacZ was also expressed throughout the developing ovary (J,L). Expression was concentrated particularly in the ovarian medulla (arrowhead), and in cells surrounding the developing follicles, which may represent theca cell progenitors. The inset (L) shows Pod1 expression in pericytes (pe) associated with a capillary. go, gonad; ce, coelomic epithelium; m, mesonephros; le, Leydig cells; pm, peritubular myoid cells; tc, testicular cords; pe, pericyte; en, endothelial cell.