Fig. 2. Male embryos lacking Hoxa13 exhibit decreased programmed cell death (PCD) in the developing genital tubercle. (A) At E11.5, PCD is restricted to the dUPE (arrowhead) and proximal UPE (pUPE) in heterozygous controls. (B) PCD is reduced in the dUPE (arrowhead), but not in the pUPE of Hoxa13^GFP-homozygous mutants. (C) By E12.5, PCD shifts from the dUPE to the mesenchyme (M) flanking the dUPE (arrow). (D) Homozygous mutants also exhibit a shift in PCD to the flanking mesenchyme, although the number of TUNEL-positive cells in the mutant mesenchyme is consistently reduced when compared with heterozygous controls. Scale bars: 50 µm.