Fig. 4. Bmp-receptor expression is affected in Hoxa13^GFP-homozygous mutants. (A,B) Low levels of Bmpr1a can be detected in both wild-type and mutant E12.5 embryos in the dUPE and GSM. (C,D) Bmpr1b expression is elevated in developing rectum (R) (black arrows) of homozygous mutant E12.5 embryos. (E,F) Bmpr2 expression is present in the UPE and GSM of both wild-type and mutant E12.5 embryos. (G,H) In E13.5 embryos, Bmpr1a expression is restricted to the distal genital tubercle and the developing preputial glands (P) in both wild-type and homozygous mutants. (I,J) Bmpr1b expression is reduced in the UPE (arrows) of E13.5 homozygous mutants when compared with wild type controls. (K,L) Bmpr2 expression appears elevated in the UPE of E13.5 homozygous mutants (arrows), whereas expression in the developing preputial glands (P) appears unaffected.