Fig. 1. Gross morphology of mutant ventral prostates. Ventral prostate showing the opaque appearance of control ducts (A) and the transparent appearance of Hoxb13 homozygous mutant ducts (B) (yellow arrows). (C) X-gal staining of 5-week-old Hoxb13^lacZ heterozygote reproductive organs show preferential expression of Hoxb13 within the ventral prostate; Hoxb13 continues to be strongly expressed in the ventral prostate of 1-year-old animals. (D-F) There is a dose-dependent X-gal staining intensity between wild-type (D), Hoxb13 heterozygote (E) and Hoxb13 homozygous mutant (F) ventral prostates (white arrowheads). Homozygous mutant prostates frequently exhibit swelling in individual ducts (E; red arrowhead). (G-I) Reductions in ventral prostate duct tips are observed in Hoxb13/Hoxd13 double homozygous mutants. Dark-field micrographs of ventral prostate microdissections of wild type (G), Hoxb13 homozygous mutants (H) and Hoxb13/Hoxd13 double homozygous mutants (I). Significant reductions in number of duct tips and outgrowth of branches are only seen in double Hoxb13/Hoxd13 mutants (averages and standard deviations for number of duct tips from 3 prostates for each genotype are shown below representative photo). (J-L) Postnatal X-gal staining of developing prostates showing Hoxb13 expression during the time of extensive ductile morphogenesis. At P10, X-gal staining is barely detectable (J), but is very strong by P12 in the ventral prostate (K). (L) During development, all prostatic lobes show strong X-gal staining (P16 shown). B, bladder; VP,ventral prostate; AP, anterior prostate; dlp, dorsolateral prostate; SV, seminal vesicle. Scale bars (A-I) 2 mm, (J-L) 1 mm.