Ontogeny of Hoxa9, Hoxa10, Hoxa11, Hoxa13, Hoxd13, and Hoxb13 expression in the rat ventral prostate from birth through adulthood. Hoxa9 expression is high at birth and decreases by d 6 to a constant lower level through adulthood. *, P < 0.05; **, P < 0.01 vs. d 1; #, P < 0.05 vs. d 3. Hoxa10 levels are low at birth and gradually increase after d 10 to a 2-fold higher level in adulthood. ***, P < 0.001 vs. d 1, 3, and 6; #, P < 0.05 vs. d 6. Hoxa11 expression is highest at d 3 and decreases thereafter to one third of this level by d 90. **, P < 0.01 vs. d 1; #, P < 0.05 vs. d 3; ##, P < 0.01 vs. d 3; ###, P < 0.001 vs. d 3. The Hox13 genes are expressed at 10-fold or greater levels compared with the anterior Hoxa9–11 genes. The expression of all Hox13 genes are lowest during early prostate development and increase to the highest expression levels in the adult VP. Hoxa13 and Hoxd13 increase 2- to 3-fold, whereas Hoxb13 expression increases 200-fold by adulthood. Hoxa13, ***, P < 0.001 vs. d 1 and 6, #, P < 0.05 vs. d 3; Hoxd13, ***, P < 0.001 vs. d 1, 3 and 6, #, P < 0.05 vs. d 10; Hoxb13, ***, P < 0.001 vs. d 1, 3, and 6, #, P < 0.05 vs. d 10. Each point represents the mean ± sem for three to 11 replicates.