The sixteen 5′ Hox genes belonging to the paralogous groups 9-13 all show DNA sequence similarities to the Drosophila Abdominal-B (Abd-B) gene, which specifies the identity of the most posterior segments of the larval and adult fly. Among HOX genes, members of the HOXC and HOXD clusters, and in particular the Abd-B-related 5′ genes of these linkage groups, are the least well characterized. In the developing genitalia, prominent expression of both Hoxc10 and Hoxc11 are observed in the posterior urogenital sinus, which gives rise to urethra and vagina. Later, their expression is seen at high levels in parameso-nephric duct and in the genital tubercle.
The expression patterns of Hoxc10 and Hoxc11 are similar; however, Hoxc10 is expressed more anteriorly in the paramesone-phric duct, Hoxc11 is expressed only posterior to the pelvis, whereas Hoxc10 expression surrounds all the pelvic condensations and is also seen in the peritoneal and ventral epithelia. The posterior Hoxd genes are also expressed in female-developing genito-urinary tracts. Genes of the Hoxd cluster have been shown to be expressed in the genital tubercle, the ovary, and the oviduct of the developing reproductive tract of mouse fetus. Homozygous Hoxd10 mutant female mice are able to produce offspring.