Implantation in the human: The role of HOX genes

HOX genes are transcription factors that are essential for the proper devel opment of the mullerian tract in the embryonic period. It has been discover ed that HOX genes are expressed in the adult uterus. Two of them, Hoxa10 an d Hoxa11, have been demon strated to be necessary for uterine receptivity a nd implantation in mice. Recent evidence also suggests such a role for HOX genes in humans. They are likely to be essential regulators of endometrial development in preparation for implantation. This article reviews the role of the HOX genes in the reproductive tract, their patterns of expression an d regulation, the outcome of deficient HOX gene expression, and their poten tial mechanisms of action. The process of implantation is complex, and many molecular markers have been found expressed at high levels in the endometr ium in the peri-implantation window. Targeted disruption has revealed that most of these molecules are redundant and not essential for implantation. T he importance of Hox genes in this process has been well documented, and th ey remain one of the few well-characterized molecules necessary for implant ation.