Mammalian uterine morphogenesis and variations.

In eutherian and marsupial mammals, the site of embryo implantation and gestation is the uterus. Uterine morphologies vary between mammalian species. For example, laboratory mice have a bipartite uterus with two uterine horns and a single cervix, whereas humans have a simplex uterus with a single chamber and single cervix. The precursor tissue of the uterus, oviducts, and upper vagina is the Müllerian duct epithelium and its adjacent mesenchyme. Morphological variation between species is established during embryogenesis by species-specific differences in Müllerian duct fusion at the midline, growth, and differentiation. In humans, alterations in Müllerian duct development can lead to variations in uterine morphology that correlate with increased risks of miscarriage and infertility. Here we review the developmental genetic factors that regulate Müllerian duct development, uterine morphogenesis, and human uterine variation.