Sonic hedgehog through Gli2 and Gli3 is required for the proper development of placental labyrinth

Sonic hedgehog (Shh) functions as a conserved morphogen in the development of various organs in metazoans ranging from Drosophila to humans. Here, we have investigated the potential roles and underlying mechanisms of Shh signaling in murine placentation. Immunostaining revealed the abundant expression of the main components of Shh pathway in both the trophectoderm of blastocysts and developing placentas. Disruption of Shh led to impaired vascularogenesis of yolk sac, less branching and malformation of placental labyrinth, thereby leading to a robust decrease in capacity of transplacental passages. Moreover, placenta-specific gene incorporation by lentiviral transduction of mouse blastocysts and blastocyst transplantation robustly knocked down the expression of Gli3 and Gli2 in placenta but not in embryos. Finally, Gli3 knockdown in Shh(-/-) placentas partially rescued the defects of both yolk sac and placental labyrinth, and robustly restored the capacity of transplacental passages. Gli2 knockdown in Shh(+/-) placentas affected neither the capacity of tranplacental passages nor the vascularogenesis of yolk sac, however, it partially phenocopied the labyrinthine defects of Shh(-/-) placentas. Taken together, these results uncover that both Shh/Gli2 and Shh/Gli3 signals are required for proper development of murine placentas and are possibly essential for pregnant maintenance.