PDGFB and obesity due to melanocortin 4 receptor deficiency: Furthermore, Pdgfb is a key gene involved in placental labyrinth development [115,116], and expression of Pdgfb was also downregulated in the placenta in a related model of maternal diet-induced obesity [117], as well as in the placenta in late gestation in mice with reduced uteroplacental perfusion pressure [118].