ESSENTIAL ROLE OF PLATELET-DERIVED GROWTH-FACTOR RECEPTOR-ALPHA IN THE DEVELOPMENT OF THE INTRAPLACENTAL YOLK-SAC SINUS OF DUVAL IN MOUSE PLACENTA

Platelet-derived growth factor receptor alpha (PDCFR alpha) is express ed in multiple tissues and exerts its function throughout mouse embryo genesis. Upon screening the PDCFR alpha-expressing tissues in mouse em bryos by immunohistochemistry using our established monoclonal antibod y against murine PDGFRa, we found its expression in an epithelium lini ng a sinusoidal structure in placenta. This structure was proven to be the sinus of Duval, and the PDGFR alpha-positive epithelium to be the intraplacental yolk sac (IPY). The IPY has been postulated to be a de rivative of primitive endoderm because of its morphology and its expre ssion of vitamin D-dependent 9-kDa calcium-binding protein, and to pla y some roles in materno-fetal transport. In this study, we demonstrate d that the IPY develops from primitive endoderm by its invagination in to chorioallantoic placenta and continues to strongly express PDCFR al pha until the prenatal stage. Moreover, we found that the IPY is compl etely absent in Pdgfra(Ph)/Pdgfra(Ph) mutant embryos, which lack the P dgfra gene, suggesting that the function of PDGFR alpha is essential t o its formation. Hence, PDGFR alpha expressed in the IPY should be lis ted as a component of the cytokine network of murine placental develop ment.