Essential Role of Platelet-Derived Growth Factor Receptor a in the Development of the Intraplacental Yolk Sac/Sinus of Duval in Mouse Placenta(2)
The sinus of Duval is an extension of the yolk sac cavity expanding into the chorioallantoic placental disc of mice or rats. This sinus is lined by two types of epithelium— high columnar epithelium, which faces fetal blood vessels, and squamous epithelium, which faces maternal blood sinuses in the chorioallantoic disc. That the lining epithelium is a derivative of the inverted yolk sac endoderm was surmised from its morphology and the fact that both the visceral yolk sac endoderm and the columnar epithelium of the sinus of Duval express the vitamin D-dependent 9-kDa calcium-binding protein (calbindin-D9k); therefore the epithelium of the sinus of Duval is called the intraplacental yolk sac (IPY). From its structure and the expression of calbindin-D9k, it can be inferred that the IPY develops to connect the yolk sac placental system to the chorioallantoic placental system for special matemo-fetal transport, although the precise function of the IPY remains unclear.
We have been studying the functions of platelet-derived growth factor receptor (PDGFR)-family tyrosine kinases during mouse embryogenesis. The PDGFRa, the receptor for all three isoforms of PDGFs—PDGF-AA, PDGF-AB, and PDGF-BB —is known to exert its function through multiple processes of mouse development, such as cardiovascular morphogenesis, angiogenesis, lung branching, neural crest cell differentiation, glial cell development, development of the retina, hair-canal formation, and so on. In fact, the multiple organ defect of homozygous Pdgfraph mutant results from a large genomic deletion of the region including the entire pdgfra gene on chromosome 5. Recently, we made a monoclonal antibody against murine PDGFRa, APA5, and reported the immunolocalization of PDGFRa in mouse embryos. Buy Asthma Inhalers Online
Upon screening the PDGFRa-expressing extraembryon-ic tissues, we found that APA5 stained the epithelium lining a sinusoidal structure in the placental disc, which is similar to the sinus of Duval. In this study, we demonstrated that PDGFRa is expressed in the IPY and defined the developmental course of the IPY by using APA5 as a marker. Moreover, we found that the homozygous Pdgfraph mutant lacks this sinus. This mutation is known to exhibit phenotypes caused not only by the loss of PDGFRa but also by the aberrant expression of с-kit; therefore, we examined whether с-kit expression is altered in the placenta of this mutant.
Tags: Growth Factor, Mouse Placenta, Platelet-Derived, Yolk Sac