The mouse fetal‐placental arterial connection: A paradigm involving the primitive streak and visceral endoderm with implications for human development. (17th October 2019)

• Record Type: Journal Article
• Authors: Downs, Karen M.; Rodriguez, Adriana M.
• Is Part Of: Wiley interdisciplinary reviews. Volume 9:Number 2(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2019-10-17
• Subjects: allantoic core domain -- allantois -- arterial vasculature -- Brachyury -- caspase‐3 -- embryonic‐extraembryonic interface -- epithelial‐to‐mesenchymal transition -- fetal‐placental connection -- gastrula -- Hedgehog -- hypoblast -- mesoderm -- node -- notochord -- orphan diseases -- placenta -- primitive streak -- umbilical cord -- visceral endoderm -- yolk sac; Developmental biology -- Periodicals; 571.805
• DOI: 10.1002/wdev.362
• Languages: English
• ISSNs: 1759-7684

Abstract

Abstract: In Placentalia, the fetus depends upon an organized vascular connection with its mother for survival and development. Yet, this connection was, until recently, obscure. Here, we summarize how two unrelated tissues, the primitive streak, or body axis, and extraembryonic visceral endoderm collaborate to create and organize the fetal‐placental arterial connection in the mouse gastrula. The primitive streak reaches into the extraembryonic space, where it marks the site of arterial union and creates a progenitor cell pool. Through contact with the streak, associated visceral endoderm undergoes an epithelial‐to‐mesenchymal transition, contributing extraembryonic mesoderm to the placental arterial vasculature, and to the allantois, or pre‐umbilical tissue. In addition, visceral endoderm bifurcates into the allantois where, with the primitive streak, it organizes the nascent umbilical artery and promotes allantoic elongation to the chorion, the site of fetal‐maternal exchange. Brachyury mediates streak extension and vascular patterning, while Hedgehog is involved in visceral endoderm's conversion to mesoderm. A unique CASPASE‐3‐positive cell separates streak‐ and non‐streak‐associated domains in visceral endoderm. Based on these new insights at the posterior embryonic‐extraembryonic interface, we conclude by asking whether so‐called primordial germ cells are truly antecedents to the germ line that segregate within the allantois, or whether they are placental progenitor cells. Incorporating these new working hypotheses into mutational analyses in which the placentae are affected will aid understanding a spectrum of disorders, including orphan diseases, which often include abnormalities of the umbilical cord, yolk sac, and hindgut, whose developmental relationship to each other has, until now, been poorly understood. This article is categorized under: Birth Defects > Associated with Preimplantation and Gastrulation Early Embryonic Development > Gastrulation and Neurulation Abstract : The fetal‐placental connection in the mouse gastrula. Recent discoveries at the posterior embryonic‐extraembryonic interface of the mouse gastrula expand upon the traditional view of the allantois and associated tissues, and reveal new elements that, in the current view, together create and pattern the fetal‐placental arterial connection, whose mechanism of establishment and alignment along the anterior–posterior body axis are the focus of this review article. ACD, allantoic core domain, or extraembryonic component of the primitive streak; al, allantois; am, amnion; AX, allantois‐associated extraembryonic visceral endoderm; bi, blood island; CASP3, activated CASPASE‐3 protein; ch, chorion; dAX, distal [to] allantois‐associated extraembryonic visceral endoderm; ips, intra‐embryonic component of the primitive streak; rod, visceral‐endoderm derived bifurcation into the allantois and associated with the ACD; xve, extraembryonic visceral endoderm; vys, visceral yolk sac. The white asterisk within the red circle is the vessel of confluence.