Novel tissue interactions support the evolution of placentation. (18th January 2021)

• Record Type: Journal Article
• Authors: Griffith, Oliver W.
• Other Names: Matthias Starck J. guestEditor.; Blackburn Daniel G. guestEditor.; Stewart James R. guestEditor.
• Is Part Of: Journal of morphology. Volume 282:Number 7(2021)
• Page Start: 1047
• Page End: 1053
• Publication Date: 2021-01-18
• Subjects: implantation -- placenta -- research highlights -- signalling -- uterus -- viviparity; Morphology -- Periodicals; Physiology -- Periodicals; Anatomy -- Periodicals; 571.3
• DOI: 10.1002/jmor.21322
• Languages: English
• ISSNs: 0362-2525

Abstract

Abstract: Organ development occurs through the coordinated interaction of distinct tissue types. So, a question at the core of understanding the evolution of new organs is, how do new tissue‐tissue signalling networks arise? The placenta is a great model for understanding the evolution of new organs, because placentas have evolved repeatedly, evolved relatively recently in some lineages, and exhibit intermediate forms in extant clades. Placentas, like other organs, form from the interaction of two distinct tissues, one maternal and one fetal. If each of these tissues produces signals that can be received by the other, then the apposition of these tissues is likely to result in new signalling dynamics that can be used as a scaffold to support placenta development. Using published data and examples, in this review I demonstrate that placentas are derived from hormonally active organs, that considerable signalling potential exists between maternal and fetal tissues in egg‐laying vertebrates, that this signalling potential is conserved through the oviparity‐viviparity transition, and that consequences of these interactions form the basis of derived aspects of placentation including embryo implantation. I argue that the interaction of placental tissues, is not merely a consequence of placenta formation, but that novel interactions form the basis of new placental regulatory networks, functions, and patterning mechanisms. Abstract : Placentas are derived from a series of maternal and fetal tissues. In the ancestral oviparous (egg laying) condition, these tissues have their own cell–cell signalling dynamics. The evolution of viviparity (live birth) offers an opportunity for expressed signalling molecules and receptors in the ancestral tissues to interact across the newly apposed maternal and fetal tissues. This new signalling dynamic acts as a scaffold for the evolution of new placental regulatory networks, functions, and patterning mechanisms.