RNA-seq reveals conservation of function among the yolk sacs of human, mouse, and chicken

Abstract

The yolk sac is phylogenetically the oldest of the extraembryonic membranes. The human embryo retains a yolk sac, which goes through primary and secondary phases of development, but its importance is controversial. Although it is known to synthesize proteins, its transport functions are widely considered vestigial. Here, we report RNA-sequencing (RNA-seq) data for the human and murine yolk sacs and compare those data with data for the chicken. We also relate the human RNA-seq data to proteomic data for the coelomic fluid bathing the yolk sac. Conservation of transcriptomes across the species indicates that the human secondary yolk sac likely performs key functions early in development, particularly uptake and processing of macro-and micronutrients, many of which are found in coelomic fluid. More generally, our findings shed light on evolutionary mechanisms that give rise to complex structures such as the placenta. We identify genetic modules that are conserved across mammals and birds, suggesting these modules are part of the core amniote genetic repertoire and are the building blocks for both oviparous and viviparous reproductive modes. We propose that although a choriovitelline placenta is never established physically in the human, the placental villi, the exocoelomic cavity, and the secondary yolk sac function together as a physiological equivalent.yolk sac | placenta | evolution

Distribution of Cadherin in the Parahippocampal Area of Developing Domestic Chicken Embryos

“…Our results regarding the changes between different subregions indicate that Cdh2, Cdh8, Pcdh8 and Pcdh10 might have regionally homologous expression in chicken and mouse hippocampal formations. This is consistent with Cindrova-Davies' research [60] on the functionally conservation of yolk sac among human, mouse and chicken [61]. Similarly, the complicated brain has its own evolutionary mechanism and conserved genetic system.…”

Zebrafish as a Model for Toxicological Perturbation of Yolk and Nutrition in the Early Embryo

“…Thorough characterization of yolk defects, composition, and utilization has potential to provide mechanistic insights into the developmental origins of health and disease. Several studies have now demonstrated that the yolk is metabolically active [16, 86], and thus should be recognized as another target tissue for developmental toxicology studies. Because the yolk is lipophilic, it also provides an ideal compartment in which hydrophobic toxicants may accumulate and facilitate embryonic exposures throughout the yolk-based feeding period.…”

Malaria in pregnancy regulates P‐glycoprotein (P‐gp/Abcb1a) and ABCA1 efflux transporters in the Mouse Visceral Yolk Sac

“…24 Emerging evidence suggests the yolk sac is an important nutrient exchange site between the coelomic fluid and the fetal capillaries present in its mid-mesodermal layer; or alternatively, it delivers nutrients to the embryo primitive gut via the vitelline duct. [24][25][26] In mice, the visceral portion of the yolk sac involves the embryo amniotic membrane and is functional throughout pregnancy, mediating the transport of critical substances from the mother to the fetus, acting as a syncytiotrophoblast equivalent throughout intrauterine development. 27,28 It is known that human 24 and mouse 24,29 yolk sac express different ABC transport carriers, suggesting that this membrane acts together with the placenta and other fetal membranes to form an efficient protective barrier during gestation.…”