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

Tereza Cindrova-Davies, Eric Jauniaux, Michael G. Elliot, Sungsam Gong, Graham J. Burton, D. Stephen Charnock-Jones*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

25 Citations (Scopus)

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.

Original languageEnglish
Pages (from-to)E4753-E4761
Number of pages9
JournalProceedings of the National Academy of Sciences of the United States of America
Volume114
Issue number24
DOIs
Publication statusPublished - 13-Jun-2017
Externally publishedYes

Keywords

  • yolk sac
  • placenta
  • evolution
  • HUMAN GESTATIONAL SAC
  • EXTRAEMBRYONIC CELOMIC FLUID
  • 1ST TRIMESTER
  • FETAL MEMBRANES
  • BIOCHEMICAL-COMPOSITION
  • EMBRYOLOGICAL FLUIDS
  • EARLY-PREGNANCY
  • MATERNAL SERUM
  • SONIC HEDGEHOG
  • HUMAN FETUS

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