TY - JOUR
T1 - RNA-seq reveals conservation of function among the yolk sacs of human, mouse, and chicken
AU - Cindrova-Davies, Tereza
AU - Jauniaux, Eric
AU - Elliot, Michael G.
AU - Gong, Sungsam
AU - Burton, Graham J.
AU - Charnock-Jones, D. Stephen
PY - 2017/6/13
Y1 - 2017/6/13
N2 - 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.
AB - 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.
KW - yolk sac
KW - placenta
KW - evolution
KW - HUMAN GESTATIONAL SAC
KW - EXTRAEMBRYONIC CELOMIC FLUID
KW - 1ST TRIMESTER
KW - FETAL MEMBRANES
KW - BIOCHEMICAL-COMPOSITION
KW - EMBRYOLOGICAL FLUIDS
KW - EARLY-PREGNANCY
KW - MATERNAL SERUM
KW - SONIC HEDGEHOG
KW - HUMAN FETUS
U2 - 10.1073/pnas.1702560114
DO - 10.1073/pnas.1702560114
M3 - Article
SN - 0027-8424
VL - 114
SP - E4753-E4761
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 24
ER -