哺乳類の胎盤はどのように進化してきたか(How placentas evolved in mammals)

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妊娠の起源を探る研究、真獣類の最後の共通祖先に胎盤が侵入していたことを指摘 Research delves into the origins of pregnancy, pointing to an invasive placenta in the last common ancestor of eutherian mammals

2022-07-01 バッファロー大学(UB)

トランスクリプトームと呼ばれる遺伝子発現パターンを用いて、妊娠に不可欠な胎盤という臓器の古代の起源を調査することに成功した。
遺伝子発現パターンを使って胎盤の進化を再構築し、真獣類哺乳類の最後の共通祖先の胎盤がどのようなものであったかを予測します。データは、この胎盤は侵入型であり、非侵入型の胎盤は哺乳類の間で何度も進化してきたことを示しています。これは150年来の謎を解くものです。

<関連情報>

遺伝子発現系統と祖先トランスクリプトームの再構成により、妊娠の起源における主要な変遷を解明 Gene expression phylogenies and ancestral transcriptome reconstruction resolves major transitions in the origins of pregnancy

Katelyn Mika,Camilla M Whittington,Bronwyn M McAllan,Vincent J Lynch
eLife  Published:Jun 30, 2022
DOI:https://doi.org/10.7554/eLife.74297

Abstract

Structural and physiological changes in the female reproductive system underlie the origins of pregnancy in multiple vertebrate lineages. In mammals, the glandular portion of the lower reproductive tract has transformed into a structure specialized for supporting fetal development. These specializations range from relatively simple maternal nutrient provisioning in egg-laying monotremes to an elaborate suite of traits that support intimate maternal-fetal interactions in Eutherians. Among these traits are the maternal decidua and fetal component of the placenta, but there is considerable uncertainty about how these structures evolved. Previously we showed that changes in uterine gene expression contributes to several evolutionary innovations during the origins of pregnancy (Marinic, Mika, and Lynch 2021). Here we reconstruct the evolution of entire transcriptomes (‘ancestral transcriptome reconstruction’) and show that maternal gene expression profiles are correlated with degree of placental invasion. These results indicate that an epitheliochorial-like placenta evolved early in the mammalian stem-lineage and that the ancestor of Eutherians had a hemochorial placenta, and suggest maternal control of placental invasiveness. These data resolve major transitions in the evolution of pregnancy and indicate that ancestral transcriptome reconstruction can be used to study the function of ancestral cell, tissue, and organ systems.

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