Single-cell transcriptomic atlases of midgestation fetal-maternal interface from opossum, tenrec, guinea pig, and mouse

The origin of this chimeric fetal-maternal tissue poses a unique evolutionary puzzle. We present a multi-species atlas integrating single-cell transcriptomes from opossum (a marsupial), Malagasy common tenrec (an afrotherian), mouse and guinea pig (rodents) with previous macaque and human data (primates). Invasive trophoblasts share a transcriptomic signature across eutherians, likely representing a cell type family that radiated following the evolution of hemochorial placentation. Our data suggest that decidual stromal cells evolved stepwise from an immunomodulatory cell found in Tenrec, followed by acquisition of an endocrine decidual cell in Boreoeutherian mammals. Finally, we identify evolutionary patterns in ligand-receptor signaling among fetal and maternal cells: Consistent with theoretical predictions, fetal and maternal cells show a strong tendency towards disambiguated signaling, however, a predicted escalatory arms race dynamic between them is restricted to few ligands. We reconstruct the uteroplacental cell-cell communication network of the eutherian common ancestor, and infer accelerated signaling loss in Euarchontoglires and accelerated gains in primates. Unexpectedly, fetal trophoblast cell types display strong integration into maternal signaling networks despite their recent evolutionary origin. The tailless tenrec Tenrec ecaudatus is an afrotherian mammal native to Madagascar, related to the elephant and aardvark, and is remarkable for retaining a collection of ancestral eutherian traits. The single known description of the decidual tissue of T. ecaudatus was collected by zoologist and explorer R.H. Goetz in 1936 from a female during mid-gestation. We collected fresh, timed-pregnant uteri from T. ecaudatus at mid-gestation (days 28-30) to address: Which cell types are present in the decidua of a basally branching placental mammal, and how do they, if present, interact with other cells? Furthermore, how does gene expression of the tenrec decidual stromal cell differ from the human? We find that the tenrec possesses a uterine process akin to human predecidualization, involving the upregulation of key decidual transcription factors FOXO1 and KLF7 and effector genes such as IL15, and that this cell type is unique to pregnant animals. Cells from midgestation fetal-maternal interface (whole-thickness uterus and placenta) were isolated and subjected to 10x Genomics 3 v3 single-cell RNA-seq.这种嵌合型胎儿-母体组织的起源，是一道独特的演化谜题。本研究构建了多物种图谱，整合了负鼠（opossum，有袋类）、马岛普通马岛猬（Malagasy common tenrec，非洲兽总目）、小鼠与豚鼠（rodents，啮齿类）的单细胞转录组（single-cell transcriptome）数据，以及已发表的猕猴与人类（primates，灵长类）相关数据。侵入性滋养层细胞（invasive trophoblasts）在真兽类（eutherians）中共享一套转录组特征，这大概率代表了一个在血绒毛膜胎盘（hemochorial placentation）演化之后发生辐射演化的细胞类型家族。本研究数据表明，蜕膜基质细胞（decidual stromal cells）的演化是一个逐步过程：其起源为马岛猬体内存在的免疫调节细胞（immunomodulatory cell），随后在北方兽总目（Boreoeutherian）哺乳动物中演化出内分泌型蜕膜细胞。最后，本研究揭示了胎儿与母体细胞间配体-受体信号传导（ligand-receptor signaling）的演化模式：与理论预测一致，胎儿与母体细胞表现出强烈的信号通路特异性分化趋势；然而，二者间理论上存在的升级式军备竞赛动态，仅局限于少数配体。本研究重构了真兽类共同祖先的子宫胎盘细胞间通讯网络（uteroplacental cell-cell communication network），并推断：灵长总目（Euarchontoglires）类群中存在信号传导通路的加速丢失现象，而灵长类中则出现信号通路的加速获得现象。令人意外的是，尽管演化起源较晚，胎儿滋养层细胞类型仍能与母体信号网络实现高度整合。无尾马岛猬（Tenrec ecaudatus）是马达加斯加本土的非洲兽总目哺乳动物，与大象、土豚亲缘关系较近，其显著特征是保留了大量真兽类祖先性状。目前已知的唯一一篇关于无尾马岛猬蜕膜组织的描述，由动物学家兼探险家R.H. Goetz于1936年从一只妊娠中期的雌性个体中采集得到。本研究采集了妊娠中期（第28至30天）的定时妊娠无尾马岛猬子宫样本，旨在解答以下问题：基部分支胎盘哺乳动物的蜕膜中存在哪些细胞类型？若存在此类细胞，它们与其他细胞的相互作用方式如何？此外，马岛猬蜕膜基质细胞的基因表达模式与人类存在何种差异？本研究发现，马岛猬存在类似于人类蜕膜前转化的子宫过程，该过程涉及关键蜕膜转录因子FOXO1与KLF7以及IL15等效应基因的上调表达，且此类细胞仅存在于妊娠个体中。研究人员分离了妊娠中期胎儿-母体界面（全层子宫及胎盘）的细胞，并采用10x Genomics 3 v3平台进行单细胞RNA测序（single-cell RNA-seq）。