Molecular mechanism of placental Development: The role of TMED2, a vesicular transport protein during labyrinth layer formation

胎盘发育的分子机制：囊泡转运蛋白 TMED2 在迷路层形成过程中的作用

• 批准号: RGPIN-2020-05168
• 负责人: JeromeMajewska, Loydie
• 金额: $ 2.33万
• 依托单位: McGill University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=740426
• 关键词: Molecular; mechanism; placental; Development; role

The placenta is the first organ formed in eutherian mammals and is essential for survival of the developing embryo. The mouse placenta, the model system that we study, is divided into three histologically distinct layers: decidual, spongiotrophoblast, and labyrinth. The labyrinth layer is the site of nutrient and gas exchange between the maternal and foetal environment. It consists of embryonic blood vessels that are in close proximity to maternal sinuses. In the mouse, labyrinth layer formation depends on attachment and fusion between two embryonic tissues: the chorion and the allantois. We showed that TMED2, a member of the emp24 domain family of cargo receptors, was expressed in the chorion and the allantois, and required for labyrinth layer formation. Thus, Tmed2 homozygous mutant embryos arrest at mid-gestation due to placental failure. To uncover the role of TMED2 in labyrinth layer development, we generated a chorioallantoic explant model and showed that it recapitulated the early molecular and morphological changes associated with labyrinth layer formation. Using this explant model, we found that TMED2 was required in the chorion for chorioallantoic attachment, and in both tissues for fusion and labyrinth layer formation. Importantly, we uncovered that TMED2 was required in the allantois for secretion of Fibronectin, an extracellular protein and potential cargo. Little is known about the function of TMED proteins during development and disease, although this family is conserved in all eukaryotes and essential for normal development. However, our work in the context of the placenta and the liver, combined with the work of others in multiple species and cell lines, indicates that TMED proteins are cargo receptors. Therefore, we will test two hypotheses: (1) TMED2-mediated transport of fibronectin is required in the allantois for chorioallantoic fusion; and (2) distinct TMED2-regulated pathways in the chorion and in the allantois are essential for labyrinth layer formation. The aims of this proposal are: (1) To determine if fibronectin is a TMED2 cargo protein and to uncover its role in labyrinth layer development; (2) To determine if TMED2 is required in both chorionic mesothelium and ectoderm for chorioallantoic attachment and fusion; and (3) To identify the TMED2-regulated pathways in the chorion and the allantois that are required for labyrinth layer formation. Our studies reveal a crucial role for TMED2 in placental development and, more specifically, in mediating communication between the chorion and allantois. Similar types of communication are essential for organogenesis. For example, during development of the lung where ventral foregut endodermal epithelium interacts with mesoderm to form the lungs. Since TMED2 and other members of this family are broadly expressed, we expect that our work will shed significant insight into the role of this protein and its cargoes in organogenesis.

胎盘是真兽目哺乳动物形成的第一个器官，对发育中的胚胎的生存至关重要。小鼠胎盘，我们研究的模型系统，分为三个组织学上不同的层：蜕膜，海绵滋养层，和迷路。迷路层是母体和胎儿环境之间进行营养和气体交换的场所。它由靠近母体鼻窦的胚胎血管组成。在小鼠中，迷路层的形成取决于两个胚胎组织之间的附着和融合：绒毛膜和尿囊。我们发现，TMED 2，货物受体的emp 24域家族的成员，在绒毛膜和尿囊中表达，并需要迷宫层的形成。因此，Tmed 2纯合突变胚胎在妊娠中期由于胎盘衰竭而停滞。为了揭示TMED 2在迷路层发育中的作用，我们产生了一个绒毛尿囊外植体模型，并表明它概括了与迷路层形成相关的早期分子和形态学变化。使用该外植体模型，我们发现TMED 2在绒毛膜尿囊附着中是必需的，并且在融合和迷路层形成的两种组织中都是必需的。重要的是，我们发现TMED 2在尿囊中是分泌纤连蛋白（一种细胞外蛋白和潜在货物）所必需的。 关于TMED蛋白在发育和疾病期间的功能知之甚少，尽管该家族在所有真核生物中是保守的并且对于正常发育是必需的。然而，我们在胎盘和肝脏中的工作，结合其他人在多个物种和细胞系中的工作，表明TMED蛋白是货物受体。因此，我们将测试两个假设：（1）TMED 2介导的纤连蛋白转运是绒毛膜尿囊融合所必需的;（2）绒毛膜和尿囊中不同的TMED 2调节途径对迷路层形成至关重要。本提案的目的是：（1）确定纤连蛋白是否是TMED 2货物蛋白，并揭示其在迷路层发育中的作用;（2）确定绒毛膜尿囊附着和融合是否需要绒毛膜间皮和外胚层中的TMED 2;（3）确定迷路层形成所需的绒毛膜和尿囊中的TMED 2调节途径。我们的研究揭示了TMED 2在胎盘发育中的关键作用，更具体地说，在介导绒毛膜和尿囊之间的通信中。相似类型的通讯对于器官发生是必不可少的。例如，在肺的发育过程中，腹侧前肠内胚层上皮与中胚层相互作用形成肺。由于TMED 2和该家族的其他成员广泛表达，我们希望我们的工作将对该蛋白质及其货物在器官发生中的作用有重要的了解。