RII Track-4: Transcriptome Profile and X Chromosome Dosage Compensation in the Zonary Placenta

哺乳动物胎儿的产前发育依赖于一个被称为胎盘的重要器官。尽管胎盘在母体-胎儿界面的气体交换、营养运输和免疫中起着关键作用，但它是哺乳动物中形态最多样的器官，至少有五种不同的形式。其中一种形式包括带状胎盘，它有一个独特的带状结构，包裹着胎儿。带状胎盘由三个主要区域的多个组织组成：转移区、色素区和尿囊绒毛膜。这些区域的功能仍然知之甚少。雌性狗有两条X染色体，而雄性只有一条，导致X连锁基因的剂量不相等。剂量补偿是通过一种称为X染色体失活的过程使女性的一条X染色体失活来实现的。在哺乳动物胎盘中观察到不同的策略，包括随机和印记X染色体失活。 犬胎盘X染色体失活的机制尚不清楚。为了填补这些空白，我们建议在不同的犬胎盘组织中表征基因表达谱和X染色体失活的调控。 本研究的目的是了解带状胎盘中X染色体剂量补偿的基因表达和表观遗传学控制。哺乳动物胎盘是一个关键的进化创新，通过胚胎在子宫内的发育大大提高了生殖成功率。尽管胎盘具有重要的功能，但它是形态上最多样化的器官，有五种主要的胎盘形成形式。带状胎盘见于食肉动物，包括伴侣动物，如猫和狗。带状胎盘环绕胎儿，有三个不同的区域：转移区，色素区和尿囊绒毛膜。它们的功能和转录组谱仍然知之甚少。在哺乳动物中，雌性和雄性具有不相等的X连锁基因，这是通过称为剂量补偿（DC）的机制解决的。在真兽目哺乳动物的体细胞组织中，DC是通过雌性中的随机X染色体失活（XCI）实现的，其中两个X染色体中的一个失活并且选择是随机的。在产生胎盘的胚外组织中，在啮齿动物中观察到印记XCI，其中总是父方X失活。带状胎盘的XCI状态仍有待进一步研究。本研究的主要目的是：1）研究犬胎盘转运区、色素区和绒毛膜中的全长转录组和基因网络的功能富集; 2）研究XCI在带状胎盘中的形态、状态、逃逸模式和表观遗传调控。这项研究将通过单细胞RNA测序全面了解XCI在带状胎盘中的概况和表观遗传调控，这为剂量补偿的比较基因组学分析打开了大门。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

Prenatal development of mammalian fetuses relies on an important organ known as the placenta. Despite its critical function in gas exchange, nutrient transport and immunity at the maternal-fetal interface, the placenta is the most morphologically diverse organ in mammals, with at least five different forms. One of these forms include the zonary placenta, which has a unique belt-like structure that wraps around the fetus. The zonary placenta consists of multiple tissues in three major zones: the transfer zone, the pigmented zone and the allantochorion. The function of each of these zones remains poorly understood. Female dogs have two X chromosomes and males only have one, resulting an unequal dose of X-linked genes. Dosage compensation is achieved by inactivating one X chromosome in females through a process called X chromosome inactivation. Different strategies, including random and imprinted X chromosome inactivation, are observed in mammalian placentae. The mechanism of X chromosome inactivation in canine placenta is unknown. To fill in these gaps, we propose to characterize gene expression profiles and regulation of X chromosome inactivation in different canine placental tissues. This proposed research will lead to comprehensive understanding of regulated gene expression and a comparative analysis of dosage compensation across different types of animals.The goal of this research is to understand the gene expression and epigenetic control of X chromosome dosage compensation in the zonary placenta. The mammalian placenta is a key evolutionary innovation that dramatically improves the reproductive success through in utero development of the embryos. Despite its critical function, placenta is the most morphologically diverse organ with five major placentation forms. Zonary placenta is observed in carnivores including companion animals such as cats and dogs. The band shaped placenta encircles the fetus with three distinct zones: the transfer zone, the pigmented zone and the allantochorion. Their functions and transcriptome profiles are still poorly understood. In therian mammals, females and males have unequal dose of X-linked genes, and this is solved by a mechanism called dosage compensation (DC). In somatic tissues of eutherian mammals, DC is achieved by random X chromosome inactivation (XCI) in females, in which one of the two X chromosomes is inactivated and the choice is random. In the extraembryonic tissues that give rise to placenta, imprinted XCI was observed in rodents, in which it is always the paternal X that is inactivated. The XCI status remains to be characterized in zonary placenta. This project will achieve the following objectives: 1) Characterize the full-length transcriptomes and functional enrichment of gene networks in the transfer zone, pigmented zone and allantochorion of the canine placenta, 2) Investigate the form, status, escaping profile and epigenetic regulation of XCI in the zonary placenta. This proposed research will lead to comprehensive understanding of the profile and epigenetic regulation of XCI in zonary placenta through single-cell RNA sequencing, which opens the door to comparative phylogenomic analysis of dosage compensation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.