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。尽管胎盘在母胎界面的气体交换、营养运输和免疫方面起着关键作用，但它是哺乳动物中形态最多样化的器官，至少有五种不同的形式。其中一种形式包括带状胎盘，它有一种独特的带状结构，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、着色区和尿囊膜。这些区域中的每一个的功能仍然知之甚少。雌性狗有两条X染色体，而雄性狗只有一条，导致X连锁基因的剂量不同。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，包括随机的和印记的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X染色体失活的基因表达谱和调节。这项研究将有助于全面了解X染色体剂量补偿基因在不同类型动物中的表达，并对其进行比较分析。本研究的目的是了解X染色体剂量补偿在带状胎盘中的基因表达和表观遗传控制。哺乳动物胎盘是一项关键的进化创新，它通过胚胎的宫内发育极大地提高了生殖成功。尽管胎盘具有重要的功能，但它是形态最多样的器官，有五种主要的胎盘形式。带状胎盘见于食肉动物，包括猫和狗等伴生动物。带状胎盘以三个不同的区域环绕胎儿：转移区、着色区和尿囊膜。它们的功能和转录组图谱仍然知之甚少。在兽类哺乳动物中，雌性和雄性具有不同剂量的X连锁基因，这可以通过一种称为剂量补偿(DC)的机制来解决。在真核哺乳动物的体细胞组织中，DC是通过雌性的随机X染色体失活(XCI)获得的，其中两条X染色体中的一条是失活的，选择是随机的。在形成胎盘的胚外组织中，在啮齿类动物中观察到印记的XCI，在这些组织中，父亲的X总是被灭活。XCI状态在带状胎盘中仍未确定。本项目将实现以下目标：1)鉴定犬胎盘转移区、色素带和尿囊膜的全长转录本和功能丰富的基因网络；2)研究XCI在带状胎盘中的形式、地位、逃逸特征和表观遗传学调节。这项拟议的研究将通过单细胞RNA测序全面了解带状胎盘中XCI的概况和表观遗传学调节，这为剂量补偿的比较系统学分析打开了大门。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.