Dissertation Research: The Origin and Molecular Evolution of the Genes Encoding the Primate Hormone Chorionic Gonadotropin

绒毛膜促性腺激素（CG）是一种激素，在建立妊娠中具有关键的信号作用。 这种激素仅在灵长类动物中发现，其遗传基础仅在人类和两种猴子中发现。 到目前为止，还没有其他哺乳动物拥有这种激素。本研究将致力于阐明目前未知的起源和分子进化历史的基因编码的两个CG亚基。 研究人员将测试许多灵长类动物和相关哺乳动物物种是否存在编码CG β亚基（CG-β）的基因。 为什么人类拥有六个拷贝的这种基因，狒狒有五个拷贝，而其他哺乳动物却没有？ 基因最早出现在哪个物种中？ 成熟的Southern印迹和杂交技术将用于检测CG-β基因的存在，并绘制每个物种基因组中存在的基因拷贝数。CG-β基因的起源将通过将基因的存在或不存在映射到一棵树上来追踪，该树显示了测试物种的已知关系。 此外，对于那些拥有该基因的物种，将使用聚合酶链反应（PCR）对CG-β基因进行测序。 DNA置换率和模式将被分析，以揭示是否以及何时选择CG适应其目前的role.Chorionic促性腺激素提供了一个难得的机会，研究一个基因从其起源到随后的增殖。 因此，它有望为分子进化的研究做出独特的贡献。 这项研究也将为灵长类动物生殖过程的进化提供有价值的信息。我们知道，胎盘的结构在灵长类动物的进化中发生了巨大的变化，从低等灵长类动物的非侵入性胎盘到人类的高度侵入性胎盘，并在母亲和胎儿之间建立了亲密的联系。这种形态学上的某些变化必然与控制生殖功能的基因的变化有关。 随着时间的推移，CG可能是负责灵长类动物生殖过程主要重塑的几个基因之一。 研究CG激素基因的进化是理解人类生殖进化的重要一步，CG激素对人类生殖至关重要，但在灵长类动物之外并不存在。

Chorionic gonadotropin (CG) is a hormone which has a critical signaling role in establishing pregnancy. The hormone has been found exclusively in primates, and its genetic basis has been characterized only in humans and in two monkey species. No other mammals studied to date possess this hormone. This study will focus on elucidating the currently unknown origin and molecular evolutionary history of the genes encoding the two CG subunits. The researchers will test numerous primate and related mammalian species for the presence of genes encoding the beta subunit of CG (CG-beta). How is it that humans have come to possess six copies of this gene, and baboons five copies, while other mammals have none? In which species did the gene first arise? The well-established techniques of Southern blotting and hybridization will be used to test for the presence of CG-beta genes and to map the number of gene copies present in each species' genome. The origin of the CG-beta genes will be traced by mapping the genes' presence or absence onto a tree showing the known relationships of the species tested. Also, for those species possessing the gene, CG-beta genes will be sequenced using the polymerase chain reaction (PCR). DNA substitution rates and patterns will be analyzed to reveal whether and when selection has adapted CG to its current role.Chorionic gonadotropin presents a rare opportunity to study a gene from its origin to subsequent proliferation. Therefore it promises to make a unique contribution to the study of molecular evolution. This study will also provide valuable information about the evolution of the reproductive process in Primates. We know that the structure of the placenta has changed dramatically in primate evolution, from a placenta which is non-invasive in the lower primates to one which highly invades the mother's tissues and establishes an intimate connection between mother and fetus in humans. Some of this morphological change must be correlated with changes in the genes controlling reproductive function. CG is one of probably several genes responsible for this major remodeling of the primate reproductive process over time. Working out the evolution of the genes for the CG hormone, which is crucial for human reproduction yet does not exist outside the primates, is an important step in understanding how human reproduction has evolved.