Placental Endogenous Retrovirus Expression

描述(申请人提供)：大约1%的人类基因组似乎来源于逆转录病毒。这些“内源性”逆转录病毒成分在人类发育中的作用尚不清楚。少数器官在生理条件下表达内源性逆转录病毒，人类胎盘就是其中之一。正常人胎盘绒毛细胞滋养层细胞表达与分化相关的内源性逆转录病毒基因组(ERV-3)env区转录。ERV-3的表达与正常滋养细胞分化密切相关，提示ERV-3在胎盘发育中具有生理学作用。为了支持这一假设，以下是观察结果。1)ERV-3env基因在合体滋养细胞和自发分化的单核绒毛细胞滋养细胞中表达增强。2)分化相关的ERV-3env基因表达增加的同时，b-hCG基因和蛋白表达增加，细胞间融合增加。3)将ERV-3 env正义链导入滋养层细胞分化模型BeWo绒毛膜癌细胞，获得稳定的细胞株，细胞生长和形态分化减少，b-hCG mRNA和hCG蛋白产量增加。4)细胞诱导分化时，反义链的表达减少。这些初步数据支持一种假设，即ERV-3 env的表达是正常滋养细胞分化途径中的重要一步，可能是通过调节hCG表达来实现的。本R03应用的具体目的是为成功的R01应用积累足够的初步数据来检验这一假说，个人的特定目的是：1)开发试剂，例如单抗和转染可诱导质粒系统的细胞株，用于研究ERV-3 env在绒毛滋养层细胞分化中的作用；目的2)确定ERV-3 env的表达是否对新鲜分离的绒毛细胞滋养层细胞的分化是必需的；以及目的3)确定类固醇是否诱导ERV-3 env的表达。选择这些具体目标是为了解决以前未获成功的R01申请中提出的问题。

DESCRIPTION (provided by applicant): Approximately 1% of the human genome appears to be of retroviral origin. The purpose of these "endogenous" retroviral elements in human development remains unknown. A small number of organs express endogenous retroviruses under physiologic conditions; the human placenta is one of these. The normal human placental villous cytotrophoblast expresses differentiation-related transcription of the env region of a single copy endogenous retroviral genome (ERV-3). The strong association of ERV-3 expression with normal trophoblast differentiation suggests a physiologic role for ERV-3 in placental development. In support of this hypothesis, are the following observations. 1) ERV-3 env mRNA and Env protein are increased in syncytiotrophoblast and in spontaneously differentiating mononuclear villous cytotrophoblast. 2) Differentiation-related increase in ERV-3 env mRNA is concurrent with increased b-hCG mRNA and protein and intercellular fusion. 3) Transfection of BeWo choriocarcinoma cells, a model for trophoblast differentiation, with the sense strand of ERV-3 env resulted in a stable transfectant in which most aspects of trophoblast differentiation occurred: decreased growth, morphologic differentiation, and increased b-hCG mRNA and hCG protein production. 4) Transfection with the antisense strand decreased b-hCG mRNA production when the cells were induced to differentiate. These preliminary data support a hypothesis that ERV-3 env expression is an important step in the pathway of normal trophoblast differentiation, potentially through regulation of hCG expression. The specific aim of this R03 application is to accumulate adequate preliminary data for a successful R01 application to test this hypothesis, The individual specific Aims are: Aim 1) is to develop reagents, e.g.,monoclonal antibody and cell lines transfected with inducible plasmid systems, for studying the role of ERV3 env in villous trophoblast differentiation; Aim 2) is to determine whether ERV-3 env expression is necessary for differentiation of freshly isolated villous cytotrophoblasts; and Aim 3) is to determine whether ERV-3 env expression is inducible by steroids. These specific aims were chosen to address issues raised in previously unsuccessful R01 applications.