PROJ 5: IDENTIFICATION & FUNCTIONAL CHARACTERIZATION OF SNPS IN RXRA GENE

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 该项目的总体目标是：确定视黄醇X受体a(RXRA)基因的遗传多态，确定美国人群中的主要单倍型，并表征所定义的单倍型对RXRA靶基因表达的转录调控的功能影响。主要的假设是RXRA基因的遗传多态存在于美国人群中；这些多态在不同的种族中以特定的单倍型组织起来；可能导致RXRcc基因表达的个体间差异的单倍型尚未被定义；这种变化可能通过改变转录调控而导致RXRA靶基因表达的差异。RXRA是9-顺式维甲酸的核受体，在基因转录调控中发挥重要作用。RXRA与其他维甲酸受体(RARA、p和y)形成异二聚体，从而激活多种维甲酸介导的信号通路，控制正常的细胞分化和增殖。RXRA在肝脏中高度表达，其中含有不同RXRA的异源二聚体(FXR、PXR、CAR、PPARa、PPARy等)与靶基因启动子中的特定DNA反应元件结合，调节其转录，控制重要功能，如维持糖脂平衡、胆汁酸合成和药物代谢。本项目将致力于三个具体目标：(1)通过对100名美国白人、非裔美国人、东亚人和墨西哥裔美国人的测序，确定RXRA基因外显子、内含子/外显子边界、3‘-非翻译区和5’-启动子区域的遗传多态(主要是单核苷酸多态，SNPs)；(2)通过对美国4个主要种族400份样本(每组100份)RXRA基因的12-15个SNP进行基因分型，确定主要的单倍型模式；(3)通过体外和体内两种方法研究所确定的单倍型对RXRA-靶基因表达的功能影响。这个项目完成后，我们希望了解在我们的人群中存在什么遗传多态，它们是如何以不同的单倍型组织起来的，以及它们是如何影响RXRA靶基因的表达的。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The overall goals of this project are to: identify genetic polymorphisms in the retinoid-X-receptor a (RXRa) gene, determine major haplotypes in American populations, and characterize functional effects of the defined haplotypes on the transcriptional regulation of RXRa-target-gene expression. The main hypothesis is that genetic polymorphisms in the RXRa gene exist in American populations; these polymorphisms are organized in specific haplotypes in different ethnic groups; that the haplotypes, which may contribute to inter-individual variations of RXRcc-gene expression, have not yet been defined; and that such variations may cause differences of RXRa-target-gene expression by altering transcriptional regulation. RXRa is a nuclear receptor for 9-cis-retinoic acid and plays a central role for gene transcriptional regulation. RXRa forms heterodimers with the other retinoic-acid receptors (RARa, p, and y) resulting in activation of various retinoid-mediated-signal pathways for controlling normal cell differentiation and proliferation. RXRa is highly expressed in liver, where different RXRa-containing heterodimers (FXR, PXR, CAR, PPARa, PPARy, etc.) bind to specific DNA- response elements in the promoters of target genes, to regulate their transcription and to control important functions, such as the maintenance of glucose and lipid homeostasis, synthesis of bile acids, and the metabolism of drugs. Three specific aims will be addressed in this project: (1) to identify genetic polymorphisms (mostly single nucleotide polymorphisms, SNPs) in exons, intron/exon boundaries, 3'-untranslated region, and 5'-promoter region of the RXRa gene by sequencing 100 human subjects from the four major American ethnic groups: Caucasian, African-American, East-Asian and Mexican-American; (2) To determine major haplotype patterns by genotyping 12-15 identified SNPs evenly distributed in the RXRa gene in 400 samples from the 4 major American ethnic groups (100 from each); (3) to characterize functional effects of the defined haplotypes on RXRa-target-gene expression by using both in vitro and in vivo approaches. After completion of this project, we expect to learn what genetic polymorphisms exist in our population, how they are organized in different haplotypes, and how they affect RXRa-target-gene expression.