Identification of Primate-Specific Regulatory Elements of Cholesterol Homeostasis

描述（由申请人提供）：尽管小鼠和其他非灵长类脊椎动物在研究人类脂质代谢方面的效用，但许多人类代谢特征在灵长类动物身上得到了最好的模拟，特别是我们对饮食胆固醇的反应。在人类和小鼠中，参与胆固醇稳态的基因调控的差异被认为是导致这些物种对饮食胆固醇反应差异的重要原因。我们之前已经证明，多个灵长类物种的序列比较可以成功地识别灵长类动物特有的功能元素，并补充了传统的与非灵长类哺乳动物（如人类和小鼠）的序列比较。因此，本提案的目标是将多个灵长类动物序列比较与功能研究相结合，以发现影响脂质代谢的灵长类动物特异性调节元件。这将包括对参与脂质代谢的几个基因的分析，重点是对核激素受体LXR-a及其靶基因的转录网络的解剖，这些基因是胆固醇稳态的关键调节因子，在人类和小鼠中似乎有不同的调节。我们将：1)通过对含有已知“脂质”基因的大基因组区间的比较分析，鉴定和功能表征灵长类谱系中优先保守的调控序列；2)鉴定和功能表征灵长类动物与非灵长类动物共有的已知和计算预测的调控元件中灵长类动物特异性转录因子结合位点；3)在细胞培养和体内研究中研究灵长类特异性调控序列对邻近人类基因的功能，并确定它们对灵长类特异性表型的贡献。这些研究将为胆固醇稳态的临床相关调控提供基因组衍生的见解，并有助于我们理解灵长类动物对环境刺激的特异性反应。

DESCRIPTION (provided by applicant): Despite the utility of the mouse and other non-primate vertebrates in studying human lipid metabolism, many human metabolic features are best modeled in primates, particularly our response to dietary cholesterol. The differential regulation of genes involved in cholesterol homeostasis in humans and mice is believed to significantly contribute to differences in response to dietary cholesterol between these species. We have previously shown that sequence comparisons of multiple primate species are successful at identifying functional elements specific to primates and complement traditional sequence comparisons with non-primate mammals, such as between human and mouse. Accordingly, the goal of this proposal is to couple multiple primate sequence comparisons with functional studies to discover primate-specific regulatory elements impacting on lipid metabolism. This will include the analysis of several genes participating in lipid metabolism, with an emphasis on the dissection of the transcriptional network of the nuclear hormone receptor LXR-a and its target genes, crucial regulators of cholesterol homeostasis which appear to have differential regulation in human and mouse. We will: 1) identify and functionally characterize regulatory sequences preferentially conserved in the primate lineage through the comparative analysis of large genomic intervals containing known "lipid" genes; 2) identify and functionally characterize primate specific transcription factor binding sites in both known and computationally predicted regulatory elements shared between primates and non-primate mammals; and 3) investigate the function of primate-specific regulatory sequences on their neighboring human genes in cell culture and in vivo studies and determine their contribution to primate-specific phenotypes. These studies will provide genomically derived insights into the clinically relevant regulation of cholesterol homeostasis and contribute to our understanding of primate-specific responses to environmental stimuli. The mouse, while a valuable model of human diseases such as plasma lipid disorders leading to atherosclerosis, has many differences from human, with the immediate consequence that many drugs first tested successfully in mice fail in later clinical studies in humans. In this proposal, we plan to identify segments of the human genome which determine differences in plasma lipid metabolism between human and mouse. Discovery of this kind of molecular genomic structures will shed new light into the pathogenic mechanisms leading to human lipid disorders, promising to lead to the engineering of better mouse models for this important human disease.