Identification of Primate-Specific Regulatory Elements of Cholesterol Homeostasis

描述(申请人提供)：尽管老鼠和其他非灵长类脊椎动物在研究人类脂肪代谢方面很有用，但许多人类代谢特征在灵长类动物身上模拟得最好，特别是我们对饮食胆固醇的反应。人类和小鼠对胆固醇稳态相关基因的不同调控被认为是导致这两个物种对饮食胆固醇反应不同的重要原因。我们之前已经证明，多个灵长类物种的序列比较在识别灵长类特有的功能元件方面是成功的，并补充了传统的与非灵长类哺乳动物的序列比较，例如人和鼠之间的序列比较。因此，这项建议的目标是将多个灵长类序列比较与功能研究结合起来，以发现灵长类特有的调节元件对脂代谢产生影响。这将包括几个参与脂质代谢的基因的分析，重点是对核激素受体LXR-a及其靶基因的转录网络的剖析，LXR-a是胆固醇稳态的关键调节因子，似乎在人类和小鼠中具有不同的调节作用。我们将：1)通过对包含已知“脂类”基因的大基因组间隔的比较分析，确定灵长类中优先保守的调控序列的功能特征；2)在灵长类和非灵长类哺乳动物之间共享的已知调控元件和计算预测的调控元件中，识别并功能表征灵长类特异的转录因子结合位点；以及3)在细胞培养和活体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。这些研究将为临床上相关的胆固醇稳态调节提供基因组学上的见解，并有助于我们理解灵长类动物对环境刺激的特异性反应。 虽然小鼠是人类疾病的宝贵模型，如导致动脉粥样硬化的血脂紊乱，但它与人类有许多不同，直接的后果是，许多药物首先在小鼠身上测试成功，但在后来的人类临床研究中失败。在这项提议中，我们计划确定决定人类和小鼠之间血浆脂代谢差异的人类基因组片段。这种分子基因组结构的发现将为揭示导致人类血脂紊乱的致病机制提供新的线索，有望为这种重要的人类疾病设计出更好的小鼠模型。

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.