Integrated cellular, mouse and human research on a novel missense variant influencing adiposity in Samoans

项目摘要 在这次竞争性更新中，我们专注于表征一种新的错义变体，该变体是通过基因组鉴定的， 广泛关联分析（GWAS）的肥胖相关性状在萨摩亚人在前一个资助期间。这 错义变异与体重指数（BMI）高度相关，其效应量大于任何其他变量 已知的常见肥胖风险变体。含有这种错义变体的基因编码一种假定的转录 一种最近被认为与果蝇的能量代谢有关，但仍然很弱的TF因子 特别是在高等生物中。本申请中提供的初步数据表明， 野生型人基因及其错义变体在3 T3 L1脂肪细胞中的过表达增强了 脂肪生成，促进脂质储存，并改善细胞存活。此外，错义基因的过度表达 变体促进更大的脂质储存并减少能量底物氧化，这表明它是一种 “节俭”变体。考虑到肥胖对疾病的巨大贡献，迫切需要进行更多的研究 以了解这种错义变异导致人类肥胖的机制。中央 这个建议的目的是确定TF基因和它的错义变体如何贡献能量 体内平衡，并确定介导这些影响的转录途径。我们将实现这一目标 利用细胞、小鼠和人类的综合研究，了解分子、生理和临床 错义变体的相关性。将追求以下具体目标：目标1将确定和 表征介导TF基因及其错义变体对能量的影响的基因网络 在培养的细胞中的稳态和能量底物代谢，一系列代谢相关的组织， 小鼠和123名萨摩亚人的脂肪组织; Aim 2将描述错义变体对 使用变异体特异性 敲入小鼠;目标3将更精确地表征错义变体对代谢和 影响500名萨摩亚GWAS参与者的能量稳态的行为特征， 根据他们的基因型进行选择。这些更深层次的表型将在萨摩亚进行新的实地考察， 重新联系最初GWAS研究的参与者，在此期间， 将测试与目标1和2中使用的条件/暴露类似的条件/暴露;目标4将更全面地表征 使用包括测试选择性签名的综合统计方法的错义变体， 通过多变量分析检测多效性，进行通路分析，检测错义变体x 环境相互作用，重点是饮食和体力活动，测试TF基因x基因相互作用 重点关注目标1和2中鉴定的基因，并检测与来自 目标3：这些目标的成功完成将促进对肥胖及其下游的认识 健康结果以及确定药物干预的新靶点。

PROJECT SUMMARY In this competitive renewal we focus on characterizing a novel missense variant that was identified by genome- wide association analysis (GWAS) of obesity-related traits in Samoans during the previous funding period. This missense variant is highly associated with body mass index (BMI) with an effect size greater than any other known common obesity risk variant. The gene harboring this missense variant encodes a putative transcription factor (TF) that has recently been implicated in energy metabolism in Drosophila but remains poorly characterized, particularly in higher organisms. Preliminary data presented in this application indicate that overexpression of both the wild-type human gene and its missense variant in 3T3L1 adipocytes enhances adipogenesis, promotes lipid storage, and improves cell survival. In addition, overexpression of the missense variant promotes even greater lipid storage and reduces energy substrate oxidation, suggesting that it is a “thrifty” variant. Given the enormous contribution of obesity to disease, additional studies are urgently needed to understand the mechanisms by which this missense variant contributes to obesity in humans. The Central Aim of this proposal is to determine how the TF gene and its missense variant contribute to energy homeostasis and to identify the transcriptional pathways mediating these effects. We will achieve this goal using integrated studies in cells, mice, and humans to understand the molecular, physiological, and clinical relevance of the missense variant. The following Specific Aims will be pursued: Aim 1 will identify and characterize the gene networks mediating the effects of the TF gene and its missense variant on energy homeostasis and energy substrate metabolism in cultured cells, a range of metabolically-relevant tissues from mice, and adipose tissue from 123 Samoans; Aim 2 will characterize the impact of the missense variant on whole body and tissue-specific energy homeostasis and energy substrate metabolism using variant-specific knockin mice; Aim 3 will more precisely characterize the impact of the missense variant on metabolic and behavioral traits that impact energy homeostasis in a subset of 500 Samoans GWAS participants who will be selected based on their genotype. These deeper phenotypes will be measured with new fieldwork in Samoa by re-contacting participants from the original GWAS study, during which metabolic and nutritional conditions/exposures analogous to those used in Aims 1 and 2 will be tested; Aim 4 will more fully characterize the missense variant using comprehensive statistical approaches including testing for selective signatures, testing for pleiotropy via multivariate analyses, performing pathway analyses, testing for missense variant x environment interactions with a focus on diet and physical activity, testing for TF gene x gene interactions focusing on genes identified in Aims 1 and 2, and testing for association with newly gathered phenotypes from Aim 3. Successful completion of these aims will promote the understanding of obesity and its downstream health outcomes as well as identify novel targets for pharmacological interventions.