Mechanisms of adipocyte loss in mouse models of familial partial lipodystrophy 2

家族性部分脂肪营养不良小鼠模型脂肪细胞丢失的机制2

• 批准号: 10748790
• 负责人: Jessica Nanda Maung
• 金额: $ 4.08万
• 依托单位: UNIVERSITY OF MICHIGAN AT ANN ARBOR
• 依托单位国家: 美国
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-07-01 至 2025-12-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10748790
• 关键词: Acute; Adipocytes; Adipose tissue; Adult; Age; Alleles; Architecture; Blood Glucose; Cell Death; Cells; Characteristics; Chromatin; DNA Binding; Data; Deposition; Development; Diabetes Mellitus; Down-Regulation; Familial partial lipodystrophy; Fatty Liver; Fluorescent in Situ Hybridization; Foundations; Functional disorder; Future; Gene Expression; Genes; Global Change; Health; Hepatic; Homeostasis; Human; Hyperlipidemia; Immune; Inflammatory; Injections; Insulin; Knock-out; Knockout Mice; Knowledge; Lamin Type A; Lead; Leptin; Lipids; Lipodystrophy; Lipolysis; Location; LoxP-flanked allele; Maintenance; Metabolic dysfunction; Mitochondria; Modeling; Molecular; Morphology; Mus; Mutation; Nuclear; Nuclear Lamina; Pathogenicity; Pathway interactions; Patients; Phenotype; Positioning Attribute; Proteins; Proteomics; Puberty; Publishing; Rare Diseases; Reporter; Role; Secondary to; Shapes; Structure; Tamoxifen; Testing; Tracer; Triglycerides; Up-Regulation; Variant; Visceral; adipocyte biology; adiponectin; autosome; comparison control; experimental study; functional loss; gene synthesis; in vivo; insight; lipid biosynthesis; lipid metabolism; mouse model; new therapeutic target; postnatal; prevent; subcutaneous; therapeutic target; transcription factor; transcriptome sequencing; vector

PROJECT SUMMARY/ABSTRACT Lipodystrophies are rare diseases, characterized by a striking loss, redistribution, and dysfunction of adipose tissue, and accompanied by metabolic dysfunction. Familial partial lipodystrophy 2 (FPLD2) is the most common type of lipodystrophy, caused by mutations in LMNA, which encodes the nuclear lamina proteins lamin A/C. Lamin A/C is crucial for nuclear function and controls gene expression, but its role in adipocyte maintenance and function is incompletely understood. Our lab created a constitutive adipocyte specific Lmna knockout mouse model (LmnaADKO) to better characterize the roles of Lmna in adipocytes. LmnaADKO mice develop adipose tissues that are subsequently lost starting at 4 weeks of age; LmnaADKO mice have hepatic steatosis and reduced circulating leptin concentrations, closely recapitulating FPLD2. Analyses of LmnaADKO mice suggest that lamin A/C is required for adipocyte maintenance, substantially advancing our mechanistic understanding, since previous studies did not reveal how loss of Lmna function leads to lipodystrophy. To study mechanisms of how knockout of Lmna in adipocytes leads to subsequent loss of adipocytes, we generated mice in which Lmna can be inducibly knocked out with administration of tamoxifen (LmnaiADKO). This approach allows us to use adult mice, which have more adipose tissue, and to temporally synchronize adipocyte loss. In preliminary experiments, we have tested multiple mechanisms in vivo that could contribute to loss of adipocytes in LmnaiADKO mice. Altered adipogenesis seems unlikely, considering that functional white adipose tissue (WAT) develops in LmnaADKO mice and patients with FPLD2. We also did not observe signs of increased lipolytic capacity or increased acute cell death in WAT lacking Lmna in adipocytes. However, we did observe that adipocytes lacking Lmna are visibly smaller and misshapen compared to controls, suggesting adipocytes are losing their lipid stores, and are unable to maintain viability. Bulk RNA-seq and proteomics from LmnaiADKO WAT revealed downregulation of lipogenic pathways, and upregulation of inflammatory genes. We hypothesize that lamin A/C is required to maintain mature adipocyte characteristics, and that absence of functional lamin A/C leads to adipocyte loss through reduced lipogenic gene expression, driven by altered interactions between Lmna and chromatin. My project will test this hypothesis by (1) evaluating changes in lipogenic and mitochondrial genes in Lmna knockout adipocytes and performing DamID and FISH to study changes in chromatin-lamina interactions that may underlie changes in gene expression and (2) assessing decreased de novo lipogenesis in LmnaiADKO mice, in addition to restoring lipogenic gene expression to Lmna KO adipocytes to prevent WAT loss. Ultimately, these studies will reveal underlying molecular mechanisms of FPLD2, uncovering novel therapeutic targets for lipodystrophy patients while bolstering our understanding of fundamental adipocyte biology.

项目总结/摘要 脂肪营养不良是一种罕见的疾病，其特征是脂肪的显著损失、重新分布和功能障碍。 组织，并伴有代谢功能障碍。家族性部分脂肪营养不良2（FPLD 2）是最常见的 一种常见的脂肪营养不良，由编码核纤层蛋白的LMNA突变引起 核纤层蛋白A/C。核纤层蛋白A/C对核功能至关重要，并控制基因表达，但其在脂肪细胞中的作用， 维护和功能不完全理解。我们的实验室创造了一种组成型脂肪细胞特异性Lmna 敲除小鼠模型（LmnaADKO）以更好地表征Lmna在脂肪细胞中的作用。LmnaADKO小鼠 产生脂肪组织，随后从4周龄开始丢失; LmnaADKO小鼠具有肝脏 脂肪变性和降低的循环瘦素浓度，密切重演FPLD 2。LmnaADKO分析 小鼠表明核纤层蛋白A/C是脂肪细胞维持所必需的，这大大推进了我们的机制， 这是因为以前的研究没有揭示Lmna功能的丧失如何导致脂肪代谢障碍。 为了研究Lmna在脂肪细胞中的敲除如何导致随后的脂肪细胞损失的机制，我们 产生其中Lmna可通过施用他莫昔芬（Lmna 1ADKO）而被诱导性敲除的小鼠。这 这种方法允许我们使用成年小鼠，它们有更多的脂肪组织，并在时间上同步 脂肪细胞损失。在初步实验中，我们已经测试了多种体内机制，这些机制可能有助于 LmnaiADKO小鼠中脂肪细胞的损失。考虑到功能性白色 脂肪组织（WAT）在LmnaADKO小鼠和患有FPLD 2的患者中形成。我们也没有观察到 脂肪细胞中缺乏Lmna的WAT中增加的脂解能力或增加的急性细胞死亡。然而，我们 观察到缺乏Lmna的脂肪细胞与对照组相比明显较小且畸形，这表明 脂肪细胞正在失去它们的脂质储存，并且不能维持生存能力。批量RNA测序和蛋白质组学 LmnaiADKO WAT揭示了脂肪生成途径的下调和炎症基因的上调。我们 假设核纤层蛋白A/C是维持成熟脂肪细胞特征所必需，且缺乏核纤层蛋白A/C 功能性核纤层蛋白A/C通过减少脂肪生成基因表达导致脂肪细胞损失， Lmna和染色质之间的相互作用。我的项目将通过（1）评估 Lmna敲除脂肪细胞中的脂肪生成和线粒体基因，并进行DamID和FISH研究 染色质-纤层相互作用的变化可能是基因表达变化的基础，以及（2）评估 除了恢复Lmna的脂肪生成基因表达外， KO脂肪细胞以防止WAT损失。最终，这些研究将揭示潜在的分子机制， FPLD 2，揭示了脂肪代谢障碍患者的新治疗靶点，同时加强了我们对 基础脂肪细胞生物学。