Chromatin landscape of human visceral and subcutaneous adipocytes. Homo sapiens

Obesity is characterized by the excess of body fat leading to impaired health. Abdominal fat is particularly harmful and is associated with cardiovascular and metabolic diseases and cancer. In contrast, subcutaneous fat is generally considered less detrimental. The mechanisms that establish the cellular characteristics of these distinct fat types in humans are not fully understood. Here, we explored whether differences of their gene regulatory mechanisms can be investigated in vitro. For this purpose, we in vitro differentiated human visceral and subcutaneous pre-adipocytes into mature adipocytes and obtained their gene expression profiles and genome-wide H3K4me3, H3K9me3 and H3K27ac patterns. Subsequently, we compared those data with public gene expression data from visceral and subcutaneous fat tissues. We found that the in vitro differentiated adipocytes show significant differences in their transcriptional landscapes, which correlate with biological pathways that are characteristic for visceral and subcutaneous fat tissues, respectively. Unexpectedly, visceral adipocyte enhancers are rich on motifs for transcription factors involved in the Hippo-YAP pathway, cell growth and inflammation, which are not typically associated with adipocyte function. In contrast, enhancers of subcutaneous adipocytes show enrichment of motifs for common adipogenic transcription factors, such as C/EBP, NFI and PPARgamma, implicating substantially disparate gene regulatory networks in visceral and subcutaneous adipocytes. Consistent with the role in obesity, predominantly the histone modification pattern of visceral adipocytes is linked to obesity-associated diseases. Thus, this work suggests that the properties of visceral and subcutaneous fat tissues can be studied in vitro and provides preliminary insights into their gene regulatory processes. Overall design: ChIP-Seq for H3K4me3, H3K9me3 and H3K27ac of in vitro differentiated human visceral and subcutaneous adipocytes. Two biological replicates were performed. RNA-Seq of visceral and subcutaneous pre-adipocytes (1x) and mature adipocytes (2x).

肥胖以体内脂肪过量蓄积引发健康受损为特征。其中腹部脂肪危害尤甚，与心血管疾病、代谢性疾病及癌症存在显著关联。与之相对，皮下脂肪通常被认为危害性更低。目前学界尚未完全阐明人类体内这两类截然不同的脂肪组织细胞特征的形成机制。本研究旨在探索能否通过体外实验探究二者基因调控机制的差异。为此，我们将人类内脏前脂肪细胞与皮下前脂肪细胞体外诱导分化为成熟脂肪细胞，并获取了它们的基因表达谱以及全基因组范围内的H3K4me3、H3K9me3与H3K27ac修饰图谱。随后，我们将这些数据与公开的内脏及皮下脂肪组织基因表达数据进行了比对分析。研究发现，体外分化得到的脂肪细胞其转录调控景观存在显著差异，且分别与内脏脂肪组织、皮下脂肪组织的特征性生物学通路相关。出乎意料的是，内脏脂肪细胞的增强子区域富集了大量与Hippo-YAP通路、细胞生长及炎症相关的转录因子结合基序，而这些通路通常并不被认为与脂肪细胞功能相关。与之相反，皮下脂肪细胞的增强子区域则富集了常见成脂转录因子（如CCAAT增强子结合蛋白（C/EBP）、核因子I（NFI）与过氧化物酶体增殖物激活受体γ（PPARγ））的结合基序，这表明内脏与皮下脂肪细胞的基因调控网络存在显著差异。与肥胖的致病作用一致，内脏脂肪细胞的组蛋白修饰模式主要与肥胖相关疾病存在关联。综上，本研究表明可通过体外实验研究内脏与皮下脂肪组织的特性，并为二者的基因调控过程提供了初步见解。整体实验设计：针对体外分化获得的人类内脏与皮下脂肪细胞，开展H3K4me3、H3K9me3及H3K27ac的染色质免疫共沉淀测序（ChIP-Seq），该实验设置2次生物学重复；同时对内脏及皮下前脂肪细胞（1次生物学重复）与成熟脂肪细胞（2次生物学重复）进行RNA测序（RNA-Seq）。