MicroRNAs are required for the feature maintenance and differentiation of brown adipocytes

Brown adipose tissue is specialized to burn lipids for heat generation as a natural defense against cold and obesity. Previous studies established microRNAs as essential regulators of brown adipocyte differentiation, but it remains unknown whether microRNAs are required for the feature maintenance of mature brown adipocytes. To address this question, we ablated Dgcr8, a key regulator of the microRNA biogenesis pathway, in mature brown as well as white adipocytes. The adipose tissue -specific Dgcr8 knockout mice displayed enlarged but pale interscapular brown fat with decreased expression of genes characteristic of brown fat, and the mice were intolerant to cold exposure. In vitro primary brown adipocyte cultures confirmed that microRNAs are required for marker gene expression in mature brown adipocytes. We also demonstrated that microRNAs are essential for the browning of subcutaneous white adipocyte both in vitro and in vivo. Using this animal model, we performed microRNA expression profiling analysis and identified a set of BAT-specific microRNAs that are up-regulated during brown adipocyte differentiation and enriched in brown fat compared to other organs. We identified miR-182 and miR-203 as new regulators of brown adipocyte development. Taken together, our study demonstrates an essential role of microRNAs in the maintenance as well as the differentiation of brown adipocytes. TotalRNAs were extracted using a Qiagen kit, and 5 μg of total RNAs for each sample were used to prepare the mRNA- Seq library according to the manufacturer’s instruction (NEB). cDNA libraries were prepared and sequenced by Hi-seq in Whitehead Genome Core. 2 replicates of each treatment were analyzed.