Project description:Increasing energy expenditure by promoting the thermogenic program in brown adipocytes is a promising approach to combat human obesity. To fully exploit the potential of this approach a comprehensive understanding of the gene regulatory network that controls both lineage commitment and differentiation of brown cells is necessary. Here, we systematically examine the transcriptomic and epigenomic transitions from mesenchymal stem cells to brown adipocytes (BA) and we perform a comparative analysis with differentiating white adipocytes (WA). We identify coding genes, lncRNA genes, and microRNA genes that are differentially regulated upon BA differentiation. In addition, we generate genome wide reference maps for several chromatin marks throughout brown adipogenesis. We identify putative (super-)enhancers, super-enhancers controlled genes in brown and white adipocytes, as well as target genes of the brown lineage-committing factor BMP7. Finally we show that overexpression and knockdown of four putative novel adipogenic regulators (the kinase Pim1, and the transcription factors Six1, Rreb1, and Sox13), indeed affects BA differentiation, suggesting an important role in brown adipogenesis.
Project description:Despite their opposing actions on food intake, POMC and NPY/AgRP neurons in the arcuate nucleus of the hypothalamus (ARH) are derived from the same progenitors that give rise to ARH neurons. However, the mechanism whereby common neuronal precursors subsequently adopt either the anorexigenic (POMC) or the orexigenic (NPY/AgRP) identity remains elusive.We hypothesize that POMC and NPY/AgRP cell fates are specified and maintained by distinct intrinsic factors. In search of them, we profiled the transcriptomes of developing POMC and NPY/AgRP neurons in E15.5 mice embryos. Moreover, cell-type-specific transcriptomic analyses revealed transcription regulators that are selectively enriched in either population, but whose developmental functions are unknown in these neurons.Among them, we found the expression of the PR domain-containing factor 12 (Prdm12) was enriched in POMC neurons but absent in NPY/AgRP neurons. To study the role of Prdm12 in vivo, we developed and characterized a floxed Prdm12 allele. Selective ablation of Prdm12 in embryonic POMC neurons led to significantly reduced Pomc expression as well as early-onset obesity in mice of either sex that recapitulates symptoms of human POMC deficiency. Interestingly, however, specific deletion of Prdm12 in adult POMC neurons showed that it is no longer required for Pomc expression nor energy balance. Collectively, these findings establish a critical role for Prdm12 in the anorexigenic neuron identity and suggest that it acts developmentally to program body weight homeostasis. Finally, the combination of cell-type-specific genomic and genetic analyses provides a means to dissect cellular and functional diversity in the hypothalamus whose neurodevelopment remains poorly studied.