Aims/hypothesis: Pro-opiomelanocortin (POMC) neurons in the arcuate nucleus (ARC) regulate energy homeostasis by secreting α-melanocyte-stimulating hormone (α-MSH), derived from POMC precursor, in response to leptin signalling. Expression of Pomc is subject to multiple modes of regulation, including epigenetic regulation. Methyl-CpG-binding protein 2 (MeCP2), a nuclear protein essential for neuronal function, interacts with promoters to influence gene expression. We aim to address whether MeCP2 regulates hypothalamic Pomc expression and to investigate the role of epigenetics, particularly DNA methylation, in this process.
Methods: We generated a mouse line with MeCP2 specifically deleted in POMC neurons (Mecp2 flox/y /Pomc-Cre [PKO]) and characterised its metabolic phenotypes. We examined the DNA methylation pattern of the Pomc promoter and its impact on hypothalamic gene expression. We also studied the requirement of MeCP2 for, and the effects of, DNA methylation on Pomc promoter activity using luciferase assays.
Results: PKO mice are overweight, with increased fat mass resulting from increased food intake and respiratory exchange ratio. PKO mice also exhibit elevated plasma leptin. Deletion of MeCP2 in POMC neurons leads to increased DNA methylation of the hypothalamic Pomc promoter and reduced Pomc expression. Furthermore, in vitro studies show that hypermethylation of the Pomc promoter reduces its transcriptional activity and reveal a functional synergy between MeCP2 and cAMP responsive element binding protein 1 (CREB1) in positively regulating the Pomc promoter.
Conclusions/interpretation: Our results demonstrate that MeCP2 positively regulates Pomc expression in the hypothalamus. Absence of MeCP2 in POMC neurons leads to increased DNA methylation of the Pomc promoter, which, in turn, downregulates Pomc expression, leading to obesity in mice with an accentuating degree of leptin resistance.