DNA methylation in AgRP neurons regulates voluntary exercise behavior in mice

Authors: MACKAY, HARRY - Children'S Nutrition Research Center (CNRC); SCOTT, C. ANTHONY - Children'S Nutrition Research Center (CNRC); DURYEA, JACK - Children'S Nutrition Research Center (CNRC); BAKER, MARIA - Children'S Nutrition Research Center (CNRC); LARITSKY, ELEONORA - Children'S Nutrition Research Center (CNRC); ELSON, AMANDA - Vanderbilt University; GARLAND, THEODORE JR. - University Of California; FIOROTTO, MARTA - Children'S Nutrition Research Center (CNRC); CHEN, RUI - Baylor College Of Medicine; LI, YUMEI - Baylor College Of Medicine; COARFA, CRISTIAN - Baylor College Of Medicine; SIMERLY, RICHARD - Vanderbilt University; WATERLAND, ROBERT - Children'S Nutrition Research Center (CNRC)

Submitted to: Nature Communications
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/16/2019
Publication Date: 12/2/2019
Citation: MacKay, H., Scott, C., Duryea, J.D., Baker, M.S., Laritsky, E., Elson, A.E., Garland, T., Fiorotto, M.L., Chen, R., Li, Y., Coarfa, C., Simerly, R.B., Waterland, R.A. 2019. DNA methylation in AgRP neurons regulates voluntary exercise behavior in mice. Nature Communications. 10:5364. https://doi.org/10.1038/s41467-019-13339-3.
DOI: https://doi.org/10.1038/s41467-019-13339-3

Interpretive Summary: Epigenetics is a system for molecular marking of DNA – it tells the different cells in the body which genes to turn on or off in that cell type. A key epigenetic mechanism is methylation of cytosine nucleotides in DNA, which is orchestrated by enzymes called DNA methyltransferases. Once established during development, DNA methylation can stably silence gene expression. There is growing interest in the idea that epigenetic mechanisms are contributing to our current worldwide obesity epidemic. To test this, we generated mice that lack the main brain DNA methyltransferase (Dnmt3a) in in one cell type in the brain – Agrp neurons. Agrp neurons are in the hypothalamus, a region of the brain recognized as the master regulator of food intake and energy expenditure. As expected, the knockout mice showed differences in their tendency to gain weight; as adults they became fatter than wild type mice. Surprisingly, however, this was not because they ate more, but because they moved less. Extensive studies on voluntary wheel-running showed that knockout mice ran only about half as much as controls – an 'epigenetic couch potato'. We performed detailed analysis of DNA methylation and gene expression in the hypothalamus, and applied a novel analytical approach to identify methylation changes that occurred specifically in Agrp neurons. Our results provide definitive evidence that DNA methylation in the brain plays an important role in determining risk of obesity, and the surprising insight that this may occur more through altering physical activity behavior rather than food intake.

Technical Abstract: DNA methylation regulates cell type-specific gene expression. Here, in a transgenic mouse model, we show that deletion of the gene encoding DNA methyltransferase Dnmt3a in hypothalamic AgRP neurons causes a sedentary phenotype characterized by reduced voluntary exercise and increased adiposity. Whole-genome bisulfite sequencing (WGBS) and transcriptional profiling in neuronal nuclei from the arcuate nucleus of the hypothalamus (ARH) reveal differentially methylated genomic regions and reduced expression of AgRP neuron-associated genes in knockout mice. We use read-level analysis of WGBS data to infer putative ARH neural cell types affected by the knockout, and to localize promoter hypomethylation and increased expression of the growth factor Bmp7 to AgRP neurons, suggesting a role for aberrant TGF-B signaling in the development of this phenotype. Together, these data demonstrate that DNA methylation in AgRP neurons is required for their normal epigenetic development and neuron-specific gene expression profiles, and regulates voluntary exercise behavior.