RESUMO
Epigenetic mechanisms, in particular the enzymatic modification of histones, are a crucial element of cell differentiation, a regulated process that allows a precursor cell basically to turn into a different cell type while maintaining the same genetic equipment. We have previously described that the promoters of adipogenic genes display significant levels of dimethylation at the Lys(4) of histone H3 (H3K4) in preadipocytes, where these genes are still silenced, thus maintaining the chromatin of the precursor cell in a receptive state. Here, we show that the expression of several histone demethylases and methyltransferases increases during adipogenesis, suggesting an important role for these proteins in this process. Knockdown of the H3K4/K9 demethylase LSD1 results in markedly decreased differentiation of 3T3-L1 preadipocytes. This outcome is associated with decreased H3K4 dimethylation and increased H3K9 dimethylation at the promoter of transcription factor cebpa, whose expression must be induced >200-fold upon stimulation of differentiation. Thus, our data suggest that LSD1 acts to maintain a permissive state of the chromatin in this promoter by opposing the action of a H3K9 methyltransferase. Knockdown of H3K9 methyltransferase SETDB1 produced the opposite results, by decreasing H3K9 dimethylation and increasing H3K4 dimethylation levels at the cebpa promoter and favoring differentiation. These findings indicate that the histone methylation status of adipogenic genes as well as the expression and function of the proteins involved in its maintenance play a crucial role in adipogenesis.
Assuntos
Adipócitos/metabolismo , Adipogenia/fisiologia , Diferenciação Celular/fisiologia , Epigênese Genética/fisiologia , Oxirredutases N-Desmetilantes/metabolismo , Células-Tronco/metabolismo , Células 3T3-L1 , Adipócitos/citologia , Animais , Proteínas Estimuladoras de Ligação a CCAAT/genética , Proteínas Estimuladoras de Ligação a CCAAT/metabolismo , Cromatina/genética , Cromatina/metabolismo , Técnicas de Silenciamento de Genes , Histona Desmetilases , Histona-Lisina N-Metiltransferase , Histonas/genética , Histonas/metabolismo , Camundongos , Oxirredutases N-Desmetilantes/genética , Regiões Promotoras Genéticas/fisiologia , Proteínas Metiltransferases/genética , Proteínas Metiltransferases/metabolismo , Células-Tronco/citologiaRESUMO
Myotonic dystrophy 1 (MD1) is caused by a CTG expansion in the 3'-unstranslated region of the myotonic dystrophy protein kinase (DMPK) gene. MD1 patients frequently present insulin resistance and increased visceral adiposity. We examined whether DMPK deficiency is a genetic risk factor for high-fat diet-induced adiposity and insulin resistance using the DMPK knockout mouse model. We found that high-fat fed DMPK knockout mice had significantly increased body weights, hypertrophic adipocytes and whole-body insulin resistance compared with wild-type mice. This nutrient-genome interaction should be considered by physicians given the cardiometabolic risks and sedentary lifestyle associated with MD1 patients.
