RESUMEN
Chronic stressors, during developmental sensitive periods and beyond, contribute to the risk of developing psychiatric conditions, including major depressive disorder (MDD). Epigenetic mechanisms including DNA methylation and histone modifications, at key stress response and neurotrophin genes, are increasingly implicated in mediating this risk. Although the exact mechanisms through which stressful environmental stimuli alter the epigenome are still unclear, research from the learning and memory fields indicates that epigenomic marks can be altered, at least in part, through calcium-dependent signaling cascades in direct response to neuronal activity. In this review, we highlight key findings from the stress, MDD, and learning and memory fields to propose a model where stress regulates downstream cellular functioning through activity-dependent epigenetic changes. Furthermore, we suggest that both typical and novel antidepressant treatments may exert positive influence through similar, activity-dependent pathways.
Asunto(s)
Trastorno Depresivo Mayor/genética , Epigénesis Genética/genética , Cromatina/fisiología , Metilación de ADN/genética , Metilación de ADN/fisiología , Trastorno Depresivo Mayor/fisiopatología , Trastorno Depresivo Mayor/terapia , Epigenómica/métodos , Código de Histonas/genética , Código de Histonas/fisiología , Humanos , Estrés Psicológico/genéticaRESUMEN
Genes implicated in neurodevelopmental disorders (NDDs) important in cognition and behavior may have convergent function and several cellular pathways have been implicated, including protein translational control, chromatin modification, and synapse assembly and maintenance. Here, we test the convergent effects of methyl-CpG binding domain 5 (MBD5) and special AT-rich binding protein 2 (SATB2) reduced dosage in human neural stem cells (NSCs), two genes implicated in 2q23.1 and 2q33.1 deletion syndromes, respectively, to develop a generalized model for NDDs. We used short hairpin RNA stably incorporated into healthy neural stem cells to supress MBD5 and SATB2 expression, and massively parallel RNA sequencing, DNA methylation sequencing and microRNA arrays to test the hypothesis that a primary etiology of NDDs is the disruption of the balance of NSC proliferation and differentiation. We show that reduced dosage of either gene leads to significant overlap of gene-expression patterns, microRNA patterns and DNA methylation states with control NSCs in a differentiating state, suggesting that a unifying feature of 2q23.1 and 2q33.1 deletion syndrome may be a lack of regulation between proliferation and differentiation in NSCs, as we observed previously for TCF4 and EHMT1 suppression following a similar experimental paradigm. We propose a model of NDDs whereby the balance of NSC proliferation and differentiation is affected, but where the molecules that drive this effect are largely specific to disease-causing genetic variation. NDDs are diverse, complex and unique, but the optimal balance of factors that determine when and where neural stem cells differentiate may be a major feature underlying the diverse phenotypic spectrum of NDDs.
Asunto(s)
Diferenciación Celular/genética , Proliferación Celular/genética , Proteínas de Unión al ADN/genética , Proteínas de Unión a la Región de Fijación a la Matriz/genética , Células-Madre Neurales/metabolismo , Trastornos del Neurodesarrollo/genética , Neurogénesis/genética , Factores de Transcripción/genética , Células Cultivadas , Deleción Cromosómica , Cromosomas Humanos Par 2 , Metilación de ADN , Epigénesis Genética , Dosificación de Gen , Regulación del Desarrollo de la Expresión Génica , Secuenciación de Nucleótidos de Alto Rendimiento , Humanos , MicroARNs , Modelos Moleculares , Análisis de Secuencia de ARNRESUMEN
In gram-positive bacteria, the HPr protein of the phosphoenolpyruvate:sugar phosphotransferase system (PTS) can be phosphorylated on a histidine residue at position 15 (His(15)) by enzyme I (EI) of the PTS and on a serine residue at position 46 (Ser(46)) by an ATP-dependent protein kinase (His approximately P and Ser-P, respectively). We have isolated from Streptococcus salivarius ATCC 25975, by independent selection from separate cultures, two spontaneous mutants (Ga3.78 and Ga3.14) that possess a missense mutation in ptsH (the gene encoding HPr) replacing the methionine at position 48 by a valine. The mutation did not prevent the phosphorylation of HPr at His(15) by EI nor the phosphorylation at Ser(46) by the ATP-dependent HPr kinase. The levels of HPr(Ser-P) in glucose-grown cells of the parental and mutant Ga3.78 were virtually the same. However, mutant cells growing on glucose produced two- to threefold less HPr(Ser-P)(His approximately P) than the wild-type strain, while the levels of free HPr and HPr(His approximately P) were increased 18- and 3-fold, respectively. The mutants grew as well as the wild-type strain on PTS sugars (glucose, fructose, and mannose) and on the non-PTS sugars lactose and melibiose. However, the growth rate of both mutants on galactose, also a non-PTS sugar, decreased rapidly with time. The M48V substitution had only a minor effect on the repression of alpha-galactosidase, beta-galactosidase, and galactokinase by glucose, but this mutation abolished diauxie by rendering cells unable to prevent the catabolism of a non-PTS sugar (lactose, galactose, and melibiose) when glucose was available. The results suggested that the capacity of the wild-type cells to preferentially metabolize glucose over non-PTS sugars resulted mainly from inhibition of the catabolism of these secondary energy sources via a HPr-dependent mechanism. This mechanism was activated following glucose but not lactose metabolism, and it did not involve HPr(Ser-P) as the only regulatory molecule.