Intrinsic and extrinsic regulation of MeCP2 in brain cell types and their implications in MeCP2-related neurodevelopmental disorders
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Date
2013-11-15, 2015-03
Authors
Batuwita Liyanage, Vichithra Rasangi
Journal Title
Journal ISSN
Volume Title
Publisher
Biomed Central and Springer
Elsevier
Elsevier
Abstract
MeCP2 is a key epigenetic regulator in the brain, which regulates gene expression. There are two Mecp2/MeCP2 isoforms - MeCP2E1 and MeCP2E2 - with both overlapping and non-overlapping expression and functions in the brain. MeCP2 is widely expressed in different brain cell types but predominantly expressed in neurons. MECP2/MeCP2-deficiency and overexpression are associated with Rett Syndrome (RTT), MECP2 duplication syndrome (MDS) and alcohol (ethanol)-mediated neurological damage, such as Fetal Alcohol Spectrum Disorders (FASD). These disorders have no cure. Rescuing the expression levels of MeCP2 could be a potential therapeutic approach for these diseases. A thorough understanding of MeCP2 expression regulation is essential to achieve this goal. The objective of my Ph.D. project presented in this thesis is to address the knowledge gap on Mecp2 regulation in the brain, which has been carried out using cellular models of in vitro neural stem cell (NSC) differentiation and in vivo differentiated neurons and astrocytes. As such, the intrinsic regulation of Mecp2 isoforms by epigenetic and transcriptional mechanisms, and extrinsic regulation of Mecp2 isoforms by the insult of ethanol exposure were explored in this thesis.
We identified six regulatory elements (REs) within the Mecp2 promoter and intron 1, DNA methylation of which correlated with the expression of Mecp2 isoforms during NSC differentiation [Liyanage et al. (2013), Molecular Autism]. The role of DNA methylation in Mecp2 regulation was studied by treatment with a DNA demethylating agent decitabine, which was identified as a potential drug that induces Mecp2/MeCP2 expression in an isoform-specific manner. In terms of the extrinsic regulation by ethanol, dynamic DNA methylation patterns at these REs was associated with the alterations of Mecp2 levels by ethanol exposure and withdrawal during NSC differentiation [Liyanage et al. (2015), Experimental Neurology]. We also found that expression of Mecp2 isoforms in primary neurons and astrocytes is cell type- and sex-specific. The higher expression of Mecp2 isoforms in neurons as compared to astrocytes is possibly mediated through lower DNA methylation levels in these identified REs.
Taken together, my studies provide evidence for the role of DNA methylation in epigenetic regulation of Mecp2 in these brain cells, under normal conditions and in response to extrinsic deregulation by ethanol exposure. The ability of the DNA methylation inhibitor decitabine to upregulate Mecp2 levels provides insights on potential future drug treatment strategies for MeCP2-deficiency-associated neurological conditions. The knowledge gained from this study will hold promise for utilizing these intrinsic and extrinsic regulatory mechanisms of Mecp2 isoforms for a better understanding of diseases pathology and provides insights into translational knowledge on further MeCP2 research and therapy strategies for MeCP2-associated neurological disorders.
Description
Keywords
MeCP2, DNA methylation, Epigenetics, FASD, Rett syndrome, Autism, MeCP2 isoforms, Alcohol
Citation
Liyanage, V. R., Zachariah, R. M., & Rastegar, M. (2013). Decitabine alters the expression of Mecp2 isoforms via dynamic DNA methylation at the Mecp2 regulatory elements in neural stem cells. Mol Autism, 4(1), 46. doi:10.1186/2040-2392-4-46
Liyanage, V. R., Zachariah, R. M., Davie, J. R., & Rastegar, M. (2015). Ethanol deregulates Mecp2/MeCP2 in differentiating neural stem cells via interplay between 5-methylcytosine and 5-hydroxymethylcytosine at the Mecp2 regulatory elements. Exp Neurol, 265, 102-117. doi:10.1016/j.expneurol.2015.01.006
Liyanage, V. R., Zachariah, R. M., Davie, J. R., & Rastegar, M. (2015). Ethanol deregulates Mecp2/MeCP2 in differentiating neural stem cells via interplay between 5-methylcytosine and 5-hydroxymethylcytosine at the Mecp2 regulatory elements. Exp Neurol, 265, 102-117. doi:10.1016/j.expneurol.2015.01.006