Journal
CELLS
Volume 11, Issue 9, Pages -Publisher
MDPI
DOI: 10.3390/cells11091442
Keywords
epigenetics; MeCP2 isoforms; gene transcription; BDNF; brain development; protein translation; RTT; mTOR signaling; miR-132
Categories
Funding
- Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant [2016-06035]
- Ontario Rett Syndrome Association (ORSA) Hope Fund
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Eukaryotic gene expression is controlled by methyl CpG binding protein 2 (MeCP2), which plays key roles in gene transcription and protein translation initiation. Mutations in MECP2 lead to Rett Syndrome and MECP2 Duplication Syndrome. Researchers found that overexpression of MeCP2 isoforms resulted in protein degradation of MeCP2E1, while impaired protein translation initiation was observed in Rett Syndrome brains.
Eukaryotic gene expression is controlled at multiple levels, including gene transcription and protein translation initiation. One molecule with key roles in both regulatory mechanisms is methyl CpG binding protein 2 (MeCP2). MECP2 gain- and loss-of-function mutations lead to Rett Syndrome and MECP2 Duplication Syndrome, respectively. To study MECP2 gain-of-function, we generated stably transduced human brain cells using lentiviral vectors for both MECP2E1 and MECP2E2 isoforms. Stable overexpression was confirmed by Western blot and immunofluorescence. We assessed the impact of MeCP2E1-E2 gain-of-function on the MeCP2 homeostasis regulatory network (MECP2E1/E2-BDNF/BDNF-miR-132), mTOR-AKT signaling, ribosome biogenesis, markers of chromatin structure, and protein translation initiation. We observed that combined co-transduction of MeCP2 isoforms led to protein degradation of MeCP2E1. Proteosome inhibition by MG132 treatment recovered MeCP2E1 protein within an hour, suggesting its induced degradation through the proteosome pathway. No significant change was detected for translation initiation factors as a result of MeCP2E1, MeCP2E2, or combined overexpression of both isoforms. In contrast, analysis of human Rett Syndrome brains tissues compared with controls indicated impaired protein translation initiation, suggesting that such mechanisms may have differential sensitivity to MECP2 gain- and loss-of-function. Collectively, our results provide further insight towards the dose-dependent functional role of MeCP2 isoforms in the human brain.
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