MeCP2: a novel Huntingtin interactor

Transcriptional dysregulation has been proposed to play a major role in the pathology of Huntingtons disease (HD). However, the mechanisms that cause selective downregulation of target genes remain unknown. Previous studies have shown that mutant huntingtin (Htt) protein interacts with a number of transcription factors thereby altering transcription. Here we report that Htt directly interacts with methyl-CpG binding protein 2 (MeCP2) in mouse and cellular models of HD using complimentary biochemical and Fluorescent Lifetime Imaging to measure Frster Resonance Energy Transfer approaches. HttMeCP2 interactions are enhanced in the presence of the expanded polyglutamine (polyQ) tract and are stronger in the nucleus compared with the cytoplasm. Furthermore, we find increased binding of MeCP2 to the promoter of brain-derived neurotrophic factor (BDNF), a gene that is downregulated in HD, in the presence of mutant Htt. Finally, decreasing MeCP2 levels in mutant Htt-expressing cells using siRNA increases BDNF levels, suggesting that MeCP2 downregulates BDNF expression in HD. Taken together, these findings suggest that aberrant interactions between Htt and MeCP2 contribute to transcriptional dysregulation in HD.