Abstract
Mutations in the MeCP2 gene are responsible for the neurodevelopmental disorder Rett syndrome (RTT). MeCP2 is a DNA-binding protein whose abundance and ability to complex with histone deacetylase 3 is linked to the regulation of chromatin structure. Consequently, loss-of-function mutations in MeCP2 are predicted to have broad effects on gene expression. However, to date, studies in mouse models of RTT have identified a limited number of gene or pathway-level disruptions, and even fewer genes have been identified that could be considered amenable to classic drug discovery approaches. Here, we performed RNA sequencing (RNA-seq) on nine motor cortex and six cerebellar autopsy samples from RTT patients and controls. This approach identified 1887 significantly affected genes in the motor cortex and 2110 genes in the cerebellum, with a global trend toward increased expression. Pathway-level analysis identified enrichment in genes associated with mitogen-activated protein kinase signaling, long-term potentiation, and axon guidance. A survey of our RNA-seq results also identified a significant decrease in expression of the CHRM4 gene, which encodes a receptor [muscarinic acetylcholine receptor 4 (M4)] that is the subject of multiple large drug discovery efforts for schizophrenia and Alzheimer’s disease. We confirmed that CHRM4 expression was decreased in RTT patients, and, excitingly, we demonstrated that M4 potentiation normalizes social and cognitive phenotypes in Mecp2+/− mice. This work provides an experimental paradigm in which translationally relevant targets can be identified using transcriptomics in RTT autopsy samples, back-modeled in Mecp2+/− mice, and assessed for preclinical efficacy using existing pharmacological tool compounds.
Footnotes
- Received December 8, 2017.
- Accepted March 8, 2018.
C.K.J., C.W.L., P.J.C., and C.M.N. are inventors of patents protecting M4 positive allosteric modulators and have received royalties and research funding from AstraZeneca and Lundbeck for the development of M4 positive allosteric modulators for schizophrenia and other central nervous system disorders. This funding was not used to support the studies in the current paper.
The Harvard Brain Tissue Resource Center is supported by a Public Health Service contract [Contract HHSN-271-2013-00030] and the University of Maryland Brain Bank is a Tissue Repository of the National Institutes of Health NeuroBioBank. R.G.G. received support by a Mentored Training Fellowship from Rettsyndrome.org, a Young Investigator Award from Brain and Behavior Research Foundation, and National Institutes of Health National Institute of Mental Health K01 [Grant MH112983]. N.M.F. was supported by National Institutes of Health T32 training grant [Grant GM007628-36], the Vanderbilt Program in Molecular Medicine through Vanderbilt University, and National Institutes of Health F31 [Grant MH113259]. B.J.S. was supported by a National Institutes of Health F32 training grant [Grant MH111124-01]. The authors would also like to acknowledge National Institute of Mental Health U54 [Grant MH084659] (C.W.L.), National Institute of Mental Health R01 [Grant MH087965-01] (P.J.C.), as well as a Basic Research grant from Rettsyndrome.org (C.M.N.), a Treatment Grant from Autism Speaks (C.M.N), and National Institute of Mental Health R21 [Grant MH102548] (C.M.N.).
↵This article has supplemental material available at jpet.aspetjournals.org.
- Copyright © 2018 by The American Society for Pharmacology and Experimental Therapeutics
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