Abstract

Dominant mutations in the MORC2 gene have recently been shown to cause axonal Charcot–Marie–Tooth (CMT) disease, but the cellular function of MORC2 is poorly understood. Here, through a genome-wide CRISPR–Cas9-mediated forward genetic screen, we identified MORC2 as an essential gene required for epigenetic silencing by the HUSH complex. HUSH recruits MORC2 to target sites in heterochromatin. We exploited a new method, differential viral accessibility (DIVA), to show that loss of MORC2 results in chromatin decompaction at these target loci, which is concomitant with a loss of H3K9me3 deposition and transcriptional derepression. The ATPase activity of MORC2 is critical for HUSH-mediated silencing, and the most common alteration affecting the ATPase domain in CMT patients (p.Arg252Trp) hyperactivates HUSH-mediated repression in neuronal cells. These data define a critical role for MORC2 in epigenetic silencing by the HUSH complex and provide a mechanistic basis underpinning the role of MORC2 mutations in CMT disease.

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Acknowledgements

We are indebted to CIMR core facilities: R. Schulte and his team for FACS, and M. Gratian and M. Bowen for microscopy. We thank S. Andrews for assistance with data analysis with SeqMonk, and S. Kundu and M. Tolstorukov for helpful discussions. We thank B. Cochran (Tufts University), F. Randow (MRC-LMB), D. Rubinsztein (CIMR) and M. Brenner (Harvard Medical School) for providing materials. This work was supported by the Wellcome Trust, through a Principal Research Fellowship to P.J.L. (101835/Z/13/Z), a Senior Research Fellowship to Y.M. (101908/Z/13/Z), a Sir Henry Wellcome Postdoctoral Fellowship to R.T.T. (201387/Z/16/Z) and a PhD studentship to I.A.T., and by the BBSRC, through a Future Leader Fellowship to C.H.D. I.A.T. is supported as a Damon Runyon Fellow by the Damon Runyon Cancer Research Foundation (DRG-2277-16). The CIMR is in receipt of a Wellcome Trust strategic award.

Author information

Author notes

    • Iva A Tchasovnikarova
    •  & Richard T Timms

    These authors contributed equally to the work.

Affiliations

  1. Department of Medicine, Cambridge Institute for Medical Research, Cambridge, UK.

    • Iva A Tchasovnikarova
    • , Richard T Timms
    •  & Paul J Lehner
  2. Department of Molecular Biology, Massachusetts General Hospital, and Department of Genetics, Harvard Medical School, Boston, Massachusetts, USA.

    • Iva A Tchasovnikarova
    •  & Robert E Kingston
  3. Department of Medicine, University of Cambridge, MRC Laboratory of Molecular Biology, Cambridge, UK.

    • Christopher H Douse
    •  & Yorgo Modis
  4. Department of Clinical Neurosciences, Cambridge Institute for Medical Research, Cambridge, UK.

    • Rhys C Roberts
  5. Wellcome Trust Sanger Institute, Hinxton, UK.

    • Gordon Dougan

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Contributions

I.A.T., R.T.T. and P.J.L. conceived the study. Except for the in vitro expression and purification experiments, which were carried out by C.H.D., I.A.T. and R.T.T. performed all of the experiments and, together with Y.M. and P.J.L., analyzed the data and wrote the manuscript. G.D., R.C.R. and R.E.K. contributed essential reagents.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Paul J Lehner.

Supplementary information

PDF files

  1. 1.

    Supplementary Text and Figures

    Supplementary Figures 1–10.

Excel files

  1. 1.

    Supplementary Table 1

    Composition of MORC2 mutants.

  2. 2.

    Supplementary Table 2

    Full DIVA data quantifying viral accessibility across all genomic loci in wild-type versus MORC2 knockout HeLa cells.

  3. 3.

    Supplementary Table 3

    Oligonucleotide sequences.

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DOI

https://doi.org/10.1038/ng.3878

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