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A suppressor screen in Mecp2 mutant mice implicates cholesterol metabolism in Rett syndrome

Nature Genetics volume 45, pages 1013–1020 (2013)Cite this article

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Abstract

Mutations in MECP2, encoding methyl CpG-binding protein 2, cause Rett syndrome, the most severe autism spectrum disorder. Re-expressing Mecp2 in symptomatic Mecp2-null mice markedly improves function and longevity, providing hope that therapeutic intervention is possible in humans. To identify pathways in disease pathology for therapeutic intervention, we carried out a dominant N-ethyl-N-nitrosourea (ENU) mutagenesis suppressor screen in Mecp2-null mice and isolated five suppressors that ameliorate the symptoms of Mecp2 loss. We show that a stop codon mutation in Sqle, encoding squalene epoxidase, a rate-limiting enzyme in cholesterol biosynthesis, underlies suppression in one line. Subsequently, we also show that lipid metabolism is perturbed in the brains and livers of Mecp2-null male mice. Consistently, statin drugs improve systemic perturbations of lipid metabolism, alleviate motor symptoms and confer increased longevity in Mecp2 mutant mice. Our genetic screen therefore points to cholesterol homeostasis as a potential _target for the treatment of patients with Rett syndrome.

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Figure 1: A dominant suppressor screen shows inheritance of longevity in five lines.
Figure 2: Survival curves for each line with a confirmed map location for the modifier are shown assessed at the N3 generation.
Figure 3: A stop codon mutation in Sqle confers rescue at Sum3m1Jus.
Figure 4: Cholesterol metabolism is disrupted in Mecp2-null male mice.
Figure 5: Statin treatment improves health in 129.
Figure 6: Fluvastatin treatment improves health in 129.

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Acknowledgements

The Genetics Analysis Facility (T. Patton and C. Marshall) at the Centre for Applied Genomics, Toronto Hospital for Sick Kids, Toronto, Ontario, Canada performed the Illumina Goldengate SNP analysis. We thank J. Crowe, M. Schrock, J. Borkey, M. Hill, A. Willis and J. Shaw (Justice laboratory), C. Lee, A. MacKenzie and L. Felker (Shendure laboratory), I. Adams (Katz laboratory), B. Thompson (McDonald and Russell laboratory) and K.S. Posey and A.M. Lopez (Turley laboratory) for technical assistance. We thank C. Spencer and R. Paylor for advice on assessing mouse behavior, which was carried out in the Baylor College of Medicine (BCM) Mouse Neurobehavior Core, and C. Reynolds for advice on plethysmography, which was carried out in the BCM Mouse Phenotyping Core. We thank H. Zoghbi and J. Neul (BCM) for Mecp2 mutant mice. We also thank H. Zoghbi (BCM) and R. Behringer (University of Texas MD Anderson Cancer Center) for valuable discussions during revision of the manuscript. M. Coenraads of the Rett Syndrome Research Trust (RSRT) provided crucial moral and uninterrupted financial support while she aided intellectually through literature searches and advice.

The work was supported by grants from the RSRT, the Rett Syndrome Research Foundation, the International Rett Syndrome Foundation (ANGEL award 2608 to M.J.J. and ANGEL award 2583 to D.M.K.), Autism Science Foundation predoctoral fellowship #11-1015, US National Institutes of Health (NIH) grants NIH T32 GM08307 to C.M.B., NIH U54 GM69338 to D.W.R., NIH R01 HL09610 to S.D.T. and NIH R01 CA115503 to M.J.J. and the National Institute of Neurologic Diseases and Stroke, including funding from the American Recovery and Reinvestment Act (D.M.K.). Grants to the BCM Diabetes and Endocrinology Research Center (2P30DK079638-05) and the BCM Intellectual and Developmental Disabilities Research Center (5P30HD024064-23) from the NIH Eunice Kennedy Shriver National Institute of Child Health and Human Development also supported this work. The content is solely the responsibility of the authors and does not necessarily represent the official views of the Eunice Kennedy Shriver National Institute of Child Health and Human Development or the NIH.

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Author notes

  1. Hannah M Brown, Andrew A Pieper & Wenhui Huang

    Present address: Present addresses: Research Centre for Reproductive Health, School of Paediatrics and Reproductive Health, The University of Adelaide, Adelaide, South Australia, Australia (H.M.B.), Department of Psychiatry, University of Iowa Carver College of Medicine, Iowa City, Iowa, USA (A.A.P.), Department of Neurology, University of Iowa Carver College of Medicine, Iowa City, Iowa, USA (A.A.P.) and Fred Hutchinson Cancer Research Center, Seattle, Washington, USA (W.H.).,

Authors and Affiliations

  1. Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA

    Christie M Buchovecky, Hannah M Brown, Stephanie M Kyle & Monica J Justice

  2. Department of Internal Medicine, University of Texas Southwestern Medical School, Dallas, Texas, USA

    Stephen D Turley & Benny Liu

  3. Department of Molecular Genetics, University of Texas Southwestern Medical School, Dallas, Texas, USA

    Jeffrey G McDonald & David W Russell

  4. Department of Psychiatry, University of Texas Southwestern Medical School, Dallas, Texas, USA

    Andrew A Pieper

  5. Department of Biochemistry, University of Texas Southwestern Medical School, Dallas, Texas, USA

    Andrew A Pieper

  6. Department of Genome Sciences, University of Washington, Seattle, Washington, USA

    Wenhui Huang & Jay Shendure

  7. Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA

    David M Katz

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Contributions

M.J.J. conceived of the work, carried out the genetic screen and dissected embryos. J.S. and W.H. carried out the capture sequencing and analysis. C.M.B. confirmed map locations and lesions, performed statin injections and carried out behavior and plethysmography testing and quantitative RT-PCR (qRT-PCR). S.M.K. performed protein blotting and liver histopathology. H.M.B. performed preliminary qRT-PCR. J.G.M., B.L. and S.D.T. analyzed sterols and performed synthesis studies. S.D.T. evaluated liver cholesterol and triglycerides. A.A.P. and D.M.K. provided Jaenisch mice and laboratory facilities. D.M.K. helped analyze plethysmography data. M.J.J., D.W.R., D.M.K., S.D.T., S.M.K. and C.M.B. wrote the manuscript with input from the other coauthors.

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Correspondence to Monica J Justice.

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Supplementary information

Supplementary Text and Figures

Supplementary figures 1-10 and supplementary tables 1-5 (PDF 6794 kb)

Statin treatment improves home cage activity

30 second videos of mice treated with lovastatin and vehicle at P56 showing an increase in home cage activity in statin treated Mecp2tm1.1Bird/Y mice immediately following removal of the cage lid. (MOV 104247 kb)

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Buchovecky, C., Turley, S., Brown, H. et al. A suppressor screen in Mecp2 mutant mice implicates cholesterol metabolism in Rett syndrome. Nat Genet 45, 1013–1020 (2013). https://doi.org/10.1038/ng.2714

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