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Circulation. 2019 Jun 5. doi: 10.1161/CIRCULATIONAHA.118.037227. [Epub ahead of print]

iPSC-Derived Cardiomyocytes Reveal Aberrant ERK5 and MEK1/2 Signaling Concomitantly Promote Hypertrophic Cardiomyopathy in RAF1-Associated Noonan Syndrome.

Author information

1
Department of Medicine, Division of Cardiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA & Department of Surgery, Weill Cornell Medical College, New York, NY.
2
Center for Public Health Genomics, Department of Public Health Sciences, Biochemistry and Molecular Genetics, and Biomedical Engineering, University of Virginia, Charlottesville, VA.
3
Institute of Neuropathology, University Hospital Giessen, Justus Liebig University Giessen, Germany.
4
Department of Surgery, Weill Cornell Medical College, New York, NY.
5
Department of Cardiology, Division of Genetics, Boston Children's Hospital, Boston, MA.
6
Department of Child Neurology, University Hospital Giessen, Justus-Liebig University, Giessen, Germany.
7
Department of Medicine, Division of Cardiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA; Harvard Stem Cell Institute, Harvard University, Cambridge, MA; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA; Masonic Medical Research Institute, Utica, NY.

Abstract

BACKGROUND:

More than 90% of Noonan syndrome (NS) individuals with mutations clustered in the CR2 domain of RAF1 present with severe and often lethal hypertrophic cardiomyopathy (HCM). The signaling pathways by which NS RAF1 mutations promote HCM remain elusive, and so far, there is no known treatment for NS-associated-HCM.

METHODS:

We used patient-derived RAF1S257L/+ and CRISPR-Cas9-generated isogenic control iPSC-derived cardiomyocytes (iCMs) to model NS RAF1-associated HCM and to further delineate the molecular mechanisms underlying the disease.

RESULTS:

We show that mutant iCMs phenocopy the pathology seen in patient NS hearts by exhibiting hypertrophy and structural defects. Through pharmacological and genetic targeting, we identify two perturbed concomitant pathways that, together, mediate HCM in RAF1 mutant iCMs; hyper-activation of MEK1/2, but not ERK1/2, causes myofibrillar disarray, whereas the enlarged cardiomyocyte phenotype is a direct consequence of increased ERK5 signaling, a pathway not previously known to be involved in NS. RNA-sequencing reveals genes with abnormal expression in RAF1 mutant iCMs and identifies subsets of genes dysregulated by aberrant MEK1/2 or ERK5 pathways that could contribute to the NS-associated HCM.

CONCLUSIONS:

Taken together, our study identifies the molecular mechanisms by which NS RAF1 mutations cause HCM and reveals downstream effectors that could serve as therapeutic targets for treatment of NS, and perhaps other, more common, congenital HCM disorders as well.

KEYWORDS:

CRISPR; Induced pluripotent stem cells; Noonan Syndrome; disease modeling; genome editing

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