De novo RRAGC mutation activates mTORC1 signaling in syndromic fetal dilated cardiomyopathy

Pamela A. Long, Michael T. Zimmermann, Maengjo Kim, Jared M. Evans, Xiaolei H Xu, Timothy Mark Olson

Research output: Contribution to journalArticle

10 Scopus citations

Abstract

Idiopathic dilated cardiomyopathy (DCM) is a heritable, genetically heterogeneous disorder with variable age-dependent penetrance. We sought to identify the genetic underpinnings of syndromic, sporadic DCM in a newborn female diagnosed in utero. Postnatal evaluation revealed ventricular dilation and systolic dysfunction, bilateral cataracts, and mild facial dysmorphisms. Comprehensive metabolic and genetic testing, including chromosomal microarray, mitochondrial DNA and targeted RASopathy gene sequencing, and clinical whole exome sequencing for known cardiomyopathy genes was non-diagnostic. Following exclusion of asymptomatic DCM in the parents, trio-based whole exome sequencing was carried out on a research basis, filtering for rare, predicted deleterious de novo and recessive variants. An unreported de novo S75Y mutation was discovered in RRAGC, encoding Ras-related GTP binding C, an essential GTPase in nutrient-activated mechanistic target of rapamycin complex 1 (mTORC1) signaling. In silico protein modeling and molecular dynamics simulation predicted the mutation to disrupt ligand interactions and increase the GDP-bound state. Overexpression of RagCS75Y rendered AD293 cells partially insensitive to amino acid deprivation, resulting in increased mTORC1 signaling compared to wild-type RagC. These findings implicate mTORC1 dysregulation through a gain-of-function mutation in RagC as a novel molecular basis for syndromic forms of pediatric heart failure, and expand genotype–phenotype correlation in RASopathy-related syndromes.

Original languageEnglish (US)
Pages (from-to)909-917
Number of pages9
JournalHuman Genetics
Volume135
Issue number8
DOIs
StatePublished - Aug 1 2016

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ASJC Scopus subject areas

  • Genetics(clinical)
  • Genetics

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