De Novo Variants in the ATPase Module of MORC2 Cause a Neurodevelopmental Disorder with Growth Retardation and Variable Craniofacial Dysmorphism

Am J Hum Genet. 2020 Aug 6;107(2):352-363. doi: 10.1016/j.ajhg.2020.06.013. Epub 2020 Jul 20.

Abstract

MORC2 encodes an ATPase that plays a role in chromatin remodeling, DNA repair, and transcriptional regulation. Heterozygous variants in MORC2 have been reported in individuals with autosomal-dominant Charcot-Marie-Tooth disease type 2Z and spinal muscular atrophy, and the onset of symptoms ranges from infancy to the second decade of life. Here, we present a cohort of 20 individuals referred for exome sequencing who harbor pathogenic variants in the ATPase module of MORC2. Individuals presented with a similar phenotype consisting of developmental delay, intellectual disability, growth retardation, microcephaly, and variable craniofacial dysmorphism. Weakness, hyporeflexia, and electrophysiologic abnormalities suggestive of neuropathy were frequently observed but were not the predominant feature. Five of 18 individuals for whom brain imaging was available had lesions reminiscent of those observed in Leigh syndrome, and five of six individuals who had dilated eye exams had retinal pigmentary abnormalities. Functional assays revealed that these MORC2 variants result in hyperactivation of epigenetic silencing by the HUSH complex, supporting their pathogenicity. The described set of morphological, growth, developmental, and neurological findings and medical concerns expands the spectrum of genetic disorders resulting from pathogenic variants in MORC2.

Keywords: CMT2Z; Leigh-like disease; MORC2; developmental delay; intellectual disability; microcephaly.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adenosine Triphosphatases / genetics*
  • Adolescent
  • Adult
  • Child
  • Child, Preschool
  • Craniofacial Abnormalities / genetics*
  • Female
  • Genetic Diseases, Inborn / genetics
  • Growth Disorders / genetics*
  • Heterozygote
  • Humans
  • Infant
  • Intellectual Disability / genetics
  • Male
  • Microcephaly / genetics
  • Middle Aged
  • Mutation / genetics*
  • Neurodevelopmental Disorders / genetics*
  • Phenotype
  • Transcription Factors / genetics*
  • Young Adult

Substances

  • MORC2 protein, human
  • Transcription Factors
  • Adenosine Triphosphatases