TM4SF20 ancestral deletion and susceptibility to a pediatric disorder of early language delay and cerebral white matter hyperintensities

Am J Hum Genet. 2013 Aug 8;93(2):197-210. doi: 10.1016/j.ajhg.2013.05.027. Epub 2013 Jun 27.

Abstract

White matter hyperintensities (WMHs) of the brain are important markers of aging and small-vessel disease. WMHs are rare in healthy children and, when observed, often occur with comorbid neuroinflammatory or vasculitic processes. Here, we describe a complex 4 kb deletion in 2q36.3 that segregates with early childhood communication disorders and WMH in 15 unrelated families predominantly from Southeast Asia. The premature brain aging phenotype with punctate and multifocal WMHs was observed in ~70% of young carrier parents who underwent brain MRI. The complex deletion removes the penultimate exon 3 of TM4SF20, a gene encoding a transmembrane protein of unknown function. Minigene analysis showed that the resultant net loss of an exon introduces a premature stop codon, which, in turn, leads to the generation of a stable protein that fails to target to the plasma membrane and accumulates in the cytoplasm. Finally, we report this deletion to be enriched in individuals of Vietnamese Kinh descent, with an allele frequency of about 1%, embedded in an ancestral haplotype. Our data point to a constellation of early language delay and WMH phenotypes, driven by a likely toxic mechanism of TM4SF20 truncation, and highlight the importance of understanding and managing population-specific low-frequency pathogenic alleles.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Age of Onset
  • Aging, Premature / complications
  • Aging, Premature / ethnology
  • Aging, Premature / genetics*
  • Aging, Premature / pathology
  • Asian People
  • Base Sequence*
  • Brain / metabolism
  • Brain / pathology
  • Child
  • Child, Preschool
  • Chromosomes, Human, Pair 2
  • Exons
  • Female
  • Genetic Predisposition to Disease*
  • Humans
  • Language Development Disorders / complications
  • Language Development Disorders / ethnology
  • Language Development Disorders / genetics*
  • Language Development Disorders / pathology
  • Leukoencephalopathies / complications
  • Leukoencephalopathies / ethnology
  • Leukoencephalopathies / genetics*
  • Leukoencephalopathies / pathology
  • Magnetic Resonance Imaging
  • Male
  • Molecular Sequence Data
  • Pedigree
  • Sequence Analysis, DNA
  • Sequence Deletion*
  • Tetraspanins / genetics*

Substances

  • TM4SF20 protein, human
  • Tetraspanins