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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.

Original publication

DOI

10.1016/j.ajhg.2013.05.027

Type

Journal article

Journal

Am J Hum Genet

Publication Date

08/08/2013

Volume

93

Pages

197 - 210

Keywords

Age of Onset, Aging, Premature, Asian Continental Ancestry Group, Base Sequence, Brain, Child, Child, Preschool, Chromosomes, Human, Pair 2, Exons, Female, Genetic Predisposition to Disease, Humans, Language Development Disorders, Leukoencephalopathies, Magnetic Resonance Imaging, Male, Molecular Sequence Data, Pedigree, Sequence Analysis, DNA, Sequence Deletion, Tetraspanins