TM4SF20 Ancestral Deletion and Susceptibility to a Pediatric Disorder of Early Language Delay and Cerebral White Matter Hyperintensities

Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA.
The American Journal of Human Genetics (Impact Factor: 10.93). 06/2013; 93(2). DOI: 10.1016/j.ajhg.2013.05.027
Source: PubMed


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.

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Available from: Sau Wai Cheung, Mar 26, 2014
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    • "Non-European populations carry a number of unique genetic variants not found in Europeans, some of which might contribute to risk of language-related problems. A recent example is the report of a deletion in TM4SF20 in southeast Asian populations implicated in language delay and cerebral white matter hyperintensities, probably via production of a toxic protein (OMIM 615432) (Wiszniewski et al. 2013). Second, languages are diverse in their phonology and syntax (Evans and Levinson 2009), and also in their orthographic systems, which leads to different manifestations of disorders such as SLI and dyslexia (Leonard 2014; Richlan 2014). "
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