A new syndrome characterized by mental retardation, epilepsy, and facial and digital abnormalities is associated with a small deletion on chromosome 15, according to a study published online in Nature Genetics. This microdeletion accounts for 1 in 330 cases of mental retardation, and is present in 1 in 40,000 individuals in the general population.
Evan Eichler and colleagues used a high-resolution method to scan the genomes of 757 individuals with mental retardation and other anomalies, in search of chromosomal deletions and duplications. They identified an identical 1.5 million base pair deletion on chromosome 15, spanning 6 genes, in 2 unrelated individuals. The same microdeletion was later found in an additional seven individuals. One of the six deleted genes is CHRNA7, which encodes a synaptic ion channel protein that mediates neuronal signaling, and has been suggested previously to be a susceptibility factor for certain forms of epilepsy.
The authors suggest that the increasing use of high-resolution methods to identify 'submicroscopic' deletions will lead to the identification of additional syndromes with a common genetic origin.
Evan Eichler (University of Washington School of Medicine, Seattle, WA, USA)
Abstract available online.
(C) Nature Genetics press release.
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