Late onset X-linked CMT: mild form caused by 9-bp in GJB1 gene

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Neuromuscul Disord. 2006 Oct 16

A novel 9-bp insertion in the GJB1 gene causing a mild form of X-

linked CMT with late onset.

Vazza G, Merlini L, Bertolin C, Zortea M, Mostacciuolo ML.

Department of Biology, University of Padova, Italy.

X-linked Charcot-Marie-Tooth disease is the second most common

variant of CMT. CMTX1 is caused by mutations in the GJB1 gene

encoding for connexin 32. We describe an Italian family with an

intermediate CMTX phenotype with late onset. Mutation screening of

the GJB1 gene revealed a 9-bp duplication leading to the insertion

of three aminoacids (Thr-Val-Phe) between the end of the second

extracellular domain and the beginning of the fourth transmembrane

domain. This is the third in-frame insertion in the GJB1 gene

identified so far and, like the previous ones, it consists in the

duplication of the flanking sequence which is repeated in tandem in

the wild-type gene.