Exonic duplication CNV of NDRG1 associated with autosomal-recessive HMSN-Lom/CMT4D

• DOI: 10.1038/gim.2013.155
• Publication Date: 2013-10-17T15:14:33Z
• Authors: Yuji Okamoto; Meryem Tuba Goksu...; Davut Pehlivan; Christine R. Beck; Claudia Gonzaga-J...; Donna M. Muzny; Mehmed M. Atik; Claudia M.B. Carv...; Zeliha Matur; Serife Bayraktar; Philip M. Boone; Kaya Akyuz; Richard A. Gibbs; Esra Battaloglu; Yesim Parman; James R. Lupski
• Keywords: Comparative genomic hybridization; Gene dosage; Breakpoint; Copy number analysis

Copy-number variations as a mutational mechanism contribute significantly to human disease. Approximately one-half of the patients with Charcot-Marie-Tooth (CMT) disease have a 1.4 Mb duplication copy-number variation as the cause of their neuropathy. However, non-CMT1A neuropathy patients rarely have causative copy-number variations, and to date, autosomal-recessive disease has not been associated with copy-number variation as a mutational mechanism.We performed Agilent 8 × 60 K array comparative genomic hybridization on DNA from 12 recessive Turkish families with CMT disease. Additional molecular studies were conducted to detect breakpoint junctions and to evaluate gene expression levels in a family in which we detected an intragenic duplication copy-number variation.We detected an ~6.25 kb homozygous intragenic duplication in NDRG1, a gene known to be causative for recessive HMSNL/CMT4D, in three individuals from a Turkish family with CMT neuropathy. Further studies showed that this intragenic copy-number variation resulted in a homozygous duplication of exons 6-8 that caused decreased mRNA expression of NDRG1.Exon-focused high-resolution array comparative genomic hybridization enables the detection of copy-number variation carrier states in recessive genes, particularly small copy-number variations encompassing or disrupting single genes. In families for whom a molecular diagnosis has not been elucidated by conventional clinical assays, an assessment for copy-number variations in known CMT genes might be considered.