Two Novel Mutations Of DSRAD Gene In Chinese Families With Dyschromatosis Symmetrica Hereditaria

SUMMARYBackground Dyschromatosis symmetrica hereditaria (DSH) is a rare autosomal dominantcutaneous disorder characterized by a mixture of hyperpigmented and hypopigmented macules of various sizes on the limbs. Genetic studies have identified mutations in the DSRAD gene, encoding double-stranded RNA-specific adenosine deaminase, to be responsible for this disorder. In this study, we identified a novel mutation of DSRAD gene in a Chinese family with DSH.Objective To identify DSRAD mutations in three Chinese families with Dyschromatosis symmetrica hereditaria and to obtain insight into the pathogenic mechanism of heterozygous ADAR mutations.Methods Peripheral blood samples were taken from all the available affected and unaffected individuals. Genomic DNAs were extracted from the blood samples using a blood kit. In addition, genomic DNA samples were extracted from 100 unrelated healthy volunteers as controls to exclude the polymorphisms in the ADAR gene. The primers that flanked all 15 coding exons and intron-exon boundaries of the ADAR gene were designed using the web-based version of the Primer 3.0 program (http://www.genome.wi.mit.edu/ cgi-bin /primer/ primer3_www.cgi). All exons of the ADAR gene were amplified by PCR. PCR was performed in 20-μl reactionvolume containing 25 ng of genomic DNA,0.3 mM dNTPs,0.3μM of each primer,3.0 mM MgCl2 and 0.1 U of Taq DNA polymerase. The PCR conditions were: Taq activation at 94℃for 5 min, followed by 35 cycles consisting of denaturation at 94℃for 1 min, annealing at 56℃for 1 min, and extension at 72℃forl min, and the final extension was 72℃for 10 min. After the amplification, the products were purified on a 1.5% agarose gel. We directly sequenced ADAR gene automated sequencer ((Eppendorf, Gemony)). Sequence comparisons and analysis were performed using Phred-Phrap-Consed program, version 12.0. We describe amino acid position in ADAR according to ADAR GenBank sequence:NM₀01111.Results Three mutations were identified, including two missense Mutations (p.Y587C, p.G1207V) respectively in family A and C, one deletation mutations (c.2433-2434delAG) in family B. No same mutations were found in unaffected individuals in the families and the controls.Conclusion (1) Two novel and one known DSRAD mutations were found in three Chinese families with DSH. These mutations may impair DSRAD protein funtion, and as a consequence, cause skin dyschromatosis. (2) We summarized a total of 90 mutations in the DSRAD gene with DSH by pervious reports but failed to find a clear correlation between genoytpes and phenotypes.