OBJECTIVEDuchenne muscular dystrophy (DMD) is an X-linked recessive disease caused by dystrophin gene mutations; 55%-65% of these pathogenic mutations are large deletion and duplication mutations that can be detected by multiplexed polymerase chain reaction. However, finding the remaining micro-mutations (substitutions, deletions or insertions of one or several nucleotides) cannot be achieved in this way. The aim of the present study was to detect mutations of the dystrophin gene in individuals with Duchenne muscular dystrophy (DMD) by denaturing high-performance liquid chromatography (DHPLC) and to establish a rapid and sensitive screening platform for micro-mutations leading to DMD.

METHODSTwenty patients negative for large deletions in the dystrophin gene by multiplex PCR were selected for further screening by DHPLC and 20 normal male without DMD family history as the control cohort. Dystrophin exons and their flanking sequences were individually amplified by genomic PCR and the amplicons showing abnormal DHPLC profile were directly sequenced to identify the position and the type of the mutations.

RESULTSAfter screening 68 exons covering the two deletion hotspots and 3'UTR region, four pathogenic mutations, including c.6808_6811del TTAA, c.4959_4960insA, c.8656C > T and c.8608C > T, were found in four DMD patients. Moreover, c.6808_6811del TTAA, c.4959_4960ins and c.8656C > T have not been reported previously. The first two frameshift mutations were predicted to produce premature stop codons, p.Leu2270MetfsX9 and p.Ser1654LysfsX5, respectively. The remaining two were nonsense mutations, leading to p.R2886X and p.R2870X, respectively.

CONCLUSIONThree novel and one recurrent dystrophin mutations have been identified in Chinese DMD patients. This study has demonstrated that DHPLC is an effective screening method for micro-mutation associated with DMD.