ABSTRACT
Background Leber hereditary optic neuropathy (LHON)is a mitochondrial DNA (mtDNA)hereditary disease,so it is significant to understand the influence of DNA mutation on the occurrence of LHON.Objective This survey was to evaluate the role of mtDNA mutation in the development of LHON.Methods This survey study was approved by the Ethic Committee of Wuhan General Hospital of Guangzhou Military Command and written informed consent was obtained from each subject before the relative medial examination.Seventy-two matrilineal relatives from a family with LHON were collected for a pedigree analysis and mutation screening.Regular eye examination was performed on 11 patients,13 mutant gene carriers and 49 individuals with normal phenotype,and the degree of visual damage was graded as follows: ＞0.3 was normal,0.1-0.3 was mild damage,＜0.05-0.1 was moderate damage,＜0.02-0.05 was severe damage and ＜0.01 was very severe damage.Clinical characteristics of LHON was evaluated.The periphery blood sample of 2-4 ml was collected from individuals to separate the mononuclear cells,and the mtDNA was extracted by modified high salt method.MtDNA was amplified by PCR and the mutation loci was sequenced.Results PCR amplification product sequencing of mutant gene showed that both G11778A and T14502C mutations were detected in 24 of 72 matrilineal relatives,but only 11 of 24 carriers developed LHON.No abnormal clinical findings were seen in the 13 carriers,showing a less 50％ penetrance in this family.There was no G11778A or/and T14502C mutation in the normal phenotype individuals of this family.The onset age for vision impairment in 11 affected matrilineal relatives varied from 8 to 50 years old,with the mean age of 24.36 years old,showing a significantly lower age than that of the 13 carriers (5-72 years old,mean 40.38 years old) (t =2.102,P=0.049).Conclusions This study suggests that the Gl1778A and T14502C mutation in mitochondrial DNA is one of causes in the development of LHON.The primary G11778A mutation together with T14502C mutation in mtDNA is a factor for the occurrence of LHON,hut it is not sufficient to the development of LHON.An effective “second hit” process will play an inducing role for LHON.