Objective: To investigate the proportion of mtDNA mutation in the non-syndromic genetic hearing loss (NSHL) pedigrees and the genetics statistical formulae for maternal inheritance, to study the relationship of mtDNA mutation and inherited deafness, to identify the incidence of the mtDNA mutation in such pedigrees and sporadic patients with Sensorineural hearing loss (SNHL).
Method: Twenty-nine pedigrees with NSHL were collected. Pedigree Investigation was taken. Modal Genetics Analysis. Segregation Analysis were taken. Blood samples were obtained from these pedigrees. DNA was extracted from the isolated leukocytes. The mtDNA 1555G, 7445G, 3243G mutation were examined by multiplex PCR. The sequence of 12SrRNA, tRNA(Leu(UUR)) and tRNA(Ser(UCN)) gene were examined.
Result: There are 12 pedigrees with mtDNA mutation (i.e. 10 with 1555G and 2 with 7445G) examing by multiplex PCR. Modal Genetics Analysis showed that in irregular dominate genetic pedigrees, the incidence of mtDNA mutation is higher than that of regular dominate pedigrees. Segregation Analysis with Screening for mtDNA mutation showed that maternal inherited pedigrees did not have the segregate ratio that the autosomal inheritance had. Sequence analysis confirmed that the 12 pedigrees carried mtDNA mutation, among them 10 pedigrees with 1555G mutation, 2 pedigrees with 7445G mutation, no pedigrees with 3243G.
Conclusion: Maternal inherited pedigrees do not have the segregate ratio of the autosomal inheritance, mtDNA mutation have high incidence in NSHL, mostly are 1555G and 7445G mutation. Screening for mtDNA 7445G mutation combined with 1555G examination is of value to clinical use. Multiplex PCR can diagnose mtDNA multi-mutation quickly and facilely.