[Correlation between degree of mitochondrial DNA 1555 mutation and clinical phenotype of nonsyndromic hearing loss].

OBJECTIVE:To study the correlation between the number of mtDNA (mitochondrial DNA) copies containing mtDNA A1555G mutation site and phenotype and further elucidate the molecular genetic basis of phenotype diversity of nonsyndromic hearing loss. METHODS:Real time-amplification refractory mutation system-quantitative PCR was employed to detect the number of mtDNA copies in mild type and mutant type of mtDNA 1555. RESULTS:In the sporadic group, there was no significant correlation between mtDNA A1555G homogeneity mutation copies and phenotype (R = 0.001, P = 0.997) while significant correlation existed between mtDNA A1555G heteroplasmic mutations and phenotype (R = 0.771, P = 0.003). In the familial group there was significant correlation mtDNA 1555 homogeneity mutation copies and phenotype (R = 0.341, P = 0.022) and significant correlation existed between mtDNA 1555 heterogenicity mutation copies and phenotype (R = 0.85, P = 0.015). CONCLUSION:There is significant correlation between the mtDNA A1555G mutation copies and the severity of hearing loss.