Abstract: To study the mitochondrial deletion DNAs of skeletal muscle from patients with chronic progressive external ophthalmoplegia(CPEO) and KearnsSayre syndrome. Methods: DNA samples extracted from skeletal muscles of 11 patients with CPEO and KearnsSayre syndrome were digested with the restriction endonuclease PvuⅡ. DNA fragments were separated by standard protocols of an agarose gel electrophoresis. The DNAs in the agarose gel then were transfered to positively charged nylon membrane by capillary transfer. Total mitochondrial DNA was extracted from normal people′s blood as probes，which were labeled with digoxigenindUTP. The positively charged nylon membranes were studied by prehybridization, hybridization, posthybridization washes, and immunological detection. Results: One normal and one abnormal bands, corresponding to single mitochondrial DNA deletion were presented in 7 patients. The proportion of deleted fragments ranged from 50％～75％. The deletions ranged in size from 4.5～5.5 kb. Conclusion: We found a high frequency of mitochondrial DNA deletions in Chinese patients with CPEO and KSS. Thus, the mitochondrial DNA deletion is considered to be closely related with CPEO and KSS.

Key words: Chronic progressive external ophthalmoplegia, Mitochondrial myopathy, KearnsSayre syndrome, Mitochondrial DNA, Mutation analysis