CHARACTERIZATION OF A 5025-BASE-PAIR MITOCHONDRIAL-DNA DELETION IN KEARNS-SAYRE SYNDROME

We characterized a mitochondrial DNA deletion in a patient with Kearns -Sayre syndrome. Southern blot hybridization showed that 86 to 93% of the mitochondrial genome harbored a 5.0 kb deletion. The percentage of affected genomes is higher than in previously described cases. Direct sequencing of the breakpoint region revealed that the deletion extend ed 5025 bp from nt 10050 in the tRNA Gly gene to nt 15076 in the cytoc hrome b gene, thus 30% of the total mitochondrial genome was lost by t his deletion. A pair of extremely short mirror sequences flanking the mitochondrial DNA breakpoints were identified. These flanking sequence s differ from previously published consensus 'hot-spots', known to giv e rise to deletions in human mitochondrial DNA.