A unique 3.5-kb deletion of the mitochondrial genome in Thai patients withKearns-Sayre syndrome

Kearns-Sayre syndrome is one of the neurological diseases caused by a defec t in the energy-producing system of mitochondria. Kearns-Sayre is known to be associated with a deletion in the mitochondrial genome and is usually de tected in muscle biopsies of the patients. In this study, we report the mol ecular lesion of mitochondrial DNA (mtDNA) in four Thai patients admitted t o hospital with encephalomyopathies. The 3.5-kb deletion of mtDNA was detec ted by Southern analysis, mapped by amplification with five primer pairs co vering almost the total mitochondrial genome, and confirmed by PCR primer s hift analysis. The deleted position was localized to nt 10208/13765 or nt 1 0204/13761 spanning the coding area of subunits 3 (ND3), 4L (ND4L), 4 (ND4) , and 5 (ND5) of respiratory chain enzyme complex I and the tRNA genes for histidine, serine, leucine, and arginine. The sequence flanking the deletio n was a 4-bp repeat of TCCC. All four patients have exactly the same 3558-b p mtDNA deletion; this is the only deleted position in their mtDNA but is d ifferent from those reported in the literature. The deletion seems to be fo und only in Thai patients, although they present with different clinical ma nifestations and none of them is not related.