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We have found out a new PI restriction site in a patient with mitochondria1 encephalomyopathy, Mo st human mitcchondri sI DNA (mtDNA) has a single Pvu I restriction site at position 2 650 of mi rochondria] genome. Therefore, PvL1 I is the main restr iction en—zyme generally used to 1ineari sed mitochondrial DNA. The index patient js a female of Chinese with mito—ehond rial encephalomyopathy. T0taI eellular DNA iso lated from the patient s skeletal muscle was digested with Pvu I and subjected to Southern analysis with a tota1 mtDNA probe. Instead of the norlT1a1 16.5 kb 1in—earized mtDNA, a mtDNA fragment of approximately 8.3 kh was observe d. Restdef ion mapping of the same DNA digested by Hind 11 is norn-I compared with contro1. These resuhs suggest a secondPvu Ⅱ site con exi st io the position 10 900 (2 650 plus 8 300) of the citeular mitoehondrial genome. The patient is homop [as—mie forthe ext raPvu I site. DNA from thea realikely to harbor the restriction site was amplified by PCR usi ng primer s corresponding to p o sitions 10 800—11 060. Sequenci ng of ampl 璃 ed DNA demaonstrated a T to

C transition at p o sition 10 909, resulting i na sequence change from TAGCTG 幻 CAGCTG and cre sti ng a Pvu Ⅱ restriction site. The hase ch ange is predicte d to b e conservative, as both codon m(norma1) a nd eodon TTC (patient) encode phenylalanine in the NADH de—hydrogenase—uhiquinone 0xidoreductase subunit Ⅳ se_ quenee. These date clearly demonstrate th at the extra Pvu Ⅱ restriction site observe d in 山 e patient doesntt repres ent a disease—related mutation. mtDNA has a high mutation rate due to ineff icient …