Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.30.2 (endonuclease)
 18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We describe a 15-year-old boy with full-blown mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) and chronic progressive external ophthalmoplegia (CPEO). He presented with visual disturbance, hearing impairment, continuous partial epilepsy on the right aspect of the face, and right hemiparesis since the age of 13. Four months later, he experienced another strokelike episode with continuous partial epilepsy on the left hand. Serial computed tomographic scans revealed bilateral parieto-occipital hypodense lesions with gyral enhancement and an additional low-density lesion in the right frontal area 4 months later, respectively. Results of laboratory examinations disclosed lactic acidosis and mitochondrial myopathy with many ragged-red fibers. To identify the defective gene in mitochondrial DNA, a simple molecular test was performed by using restriction endonuclease Apa I. A transition from A to G was found at nucleotide position 3243 of the tRNA(Leu) gene. Interestingly, the patient also had marked external ophthalmoplegia and ptosis commonly found in patients with CPEO. Therefore, we suggest that ophthalmoplegia also occurs in the MELAS syndrome.
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PMID:Ophthalmologic manifestations in MELAS syndrome. 836 52

Background: Several mutations in mitochondrial DNA (mtDNA) are associated with the syndrome of mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS). The "common" MELAS mutation, A3243G in the tRNA leucine (UUR) gene, affects approximately 80% of cases and is associated with respiratory chain complex I deficiency. Methods and Results: The A3243G mutation creates an ApaI restriction endonuclease site and can be detected by polymerase chain reaction (PCR) amplification of a region of mtDNA containing nt 3243, followed by ApaI digestion and electrophoretic analysis of the resulting fragments. Analysis of mtDNA from a child with complex I deficiency indicated the presence of the mutation homoplasmically in heart, liver, and skeletal muscle. Sequencing revealed only normal tRNA leucine (UUR) sequence, and a novel variant at nt 3426 in the ND1 subunit of complex I, which creates an ApaI site. ApaI digestion results in fragments of similar size to those found in patients with the A3243G mutation. Conclusions: A novel variant at nt 3426 of mtDNA creates an ApaI site and can potentially cause a false-positive result for the presence of the A3243G mutation. Given the highly polymorphic nature of mtDNA, care must be exercised in choosing primers for restriction endonuclease-based diagnostic tests for point mutations, and confirmation of a mutation by an independent method is recommended.
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PMID:A False-Positive Diagnosis for the Common MELAS (A3243G) Mutation Caused by a Novel Variant (A3426G) in the ND1 Gene of Mitochondria DNA. 1008 79