Abstract
Mitochondrial respiratory chain disorders (RCD) are a group of genetically and clinically heterogeneous diseases, caused due to defects of the respiratory chain. This study aimed to investigate the presence of common mtDNA point mutations in tRNALeu (UUR), tRNALys, MT-ATPase 6, MT-ND4, MT-ND1, MT-ND6 genes in eight Egyptian patients suspected to have mtDNA disease and optic atrophy.PCR-RFLP analysis was done for the detection of 3243A>G, 3271T>C, 8344A>G, and 8993T>G/C mtDNA point mutations. DNA direct sequencing was pursued for the detection of 11778G>A, 3460G>A and 14484T>C mtDNA point mutations. No point mutation of 3243A>G, 3271T>C, 8344A>G, and 8993T>G/C was detected in our group of patients. Four mtDNA polymorphisms in MT-ND1 and MT-ND4 genes (11467A>G, 11719G>A, 3348A>G and 3357G>A) were detected in three patients.Mitochondrial disorders are caused by a variety of genetic and racial factors, which differ among populations. The negative results of this study indicate that the chosen mutations might not be specific in Egyptians. Another explanation might be due to the low heteroplasmic levels of the mtDNA mutation. A registry for the different mtDNA mutations in Egyptian patients is highly recommended.
Highlights
Mitochondrial respiratory chain diseases (RCDs) are a heterogeneous group of inherited disorders characterized by impaired energy metabolism due to oxidative phosphorylation (OXPHOS) dysfunction [1,2]
In this study we aimed to investigate the presence of the most common mtDNA point mutations (3243A > G, 3271T > C, 8344A > G, 8993T > G/C, 11778G > A, 3460G > A and 14484T > C) in Egyptian patients who are suspected to have mtDNA diseases and optic atrophy
Neurophysiological investigations: EMG revealed myopathy in all cases; Magnetic resonance imaging (MRI) brain showed cortical atrophy, white matter demyelination and/or basal ganglia degeneration
Summary
Mitochondrial respiratory chain diseases (RCDs) are a heterogeneous group of inherited disorders characterized by impaired energy metabolism due to oxidative phosphorylation (OXPHOS) dysfunction [1,2]. A number of ‘classical’ syndromes have been described that are often, but not always, associated with a particular genotype. They include mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS), myoclonic epilepsy and ragged red fibers (MERRF), maternal inherited Leigh’s syndrome (MILS), neurogenic muscle weakness, ataxia, and retinitis pigmentosa (NARP), Leber’s hereditary optic neuropathy (LHON), and progressive external ophthalomoplegia (PEO). A substantial group of patients, children, do not fulfill the clinical criteria for a particular syndrome and may have symptoms or signs that overlap one or more clinical syndromes [8,9]
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