Browsing by Author "Dawod, Phepy Gamal Amvar"

Background: Mitochondriopathies (MCPs) are considered as diverse group of genetically caused diseases due to deficiencies of the energy production in mitochondria. MCPs can be expressed in many tissues, especially those with higher metabolic demands so they affect most commonly nervous system and muscles. MCPs are characterized by clinical heterogeneity presented by varioaus clinical phenotypes, occur at any age and.could be mild or severe. Besides nervous system and muscles, eye, heart, liver, kidney, bone marrow and other organs could be involved. The main cause of MCPs are genetic changes but interaction with environmental factors plays a role also. Mitochondrial function is controlled by genes located in both nuclear and mitochondrial genome. Mitochondrial genome is represented by maternally inherited mitochondrial DNA (mtDNA), which is considered as a genetic hotspot for MCPs. Molecules of mtDNA show 10–20 times higher mutational rate compared to nuclear genetic material, and could be affected by point mutations, larger deletions or even deplecion, all leading to MCPs. Estimated prevalence of MCPs is 1 in 8.000 to 20.000. Some examples of the disorders caused by pathogenic mtDNA mutations are: Leber hereditary optic neuropathy (LHON), mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS), maternally inherited Leigh syndrome (LS), neuropathy, ataxia and retinitis pigmentosa (NARP), myoclonic epilepsy with ragged-red fibers (MERRF), etc. Genetics background of the pathogenic mtDNA mutations, represented by secondary mutations and mitochondrial haplogroups, affects penetrance and expressivitiy of MCPs. Geographic and/or ethnic specificity of this background emphasizes its role. Aim: The main aim of thic study was determination and characterisation of primary and secondary mutations of mtDNA in patients clinically diagnosed with MCPs. The majority of cases had LHON, but MELAS and other mitochondriopathies were included also. It was planned to detect the well-known LHON mutations m.3460G>A, m.11778G>A, and m.14484T>C, major MELAS mutation m.3243A>G and other mutations specific for MCPs in Serbian patients. Another objective was establishement of the specific genetic background with determination of mtDNA haplogroups of the respondents and construction of the corresponding phylogenetic tree. Finally, the aim was correlation between genotype and phenotype in MCPs patients. Material and methods: This study included total number of eleven unrelated Serbian subjects – probands diagnosed with MCPs and four their asymptomatic relatives. Probands were diagnosed in the Clinic for Neurology and Psychiatry for Children and Youth and Clinic of Neurology, Clinical Centre of Serbia, Belgrade. In all respondents full clinical examination was performed. Demographic data, habits and risk factors, past personal and familial history were evaluated. Family history for maternal relatives was clarified in detail. All molecular genetic analyses of mtDNA were performed in the Laboratory for genetic and molecular diagnostics of neurological diseases at the Clinic for Neurology, Clinical Centre of Serbia. The detection of mtDNA mutations was performed by direct Sanger sequencing of whole mitochondrial genome. Revised Cambridge Reference Sequence of human mtDNA was used for comparision. Prediction of mtDNA mutations‘ pathogenicity was done by in silico analysis using available softwares. MITOMASTER analysis was used for the determination of haplogroups and characterization of pathogenic variants. The phylogenetic tree was constructed according to mtDNA tree Build 17 nomenclature...