The Study Of Pathology And Gene Mutation In Patients With Mitochondrial Encephalomyopathies

Mitochondria are important and unique cytoplasmic organelles in eukaryotic cells,which are called"power plant". Mitochondria are take part in production of energy required for metabolic processes of a cell in the course of oxidative phosphorylation . They also play an important role in the apoptosis and metabolic pathway. Mitochondria are susceptible cytoplasmic organelles , which can display the injury level of the cell.Double-stranded circular mitochondrial DNA is independent on nuclear DNA,which posses independent DNA replication ,transcription, translation system relatively. The feature of its heredity is non-Mendelian inheritance. unique Structures and replication make mitochondrial DNA has many difference with nuclear gene.The mitochondrial genome ismaternally inherited.Mitochondrial encephalomyopathies are a group of multisystemic disorders that caused by Mitochondrial DNA or nuclear mutations to result in disturbance of mitochondrial Structures and function, which involve central nervous system and muscle mainly.According to clinical manifestation the nosology of mitochondrial encephalomyopathy was introduced.The successful complete sequencing of human mitochondrial DNA by Anderson et al heralded a new era of mitochondrial medicine.People detect that mutations of mtDNA in humans cause many disorders without intermission.Along with the development of molecular biology and Functional Genomics, we get further understand the mitochondrial encephalomyopathies, and research the gene and genetic, which can provide diagnosis method of the disease.Make a further study of pathogenesis of mitochondrial encephalomyopathy, which can guide treatment and prevention. Mitochondria have important role and unique genetic features,so mitochondrial encephalomyopathies have wide variety of clinical presentations with genetically heterogeneous, which make diagnosis of mitochondrial diseases is frequently difficult.Therefore,we make a study of pathology and gene mutation in patients With Mitochondrial Encephalomyopathies, which can provide diagnosis method of the disease. To investigate the heredity characteristics, detect the gene mutations in muscle of asymptomatic family members,which can provide genetic counseling for the probandObjective:(1)To further understand the different clinical manifestations of mitochondrial encephalomyopathies. (2)To investigate the histopathologic findings of patients with Mitochondrial Encephalpmyopathies and mutations of DNA genes,which can provide diagnosis method of the disease.(3)To understand the relation between genotype and phenotypy of the disease, which can help us to forecast prognosis of the patients with any mutation and the possible risk.(4)To investigate the heredity characteristics, detect the gene mutations in muscle of asymptomatic family members,which will allow the identification of individuals who are at risk of developing specific complications.Methods:This study involved eight patients (two MELAS and six Mitochondrial myopathies) from unrelated families. Clinical manifestations was summarized on the basis of the clinical data. Serially sectioned frozen muscle specimens with a battery of histochemical stains were reviewed under light microscope.Total DNA was extracted from muscle specimens or(and) whole blood using alkaline denaturation method. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis with restriction enzyme was performed to confirm these common point mutations, which include mtDNA A3243G, A8344G, T8993G and T8993C.A group of 10 non- Mitochondrial Diseases controls was also involved for this study.In one MELAS family, the A3243G mutationwas observed in blood sample among some family members.Results:The histopathologic findings of ragged red fibers (RRF) on modified Gomori trichrome histochemical stain were reviewed, the frequency of occurrence of RRF larger than 4%.The mtDNA A3243G point mutation was identified in one case with MELAS and one case with mitochondrial myopathy. The mtDNA A8344G point mutation was identified in one case with mitochondrial myopathy. The mtDNA T8993G and T8993C point mutations were not observed in all of the cases. The controls were not harboring any of the mutations .The study of blood samples of some maternal relatives from one MELAS family showed that the brothers of the proband were harboring A3243G mutation ,however ,the identical mutation was not observed in blood sample of their mother. The proportion of mtDNA A3243G was 64.35 %in muscle as well as38.09 % in blood. In the MELAS family with blood cells available,the proportion of mutant mtDNA were 38.09 % ,22.99% and 25.13% from their 3 family members.Conclusion : Diagnosis of mitochondrial diseases is frequently difficult because of the wide variety of clinical presentations with genetically heterogeneous ,it is likely that the histopathologic method and molecular biological study are useful for the confirmation and differentiation of mitochondrial disease. we can detect the gene mutation in muscle of asymptomatic family members,which will allow the identification of individuals who are at risk of developing specific complications,thus improving the prognostic advice that can be given to patients and family members who carry these mutations.