Multiple mitochondrial DNA deletions: etiology and morphological, biochemical and molecular changes in skeletal muscle and myoblast culture

• Grant number: 05/05204-7
• Support Opportunities: Regular Research Grants
• Start date: August 01, 2006
• End date: July 31, 2009
• Field of knowledge: Health Sciences - Medicine - Medical Clinics
• Principal Investigator: Cláudia Ferreira da Rosa Sobreira
• Grantee: Cláudia Ferreira da Rosa Sobreira
• Host Institution: Faculdade de Medicina de Ribeirão Preto (FMRP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil

Abstract

We propose the study of the class of mitochondrial diseases associated with the occurrence of multiple mitochondrial DNA (mtDNA) deletions, through the analysis of its causes and the morphological, biochemical and molecular alterations that accompany those diseases. The studies will be performed both in skeletal muscle biopsies and myoblast cultures, aiming at improving our knowledge on mitochondrial physiology and physiopathology of mitochondrial diseases, and at developing new treatment strategies. We will analyze the clinical picture and laboratorial findings in a group of patients with multiple mtDNA deletions followed at the HC-FMRP-USP to classify the patients according to the clinical phenotype. Subsequently, we will analyze the causes responsible for the development of multiple mtDNA deletions by quantifying thymidine phosphorylase activity, and defining the molecular defects at the nuclear DNA by studying the genes POLG1, ANT1, Twinkle and from thymidine phosphorylase, determing the phenotypes associated with each mutation. The morphological alterations will be investigated using histoenzymological and morphometric techniques to analyze the trophic changes in the different fiber types, in comparison to changes observed in other forms of mitochondrial myopathies; to compare the presence and magnitude of myalgia in patients with mitochondrial myopathy versus patients with exclusively type 1 fiber atrophy (fiber type disproportion myopathy). The biochemical consequences will be analyzed by measuring the activities of the respiratory chain enzymes, and correlating the biochemical and clinical findings in each patient. The study will proceed with the analysis of the multiple mtDNA deletions in muscle biopsies as well as in myoblast cultures, to determine whether the pattern of deletions vary in different cells and the influence of environmental factors in the development of such deletions. Then, we will verify the effect of coenzyme Q10 and vitamin C, both potent antioxidant substances, in the behavior of the multiple mtDNA deletions in cell cultures. (AU)