Mitochondria and Mitochondrial Diseases, December 4, 2004

Mitochondria and Mitochondrial Diseases, December 4, 2004

Mitochondria are located in the cytoplasm and exist in all eukaryotic cells. Each cell contains approximately 1 to 2,000 mitochondria. Their primary functions are participating in oxidation and phosphorylation to provide ATP and store energy. Another crucial role is collaborating with chromatin in the nucleus to regulate gene expression. Mitochondrial genes are encoded in mtDNA, while nuclear genes are encoded in NDNA; the former is also called Mendelian genes, the latter nuclear genes; the former is paternal genes, the latter maternal genes. Both types of genes also contain some wild-type and mutant genes. Although mutations and wild-type/mutant genes are related, their small numbers usually do not cause organ or tissue damage or functional abnormalities. However, when the number of wild-type and mutant genes reaches (or exceeds) a certain threshold, related organs and tissues may experience lesions or dysfunction. The most susceptible tissues are the heart, brain, and muscles, with common symptoms including ptosis, cardiomyopathy, proximal muscle disease, sensorineural deafness, diabetes, dementia, and migraine—most frequently seen in children, often inherited maternally. Lactate concentration and phosphokinase are the most important diagnostic tools.