Implications of mtDNA in human health and diseases.

The maternally inherited autonomous organelles, mitochondria, are responsible for a myriad of functions within the cell. They may contain more than one copy of DNA and can themselves be present in multiple numbers within a cell. The integrity of the mitochondrial genome is affected by variations in DNA copy number or the presence of mutations. Compromising this integrity has been documented to result in disorders affecting various systems. Focusing on such trends could enhance knowledge essential for developing strategies to manage these disorders. Irregular patterns of mitochondrial DNA (mtDNA) copy number (CN) variation have been identified in various cancers. Reduced mtDNA CN has been associated with neurodegenerative disorders, cardiovascular diseases, and kidney disorders. Mutations in the mitochondrial respiratory chain complex have been linked to cardiomyopathy. High rates of mtDNA deletions have been found in aging patients and subjects with Parkinson's disease. While sperm function appears to deteriorate with increased mtDNA CN, oogenesis involves a significant increase to enable the oocyte to achieve fertilization and further development. Prospective therapies to treat mitochondrial diseases may include approaches that aim to reduce the levels of mutant mtDNA below the disease-causing threshold, such as targeted removal of defective mitochondria. Mutations in mitochondrial DNA contribute to various diseases; some single substitutions appear to disrupt the normalcy of more than one organ, underscoring the importance of mitochondrial genome integrity. The presence of mutations and copy number variations may serve as diagnostic markers and also provide insight into prognosis.