Britannica
Sources used in this answer
How does heteroplasmy affect the symptoms of a mitochondrial disorder?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
human genetic disease
Photomicrograph of the BRCA2 tumor suppressor gene on chromosome 13 of the human genome. Inactivation of this growth-regulating gene is associated with a higher risk of developing breast cancer.
Heteroplasmy is a critical factor in the clinical presentation of mitochondrial disorders. It refers to the presence of a mixed population of both normal and mutant mitochondrial DNA within a single cell.123
The severity of symptoms in an individual is largely determined by the proportion of dysfunctional mitochondria present in their tissues. Because mitochondria are randomly distributed to daughter cells during cell division, the ratio of mutant to normal DNA can vary significantly between different cells and tissues.14
Key effects of heteroplasmy on symptoms include:
- Variable Severity: Individuals may exhibit a wide spectrum of symptoms, ranging from appearing completely healthy or mildly affected to being severely compromised.13
- Threshold Effects: A cell may function normally if the number of healthy mitochondria is sufficient to meet energy demands. However, if the percentage of abnormal mitochondria exceeds a certain threshold, the cell and the tissues containing those cells will exhibit impaired function.1
- Tissue-Specific Impact: Symptoms often manifest prominently in tissues with high energy requirements, such as the nervous and muscular systems, as these are most sensitive to mitochondrial dysfunction.4