Researchers have now shown how mitochondrial DNA is synthesized and replicated. The mitochondrion is an important cellular structure that provides energy to the rest of the cell. These new findings, just published in Science, have important implications for studying aging and many types of metabolic disease.
Mitochondria are cellular structures that use oxygen to generate ATP, an important form of energy. The mitochondria originally evolved from bacteria that formed an endosymbiotic relationship with cells. The cells gained ATP while the mitochondria were provided with a safe place to live. Over time, the mitochondria developed into cellular structures and this origin resulted in them retaining some of their original DNA. Mitochondrial DNA is replicated during reproduction and is only inherited from your mother. Until now, researchers weren’t sure how this process worked or if it was even organized.
Researchers from the University of California used fluorescent markers to dye mitochondria, chromosomes, and the endoplasmic reticulum. They were then able to observe the process of mitochondrial division using microscopy. The endoplasmic reticulum, or ER, is a series of tubes found throughout a cell. The structure is responsible for several functions, including protein transport. The researchers found that spots where the ER touched the mitochondria were predictive of chromosome division. The only mitochondrial chromosomes to divide were the ones touching this structure. These were also the only points where the mitochondrion itself would split during reproduction, a process resulting in new copies of mitochondria. It appeared that the ER was providing a cue for the mitochondrion to divide.
The replication of mitochondrial DNA and the division of the structure itself is controlled by the endoplasmic reticulum. Division is highly organized, only occurring in places where the ER touches the mitochondrion. Many neurodegenerative disorders and metabolic diseases are caused by mutations in mitochondrial DNA. Understanding mitochondrial processes allows scientists to further research these types of mutations and how they might arise. The authors hope that these findings will help lead to improved treatments for certain human health problems.
C. Lewis et al. ER-mitochondria contacts couple mtDNA synthesis with mitochondrial division in human cells. Science (2016).