Human Mitochondrial Diseases and What Birds Can Tell Us About Them

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by Chris Comish |

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Australian scientists from Deakin University and the University of New South Wales Australia found a rare genetic mutation in wild starlings that could help them understand mitochondrial disease in humans.

The finding may also help shed light on how human populations respond and adapt to changes in the environment. The report, Selection on mitochondrial variants occurs between and within individuals in an expanding invasion, appeared in the journal Molecular Biology and Evolution.

Mitochondria are the cell’s power supply, generating energy in the form of adenosine triphosphate (ATP). Diseases that affect mitochondria can lead to a variety of problems. Mitochondrial diseases are inherited or chronic illnesses, and they can occur either at birth or may develop later, and are usually linked to development and cognition deficits. This type of disease may cause poor growth, lack of coordination, weakness, pain and seizures.

Mitochondrial disorders currently have no cure. It is estimated that about 1 in 2,000 people suffers from a mitochondrial disorder.

Led by Deakin University scientist Dr. Lee Rollins and Professor Bill Sherwin at UNSW, along with the Department of Agriculture and Food in Western Australia, the team analyzed the DNA of 279 starlings in a bird population in the southeast part of Western Australia.

The investigators found a new mitochondrial genome sequence, known as haplotype H, in the analyzed starlings. What made the finding particularly new is that this genetic trait is not found in starlings living in other parts of Australia. The scientists believe that an invasive starling population may account for the genetic change. Interestingly, over the five years in which the researchers studied the birds, the mutation increased rapidly, from 17 percent of the birds at the beginning of the study to 47 percent by the end of the study — nearly tripling the population.

“Our findings also have important implications for mitochondrial diseases in humans, because this research significantly advances our understanding of how mitochondrial DNA mutations affect individuals and populations, and provides a potential mechanism to explain how different genetic variants may affect health,” Rollins said in a UNSW news release.

The mutation found might actually improve the function of cells. “We also showed haplotype H was associated with a reduction in the number of copies of the mitochondrial DNA in cells, which might indicate that mitochondria in those cells are more efficient,” Sherwin said.

“Biological phenomena are often like the emperor’s new clothes: Everybody knows they should be there, but no one can see them,” Sherwin said. “We have found evidence of a seldom-seen but often-discussed phenomenon providing the first demonstration of rapid evolutionary selection on the mitochondrial genome within individuals in the wild, as a result of an invasive species moving into new territory.”

According to the team, a similar phenomenon could explain the rapid increase in the prevalence of mitochondrial diseases in specific human populations.