First indication that Parkinson’s disease can be caused by a defect in a protein

The findings of Finnish scientists with their multinational collaborators shed light to the mechanisms of Parkinson’s disease and early menopause.

Parkinson’s disease affects about 2% of the general population. It is caused by death of such nerve cells that utilize dopamine in their function, located in the brain nucleus called substantia nigra, black matter. The degeneration of these cells leads to for example slow movements, and rigidity. The disease is multifactorial, meaning that it can be the end result of genetic factors, environmental factors, or both.

The Finnish research group FinMIT led by Docent Anu Suomalainen-Wartiovaara studies the energy metabolism of the cell, which happens in the cellular powerplants, the mitochondria. These organelles contain their own DNA, the mitochondrial DNA. Mitochondrial DNA is replicated and repaired by a specific protein, polymerase gamma. If this protein is defective, mitochondrial DNA accumulates mutations, which disturbs the energy production and mitochondrial function.

The scientists noted that those patients, who had a polymerase gamma gene defect, also had parkinsonism, as well as muscle and periferal nerve degeneration. In addition, female patients had an early menopause, often before the age of 35 years.

Previously, mitochondrial dysfunction has been suggested to participate in mechanisms leading to Parkinson’s disease. However, the findings of the Finnish researchers are the first indication that parkinsonism can be caused by a defect in a protein of mtDNA quality control. This finding will direct the research of Parkinson’s disease to mitochondrial function and energy metabolism. In addition, studies solving the mechanism of early menopause in these patients will give new insights to the basic ovarial function.

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