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New Gene Variant Protects Against Parkinsonís

In a study spanning 15 countries and five continents, researchers have identified variants of a gene linked to Parkinson’s disease (PD) that can increase a person’s chance of developing Parkinson’s or, conversely, protect that individual from the disease. The results appear in the August 31 issue of Lancet Neurology.

In 2004, researchers first identified mutations in the leucine-rich repeat kinase 2 (LRRK2) gene that can cause PD or increase a person’s chances of developing the disease. These mutations are more common in people of Jewish or North African Berber ancestry. Since then, scientists have located dozens of other variations in LRRK2, but they did not know which variants actually influence PD risk. Moreover, the prevalence of different LRRK2 variants varies among ethnic groups, making the job of tracking down PD-linked variants all the more difficult.

To better understand how LRRK2 variants affect risk of Parkinson’s, an international team of researchers led by Owen Ross, Ph.D., at the Mayo Clinic in Jacksonville, FL, studied LRRK2 variants in 8,611 people with PD and 6,929 healthy controls. These individuals represented 15 countries and three ethnic origins: white, Asian, and Arab-Berber. The researchers studied the LRRK2 gene – specifically the DNA sequencing of its protein-coding region – by using blood samples from both people with Parkinson’s and controls.

Results

  • Scientists identified LRRK2 variants that double Parkinson’s risk in whites and Asians;
  • They found another variant that cut the risk of developing Parkinson’s by nearly 20 percent;
  • Because the Arab-Berber study group was smaller than the other two ethnic groups, the researchers could not conclusively link LRRK2 variants with PD risk or protection in this population.

What Does It Mean?

Mutations in the gene LRRK2 have already been identified as an important genetic cause of PD. However, only a small amount of people with Parkinson’s carry these mutations. This study, which is one of the largest to date on the genetics of Parkinson’s, provides valuable new information on the connection between LRRK2 and PD. Small common changes in the gene may be associated with small increase in risk for Parkinson’s, and there may actually be a protective variant that is associated with lower risk of the disease. Yet because the LRRK2 variants have relatively small effects on disease risk, and many of the variants occur in only a small percentage of the population, it is unlikely that doctors will be able to use this information to help diagnose or predict Parkinson’s in people.

Knowledge of LRRK2 variants could, however, help researchers design new therapies for Parkinson’s. LRRK2, one of the most commonly mutated genes in PD, encodes an enzyme that can trigger neuron death, possibly contributing to PD symptoms. If researchers understand how or if newly-discovered protective variant blocks this process, they doctors might someday be able to design drugs that have similar effects.

Reference: Ross, O. A., Soto-Ortolaza, A. I., Heckman, M. G., Aasly, J. O., Abahuni, N., Annesi, G., Bacon, J. A., et al. (2011). Association of LRRK2 exonic variants with susceptibility to Parkinson's disease: a case-control study. Lancet Neurology. Early Online Publication, 31 August 2011. doi:10.1016/S1474-4422(11)70175-2

Source Date: Sep 14 2011