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In Rare Inherited PD, Newly-Identified Gene May Impact Age of Diagnosis

In the past decade researchers have identified more than 20 genes linked to Parkinson’s disease (PD). However, among people with the same exact same LRRK2 mutation, some develop Parkinson’s at different ages, and others do not develop the disease at all. According to a study published online in the Lancet Neurology on September 28, finds that variants in another gene DNM3, might explain this phenomenon.

Most people with Parkinson’s do not have a family history of the disease. In the rare cases when do people inherit Parkinson’s, studying their genes can help us to better understand the disease. Among the rare genes that cause Parkinson’s, the most common is a mutation in the LRRK2 gene called G2019S. But among those with this mutation, some develop Parkinson’s in their 50s and some develop it decades later.

A team of researchers, led by Joanne Trinh, Ph.D. candidate, at the Centre for Applied Neurogenetics-University of British Columbia, wanted to understand why some people develop PD earlier than others. They conducted large-scale genomic analyses on 253 individuals from 41 Arab-Berber families from Algeria, France, Norway and North America. All of the participants carried the LRRK2 G2019S mutation; 150 had Parkinson’s, while the other 103 did not. The team also conducted similar studies in other communities with the LRRK2 mutation.

Results

  • People with PD related to the LRRK2 gene who also had a variation in the DNM3 gene, called the rs2421947 haplotype, experienced an onset of PD a median of 12.5 years earlier than those without that genetic variation.
  • For those with the DNM3 gene variation, the average age of PD onset was 56 years.
  • Only people with the LRRK2 G2019S mutation were studied, therefore it is unknown if those with other PD genetic mutations are similarly impacted.

What Does It Mean?

LRRK2 mutations are among the most common genetic risk for PD worldwide. They are more common among Ashkenazi Jews and North African Berbers, where 15 percent and 40 percent of all people with PD respectively carry a mutation.

However, before scientists can launch clinical trials that might help treat those with the mutation, science must answer these two fundamental questions. First, why most carriers of mutations do not develop PD and second, what affects age at which carriers develop PD?

Understanding why people develop LRRK2-PD at different ages is important. If researchers could pinpoint the genetic mechanisms that lead some people to develop PD earlier than others could help drive the development of new therapies that could slow or even prevent PD among LRRK2 carriers. It is difficult to know the effect of the gene identified by these researchers on people with PD without LRRK2 mutations. Future studies can test if DNM3 is also important in sporadic Parkinson’s (cases of the disease which are not inherited).

Learn More

Do you have additional questions about the genetic underpinning of Parkinson’s disease? Learn more by accessing PDF’s free resources below or try contacting our National HelpLine at (800) 457-6676 or info@pdf.org with any additional questions.

Download Fact Sheet: Genetics and Parkinson’s Disease: What Have We Learned 
Download PDF Medical Committee Statement: Understanding Direct-to-Consumer Genetic Testing: Look Before Leaping 

Reference: Trinh, J., Gustavsson, E. K., Vilariño-Güell, C., Bortnick, S., Latourelle, J., McKenzie, M. B., et al. (2016). DNM3 and genetic modifiers of age of onset in LRRK2 Gly2019Ser parkinsonism: a genome-wide linkage and association study. Lancet Neurology, 15(12), 1248–1256. http://doi.org/10.1016/S1474-4422(16)30203-4

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Source Date: Feb 06 2017