A team of scientists appears to have unearthed a previously unknown genetic trigger for Parkinson’s disease—one much more commonly seen in people with recent African ancestry. They found that those who were born with one or two copies of this associated variant were noticeably more likely to develop Parkinson’s. The results highlight the value of conducting genetic research in diverse populations, the authors say.
Parkinson’s is a neurodegenerative condition that progressively worsens people’s motor function and often eventually leads to dementia. It currently affects up to a million Americans and over 8 million people worldwide. In most cases, Parkinson’s is thought to be caused by a complex mix of genetic and environmental factors, such as age and greater exposure to certain pollutants. But there are also known mutations that substantially raise a person’s individual risk, and about 15% of all cases are thought to have a family history of Parkinson’s.
Much of the research looking into the genetic underpinnings of Parkinson’s and other diseases has been done with largely European populations. And while we’ve learned a lot from this research, the relative lack of data on other groups means we could be missing important information. A large team of scientists from the U.S., the UK, and Nigeria decided to work together to help remedy this gap.
The team conducted a genome-wide association study (GWAS)—a type of study that looks for variants statistically linked to diseases or traits in a large group of people. They focused specifically on nearly 200,000 people of African or mixed ancestry, mostly from Nigeria as well as parts of the U.S. About 1,500 individuals in this group were diagnosed with Parkinson’s, while the rest were not.
The researchers ultimately identified a novel variant of the gene that produces β-glucocerebrosidase (GBA1) that seemed to raise people’s risk of Parkinson’s. People who had one copy of the variant were 1.5 times more likely to have Parkinson’s than those who had no copies, and those with two copies were about 3.5 times more likely to develop it, they found. GBA1 is a protein that helps cells recycle other proteins, and several mutations involving this gene have already been linked to Parkinson’s. But this new variant was almost exclusively found in people with African ancestry.
The team’s findings were published last month in The Lancet Neurology.
GWASs are a crucial tool in science, but they have their limitations. Importantly, they can only find correlations between a variant and a disease or trait. So more research will be needed to confirm a causal relationship between this newly discovered mutation and Parkinson’s and to learn how it might be causing the disease. But GWASs are often intended to provide scientists with new clues to track down. And the authors say their research offers a clear example of why it’s so important to include a wide array of people in these studies.
“To effectively treat Parkinson’s and truly any disease, we must study diverse populations to fully understand what the drivers and risk factors are for these disorders,” said study author Andrew B. Singleton, director of the NIH Intramural Center for Alzheimer’s Related Dementias (CARD), in a statement released by the National Institutes of Health. “These results support the idea that the genetic basis for a common disease can differ by ancestry, and understanding these differences may provide new insights into the biology of Parkinson’s disease.”