Researchers using an innovative approach have pinpointed two locations on the human genome that might hold the key to the timing of Huntington’s disease (HD).
The findings could help researchers develop therapies that affect the onset of Huntington’s.
The study was published in the journal Cell and included input from a multi-institutional team.
Researchers analyzed samples from more than 4,000 Huntington’s patients and found that variants on two specific chromosomes were more common in patients that showed movement disorders at atypical times.
These findings imply that the genetic variant locations on those chromosomes have something to do with the timing of Huntington’s onset.
“In our circumstance, we already know the genetic variation that accounts for all of the risk of developing HD … so we were instead looking for genetic variants elsewhere in the genome that modified the age at which the disease appears,” said corresponding author James Gusella, Ph.D., director of the Center for Human Genetic Research at Massachusetts General Hospital. “That means that we were looking for variants that may not themselves have any discernible impact on an individual unless that person also has the HD mutation. “
Gusella is a professor at the Harvard Medical School and has been publishing research on Huntington’s for decades.
An Uncommon but Devastating Disease
Huntington’s disease is a neurodegenerative disorder that has no cure.
The number of people living with Huntington’s is relatively small. The Australian Huntington’s Disease Association estimates that between five and seven people per 100,000 in Western countries are affected by HD.
So, researchers were at first uncertain whether the sample size would be enough to identify genetic modifiers.
“We were pleasantly surprised when the first clue to a genetic variant that influenced onset came from studying less than 2,000 HD subjects, which occurred because the effect size of the genetic modifier was much greater than is typically seen in complex disease risk studies,” Gusella said.
The method of this study is part of what contributed to its success.
For most disease studies, researchers tend to develop genetic types in models like cell cultures, mice, and fruit flies. But that model is just that — a model of something that resembles the effect of the disease but isn’t exactly the same.
“A fundamental weakness inherent in this approach is that one makes assumptions concerning the relevance of the phenotypes and the mechanisms underlying them to the actual disease process going on in a human patient,” Gusella said.
In this study, by using actual human data, researchers were able to shed light on what could be an actual human solution.
Good News for Those Suffering
For patients living with Huntington’s and families with a history of the disease, the data in this study is good news because it indicates that there could be treatments in the future that influence onset, before symptoms appear.
“Our data demonstrates that it is possible to influence the rate of HD pathogenesis prior to the emergence of the disease, so it points the way in the future to targeting treatments before onset of symptoms rather than exclusively after the disease has made its appearance,” Gusella said.
Researchers can’t point directly at new treatments or give a timeline, but these genetic variants indicate that there is hope for therapeutic development.
“These targets already have been shown to work in humans, as that is how they were discovered,” Gusella said.
The next step is to look at the specific DNA sequence variants and define what gene is having the effect, and what biological process the gene works with. After that, researchers could develop pharmaceutical interventions that target the specific process.
This type of strategy — looking at genetic variant locations — could also be used in the study of other disorders, Gusella said.
The study of Alzheimer’s and Parkinson’s diseases, as well as other late-onset neurodegenerative disorders, could benefit from this type of approach.