Viking invasions hundreds of years ago may be responsible for the spread of a genetic mutation associated with ALS.
ALS, or amyotrophic lateral sclerosis, causes progressive paralysis and ultimately death. Known commonly as Lou Gehrig’s disease—after the famous baseball player afflicted with the condition—ALS is one of medicine’s most mysterious conditions.
Why did the mutation spread so effectively? After all, it could kill its carriers—hardly a case of survival of the fittest.
More than 150 years after its symptoms were first described, there is still no known cure for ALS.
The Viking connection
Dr. Baloh and his team in the Baloh Laboratory focused their research on the most common genetic mutation found in ALS patients—the C9orf72 gene.
The mutation is found in about 10% of patients with ALS and is also associated with frontotemporal lobar degeneration, a type of dementia that can accompany ALS.
The C9orf72 mutation seems to have originated in Northern Europe about 1,500 years ago, according to a genomic study by US and British researchers.
Likely carried across Europe by Viking invaders from the 8th to 11th centuries, the mutation has since traveled all over the globe. Today, the C9orf72 mutation remains concentrated primarily in those with European ancestry.
“Why did the mutation spread so effectively?” Dr. Baloh wondered. After all, it could kill its carriers—hardly a case of survival of the fittest.
Changes to the immune system that are linked to ALS in the long term may be beneficial in the short term.
He suspects the answer is that the mutation is a double-edged sword: It impacts the immune system but only slowly damages the nerve cells in the brain and spinal cord that control muscles.
Most Vikings had an average lifespan of 40-45 years and likely did not live long enough to experience that damage. The average age of diagnosis for ALS patients is 55 years.
Mice without the C9orf72 gene appeared to have normal brain and muscle function during their 2 year lifespans. But the mice had enlarged lymph nodes and spleens.
Dr. Baloh discovered that the enlarged lymph nodes were caused by abnormalities in the immune system, which may help explain another recent study that suggested autoimmune disorders are more frequent in ALS patients.
These changes to the immune system that are linked to ALS in the long term may be beneficial in the short term, possibly helping fight certain infections, which could have been valuable to the short-lived Vikings, Dr. Baloh speculates.
Going forward, Dr. Baloh plans to explore the mechanisms of these immune system changes and what they may mean for developing ALS treatments.
“I hope our research will impact ALS by bringing innovative therapies into the clinic for the first time, including stem cell and gene-therapy trials,” says Dr. Baloh.