More PD genes to discover?

Epidemiological studies involving islands have a long and proud history; they always provide fascinating reading and food for thought. In the Faroe islands there were no reported cases of Multiple Sclerosis until 1943 when british troops occupied the islands. After this there was an epidemic of 21 cases. This pattern led to researchers hypothesising that british troops introduced asymptomatic infection to the islands which could be linked to the development of MS. The island of Crete has also been noted to have a rate of sporadic Creutzfeldt-jakob disease that is 5 times the expected numbers for a population of that size. More relevant to Parkinson's is the island of Guam where a peculiar condition that has signs of Parkinson's and a variant of motor neurone disease (called amyotrophic lateral sclerosis) is endemic and not found anywhere else in the world. 

Again in the Faroe islands researchers have noticed that there are twice the number of people living with Parkinson's that you would normally expect for a population of that size. Analysis of the patterns of Parkinson's in families in the Faroe islands indicated that there was probably a genetic cause for this increased number of people with Parkinson's, rather than an environmental cause. But it is not caused by any of the genes we currently know are associated with Parkinson's.

The researchers had the bright idea to follow up people who had migrated from the Faroe islands to Denmark. They found that despite living in Denmark the Faroese migrants still had a much higher chance of developing Parkinson's, even when they had lived in Denmark for more than 10 years! This indicates that either; the underlying environmental factor that is driving this relationship takes place at a much younger age. Alternatively, and much more likely, is that genetics is the cause of this increased prevalence of Parkinson's disease. But the genes causing this are yet to be discovered...

Mov Disord. 2019 Apr 9. doi: 10.1002/mds.27692.

What does migration between the faroe islands and denmark tell us about the etiology of Parkinson's disease?

Petersen MS^1,2, Lophaven SN³, Lynge E⁴, Weihe P^1,2.