A rare genetic variant causing lower levels of vitamin D has been linked to multiple sclerosis (MS), according to scientists.
Mutations in the gene, CYP27B1, were identified by sequencing the genomes of 43 people from families where four or more members had MS. The team then examined the gene in 3,000 families of unaffected parents who had a child with MS. They discovered that all of the 35 parents who had one mutated copy of the gene had passed this variation onto their children.
'If inheriting the CYP27B1 gene variant was unrelated to MS, there would be a 50/50 chance of the child inheriting the variant from their parent', explained senior author Professor George Ebers from the University of Oxford. 'All 35 children inheriting the variant is like flipping a coin 35 times and getting 35 heads, entailing odds of 32 billion to one against'.
However, as parents with one copy of the gene did not always have MS, there must be other factors at play.
'Current opinion suggests that a combination of genetic predisposition, environmental factors such as exposure to sunlight and possibly some sort of trigger, such as a viral infection, interact in some way to start the development of MS', Paul Comer from the charity MS Trust told the BBC. 'This is another step towards finding ways to reduce the risk of developing MS, but it is likely to be some years yet before we can gauge the significance of vitamin D deficiency to MS'.
Norweigan researchers also found that those with two copies of this mutation had both MS and rickets, a disease caused by a vitamin D deficiency.
'Large-scale studies of vitamin D supplements for preventing multiple sclerosis are now strongly warranted', noted Professor Ebers. 'It would be important particularly in countries like Scotland and the rest of the UK where sunshine levels are low for large parts of the year'.
MS is an inflammatory disease causing degeneration of myelin sheaths on axons in the central nervous system, disrupting the transmission of nervous impulses.
The study, published online in the journal Annals of Neurology, is the result of collaborations between the University of Oxford and scientists from Canada's University of Ottawa, University of British Columbia and McGill University.