If genes alone were involved, mothers would pass the MS-related gene to their sons as often as their daughters, researcher George C. Ebers, MD, of the University of Oxford in the U.K. tells WebMD.
Ebers’ research suggests that the ability of environmental factors to alter gene expression -- a relatively new field of genetic study known as epigenetics -- plays a key role in multiple sclerosis and that this role is gender-specific.
The theory is that environmental influences such as diet, smoking, stress, and even exposure to sunlight can change gene expression and this altered gene expression is passed on for a generation or two.
“The idea that the environment would change genes was once thought to be ridiculous,” Ebers says. “Now it is looking like this is a much bigger influence on disease than we ever imagined.”
The study by Ebers and colleagues included 1,055 families with more than one person with MS. Close to 7,100 genes were tested, including around 2,100 from patients with the disease.
The researchers were looking for MS-specific alterations in the major histocompatibility complex (MHC) gene region.
They found that women with MS were 1.4 times more likely than men with the disease to carry the gene variant linked to disease risk.
A total of 919 women and 302 men had the variant in the MHC region, compared to 626 women and 280 men who did not have it.
The study was published online today, and it also appears in the Jan. 18 issue of Neurology.
Epigenetics is not evolution. Genetic alterations linked to environmental assaults can be passed down for a generation or two, but DNA usually rights itself over time, Ebers says.
“This may explain why we hardly ever see MS in families over more than three generations,” he says.
Earlier studies by Ebers and colleagues suggest that vitamin D deficiency may be the environmental stressor that triggers the MS-linked gene alterations.
Rates of the disease are highest among people living farthest from the equator, and there is widespread speculation that lack of vitamin D due to low sun exposure may explain this.
Other than Ebers’ research team, Orhun Kantarci, MD, of the Mayo Clinic in Rochester, Minn., is one of the few researches studying epigenetics as it relates to multiple sclerosis.
Kantarci calls the new research a potentially important piece of the puzzle to explain the gender difference in MS, but he adds that the research must be replicated.
“This study provides more questions than answers, but it is very interesting,” he says. “We are learning that inheritance isn’t as simple as [Gregor] Mendel described.”