In the largest study to date on multiple sclerosis (MS), researchers from The International Multiple Sclerosis Genetic Consortium have identified 233 sites or loci in the human genome that contribute to the onset of MS.

The study, published in the journal Science, included 47,429 patients with MS and 68,374 healthy individuals. The findings confirm earlier results and offer a new perspective on the molecular events that may lead some individuals to develop MS, according to the researchers. The study found that dysfunction of many different immune cell types, both in the peripheral blood and the brain, contribute to triggering a cascade of events that ultimately leads to brain inflammation and neurodegeneration.

According to the researchers, the study has created a detailed genetic map of MS, identifying 233 regions of the human genome that influence a large number of different immune cells, highlighting the fact that this disease is not caused by a single immune cell type, but a broad dysfunction of the immune system.

Although it was previously known that immune cells found in the blood that comes from bone marrow played a critical role, the current study adds that microglia, the immune cells that live in the human brain, also heavily contribute.

“[T]his study highlights the complexity of the genetic contribution to MS susceptibility by identifying several regions of the genome with multiple genetic variants that play a small role. Further, we report the first ever association of genetic variant in chromosome X with MS, a disease that affects mainly young women. This study more than doubled our knowledge of MS genetics, however our findings suggest that there is more work to be done to fully understand how the human genome is involved in MS,” said first author Nikolaos Patsopoulos, PhD, MD.

The researchers also explained that these found genetic variants are not sufficient to cause MS and instead interact with environmental factors. This makes it more likely that a viral infection or other exposure triggers an autoimmune reaction against the brain and spinal cord.

Although the study increases the understanding into the role of genetics and environment in the development in MS, it does not clarify why some patients with MS have a more severe course than others. Therefore, more research is needed to determine treatment, particularly drug-development efforts, the authors concluded.

Reference
Patsopoulos N, Baranzini S, Santaniello A, et al. Research Article Multiple sclerosis genomic map implicates peripheral immune cells and microglia in susceptibility International Multiple Sclerosis Genetics Consortium. Multiple sclerosis genomic map implicates peripheral immune cells and microglia in susceptibility. Science, 2019 DOI: 10.1126/science.aav7188