What are the genetic changes related to multiple sclerosis ?
Although the cause of multiple sclerosis is unknown, variations in dozens of genes are thought to be involved in multiple sclerosis risk. Changes in the HLA-DRB1 gene are the strongest genetic risk factors for developing multiple sclerosis. Other factors associated with an increased risk of developing multiple sclerosis include changes in the IL7R gene and environmental factors, such as exposure to the Epstein-Barr virus, low levels of vitamin D, and smoking.  The HLA-DRB1 gene belongs to a family of genes called the human leukocyte antigen (HLA) complex. The HLA complex helps the immune system distinguish the body's own proteins from proteins made by foreign invaders (such as viruses and bacteria). Each HLA gene has many different normal variations, allowing each person's immune system to react to a wide range of foreign proteins. Variations in several HLA genes have been associated with increased multiple sclerosis risk, but one particular variant of the HLA-DRB1 gene, called HLA-DRB1*15:01, is the most strongly linked genetic factor.  The IL7R gene provides instructions for making one piece of two different receptor proteins: the interleukin 7 (IL-7) receptor and the thymic stromal lymphopoietin (TSLP) receptor. Both receptors are embedded in the cell membrane of immune cells. These receptors stimulate signaling pathways that induce the growth and division (proliferation) and survival of immune cells. The genetic variation involved in multiple sclerosis leads to production of an IL-7 receptor that is not embedded in the cell membrane but is instead found inside the cell. It is unknown if this variation affects the TSLP receptor.  Because the HLA-DRB1 and IL-7R genes are involved in the immune system, changes in either might be related to the autoimmune response that damages the myelin sheath and nerve cells and leads to the signs and symptoms of multiple sclerosis. However, it is unclear exactly what role variations in either gene plays in development of the condition.