In the central nervous system of humans and all other mammals, a vital insulating sheath composed of lipids and proteins around nerve fibers helps speed the electrical signals or nerve impulses that direct our bodies to walk, talk, breathe, swallow or perform any routine physical act.

But diseases of the nervous system, including multiple sclerosis (MS) in people, degrade this essential insulation known as myelin, disrupting the flow of information between the brain and the body, impairing movement, dimming vision and blunting the ability to function normally.

And while scientists have long studied myelin and understand its role in disease when it degrades, they have puzzled over how myelin…