In ALS, Sensory Neurons Found to Be Affected Early

In a recent study published in the Journal of Comparative Neurology, researchers found that the same sensory neurons that keep a person from dropping a glass of water are implicated in amyotrophic lateral sclerosis (ALS), and because these  neurons are easier to study in the laboratory than motor neurons, they may help advance new therapies for the disease.

ALS is a neurodegenerative disease that primarily targets the motor system. Although much is known about the effects of ALS on motor neurons and glial cells, little is known about its effect on proprioceptive sensory neurons, a group of neurons that connect with muscles and motor neurons in the spinal cord to help animals and human to understand their physical sense of self (proprioception).

“We discovered that proprioceptive sensory neurons connected with muscles are affected early in ALS while those connected with tendons that sense changes in muscle tension are mostly spared,” study author Gregorio Valdez, an assistant professor of biological sciences in Virginia Tech’s College of Science, said in a recent news release. “That was a big surprise, and it shows that ALS targets select neurons, particularly those with critical functions in muscles.”

In the study titled “Degeneration of proprioceptive sensory nerve endings in mice harboring amyotrophic lateral sclerosis–causing mutations,” the team used a rodent ALS model to study proprioceptive sensory neurons. “Proprioceptive sensory neurons are much easier to study than motor neurons, the main cells affected in ALS,” Dr. Valdez said. “Sensory neurons can stay alive for weeks and even months in the laboratory. This relative longevity can give scientists a better tool to identify and test potential therapeutics for the disease.”

Researchers discovered that proprioceptive sensory neurons degenerated before the appearance of neurological symptoms, and that degeneration initiated in the cellular connections with muscles before extending to the spinal cord. “Understanding how and why certain cell types resist neurodegeneration and others succumb is a critical step in designing interventions,” said Erin Foff, an assistant professor of neurology at the University of Virginia and a medical doctor who treats ALS patients. “Dr. Valdez’s exciting work offers additional information regarding a poorly understood feature of ALS.”