Motor neurons wire muscles to the brain via the spinal cord, carrying information that helps the body coordinate movement. To figure out how these neurons develop so that their sinewy axons reach the correct destinations, researchers screened the genes at play during development in mice while tracing where the axons grew.
When a gene named Arhgap35 was mutated, the scientists observed that motor neurons failed to venture away from the spinal cord, instead snaking their way along the spinal cord’s edge, the scientists reported March 19 in Neuron. In probing Arhgap35’s role further, they found that the protein it codes for, p190RhoGAP, likely guides the axons by helping them choose which signals to follow. During motor neuron development, p190RhoGAP appears to blind the axons for some time to netrin, a protein that attracts them in the spinal cord, so that they can blaze their trail into the muscles, according to the authors.
D. Bonanomi et al., “p190RhoGAP filters competing signals to resolve axon guidance conflicts,” Neuron, doi:10.1016/j.neuron.2019.02.034, 2019.