Differential effects of myostatin deficiency on motor and sensory axons.

INTRODUCTION: Deletion of myostatin in mice (MSTN-/- ) alters structural properties of peripheral axons. However, properties like axon diameter and myelin thickness were analyzed in mixed nerves, so it is unclear whether loss of myostatin affects motor, sensory, or both types of axons.

METHODS: Using the MSTN-/- mouse model, we analyzed the effects of increasing the number of muscle fibers on axon diameter, myelin thickness, and internode length in motor and sensory axons.

RESULTS: Axon diameter and myelin thickness were increased in motor axons of MSTN-/- mice without affecting internode length or axon number. The number of sensory axons was increased without affecting their structural properties.

DISCUSSION: These results suggest that motor and sensory axons establish structural properties by independent mechanisms. Moreover, in motor axons, instructive cues from the neuromuscular junction may play a role in co-regulating axon diameter and myelin thickness, whereas internode length is established independently. Muscle Nerve 56: E100-E107, 2017.