Abstract
Type Ia sensory neurons are critical for proprioception and are responsible for encoding muscle stretch and providing feedback from muscle to the central nervous system. Although the role of different transcription factors and guiding signals has been studied in the development of the proprioceptive afferents and the spindles they innervate, little is known about how this system is post-transcriptionally regulated. In this study we identify a crucial role of microRNA(s) in the locomotor behavior of mice. Conditional ablation of Dicer through a parvalbumin driven Cre leads to severe ataxia, uncoordinated gait, and hyperextended limbs in mice. Normal morphology in type Ia afferents and muscle spindle innervation is seen, but spindle-associated sensory endings have an almost complete absence of vGluT1 in the tibialis anterior muscle of knockout animals. These findings place Dicer in the pathway for the maintenance of the proprioceptive circuit.