Spinal Motoneuron TMEM16F Acts at C-boutons to Modulate Motor Resistance and Contributes to ALS Pathogenesis

Abstract

Summary: Neuronal Ca2+ entry elicited by electrical activity contributes to information coding via activation of K+ and Cl− channels. While Ca2+-dependent K+ channels have been extensively studied, the molecular identity and role of Ca2+-activated Cl− channels (CaCCs) remain unclear. Here, we demonstrate that TMEM16F governs a Ca2+-activated Cl− conductance in spinal motoneurons. We show that TMEM16F is expressed in synaptic clusters facing pre-synaptic cholinergic C-boutons in α-motoneurons of the spinal cord. Mice with targeted exon deletion in Tmem16f display decreased motor performance under high-demanding tasks attributable to an increase in the recruitment threshold of fast α-motoneurons. Remarkably, loss of TMEM16F function in a mouse model of amyotrophic lateral sclerosis (ALS) significantly reduces expression of an activity-dependent early stress marker and muscle denervation, delays disease onset, and preserves muscular strength only in male ALS mice. Thus, TMEM16F controls motoneuron excitability and impacts motor resistance as well as motor deterioration in ALS. : Soulard et al. show that TMEM16F, a calcium-activated chloride channel, is a post-synaptic component of C-boutons that contributes to the excitability of fast α-motoneurons. They find that the loss of TMEM16F function leads to reduced performance during motor-demanding tasks but improves motor functions of male mice with amyotrophic lateral sclerosis. Keywords: C-boutons, muscarinic regulation, electrical activity, spinal motoneuron, anoctamin 6, amyotrophic lateral sclerosis