Molecular and electrophysiological properties of mouse motoneuron and motor unit subtypes

The field of motoneuron and motor unit physiology in mammals has deeply evolved the last decade thanks to the parallel development of mouse genetics, transcriptomic analysis, and electrophysiological recordings of motoneurons. We review the efforts made to investigate the electrophysiological properties of the different functional subtypes of mouse motoneurons, to decipher the mosaic of molecular markers specifically expressed in each subtype, and to elucidate which of those factors drive the identity of motoneurons. The recent development of in vivo mouse preparations, in which one can record simultaneously one motoneuron and of the force generated by its motor unit, now allows, for the first time, correlating the functional type of a motoneuron with the expression of specific genes.