KV72/3 determines the timing and precision of spinal motoneurons for sonic signaling in the western diamondback rattlesnake

The evolution of novel motor behaviors requires modifications in the central pattern generators (CPGs) controlling muscle activity. How such changes gradually lead to novel behaviors remains enigmatic due to the long-time course of evolution. Rattlesnakes provide a unique opportunity to investigate how a locomotor CPG was evolutionary modified to generate a novel behavior, in this case acoustic signaling. We show, that motoneurons (MNs) in the body and tail spinal cord (SC) of rattlesnakes possess fundamentally different physiological characteristics, which allow MNs in the tail to integrate and transmit CPG output for controlling superfast muscles with high temporal precision. Using patch-clamp electrophysiology and single cell RNA sequencing we demonstrate, that these differences in locomotor and shaker MNs are determined by KV72/3 potassium channels, which are equally expressed, but unexpectedly exert significantly different effects on both neuron types.