eLife assessment
This work examines the evolutionary origins of acid-sensing ion channels (ASICs), a class of pH-sensing receptors expressed throughout the brain and body. By combining analysis of sequences, functional measurements, and measures of tissue distribution, the authors provide solid evidence that ASICs existed far earlier than previously believed. The present data indicate that ASICs emerged after the split between bilaterians (organisms with two-fold symmetry) and Cnidaria (jellyfish, anemones, corals, etc.), approximately 680 million years ago. This evolutionary and functional analysis of ASIC channels across bilaterian lineages provides relevant information about the evolution of nervous and sensory systems.