Piezo3 is a novel mechanosensitive Piezo ion channel in vertebrates
Mechanosensing and mechanotransduction are essential for all living cells. In mammals, Piezo1 and Piezo2 are two mechanically activated cation channels that serve as mechanosensors for a variety of physiological and pathological processes, ranging from touch sensing to sickle cell disease. These two channels are well evolutionarily conserved, and orthologous genes can be traced back to the origin of vertebrates, which underwent whole-genome duplications (WGDs). The number of paralogous genes originating from the vertebrate WGD varies across gene families. Thus, whether there are more PIEZO paralogous genes in vertebrates remains understudied. Here, we identified piezo3, a new paralog of the piezo gene family, and analyzed its evolutionary history using phylogenetic and synteny analyses. The piezo3 gene is present in most vertebrate lineages but absent in birds and most mammals, likely due to nonfunctionalization after WGDs. In addition, we demonstrated that this channel could mediate calcium flux in response to mechanical stimuli in HEK293T cells, suggesting that Piezo3 exhibits PIEZO1/2-like activation and conduction channel functions. Our CRISPR mutation analysis revealed that the zebrafish piezo3 gene is not developmentally essential, possibly because its expression overlaps with other PIEZO channels. Mutant zebrafish showed elevated sensitivity to mechanical force and increased locomotor activity under (photopic) light illumination. Our results suggest that this new mechanical-sensing Piezo channel is widespread in vertebrates and may be critical for vertebrate adaptation by modulating mechanical sensing and light responses during evolution. SIGNIFICANCEAll living cells must sense mechanical forces, whether endogenous or exogenous, and respond to them by transforming these forces into biological signals, which is essential to a wide range of cellular processes, including cell division, growth, and differentiation. PIEZO channels are well-characterized, critical, versatile mechanotransducers for touch and pain physiology and for human diseases. Currently, PIEZO1 and PIEZO2 are the only two known PIEZO channels in most vertebrates. In zebrafish, there are two Piezo2 channels (Piezo2a and Piezo2b) due to extra genome duplication in the ray-finned fishes. Here, we report Piezo3 channel, a long-missing paralog of Piezo1 and Piezo2, in most vertebrates. This channel is present in the majority of vertebrate lineages, except for most birds and mammals. The zebrafish piezo3 gene is expressed during early embryogenesis, and mutation of this gene leads to zebrafish larvae responding to tapping mechanical force and light with active movement. The widespread distribution of this Piezo3 channel across most vertebrate species, but its absence in birds and most mammals, suggests it may play important roles in vertebrate physiology and evolution.