Mammalian touch catches up

Abstract

An assortment of touch receptors innervate the skin and encode different tactile features of the environment. Compared with invertebrate touch and other sensory systems, our understanding of the molecular and cellular underpinnings of mammalian touch lags behind. Two recent breakthroughs have accelerated progress. First, an arsenal of cell-type-specific molecular markers allowed the functional and anatomical properties of sensory neurons to be matched, thereby unraveling a cellular code for touch. Such markers have also revealed key roles of non-neuronal cell types, such as Merkel cells and keratinocytes, in touch reception. Second, the discovery of Piezo genes as a new family of mechanically activated channels has fueled the discovery of molecular mechanisms that mediate and mechanotransduction in mammalian touch receptors.

Figure 1. Piezo proteins are evolutionarily conserved, widely expressed ion channels

(A) Unrooted circular dendrogram clustering of Piezo1 and Piezo2 proteins (B) Piezo channels are proposed to be homomeric tetramers. Each subunit is predicted to contain over 30 transmembrance domains (orange circles).

Figure 2. The many modalities of Piezo

(A) Sample currents demonstrating mechanical activation of Piezo1-transfected HEK293T cells via pressure [19••], suction [19••], and shear stress [50]. (B) Representative touch-evoked Piezo2 currents in transfected HEK293T cells [19••], DRG neurons [19••] and Merkel cells [29•].