Osmolarity-independent electrical cues guide rapid response to injury in zebrafish epidermis

Abstract

The ability of epithelial tissues to heal after injury is essential for animal life, yet the mechanisms by which epithelial cells sense tissue damage are incompletely understood. In aquatic organisms such as zebrafish, osmotic shock following injury is believed to be an early and potent activator of a wound response. We find that, in addition to sensing osmolarity, basal skin cells in zebrafish larvae are also sensitive to changes in the particular ionic composition of their surroundings after wounding, specifically the concentration of sodium chloride in the immediate vicinity of the wound. This sodium chloride-specific wound detection mechanism is independent of cell swelling, and instead is suggestive of a mechanism by which cells sense changes in the transepithelial electrical potential generated by the transport of sodium and chloride ions across the skin. Consistent with this hypothesis, we show that electric fields directly applied within the skin are sufficient to initiate actin polarization and migration of basal cells in their native epithelial context in vivo, even overriding endogenous wound signaling. This suggests that, in order to mount a robust wound response, skin cells respond to both osmotic and electrical perturbations arising from tissue injury.

Physiological electric fields induce directional migration of mammalian cranial neural crest cells

“…CNCCs in EFs assume a morphology with long bipolar filipodia perpendicular to the field line, and smaller active protrusions projected in the direction of migration (Movie 2). Cell membrane protrusions in the direction of migration is consistent with that reported in vitro as well as in vivo (Dang et al, 2013;Kennard and Theriot, 2020;Pollard and Cooper, 2009).…”

“…Endogenous EFs occur naturally in embryos. The activity of various ion pumps and transporters generate charge difference across the epithelium that is manifested as transepithelial potential (TEP) (Kennard and Theriot, 2020;Shi and Borgens, 1995). The TEP across the embryonic ectoderm is the driving force capable of producing ioniccurrent flow through, and out, of the embryos at the region of low electric resistance.…”

“…Applied EFs of physiological strength can guide direction cell migration, suggesting involvement of EFs in directed cell migration (Chang and Minc, 2014;Levin et al, 2017;Levin et al, 2019;Mathews and Levin, 2018). Different putative sensors have been suggested that can determine cell directedness (Allen et al, 2013;Forrester et al, 2007;Kennard and Theriot, 2020;Zhao et al, 2020). In culture, avian and amphibian NCCs respond to applied EFs by directional migration (galvanotaxis / electrotaxis) towards the cathode (Cooper and Keller, 1984;Gruler and Nuccitelli, 1991;Nuccitelli and Smart, 1989).…”

Osmolarity-independent electrical cues guide rapid response to injury in zebrafish epidermis

“…Registration was performed using custom Python scripts including the following libraries: numpy ( van der Walt et al, 2011 ), scikit-image ( scikit-image contributors et al, 2014 ), Tifffile (Christoph Gohlke, University of California, Irvine), and the python bindings for OpenCV ( Bradski and Dobbs, 2000 ). Code is available on a GitLab repository ( Kennard and Theriot, 2020 ; copy archived at swh:1:rev:67bba3afe283ece6e1e1c3db3b8234217ac5332c ).…”

In vivo wide‐field voltage imaging in zebrafish with voltage‐sensitive dye and genetically encoded voltage indicator

“…Furthermore, this voltage imaging could also be used to analyze the membrane potentials of various cell types, including non‐neural cells. Interestingly, previous studies suggest the importance of electrical activity in morphogenesis and cellular migration (Allen et al., 2013; Daane et al., 2018; Kennard & Theriot, 2020). In vivo voltage imaging described here may also help elucidate these phenomena.…”