Ion channels contribute to the regulation of cell sheet forces during Drosophila dorsal closure

Abstract

We demonstrate that ion channels contribute to the regulation of dorsal closure in Drosophila, a model system for cell sheet morphogenesis. We find that Ca 2+ is sufficient to cause cell contraction in dorsal closure tissues, as UV-mediated release of caged Ca 2+ leads to cell contraction. Furthermore, endogenous Ca 2+ fluxes correlate with cell contraction in the amnioserosa during closure, whereas the chelation of Ca 2+ slows closure. Microinjection of high concentrations of the peptide GsMTx4, which is a specific modulator of mechanically gated ion channel function, causes increases in cytoplasmic free Ca 2+ and actomyosin contractility and, in the long term, blocks closure in a dose-dependent manner. We identify two channel subunits, ripped pocket and dtrpA1 (TrpA1), that play a role in closure and other morphogenetic events. Blocking channels leads to defects in force generation via failure of actomyosin structures, and impairs the ability of tissues to regulate forces in response to laser microsurgery. Our results point to a key role for ion channels in closure, and suggest a mechanism for the coordination of force-producing cell behaviors across the embryo.

In vivo optochemical control of cell contractility at single‐cell resolution

“…The detailed mechanism of how Ca 2+ is functionally linked to contractile actomyosin also remains unclear, although there is no doubt that Ca 2+ is involved in regulation of contractility in many cell types [10][11][12][13][14]16]. It is clear that Ca 2+ does not directly act on actomyosin similar to the contractile system involving troponin C, given the time lag between Ca 2+ burst and contractility in the range of many seconds.…”

“…NP-EGTA, AM (Invitrogen) was prepared in 1× injection solution [180 mM NaCl, 10 mM HEPES, 5 mM KCl, 1 mM MgCl 2 (pH 7.2)] [11]. 2 mM NP-EGTA, AM was injected for Ca 2+ uncaging in epidermal cells, and 1 mM NP-EGTA, AM was injected for Ca 2+ uncaging in amnioserosa cells.…”

“…Intracellular calcium ions (Ca 2+ ) are known to be an important regulator of contractility in many cell types. Ca 2+ plays a central role not only in muscle contraction, but also in cultured epithelial cells [10], in amnioserosa cells during dorsal closure [11], during neural tube closure [12,13], and in the folding morphogenesis of the neural plate [14]. In Drosophila oogenesis, tissue-wide increase in intracellular Ca 2+ activates myosin II and impairs egg chamber elongation [15].…”

From actomyosin oscillations to tissue‐level deformations

“…These observations suggest that the inherent mechanosensitivity of the cytoskeleton and adhesion machineries could play a role in coordinating cell behavior and in contributing to the selforganization of tissues during morphogenetic processes. On the other hand, in the amnioserosa, it has been found that some ion-channels have a role in amnioserosa morphogenesis and in the generation of forces (Hunter et al, 2014). These ionchannels, ENaC and dTRPA1, are sensitive to forces in other systems (O'Hagan et al, 2005;Kindt et al, 2007).…”

In vivo optochemical control of cell contractility at single cell resolution by Ca2+ induced myosin activation

“…Intracellular calcium ions (Ca 2+ ) are known to be an important regulator of contractility in many cell types. Ca 2+ not only plays a central role in muscle contraction, but also in cultured epithelial cells [10], in amnioserosa cells during dorsal closure [11], during neural tube closure [12,13] and in the folding morphogenesis of the neural plate [14]. In Drosophila oogenesis, tissue wide increase of intracellular Ca 2+ activates Myosin II and impairs egg chamber elongation [15].…”