Polarized microtubule dynamics directs cell mechanics and coordinates forces during epithelial morphogenesis

Abstract

Coordinated rearrangements of cytoskeletal structures are the principal source of forces that govern cell and tissue morphogenesis. However, unlike for actin-based mechanical forces, our knowledge about the contribution of forces originating from other cytoskeletal components remains scarce. Here, we establish microtubules as central components of cell mechanics during tissue morphogenesis. We find that individual cells are mechanically autonomous during early Drosophila wing epithelium development. Each cell contains a polarized apical non-centrosomal microtubule cytoskeleton that bears compressive forces, whereby acute elimination of microtubule-based forces leads to cell shortening. We further establish that the Fat planar cell polarity (Ft-PCP) signalling pathway couples microtubules at adherens junctions (AJs) and patterns microtubule-based forces across a tissue via polarized transcellular stability, thus revealing a molecular mechanism bridging single cell and tissue mechanics. Together, these results provide a physical basis to explain how global patterning of microtubules controls cell mechanics to coordinate collective cell behaviour during tissue remodelling. These results also offer alternative paradigms towards the interplay of contractile and protrusive cytoskeletal forces at the single cell and tissue levels.

Hemithioindigos for Cellular Photopharmacology: Desymmetrised Molecular Switch Scaffolds Enabling Design Control over the Isomer‐Dependency of Potent Antimitotic Bioactivity

“…Tubulin is one of many survival‐critical intracellular proteins whose activity it has not been possible to regulate directly by genetic methods, such as by the creation of optogenetic tubulin constructs, that would give the experimenter biologically meaningful (spatiotemporally precise) control over microtubule structure and biology. In this context, by enabling such previously impossible studies, the azobenzene‐based photopharmaceutical PST‐1 (azocombretastatin) has already achieved significant applications, leveraging the spatially and temporally precise photoreversible switching of its bioactivity . Alternative photoswitchable scaffolds for tubulin photocontrol that could expand the chemical substituent tolerance of practical tubulin photopharmaceuticals, as well as enable the opposite photoresponse (dark‐active) from PST‐1 and so access conceptually distinct applications, would also be of extensive interest to the cytoskeleton research community.…”

“…The requirement for correctly functional microtubule dynamics during mitosis has driven extensive work on targeted and selective microtubule‐binding agents as “antimitotic” cancer chemotherapeutics, including paclitaxel, epothilone and vinca alkaloids . In research, the sheer breadth and spatiotemporal complexity of microtubule‐dependent biological roles presents an excellent opportunity for photopharmacological intervention, and microtubule‐targeting photopharmaceuticals such as PST‐1 have quickly moved on from chemical proof‐of‐concept to find diverse cellular and animal research applications . Due to the massive clinical utility of microtubule‐binding agents in cancer therapy, as well as the systemic side‐effects of conventional antimitotics, it is also of extensive interest to find more potent photoswitchable microtubule inhibitors and evaluate whether they can be guided by localised tumour illumination to act as tumour‐specific antimitotics that spare healthy tissues from chemotherapeutic damage.…”

Photoswitchable microtubule stabilisers optically control tubulin cytoskeleton structure and function

“…9,11,12 Photopharmaceuticals have succeeded in delivering a measure of optical control over a broad range of biochemical and biological phenomena, with early cell-free studies now supplanted by applications in cellulo and recently in vivo. [13][14][15][16] In the cytoskeleton field, photopharmaceutical analogues of the MT destabiliser colchicine were recently developed, to begin addressing the need for spatiotemporally precise MT cytoskeleton studies. The azobenzene-based Photostatins (PSTs), which can be reversibly photoswitched by low-intensity visible light between their biologically inactive E-isomers and their MT-inhibiting, colchicine-like Z isomers, were first reported in 2014.…”

“…All three reagent families have enabled highly spatiotemporally precise optical control over endogenous MT network integrity, MT polymerisation dynamics, cell division and cell death; and the PSTs have already been used in animals to resolve outstanding questions e.g. in mammalian development 13,14 and neuroscience 23 . These applications illustrate the power of photopharmacology to enable previously inaccessible studies of spatiotemporally anisotropic cytoskeletal processes without genetic engineering.…”

“…These applications illustrate the power of photopharmacology to enable previously inaccessible studies of spatiotemporally anisotropic cytoskeletal processes without genetic engineering. [12][13][14]24 With the optically precise blockage of MT polymerisation addressable by a range of photopharmaceuticals, we now desired to develop photopharmaceutical MT stabilisers (hyperpolymerisers) as conceptually novel tools with an alternative spectrum of biological research applications. The biological functions of the MT cytoskeleton are primarily driven by the localisation of stable or growing MTs themselves.…”