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Contribution of actin cytoskeleton to C. elegans embryonic elongation

Abstract : Body axis elongation is a fundamental morphogenetic process, involving cell shape changes powered by mechanical forces through small incremental steps which need to be stabilized. During my PhD, I studied C. elegans embryonic elongation to define how the embryo, an elastic material, lengthens progressively upon muscle contractions. Previously, the lab found a kinase, PAK-1, to be mediator of an epidermal mechanotransduction pathway downstream of muscles. Two screens in a pak-1(Ø) background identified α-spectrin SPC-1 as an interactor of PAK-1. spc-1(-)pak-1(-) embryos elongate up to 1.5-fold and then retract to 1-fold in a muscle dependent manner. I used super-resolution microscopy to show that epidermis circumferential actin bundles are highly disorganized in these embryos; suggesting that actin rearrangement could be the lock counteracting elasticity. With a screen in spc-1(-)pak-1(-) background, I identified two severing proteins helping break actin filaments when muscle activity bends them at sharp angles. In addition, the actin bundling formin FHOD-1, was also shown to induce retraction in fhod-1(-);spc-1(-) embryos. I overexpressed a C-terminally truncated FHOD-1(ΔFH2/DAD) that partially rescued the spc-1(-)pak-1(-) retraction suggesting that FHOD-1 blocks further actin depolymerization at each cycle of contraction. To test it, we modeled the embryo as a Kelvin-Voigt material under acto-myosin force from the epidermis and muscle tension. We predicted embryo lengthening using a viscoplastic component accounting for actin shortening. Altogether I characterized a cellular network conferring mechanical plasticity to stabilize cell shape during a morphogenetic process.
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Submitted on : Tuesday, September 29, 2020 - 1:03:31 AM
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  • HAL Id : tel-02951816, version 1

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Alicia Lardennois. Contribution of actin cytoskeleton to C. elegans embryonic elongation. Development Biology. Sorbonne Université, 2019. English. ⟨NNT : 2019SORUS236⟩. ⟨tel-02951816⟩

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