Researchers at the the Developmental Biology Laboratory¹, have characterized the molecular process that makes the elongation of the C. elegans embryo irreversible. These results were published in August 2019 in the journal Nature².

During embryonic development, the worm embryo becomes twice as long under the effect of muscle contractions within a little more than an hour. These contractions gradually stretch the epithelial cells that make up the animal's skin with which the muscles are in direct contact.

By combining genetics, cell biology and physics, the researchers succeeded in establishing a mathematical model that made possible to discover that the shape of the embryo is temporarily blocked after each muscle contraction. Indeed, they determined that the coordinated action of two proteins (a kinase and a new partner, a membrane cytoskeleton protein called alpha-spectrin) allows this transient lock and therefore the stretching of the worm. When these two factors are absent, the embryo stretches and then retracts to return to its original form.

They also showed that these two proteins orchestrate the reorganization of the actin cytoskeleton of the epidermis and allow the coordinated lengthening of muscles and epidermis.

These results highlight the importance of physical plasticity in modifying cell shapes. Beyond C. elegans, they should also apply to mammals since most of our organs are composed of contractile cells juxtaposed to epithelial cells (e. g. lung, stomach, intestine, mammary gland). The contraction of contractile cells could influence the morphogenesis of the organ or its healing after injury. Moreover, cells adjacent to tumor cells may be contractile cells, and because of this proximity, their properties could alter and/or or facilitate metastasis dissemination.

This article was the subject of a short note on the INSB website and an article in the CNRS letter.

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¹Developmental Biology Department, team: Mechanical Forces Behind Tissue Morphogenesis

²RNA is a critical element for the sizing and the composition of phase-separated RNA-protein condensates, M. Garcia-Jove Navarro, S. Kashida, R. Chouaib, S. Souquere, G. Pierron, D. Weil, Z. Gueroui, Nature Communications, July 2019 DOI: 10.1038/s41467-019-11241-6