Asymmetry plays an important role in biology on every scale: thoughts about DNA spirals, the fact that the human heart is on the left, our preference to use our left or right hand … A team from the CNRS / Inserm / Université Côte d & Azur, in collaboration with colleagues from the University of Pennsylvania, showed how a protein induces spiral motion in another molecule. Through the domino effect, it causes the cells, organs and, in fact, the whole body to turn, causing later behavior. This study was published in the journal science on 23 November 2018
Our world is fundamentally asymmetrical: think about the double helix of DNA, the asymmetric separation of stem cells, or the fact that the human heart is located to the left … But how do these asymmetries appear and are connected to each other?
At the Valrosa Institute of Biology, the team led by CNRS researcher Stefan Nosseli, who also includes researchers from Inserm and Université Cote d'Azur, studied left-asymmetric asymmetry for several years to solve these puzzles. Biologists have identified the first asymmetry controlling genes in the common fruit fly (Drosophila), one of the biology-based model organisms. Recently, the team has shown that this gene plays the same role in vertebrates: the protein it produces, Myosin 1D, controls the coiling or rotation of organs in the same direction.
In this new study, researchers induced the production of Myosin 1D in the normal symmetrical organs of Drosophila, such as the respiratory trachea. Quite spectacular, it was enough to cause asymmetry at all levels: deformed cells, tracheas that wrap around themselves, twisting the whole body, and spiraling locomotive behavior among flies larvae. It is remarkable that these new asymmetries always evolve in the same direction.
To identify the origin of these cascade effects, biochemists from the University of Pennsylvania also contributed to the project: on a glass roof roof, Myosin 1D was taken in contact with a cytoskeleton component (the cell's spine), namely actin. They were able to observe that the interaction between the two proteins induces the spina of the actin.
Besides its role in right-left asymmetry among Drosophila and vertebrates, Myosin 1D appears to be a unique protein capable of inducing asymmetry on its own at all scales, first at the molecular level, then by the effect of the domino cell, tissue and behavioral level . These results suggest the possible mechanism for the sudden appearance of new morphological characteristics in the course of evolution, such as the twisting of the snails' bodies. Therefore, Myosin 1D seems to have all the necessary features for this innovation, since only its expression is sufficient to cause all scales to twist.
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