The metronome of the embryo

Jean-Léon Maître, a new chargé de recherche at the CNRS, is a passionate researcher who has long known what he wants to study. During his PhD, he identified that there is still much to discover regarding the mechanical properties of embryonic cells. Since then, he has been gathering the knowledge and tools necessary to study the forces at play during embryonic development. He first studied the mechanical properties of the zebrafish embryo in the laboratory of Prof. Carl-Philipp Heisenberg at the Max Planck Institute for Cell Biology and Genetics (Dresden, Germany) and then at the Institute of Science and Technology (Klosterneuburg, Austria). He brought his knowledge on embryo mechanics to the laboratory of Takashi Hiiragi, a pioneer in the organization of the mouse embryo at the European Molecular Biology Laboratory (Heidelberg, Germany). Using this experience he is now deciphering the forces involved in the development of the mammalian embryo.

Slower studies allow new discoveries

To date, most studies have been performed on animal models in which embryonic development is very rapid (zebrafish, nematodes, drosophila…), allowing a quick generation time. However, in mice, and in mammals in general, embryonic development takes place at a much slower pace. This system allows the study of the different stages of development in much greater detail. In the mouse embryo, Jean-Léon Maître has already discovered a rhythmic pulsation, beating every 80 seconds. Only the cells destined to form the embryo display this pulsation, those which will form the placenta do not. These pulsations, which do not propagate, were observed in other species and show the same periodicity. “We don’t know why or how these waves occur, but we know they use the same molecular motors that lead to the deformations of the embryo during development,” explains the researcher enthusiastically. He now hopes to shine light on this mysterious phenomenon, with the help of his team forming the Mechanics of mammalian development lab.

Wrestling with cells to understand how they exert forces

Jean-Léon Maître is most passionate about understanding how forces exerted during embryonic development give rise to an organized tissue, and eventually to a whole organism. To study these forces, he uses micropipettes to delicately pull on cells and measure the resisting forces of the cell, as if the researcher were arm wrestling with the cells. “By mapping the forces present in the embryo we can understand the mechanisms behind shape changes of the embryo during development,” he explains. From these studies he will be able to understand normal embryonic development and thus detect abnormalities, including those that could prevent embryo implantation. A long term objective is to develop a test that could identify the healthiest embryos for assisted reproduction techniques.

A key system to study cancer mechanisms

The medical implications of these studies are not limited to reproductive medicine but extend also to cancer. Indeed, the implantation of the embryo requires invasion of cells into the uterus, which is related to cancer metastasis. On the other hand, many of the hallmarks of tumors such as architectural defects in tissues are caused by aberrant forces exerted by the cancer cells on their environment. A better understanding of these phenomena will allow us to better fight cancer.

Institut Curie: the ideal place to study mechanics in living systems

Throughout his career, Jean-Léon Maître collaborated with many specialists in cell mechanics, all of which had spent part of their career at Institut Curie. “The institute quickly became an obvious choice when I started thinking about where to perform my research”, he says. Indeed, Institut Curie is practically tailor-made for this young researcher, with its high tech infrastructures to study mouse embryos, world-renowned researchers working on morphogenesis, and a long history of excellence in the fields of mechanics and biophysics of the cell.

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Jean-Léon Maître's research

Asymmetric division of contractile domains couples cell positioning and fate specification
Jean-Léon Maître, Hervé Turlier, Rukshala Illukkumbura, Björn Eismann, Ritsuya Niwayama, François Nédélec & Takashi Hiiragi
Nature, août 2016, doi:10.1038/nature18958

Pulsatile cell-autnomous contractility drives compaction in the mouse embryo
Jean-Léon Maître, Ritsuya Niwayama, Hervé Turlier, François Nédélec & Takashi Hiiragi
Nature Cell Biology, juin 2015, doi:10.1038/ncb3185