Researchers find mechanical signal behind decision to cell death
In many species including humans, the cells responsible for reproduction, the germ cells, are often strongly interconnected and share their cytoplasm. In the hermaphroditic nematode Caenorhabditis elegans, up to 500 germ cells are connected to each other in the gonad, the tissue that produces eggs and sperm. These cells are arranged around a central cytoplasmic “corridor” and exchange cytoplasmic material promoting cell growth, and ultimately produce oocytes ready to be fertilized.
In previous studies, researchers found that C. elegans gonads generate more germ cells than necessary and that only half of them grow into oocytes, while the rest shrink and die through physiological apoptosis. programmed cell death that occurs in multicellular organisms. Now scientists from the Biotechnology Center at TU Dresden (BIOTEC), the Max Planck Institute for Cell Biology and Molecular Genetics (MPI-CBG), the Center of Excellence in Life Physics (PoL) at TU Dresden , from the Max Planck Institute for the Physics of Complex Systems (MPI-PKS), the Flatiron Institute, NY, and the University of California, Berkeley, have found evidence to answer the question of what triggers this decision to become cellular between life and death in the germ line.
Previous studies have revealed the genetic basis and biochemical signals that cause physiological cell death, but the mechanisms that select and trigger apoptosis in individual germ cells have remained unclear. As the germ cells mature along the gonad of the nematode, they collectively first grow in size and volume homogeneously. In the study which has just been published in Physics of nature, scientists show that this homogeneous growth suddenly changes to heterogeneous growth where some cells get bigger and others smaller.
Researcher Nicolas Chartier from the Stephan Grill group, and co-first author of the study, explains: “By precisely analyzing the volumes of germ cells and the flows of cytoplasmic matter in living worms and by developing a theoretical model, we have identified hydraulic instability that amplifies small initial random volume differences, which cause some germ cells to increase in volume at the expense of shrinking others. It is a phenomenon which can be compared to the instability with two balloons, well known to physicists. Such instability occurs when simultaneously blowing two rubber balloons while trying to inflate them both. Only the larger balloon will inflate, as it has lower internal pressure than the smaller one and therefore is easier to inflate.
This is what is at stake in germ cell selection: such pressure differences tend to destabilize the symmetrical configuration at equal germ cell volumes, so called hydraulic instabilities, leading to the growth of the most large germ cell to the detriment of the smallest. . By artificially reducing the volumes of germ cells via thermoviscous pumping (FLUCS method: focused cytoplasmic diffusion by induced light), the team demonstrated that the reduction in cell volumes leads to their extrusion and cell death, indicating that once when a cell is below a critical size, apoptosis is induced and the cell dies.
Using confocal imaging, the researchers were able to image the entire living worm organism to receive a comprehensive and accurate picture of the volumes of all gonadal cells, as well as the exchange of fluids between cells. Stephan Grill, Lecturer at the Pôle d’Excellence Physique du Vivant (PoL) and supervisor of multidisciplinary work, adds: “These discoveries are very exciting because they reveal that the decision of life or death in cells is of a mechanical nature and linked to fabrics. hydraulic. This helps to understand how the body automatically selects a cell that will become an egg. Moreover, the study is another example of the excellent cooperation between biologists, physicists and mathematicians in Dresden.
Nicolas T. Chartier et al, Hydraulic instability leads to the decision of cell death in the germ line of nematodes, Physics of nature (2021). DOI: 10.1038 / s41567-021-01235-x
Quote: Researchers Find Mechanical Signal Behind Cell Death Decision (2021, May 31) Retrieved May 31, 2021 from https://phys.org/news/2021-05-mechanical- cue-cell-death-decision. html
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