How Do Our Organs Know When to Stop Growing?
upstart writes:
How do our organs know when to stop growing? A multidisciplinary team led by researchers from UNIGE and MPIPKS has solved with a mathematical equation the mystery of how an organ changes its size depending on the size of the animal.
Cells of a developing tissue proliferate and organize themselves under the action of signaling molecules, the morphogens. But how do they know what size is appropriate for the living organism to which they belong? The research groups of Marcos Gonzalez-Gaitan, Professor at the Department of Biochemistry of the Faculty of Science of the UNIGE and Frank Julicher Director at the MPIPKS in Dresden, have solved this mystery by following a specific morphogen in the cells of tissues of different sizes in the fruit fly Drosophila.
In Drosophila, the morphogen Decapentaplegic (DPP), a molecule required for the formation of the fifteen (deca-penta) appendages (wings, antennae, mandibles...) diffuses from a localized source within the developing tissue and then forms decreasing concentration gradients (or gradual variations) as it moves away from the source. In previous studies, Marcos Gonzalez-Gaitan's group, in collaboration with the German team, has shown that these concentration gradients of DPP extend over a larger or smaller area depending on the size of the developing tissue. Thus, the smaller a tissue, the smaller the spread of the DPP gradient from its diffusion source. On the other hand, the larger a tissue, the larger the spread of the DPP morphogen gradient. However, the question remained as to how this concentration gradient scales to the growing size of the future tissue/organ.
"The original approach of my team, composed of biologists, biochemists, mathematicians, and physicists, is to analyze what happens at the level of each cell, rather than placing our observations at the scale of the tissue," comments Marcos Gonzalez-Gaitan. "The central point is to deal with living matter as if it was just matter, that is to say, studying biology with the principles of physics," says Frank Julicher. The two teams have developed a battery of sophisticated tools to follow the fate of the DPP molecule in and between cells of a tissue with great precision using quantitative microscopy techniques. "These tools have allowed us to define a multitude of parameters, linked to cellular processes, for this morphogen.
Journal Reference:
Michailidi, Maria Romanova, Hadjivasiliou, Zena, Aguilar-Hidalgo, Daniel, et al. Morphogen gradient scaling by recycling of intracellular Dpp, Nature (DOI: 10.1038/s41586-021-04346-w)
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