Magic embryology: genome and mechanical forces (Introduction)

by David Turell , Wednesday, October 16, 2024, 21:53 (5 days ago) @ David Turell

A new biophysical study on gut formation:

https://phys.org/news/2024-10-gut-genetics-physics-embryonic.html

"Genes are the control panel for an embryo morphing from a ball of cells into organs, muscles, and limbs, but there's more involved than just genetics. There's also physics—the shaping of tissues by flows and forces from cellular activity and growth.

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"The Developmental Cell paper, led by...Hasreet Gill, shows how a set of developmental instructions called Hox genes dictate gut formation. For the study, Gill and colleagues traced the gut development of a chicken embryo as a model organism; Hox genes are also found in humans and all other vertebrates.

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"Gill's study built on previous work looking at how Hox genes are involved in organ differentiation. The set of genes, highly conserved throughout animal evolutionary history, was the subject of the 1995 Nobel Prize when they were recognized for their role in segmenting a fruit fly's body.

"Gill and colleagues discovered that measurable mechanical properties of the tissues that make up the large and small intestines of a chick embryo are directly involved in how they arrive at their final shapes. For example, the tissues that form the villi located in the small intestine, she found, have different stiffness parameters than those that shape the inside walls of the large intestine, which form larger, flatter, more superficial folds.

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"Gill's team repeated the experiment while running physical tests on the mechanical characteristics of the different parts of the gut, considering things like wall stiffness, growth rate, and tissue thickness. They found that the HoxD13 gene in particular regulates the mechanical properties and growth rates of the tissues that eventually lead to the large intestine's final shape. Other, related Hox genes may define those same properties for the small intestine.

"Crucially, they also illuminated the role of a downstream signaling pathway called TGF Beta, which is controlled by Hox genes. By tuning the amount of TGF beta signaling in their embryos, they could switch the shapes of the different gut regions. Seeing the importance of this pathway, long known to be involved in fibrotic conditions, was an important basic-science step toward fully understanding gut development in a vertebrate system.

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"The complementary PNAS paper, co-led by Gill and Yin, showed how geometry, elastic properties, and growth rates control various mechanical patterns in different parts of the gut.

"'We focused on how mechanical and geometric properties directly affect morphologies, especially more complicated, secondary buckling patterns, like period-doubling and multiscale creasing-wrinkling patterns," said Yin, an expert in theoretical modeling and numerical simulations of active and growing soft tissues.

"Added Mahadevan said, "These studies allow us to begin probing aspects of the developmental plasticity of gut development, especially in an evolutionary context. Could it be that natural variations in the genetic signals lead to the variety of functional gut morphologies that are seen across species? And might these signals be themselves a function of environmental variables, such as the diet of an organism?"

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"Morphogenesis is driven by forces arising from cellular events, tissue dynamics, and interactions with the environment," Yin said. "Our studies bridge the gap between molecular biology and mechanical processes." (my bold)

Comment: the bold above is a synopsis of the whole process. Obviously a band of cells as it grows exerts physical forces. The molding of any embryo uses control of the types of cells to be grown as one step, and somehow patterns the forces that develop to help in shaping the embryo into its final form. Just magical. And beyond natural development of the process.