Early embryology; branching patterns (Introduction)

by David Turell , Thursday, September 21, 2017, 19:34 (2620 days ago) @ David Turell

As organs develop their ducts follow simple branching patterns:

https://phys.org/news/2017-09-scientists-reveal-beautiful-simplicity-underlying.html

"Branching patterns occur throughout nature - in trees, ferns and coral, for example - but also at a much finer scale, where they are essential to ensuring that organisms can exchange gases and fluids with the environment efficiently by the maximising the surface area available.

"For example, in the small intestine, epithelial tissue is arranged in an array of finger-like protrusions. In other organs, such as kidney, lung, mammary glands, pancreas and prostate, exchange surfaces are packed efficiently around intricate branched epithelial structures.

"'On the surface, the question of how these structures grow - structures that may contain as many as 30 or 40 generations of branching - seems incredibly complex," says Professor Ben Simons, who led the study.

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"While there's a collective decision-making process going on involving multiple different stem cell types, our discovery that growth occurs almost at the flip of a coin suggested that there may be a very simple rule underpinning it," says Professor Simons.

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"there was very little crossover of the branches - ducts seemed to expand to fill the space, but not overlap. This led them to conjecture that the ducts were growing and dividing, but as soon as a tip touched another branch, it would stop.

"'In this way, you generate a perfectly space-filling network, with precisely the observed statistical organisation, via the simplest local instruction: you branch and you stop when you meet a maturing duct," says Dr Hannezo, a Sir Henry Wellcome Postdoctoral Fellow based at the Gurdon Institute. "This has enormous implications for the basic biology. It tells you that complex branched epithelial structures develop as a self-organised process, reliant upon a strikingly simple, but generic, rule, without recourse to a rigid, pre-determined sequence of genetically programmed events." (my bold)

"Although these observations were based on the mammary gland epithelium, by using primary data from Dr Rosemary Sampogna at Columbia University, Professor Anna Philpott in Cambridge and Dr Rakesh Heer at Newcastle University, the researchers were able to show that the same rules governed the embryonic development of the mouse kidney, pancreas and human prostate.

"'In the mammary gland, you have a hundred or more fate-restricted stem-like cells participating in this bifurcation-growth-bifurcation process, whereas in the pancreas it's just a handful; but the basic dynamics are the same," says Professor Simons. "The model is aesthetically beautiful, because the rules are so simple and yet they are able to predict the complex branching patterns of these structures."

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"A century after the publication of On Growth and Form, it's exciting to see how the concepts of self-organisation and emergence continue to offer fresh perspectives on the development of biological systems, framing new questions about the regulatory mechanisms operating at the cellular and molecular scale," Professor Simons adds.

"While it may be too early to tell whether similar rules apply to other branched tissues and organisms, there are interesting parallels: branching in trees appears to follow a similar pattern, for example, with side branches growing and bifurcating until they are shaded or until they are screened by another branch, at which point they stop."

Comment: Many of these branching patterns follow fractal formulas. I have always had the opinion that God set up patterns to be followed in early evolution. This study certainly shows that much of it can be automatically controlled without much genetic input.