Mechanosensitivity

Mechanosensitivity

As this is one of the points around which Fleury’s rhetoric articulate I think it will be helpful to have a central post on the subject to link to.

Mechanosensitivity is just another cellular property. Genetically specified as every other one.

Proteic effectors of mechanosensitivity are encoded in the genome and their function is subject to alteration by mutation. One may consult as an example: Tuning the mechanosensitivity of a BK channel by changing the linker length, Hucheng Zhao, Masahiro Sokabe, Cell Research (2008 ): 1-8

The choice of this paper [fr], to showcase the genetic determinism of mechanosensitivity, was guided by the nature of the experiments it presents. Mutants were produced by changing the length of a domain of an ion channel and the data shown that the length of this domain was inversely related to mechanosensitivity. It is not a simple on/off mechanism but a modulatory one a straightforward one.

In general, one expects that cells’ mechanosensitivity dependent signaling, specified by the expression of particular effectors acting as sensors, will integrate with other microenvironmental cues to regulate cellular fonctions.
In the case of embryogenesis mechanosensitivity may participate to the integration of pressure as positional information.

Mechanosensors being genetically specified, natural variation is expected to be observed and be subject to natural selection if one or the other variants improve or deteriorate the overall fitness of the organism.

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Abstract The origin of tetrapods is a c…

Abstract

 

The origin of tetrapods is a complex question that webs together genetic, paleontological, developmental and physical facts. 

A very interesting question of evolutionary biology indeed, mobilizing the efforts of many.

 

Basically, the development of embryos is described by a complex mix of mechanical movements and biochemical inductions of genetic origin. 

It is difficult to sort out in this scientific question what are the fundamental features imposed by conservation laws of physics, and by force equilibria, and what can be ascribed to successive, very specific, stop-and-go inductions of genetic nature.

Is it a difficult question ? From zygotes you can get individuals with no appendages or with four, six, eight, ten or many (myriapods). It is quite easy to identify what differentiate them: genomes. Genomes which specify the entire spectrum of physico-chemical properties of every part of the developing embryo, as well of the formed individual throughout its existence, in interaction with the environment. And these physico-chemical properties specify every aspect of cellular displacements from zygote to death, including embryogenesis.
That’s the easy part, easy enough for everybody to understand, even if he isn’t a specialist.
It’s much more difficult to understand the mechanisms in detail. And that’s the fun part.

 

A posteriori, evolution selects the parameters of this process as found in the observed species. 

There is a huge misunderstanding of the term “evolution”. Fleury seems to be allergic to the notion of Natural Selection and, as he say, is preoccupied by Evolution not Natural Selection, ignoring the mechanisms known to operate in biological evolution.
The persistence of such an error in the abstract of the paper calls a question: did an evolutionary (or evo-devo) biologist reviewed the paper? I hope the answer is no. I hope that no biologist reviewed the paper.

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