Oops 090428

Oops 090428

[p6, column 2, §2]

These pathways will “induce” either legs, antennas, halteres, or wings along the body by nucleation of appendage primordia at intersections of genetic boundaries. However, wings and halteres are more dorsal (hence the wings “on the back”), while antennas and legs are more ventral (hence legs hanging below the abdomen). Antennas can be genetically “upgraded” into legs, and halteres into wings, but more ventral appendages like legs cannot be morphed into more dorsal appendages, because the difference is not only a difference of genetic expressions: there is also a topological difference (what matters is both the nature of the proteins, and the spatial organization of the primordia).

Really?

How hard could it be to check for homeotic transformations of legs to wings, or halteres, that is: ventral to dorsal appendages ?

This hard.

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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.

likely adjective such as well might h…

likely
adjective

  1. such as well might happen or be true; probable :
  2. apparently suitable; promising


[p6, column 1, §1]:

The stripes of expression correspond to actual cellular lines, which are congruent with concentration level lines. Current genetic networks do not take into account this cellular reorganization, likely linked to compression forces. 

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One of the ex cathedra assertions of Vin…

One of the ex cathedra assertions of Vincent Fleury, in a general public forum where his book and theory where discussed, early 20071, was:

Je suis désolé de devoir insister : ouvrez vos yeux, ça n’a AUCUN sens d’invoquer la fonction d’un organe, si l’ensemble des modifications possibles d’un animal ne sont pas quelconques. L’influence de l’environnement sur le développement de UN animal est égal à ZERO, et l’influence sur les mutations est égale à ZERO. ZERO fois ZERO= ZERO.

Rough translation:

I’s sorry, I have to insist: open your eyes, there is no SENSE to invoque the function of an organ, if the set of possible modifications of an animal are not random2. The influence of the environment on the development of ONE animal is equal to ZERO, and the influence on the mutations is equal to ZERO. ZERO times ZERO = ZERO.

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oops 090426

oops 090426

Rarely worked on such a low quality edited paper. Not flattering for the author, neither for the journal.

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what’s that ?

what’s that ?
Solution 

cgrlike.jpg

 

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Introduction

Introduction

I plainly agree with Vincent Fleury that animal embryos are material objects and their development is according laws of condensed physics. But I wouldn’t call them “things” but rather objects and I would extend these considerations to all living organisms, not just animals, and at every phase of their lives, not just development.

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