OK, I do have a blog, so I will use it for a single entry in fact, there is no need for more to make my point. So a single entry, no comments, no trackbacks and I’ll leave it there to be visible. I don’t expect a lot of visitors, I just expect that those who will come here will continue to be interested by the stuff discussed in this post.
The subject is Vincent Fleury, a biophysicist working at a joint team between the CNRS and the University of Rennes 1, UMR CNRS 6626, managed by Dr Anne Renault, in the Biophysics team (leader Sylvie Beaufils There is a problem there, Vincent Fleury appearing as the group leader in the english page, while Dr Beaufils seems to be the group leader for french speaking people, both at the equivalent french page and the lab’s chart.). VF’s personal webspace on the university’s server is vincentfleury and is published essentially in french. Almost all the material discussed here is from the pages FAQ and Flash Info and OldCola’s blog dloale.
Fleury’s views on development are based on two major philosophical considerations:
he can’t accept that evolution could built such complexity
he consider that morphological features are platonician elements revealed by the genes
This lead him to genetics and evolution denialism associated with a reluctancy to empirically testing his hypothesis, which he calls his theory, a set of hypotheses based on mathematical modeling of the development, with a focus in the chick gastrulation, presented, even in peer-reviewed papers, published by Organogenesis, without support from experimental data.
Most of the discussion between Fleury and Oldcola I discovered afterward, but a particular point was brought-up while I was commenting the responses Fleury published in his website. And I’ll discuss in this post essentially this particular point, cell movements in the chickens epiblast and induction of the limb buds.
Before that a general remark. What Fleury calls questions by myself and Oldcola, are caricature of the questions we asked. Either he is unable to understand plain french or he is intentionally distorting them. Both interpretations are disturbing. I will add here a page with the actual questions that were asked and the distortions he produced as a permanent display of his dishonesty or inability to clearly understand what he is told.
Fleury’s interpretation of limb buds formation is mechanical. Cells’ vortices at the epiblast level creates at their centers depressions lifting mesodermal cells and thus forming the four limb buds. This is schematized for a single vortex and bud as follows (fig 1):
Thus, budding is perpendicular to the vortex’s plane, that is the epiblast’s plane. [claim 1]
Four members are produced by four buds and thus four vortices are necessary to create the buds.
Fleury presents those four vortices as follows (fig 2):
By combining fig 1 and 2 I got the following (fig 3):
That means that there must be four full vortices at the epiblast level, each one centered at the position where the corresponding limb bud will arise, L1/R1 being responsible for the forelimb buds and L2/R2 for the hind limbs buds. [claim 2]
Fleury’s take is that the orientation of the vortices produce the symmetry of flexion characteristic of the elbow and the knee, which he schematize as follows (fig 4):
Where, according to Fleury, A represents the cellular flows and B the final topology of limb anlagen. [claim 3]
And the further development of the limbs is shown as follows (fig 5):
There is a connection between the cellular flows, the representation of the anlagen and the unfolding of the limbs, apparently justifying the flexion of the eelbow and the knee and the symmetry of the system. [claim 4]
That being exposed let’s see where the flaws are.
According to claim 1, the buds are perpendicular to the epiblast plane; according to figures 2 and 3 and figure 4A, the four buds should be represented as follows (fig 6):
The buds appearing at the center of each one of the four vortices and coming out of the plane. This isn’t clear at the representation of the limb anlagen of fig 4B.
This being shown clearly, there is no connexion between fig 4 and Fig 5, where one may suspect that the direction of the presumptive cellular flows (4A) may correspond to the flexion of the articulations between stylo- and zeugopode and there is neither a connexion between fig 4A and fig 5.
Fig 5, representing the unfolding of the limbs isn’t supported by any of the previous illustrations.
If figures 4B represents the anlagen once the body folded, it is presented in a way somehow ambiguous and it would be much clearer as follows (fig 7):
The bud’s axis is perpendicular to the plane of the vortex, allegedly, inducing it, and there is no relation between the orientation of the cellular flows and the way the junction between stylo- and zeugopode, which lays in a different plane, will be oriented later. The juxtaposition of fig 3B and fig 5 may be misleading.
Problem 1 : Fleury present the cellular flows as if they was determining the way elbows and knees will form, without producing any evidence, even theoretical that there may be a connexion.
There is a series of other minor problems related to claim 1, I will bundle here as Problem 2:
Fleury hypothesize that the vortices could induce the budding but there is no demonstration that the cells forming the limb buds, that is cells of the lateral plate, are beneath the vortices while they vortcices are present at the epiblast level. In fact there is not even evidence that the vortices persist at the moment the cells that will form the lateral plate ingress. And the positioning of the vortices isn’t discussed (this concerns L1/R1, the second pair will be discussed below).
There is no demonstration that such vortices can induce the budding neither, that is by strictly mechanical means of by inducing the expression of a growth factor, induction due to the transduction of the signal represented by the depression. As this remains an unconfirmed hypothesis every assertion based on it is hypothetical as well and could not be called theory. Until such proogf is build it is more convenient to rename claim 1 to hypothesis 1 and avoid considering anything based on it otherwise than as hypothetical.
It should be easy to demonstrate that a low pressure area induce a limb bud by producing ectopic limbs, much the way it is usual to do with a chemical inducer.
One step necessary for Fleury’s hypothesis 1 to be considered as potentially interesting in order to invest the effort necessary to test experimentally, is to demonstrate the presence of four vortices at the epiblast level. Four full vortices as the one represented in fig 1 organized according to the schema of fig 2 in fig 3. This I call hypothesis 0 as it should be confirmed before any further investigation is carried out.
During the discussion between Fleury and Oldcola, Fleury failed to show the existence of L2/R2. In a first take, he mischaracterized cell trajectories as belonging to the L2/R2 vortices, misplaced them over the bright field images, alleged that the video panels where not synchronous and avoided any further comment when the proof that the panels were indeed synchronous was produced.
Thus, hypothesis 0 is not yet validated.
The best he managed to produce is another hypothesis saying that movements of some epiblastic cells could be considered as participating to the formation of the L2/R2 vortices, by extrapolation and this I call hypothesis -1 as nothing indicates that those cells will follow the extrapolated trajectories.
So, the visualization of those vortices is still to be produced. Not only because they are claimed to exist but more importantly to be able to verify if their centers are positioned over the presumptive hind limb buds.
If hypothesis -1 is validated by direct observation of the cellular flows necessary to form the vortices L2/R2, and if hypothesis 0 is validated by direct observation of the overlay of the four vortices over mesodermal cells that will participate at the formation of the lateral plate at the positions where limb buds will appear, and if hypothesis 1 is validated by experimental evidence that ectopic limb buds appear connected with depressions induced at the epiblast level, then further discussion would be possible. It belongs to the potential investigators to evaluate if those hypothesis are interesting enough to invest the necessary effort/time/money to validate them.
Further discussion would be on the connexion between the direction of the vortices and the way the stylo-zeugopodes articulation is oriented, as they do not seem connected, event in the theoretical scaffold Fleury propose.
But until evidence is produced it is unacceptable to use such hypothetical elements to propose a theory. Maybe scientific journalists or laymen are pardonable when they misuse the term “theory” but it is misleading and dishonest from a scientific researcher to talk about theory, what one may understand as “scientific theory”, knowing that none of the hypotheses on which it is based is experimentally validated.
The last part I would like to discuss is in relation to Fleury’s claim that there is a symmetry in respect to “one point”. When Oldcola initially tried to position the L2/R2 alleged vortices, Fleury proposed the following figure:
It is clearly visible that the origin of the cells that Fleury thinks will give the L2/R2 vortices come from the anterior of the epiblast. This is quite different from his description (fig 9):
Fig 9a is adapted from the figure displayed in his website, with vortices notes, L2/R2 under gray as they are not yet clearly observed, and the symmetry point represented by a red square.
Oldcola clearly designed the cell trajectories, and proposed the schema of fig 9b, at his first comment:
.
This apparently small change made a great difference, as in this case the symmetry is in respect of the anterioposterior axis (9b green line), not to a point (9a and 9b, red square). Now, this is hardly arguable as it is simply observed. So, even if the vortices L2/R2 existed, the embryo’s symmetry isn’t radial. Up to now what was showed is 9d, that is per half epiblast, a vortex and a few cells at the periphery following trajectories that doesn’t complete a vortex. And this is consistent with a symmetry to the anteroposterior axis.
Certainly, if you trace a set of coordinates, truncate the cell’s trajectories and complete them by extrapolating abusively and displacing them from one image to the other, you produce the illusion that there is a symmetry to a point. This could be named Fleury’s claim 0 and not only it isn’t proven, but there is evidence that it is false.
It is much more disturbing for me, to see what is displayed on the website of a university and that none of the colleagues of Fleury seem to ask for experimental evidence of his claims, including the editors of Organogenesis. Worst of all, when he display a Flash Info page, subtitled “A confirmation of my theory”, which it is certainly not.
To be continued, edited.
Suite à l’attrape couillon d’Antoine je me suis dit que je pourrais préparer une trappe pour Vincent Fleury directement. Si je disais que π(100)2 était loin de 50000, il aurait pu trouver une excuse ou une autre. Mais j’étais certaine que si je faisais le calcul autrement (ma notation reste correcte, mais comme il ne lit que la moitié de ce qu’il devant lui…) il viendrait me corriger et laisser une trace de son imprécision “plein pot”, pour qu’il ne puisse pas la renier par la suite.