La fin (l’infini) du bruit

Á... Á propos d’Erosphère propos d’Érosphère, dans un entretien pour la Revue LIEN2 en 1992, François Bayle explique que le projet d’une Suite fut déclenché par la composition de la 1ère œuvre du cycle – Tremblement de terre très doux. Il y indique : « je me suis petit à petit aperçu, en réalisant cette pièce, que j’y traitais d’un problème inhérent à l’acous- matique : celui du désir, [...] c’est-à-dire des sons appétissants, des sons voluptueux, ce qui m’a entraîné vers un projet plus vaste que j’ai appelé Érosphère, cette loi de gravitation du désir. »3 Plus tard le compositeur déclare : « Au moment d’Érosphère mon projet portait sur les mécanismes du désir, l’érotisme sonore, d’où le titre d’Éros- phère. Découvrir les archétypes érotiques des formes sonores. »4 Dans les notes qui accompagnaient la première édition en disque, Bayle présente sa définition du mot Érosphère : Ce tissu nerveux qui enveloppe notre monde habité d’un réseau d’ondes modulées à une infinité de fréquences, ce nuage de chaleur infra et supra sensorielle que diffusent des mégas milliards d’ émetteurs biologiques, cet anneau où circule la force de ce cosmos, je l’appelle l’érosphère.

The role of Hedgehog signaling during zebrafish larvae fin fold regeneration

Several studies have demonstrated that although the structure of the adult and larval zebrafish caudal fin is different, there are similarities at the cellular and molecular level that turn larval zebrafish fin fold a useful model to study the basic principles of regeneration. In this process, while the essential role for Hedgehog (Hh) signaling is well established in the adult zebrafish caudal fin system, its involvement in juvenile tissue regeneration is still unknown. The aim of this Master thesis was therefore to evaluate the contribution of the Hh signaling pathway to the larval zebrafish fin fold regeneration process. Accordingly, we analyzed the expression of several Hh signaling components through in situ hybridization. Here, we showed that several of these genes are effectively expressed in the larval regenerating fin tissue, suggesting a role for Hh signaling also during larval regeneration. However, divergence in the regulation of few Hh signaling components appears to exist between the adult and larval zebrafish fin regeneration processes. Nevertheless, similarly to adult caudal fin regeneration, when Hh signaling was blocked, by using cyclopamine, the larval fin fold regenerative outgrowth is severely impaired. Since larval zebrafish fin fold is ciliated, and primary cilia are closely related to Hh signaling regulation in vertebrate systems, we further addressed the role of primary cilia during larval fin fold regeneration process. To this end, we used the zebrafish iguana mutant, in which primary cilia are not formed, to study the modulation of Hh signaling expression during larval fin fold regeneration in the absence of primary cilia. Here, we found that several genes were expressed with a delay, coincident with the delay in the mutant fin fold regeneration observed in previous work. We show that Hh signaling in the fin fold is crucial to promote cell proliferation. When Hh signaling is blocked using cyclopamine there is a strong blockage of cell proliferation and regeneration is also blocked. Surprisingly, in iguana mutants where Hh signaling is impaired but not totally blocked, cell proliferation is not detected but regeneration still occurs. This raises the question about the requirement of cell proliferation in larvae fin fold regeneration. By blocking the cell cycle using aphidicolin we demonstrate that cell proliferation is not necessary for zebrafish larvae fin fold regeneration.