Introduction

The International Emerging Action project « Staining and Tracking Sponge Cells to describe morphogenetic processes » (STraS) managed by Dr E. Renard, launched a collaboration between 3 French teams and one Australian team, in order to study and compare the cell biology of 3 sponge species with different features.

Context and objectives

Gene content of sponges was characterized by transcriptomic or genomic approaches. Surprisingly, despite their simplicity sponges contain most of the developmental gene families present in bilaterians. The next step to be reached is now to understand how similar genetic toolboxes can result in widely dissimilar bodyplan organization, dynamics and life histories. To answer this question, three main axes of research have to be undertaken : 1) sequencing more whole genomes ; 2) conducting much more gene expression studies (available data remain sparse) ; 3) developing reproducible knock down protocols ; 4) reinterpreting sponge cell structure and mechanisms with nowadays tools.
The 4 partners are interested and involved in these four aspects, but the present project focuses on point 4. The present knowledge of sponge cell biology mainly relies on classical (static) observations, which fail to provide a dynamical description of cellular behaviors and mechanisms, essential to decipher morphogenetic processes.
Much remains to be tested in terms of cell specific staining and tracking to understand which key cellular processes are involved in sponge morphogenesis and to evaluate the so-called “lability” of sponge cells.

Main OBJECTIVES OF THE PROJECT

We propose to join our efforts and skills to make substantial advances in these techniques to evaluate the implications of three primordial cellular mechanisms : cell death, cell proliferation/differentiation and mesenchymal-epithelial/epithelial-mesenchymal transitions (MET/EMT). We will perform these comparisons in 3 species with different features : 1 filtering Demosponge Amphimedon queenslandica, 1 carnivorous sponge (devoid of aquiferous system) Lycopodina hypogea, 1 Homoscleromorph sponge Oscarella lobularis.

We aim at :
Aim 1 : Evaluating the relative stemness of sponge cell types
Aim 2 : Evaluating the relative involvement of EMT/MET during regeneration
Aim 3 : Evaluating the involvement of apoptotic events during regeneration

institutions and laboratories involved

France

• ISEM – Institut des Sciences de l’Evolution de Montpellier (Université de Montpellier, CNRS, IRD, EPHE, CIRAD, INRAP). Team « Morphogenesis and evolution »
• IMBE – Institut Méditerranéen de Biodiversité et d’Ecologie marine et continentale (Aix Marseille Université, CNRS, IRD, Avignon Université). Team « Origin and evolution of the biodiversity »
• CNRS UMR7288 IBDM – Institut de Biologie du Développement de Marseille. Team « cell polarity and epithelial morphogenesis ».

Australia

• Degnan’s lab, University of Queensland.

EDU staining of choanocyte nuclei of Oscarella lobularis (E.

Renard)