Origin and diversification of extraembryonic tissues in jawed vertebrates
Distinct extraembryonic tissues have arisen several times during vertebrate evolution, for instance in amniotes but also in chondrichthyans, concomitantly with a spectacular increase of the yolk mass. Our results in the catshark highlight similarities with amniote early development, suggesting parallel evolution processes.
How have the mechanisms controlling early development been altered by these adaptations?
We address this question by analysing the mechanisms controlling regionalisation and morphogenesis of the early embryo, as well as the specification of germ layers and yolk sac in the catshark S. canicula, and by comparing these data to those available in amniotes. Experimental approaches include descriptive molecular analyses (ISH, IHC including quantitative fluorescence), and functional or experimental analyses (in ovo pharmacological treatments, cell tracking using fluorescent dyes). In collaboration with the BioEmergences platform (USR 3695, N. Peyriéras), we are also implementing 4D confocal imaging approaches, in order to develop quantified descriptions and modelling of catshark early development.
Origin and diversification of the mechanisms controlling epithalamic asymmetry formation
The epithalamus is the only brain region to exhibit marked left-right asymmetries in all major vertebrate taxa. Underlying mechanisms have thus far been analysed in three model organisms, the zebrafis, lamprey and catshark. Our results have shown that these three species use very different strategies for epithalamic asymmetry formation.
How have the mechanisms controlling this process evolved across vertebrates?
We address this question by dissecting the mechanisms of asymmetry formation in the lamprey and the catshark and by comparing the results with data obtained in the zebrafish (coll. with P. Blader, CBD Toulouse). Experimental approaches include descriptive molecular analyses (ISH, IHC), functional and experimental analyses (pharmacological treatments, BrdU incorporation experiments, development of loss-of-function analyses using CRISPR-Cas9 genome editing in the lamprey) and transcriptomic analyses.
The resources developed by our group (high-throughput EST and recombinant cDNA collections in the lamprey and catshark; catshark transcriptome and genome; experimental protocols) lead to collaborations on different questions related to vertebrate development and evolution (origin of paired limbs, axial elongation, brain regionalisation, teeth formation...)