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Integrative Biology of Marine Organisms
UMR 7232



Ascidian larva


The ChorMedFin (Chordates Median Fin: Gene regulatory networks controlling median fin formation in basal chordates) project is supported by an ANR grant. It aims at understanding the evolution of median fin formation by studying tunicates and cephalochordates embryos.

Ciona larval tail epidermis is characterized by a crystal-like cellular organization of only 8 rows of cells, each endowed with a specific expression profile. We have uncovered key events that establish this patterning and control the formation of two derivatives along the midlines: the peripheral nervous system (composed of epidermal sensory neurons) and the median fin. This latter structure is a fascinating case of morphogenesis without cells. The tunic surrounding the larva is formed by the secretion of extracellular material (including cellulose) extending along the ventral and dorsal midlines to form the fin blades. We have proposed that the tail epidermal neurons and the fin may have common origins with vertebrate structures, the neural crest and/or placodes and the median fin, respectively.

In order to get insights into the formation and evolutionary history of the median fin and peripheral nervous system in chordates, we would like to:
1) Reconstruct the GRN in Ciona intestinalis.
2) Describe the development of the equivalent structures and uncover their specification in other basal chordates (tunicates and cephalochordates).
3) Test GRN conservation by comparing expression patterns and cis-regulatory elements in the different species

Sébastien Darras (sebastien.darras @ obs-banyuls.fr) - 15/04/16