Epithelia are cellsheets playing a seminal role in body integrity of all animals. Because they control physiological processes, any defect in epithelial integrity causes major diseases in vertebrates (cancer, ciliopathies, homeostasis lethal diseases …). Understanding how this fundamental cell organization emerged during early animal evolution is therefore an exciting question. According to studies focused on bilaterian models, epithelia were defined by three criteria: a basement membrane composed of Type IV collagen, Apical-basal cell polarity and cell-cell junctions.

Although there is no doubt now for the presence of physiologically functional epithelia in the last ancestor of animals harboring true adhesive, polarity and sealing properties needed to control internal-external exchanges, molecular identity of the genes and proteins responsible for this organization – and consequently the homology of these characteristics across animals- remains to be established.

The major objective of this project is thus to identify the molecular components involved in epithelium patterning and maintain in ctenophores and sponges, the most ancient animal lineages to date: this is a decisive prerequisite to embrace epithelial diversity and to propose an evolutionary scenario.