The most ancient agent of animal axial patterning regulating the posterior-anterior (PA) axis in Bilateria and the oral-aboral (OA) axis in the bilaterian sister group Cnidaria is beta-catenin signaling. In the sea anemone Nematostella and in deuterostome Bilateria, beta-catenin activates transcription factor genes, expressed along the OA/PA axis. The separation of their expression domains is achieved by more orally expressed transcription factors repressing the more aborally expressed transcription factor genes. In Nematostella, we found four oral transcription factors preventing midbody genes from expanding orally, and a midbody transcription factor preventing aboral genes from expanding into the midbody. However, we do not know what prevents the expansion of the oral genes into the midbody domain, generating very precise expression boundaries instead, and what initiates and maintains the expression of the aboral genes. In this project, we will test the hypothesis that sharp expression domain boundaries in the Nematostella gastrula are established and maintained by the formation of pairs of mutually repressive transcription factors, and identify the mechanism of how the expression of the aboral regulatory genes is initiated and maintained.

FWF Project number: P 36080