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BBB Seminar: Fabian Rentzsch

Early steps in nervous system evolution: neural development in a sea anemone

Fabian Rentzsch, Sars International Centre for Marine Molecular Biology, Bergen

The emergence of the nervous system was a fundamental step in the evolution of multicellular animals and a prerequisite for the elaboration of complex body plans found in most metazoan phyla. We are studying neural development in one of the evolutionary oldest phyla that possesses an integrated nervous system, the Cnidaria, with the aim to understand the evolutionary origin of the nervous system. The nervous system of extant cnidarians (such as sea anemones) lacks brain-like structures and clear centralization, and presumably resembles an evolutionary ancestral state. We are analyzing three aspects of neural development in the sea anemone Nematostella vectensis: (I) axon guidance, (II) synapse formation, and (III) the development of the apical sense organ.

Apical organs are common sensory structures located at the aboral pole of many free swimming marine larvae, but despite their broad phylogenetic distribution, the genetic control of their development as well as their exact function are poorly understood. We identified two Fibroblast growth factor (FGF) genes in Nematostella that are expressed exclusively in the developing apical organ. Surprisingly, functional studies using microinjection of morpholino antisense oligonucleotides show that the two FGFs have opposing activities: FGFa1 signalling via MAPK/ERK is required for the formation of the apical organ, whereas FGFa2 functions to restrict its size and prevent precocious differentiation. We further show that loss of the apical organ in FGFa1 morpholino injected embryos prevents metamorphosis of larvae into polyps. These data provide first insights into the genetic basis of the development of the apical sense organ and suggest an essential function in the transition from larval to adult stage.

Host: Donald Gullberg (Donald.Gullberg@biomed.uib.no), Department of Biomedicine

 

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