Czarkwiani, A; (2017) Towards a gene regulatory network for the regeneration of the adult skeleton in the brittle star Amphiura filiformis. Doctoral thesis , UCL (University College London).

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Abstract

The recent emergence of transcriptomic data available for echinoderms opened up the possibility of using this group of animals to study the molecular aspects underlying their extreme regenerative abilities. I use the brittle star Amphiura filiformis as a model to understand the cellular and molecular aspects of skeletogenesis during adult arm regeneration. This allowed me to begin compiling essential preparatory work for studying the gene regulatory network (GRN) underlying adult regeneration of the skeleton, which can be compared with the embryonic developmental program. I first studied the anatomy and morphogenesis of the skeleton during arm regeneration in A. filiformis, and defined a staging system relevant for the early developmental events occurring in the first 8 days post-amputation. I then established methods for spatio-temporal expression analysis and pharmacological treatments to characterise genes involved in adult arm regeneration in this brittle star. 18 genes expressed in embryonic skeletogenic cells (transcription factors, signalling receptors and downstream differentiation genes) were found to be expressed in the dermal layer of early stage regenerates, where skeletal spicules first form. This showed a very similar molecular signature of larval and regenerating arm skeletogenic cells. FGF signalling perturbation using the SU5402 inhibitor interfered with skeleton formation both in embryonic development and adult regeneration of the brittle star. A large-scale comparison revealed a conservation of a cohort of genes affected by SU5402 downstream of FGF signalling between those two developmental stages. In conclusion we found morphological and molecular similarities underlying skeletogenesis during regeneration and embryonic development suggesting that the gene regulatory network driving skeletogenic cell specification and differentiation could be re-activated in adult arm regeneration.

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