Molecular characterization of skeletal regeneration in the brittle star amphiura filiformis

Echinoderms are well known for their extensive regenerative abilities, but have been neglected in the field due to the lack of available molecular tools and resources [1]. Recently, developmental [2] and adult transcriptomes [3, 4] of the brittle star Amphiura filiformis have been sequenced, which opened up this species for molecular investigations of its rapid arm regeneration process. We use this brittle star as a model to understand the cellular and molecular aspects of skeletogenesis during adult arm regeneration and the potential role of the FGF signalling pathway in this process. Ultimately, we compare the molecular network driving regeneration of the skeleton to that underlying embryonic skeleton development [5]. Following a characterization of the anatomy and development of the skeleton during arm regeneration in A. filiformis [6], we established methods for spatio-temporal expression analysis [7] and pharmacological treatments to characterise genes involved in adult arm regeneration. We found that 18 embryonic skeletogenic mesoderm genes (transcription factors, signaling receptors and downstream differentiation genes) are also expressed in the dermal layer of the adult regenerating arm, where skeletal spicules form. FGF signalling perturbation using the SU5402 inhibitor interferes with skeleton formation during both embryonic development and adult regeneration of this brittle star. A large-scale comparison of genes affected by SU5402 in adult arm regeneration and during embryonic development revealed a conservation of network components downstream of FGF signalling between those two developmental modes. Acknowledgements: We thank the staff at the Sven Lovén Centre for Marine Sciences in Kristineberg, especially Olga Ortega-Martinez and Sam Dupont, for assistance during animal and sample collection. References: 1. Dupont S, Thorndyke M (2007) Bridging the regeneration gap: insights from echinoderm models. Nat Rev Genet 8:8–10 2. Delroisse J, Ortega-Martinez O, Dupont S, Mallefet J, Flammang P (2015) De novo transcriptome of the European brittle star Amphiura filiformis pluteus larvae. Mar Genomics. doi: 10.1016/j.margen.2015.05.014 3. Purushothaman S, Saxena S, Meghah V, Swamy CVB, Ortega-Martinez O, Dupont S, Idris M (2014) Transcriptomic and proteomic analyses of Amphiura filiformis arm tissue-undergoing regeneration. J Proteomics 1–12 4. Delroisse J, Mallefet J, Flammang P (2016) De Novo Adult Transcriptomes of Two European Brittle Stars: Spotlight on Opsin-Based Photoreception. PLoS One 11:e0152988 5. Dylus DV, Czarkwiani A, Stångberg J, Ortega-Martinez O, Dupont S, Oliveri P (2016) Large-scale gene expression study in the ophiuroid Amphiura filiformis provides insights into evolution of gene regulatory networks. Evodevo 7:2 6. Czarkwiani A, Ferrario C, Dylus D V., Sugni M, Oliveri P (2016) Skeletal regeneration in the brittle star Amphiura filiformis. Front Zool 13:18 7. Czarkwiani A, Dylus D V., Oliveri P (2013) Expression of skeletogenic genes during arm regeneration in the brittle star Amphiura filiformis. Gene Expr Patterns 13:464–472