SoxB2 in sea urchin development: implications in neurogenesis, ciliogenesis and skeletal patterning

Evgeniya Anishchenko, Maria Ina Arnone, Salvatore D’Aniello

Current studies in evolutionary developmental biology are focused on the reconstruction of gene regulatory networks in target animal species. From decades, the scientific interest on genetic mechanisms orchestrating embryos development has been increasing in consequence to the fact that common features shared by evolutionarily distant phyla are being clarified. In 2011, a study across eumetazoan species showed for the first time the existence of a highly conserved non-coding element controlling theSoxB2gene, which is involved in the early specification of the nervous system. This discovery raised several questions aboutSoxB2function and regulation in deuterostomes from an evolutionary point of view. Due to the relevant phylogenetic position within deuterostomes, the sea urchinStrongylocentrotus purpuratusrepresents an advantageous animal model in the field of evolutionary developmental biology. Herein, we show a comprehensive study ofSoxB2functions in sea urchins, in particular its expression pattern in a wide range of developmental stages, and its co-localization with other neurogenic markers, asSoxB1,SoxCandElav. Moreover, this work provides a detailed description of the phenotype of sea urchinSoxB2knocked-down embryos, confirming its key function in neurogenesis and revealing, for the first time, its additional roles in oral and aboral ectoderm cilia and skeletal rod morphology. We concluded thatSoxB2in sea urchins has a neurogenic function; however, this gene could have multiple roles in sea urchin embryogenesis, expanding its expression in non-neurogenic cells. We showed thatSoxB2is functionally conserved among deuterostomes and suggested that inS. purpuratusthis gene acquired additional functions, being involved in ciliogenesis and skeletal patterning.