Expression study of molecular markers involved in staminality and differentiation in the colonial ascidians Botryllus schlosseri

All multicellular organisms originate from a small set of totipotent embryonic cells that differentiate into a structured body plan during embryogenesis. The ability to generate an embryo from a single cell and the regenerative capabilities of metazoans suggest the presence of cell types with stem cell attributes. Compound ascidians, like Botryllus schlosseri, offer the opportunities to investigate the biology of both embryonic and adult stem cells thanks to the presence of sexual and asexual reproduction. In B. schlosseri new buds emerge as thickening of the peribranchial epithelium in a process call palleal budding. Sometimes, a vascular budding occurs, with the development of new buds formed by circulating multipotent or pluripotent cells. These two kinds of budding processes render B. schlosseri a good research tool for the study of staminality. In B. schlosseri, during the cyclical generation change, an increase in the number of hemoblasts occurs which will replace, after their differentiation, the circulating cells undergoing apoptotic cell death. Ascidian hematopoiesis occurs in close proximity to the pharyngeal vessels, in the so-called “hematopoietic nodules” and in the endostyle, the cells of which proliferate and migrate to regenerating organs in developing buds. Despite the morphologic suggestions that hemoblasts are the precursors of all the circulating cell types, immunocytes included, there is a general lack of biochemical and molecular data supporting this assumption. Here we report the first results on the characterisation of staminality and differentiation molecular markers such as ABCG2, CD133 and GATA2/3 considered hematopoiesis molecular marker in other deuterostomes.