The active stem cell specific expression of sponge Musashi homolog EflMsiA suggests its involvement in maintaining the stem cell state

► We identified EflMsiA as the first sponge stem cell (archeocyte)-specific gene. ► EflMsiA protein is predominantly localized in the nucleus in interphase archeocytes. ► M-phase archeocytes with high EflMsiA expression are probably self-renewing. ► M-phase archeocytes with low EflMsiA expression might be differentiating. ► Symmetric cell division of archeocytes is strongly suggested.