Canonical and early lineage-specific stem cell types identified in planarian SirNeoblasts

Background:The pluripotent stem cells in planarians,a model for tissue and cellular regeneration,remain further identification.We recently developed a method to enrich piwi-1+cells in Schmidtea mediterranea,by staining cells with SiR-DNA and Cell Tracker Green,named SirNeoblasts that permits their propagation and subsequent functional study in vivo.Since traditional enrichment for planarian neoblasts by Hoechst 33342 staining generates X1 cells,blocking the cell cycle and inducing cytotoxicity,this method by SiR-DNA and Cell Tracker Green represents a complementary technological advance for functional investigation of cell fate and regeneration.However,the similarities in heterogeneity of cell subtypes between SirNeoblasts and X1 remain unknown.Results:In this work,we performed single cell RNA sequencing of SirNeoblasts for comparison with differential expression patterns in a publicly available X1 single cell RNA sequencing data.We found first that all of the lineagespecific progenitor cells in X1 were present in comparable proportions in SirNeoblasts.In addition,SirNeoblasts contain an early muscle progenitor that is unreported in X1.Analysis of new markers for putative pluripotent stem cells identified here,with subsequent sub-clustering analysis,revealed earlier lineages of epidermal,muscular,intestinal,and pharyngeal progenitors than have been observed in X1.Using the gcm as a marker,we also identified a cell subpopulation resided in previously identified tgs-1+neoblasts.Knockdown of gcm impaired the neoblast repopulation,suggesting a function of gcm in neoblasts.Conclusions:In summary,the use of SirNeoblasts will enable broad experimental advances in regeneration and cell fate specification,given the possibility for propagation and transplantation of recombinant and mutagenized pluripotent stem cells that are not previously afforded to this rapid and versatile model system.

涡虫肌肉系统再生研究进展

涡虫结构简单,具有极强的再生能力。再生,是指机体受损后,细胞、组织和器官的修复,并重建适当的组织极性、结构。在同一动物的不同组织中可以采用多种模式。当受到创伤后,涡虫的任意部位均可以再生出完整的个体。这种强大的再生能力是由neoblast介导的,neoblast是一种含有多能干细胞的增殖细胞群,具有异质性。涡虫具有明显的极性,受损后,严格按照前后轴、背腹轴、左右轴进行再生。涡虫有发达的体壁肌肉组织,在整个有机体内形成复杂的肌肉网络。涡虫的体壁肌肉细胞产生的位置信息基因(position control genes, PCGs),在再生过程中控制前后模式,对干细胞介导的组织替换和再生起着重要的指导作用。文章讨论了涡虫肌肉再生以及肌肉与极性基因之间的联系。