Live tracking of basal stem cells of the epidermis during growth, homeostasis, and injury response in zebrafish

Basal stem cells of the epidermis continuously differentiate into keratinocytes and replenish themselves via self-renewal to maintain skin homeostasis. Numerous studies have attempted to reveal how basal cells undergo differentiation or self-renewal; however, this has been hampered by a lack of robust basal cell markers and analytical platforms that allow single-cell tracking. Here, we report integrin b4 (itgb4) is a useful marker for basal cell labelling, irrespective of the body region, stage, and regenerative status. We employed Cre-loxP recombination in combination with live cell tracking of single basal clones in the caudal fin and investigated the embryonic origin and behaviour of basal cells during fish growth and homeostasis. Although most basal cells, including those in fins, became quiescent in the adult stage, genetic cell ablation showed that basal cells were reactivated to either self-renew or differentiate, depending on the injured cell type. Our findings provide a platform for quantitative in vivo imaging of basal stem cells applicable at wider stages and under various conditions and reveal unanticipated basal cell dynamism in response to distinct wound signals. Overall design: To investigate whether itgb4+ epidermal basal precursors already possess a basal cell-like identity immediately after fate segregation at 1 day post fertilization (dpf), we isolated itgb4+ basal precursors, krt4+ periderm cells from zebrafish embryos at 1 dpf, and adult itgb4+ basal cells from zebrafish caudal fin by fluorescence-activated cell sorting. We then performed gene expression profiling analysis using data obtained from RNA-seq of 3 different cells at 2 time points. Comparative gene expression profiling analysis of RNA seq data for embryonic basal cell precursors, embryonic periderm, and adult basal cells.