Fig. 1

Lineage tracing of Lgr5⁺ or Sox9⁺ nephron stem/progenitor cells using the lacZ or GFP inducible genetic reporter system. a First, two transgenic mice were constructed, one was inserted with the Cre gene after the cell type or tissue-specific (TS) promoter, and the other was inserted with a reporter gene, such as GFP, after the promoter of ROSA26, and the expression of the reporter gene was stopped by the STOP sequence flanked by Loxp sites. When the mice of the two transgenic lines are crossed, the Cre enzyme will excise the STOP sequence and the reporter gene GFP will be successfully expressed in a specific cell or tissue [4]. By fusing the Cre gene to the tamoxifen-reactive hormone-binding region of the estrogen receptor (ER), a temporal restriction of expression can be achieved. In the absence of tamoxifen (TAM), Cre is inactive. After administration of tamoxifen, Cre is activated, transported from the cytoplasm to the nucleus, and mediates recombination between LoxP sites. As a result, the STOP codon is excised and the cells are permanently labeled with the reporter gene. The red arrows represent Loxp sites. b Schematic diagram of the nephron structure derived from Lgr5⁺ cells [35]. c Graphic abstract of the nephron structure derived from Sox9 positive cells [36]. Reproduced with permission from Ref. [35, 36]