Repression of interstitial cell identity in nephron progenitor cells by Pax2 establishes the nephron-interstitium lineage boundary throughout mammalian kidney development

The kidney contains the functional units, the nephrons, surrounded by the renal interstitium. Previously, we discovered that, once Six2-expressing nephron progenitor cells and Foxd1-expressing renal interstitial progenitor cells form at the onset of kidney development, descendant cells from these populations contribute exclusively to the main body of nephrons and renal interstitial tissues, respectively, indicating a lineage boundary between the nephron and renal interstitial compartments. Currently, it is unclear how lineages are regulated during kidney organogenesis. We demonstrate that nephron progenitor cells lacking Pax2 activity failed to differentiate into nephron cells, but can switch fates into renal interstitium cell types. These data suggest that Pax2 function maintains nephron progenitor cells by repressing transdifferentiation into renal interstitial cell states. Thus, the lineage boundary between the nephron and renal interstitial compartments is maintained by the Pax2 activity in nephron progenitor cells during kidney organogenesis. Overall design: We carried out single cell RNA-seq on mouse embryonic kidneys. Looking at wild type capping mesenchyme and wild type stromal cells, as well as Pax2 mutant capping mesenchyme cells.