RARA and acute kidney injury: In addition, we found increased numbers of Sox9+ PTECs (defined by LTL and DAPI staining nuclei), a transcription factor that is expressed by dedifferentiated and regenerative PTECs after AKI (56, 57), and Ki67+ PTECs, a marker of active cell proliferation, in PTEC DN RAR mice after Rhabdo-AKI (Figure 5, A–D).