PDGFRB and glomerulonephritis: For example, as platelet-derived growth factor receptor (PDGFR) signaling plays a role in FSGS [28], and Pdgfra and Pdgfrb expression are both strongly expressed in PEC-B but not in PEC-A isotypes [9], it will be intriguing to learn whether changes in Aldh1a2 expression and RA signaling play any role in the increased PEC-B cell numbers in anti-GBM glomerulonephritis, FSGS, and other kidney diseases [9, 28] and whether and how Aldh1a2, RA and PDGFR signaling pathways crosstalk in PECs.