Supplemental Figure S3.

Although phosphorylated Creb (p-Creb) expression in mutant proximal tubules is restricted to lotus tetragonolobus lectin (LTL)-negative cystic segments, total (unphosphorylated) Creb is expressed in LTL-positive Six2creFrs2α knock-out (KO) cells. A–D: Representative co-immunofluorescence images for p-Creb (red) or unphosphorylated (total) Creb (red) with LTL (green) on serial sections obtained from P21 control and Six2creFrs2αKO kidneys. A and B: P21 controls. In controls, p-Creb and total Creb both are present in stromally derived interstitium (arrows with black borders) and glomeruli (G), and in LTL-negative tubules (likely collecting ducts) (arrows); however, although p-Creb signal is absent in LTL-positive proximal tubules (A, arrowheads), total Creb signal is present in LTL-positive proximal tubules (B, arrowheads). C and D: In Six2creFrs2αKO kidneys, p-Creb is expressed ectopically in LTL-negative cyst lining cells (concave arrowhead) and is absent in LTL-positive cells in nondilated tubules (arrowhead) and in cyst lining cells (concave arrow); however, unphosphorylated Creb is expressed in both LTL-negative and LTL-positive cells (arrows indicate Creb staining in many nonproximal tubular cells). Arrows with black borders indicate p-Creb and Creb signal in stromal cells. Scale bars: 50 μm.