Confocal images of cortical sections using Ab’s against Pds (green) (A–C), AE1 (yellow) (D–G) as well as ToPro3 for nuclear staining (red). In WT kidneys, an apical/luminal staining pattern is visualized, which agrees well with previous observations (12). Apical Pds signals mark β-intercalated cells (12). In Foxi1^–/– sections, no Pds signal can be detected. In the cortex of WT mice, tubular cells are AE1 positive (D), mostly at their basolateral border (E). In the medulla, a similar pattern is visualized (F and G). The lumen is marked with a dashed white line in F. In Foxi1^–/– kidneys, no parenchymal staining can be identified; only erythrocytes stain (D–E), since the antiserum (apart from identifying the kidney and α-intercalated cell-specific isoform of AE1) also recognizes the erythrocyte isoform of AE1 (41). Scale bars: 10 ∝m.