In situ hybridization in zebrafish kidney. Whole-mount in situ hybridization was carried out in zebrafish kidney. (A-E) The expression signals from egr1 (A), gata2 (B), id1 (C), f11r (D), and krt18 (E) were visualized by nitroblue tetrazolium chloride and 5-bromo-4-chloro-3-indolyl-phosphate. Cells expressing egr1, f11r, gata2, id1, and krt18 mRNA are present on the surface of renal tubules (arrowheads). (F-J) Double-fluorescent whole-mount in situ hybridization was performed. The expressions of egr1, gata2, id1, f11r, and krt18 (left panels) and abcg2a (middle panels) were visualized by fluorescein and cyanine 3, respectively. Right panels show merged images. Cells coexpressing egr1, gata2, id1, f11r, or krt18 and abcg2a are present on the surface of renal tubules (arrowheads). Dotted lines indicate the surface of the renal tubule. All scale bars indicate 5 μm.