Fig. 1.

Renal tubule cells are polarised throughout development. (A-D) Stage 11; (E-H) stage 13; (I-L) stage 16. (A,E,I) Embryos stained for the transcription factor Cut (Ct), to mark renal tubule cells. The renal tubules bud out from the hindgut primordium during stage 11 (A, arrow) and undergo several rounds of cell division. These are completed by stage 13, when the tubules appear as short fat tubes (E, arrow). During stages 13 to 16 they elongate dramatically and narrow to a two-cell circumference (I, arrow). (B,F,J) Crb (red) and Baz (green) are localised to the apical membranes of tubule cells during stages 11-16, with Baz overlapping with, but slightly apical to Crb during stages 11-13. (C,G,K) Dlg (red) localises to the lateral membranes and shows no overlap with Baz (green). (D,H,L) ZAs, marked by Armadillo (Arm, red), are maintained between tubule cells (nuclear Ct, green) throughout cell rearrangements. Dashed white lines outline tubules.