Fig. 2.

Convergent-extension movements are linked to the mixing of stellate and principal cells. (A) Convergent-extension movements occur first in the distal region of the renal tubules, and move more proximally as the tubules elongate. Stills taken every 5.00 min from a time-lapse movie of elongating tubules in embryos expressing UAS-Src-GFP under CtB-GAL4 control. (A1–A6; Supplementary movie S1). Arrows point to the proximal region and arrowheads to the distal tip. (B–D) Stage 16 wild-type (B) and cv-c mutant embryos (C and D) stained for Tsh (green) to visualise the stellate cells and Ct (red). (B) In wild-type stage 16 embryos the tubules are long, thin tubes with stellate cells spaced out along their length. (C) In stage 16 cv-c mutants, the tubules appear as short, thick structures, due to the failure of convergent-extension movements. A 25 μm z-stack through a cv-c mutant embryo, shows that stellate cells are clustered together in the tubule epithelium. (D) A single confocal z-section of a cv-c mutant tubule confirms that stellate cells remain clustered together and do not mix with principal cells. (E) Model illustrating the behaviour of stellate cells during stages 13 and 14. They integrate into the tubules during stage 13 and are spaced out as the tubule elongates. White lines outline the tubules.