Figure 5. In WT animals, varicosities are present during excretory cell development and disappear in adult animals.

(A) Although large and irregular varicosities were not observed in WT adult animals, we found that varicosity structures were common in early larval development. In L1 larvae, varicosities were present at regular intervals along the entire length of the excretory cell. (B) By the L3 stage of development, these developmental varicosities decreased in size such that they were no longer easily visible. (C,D) A TEM image of a narrow region (C) and a varicosity (D) in the EC of a WT animal during the L1 stage of larval development. Like the varicosities observed in nhr-31 RNAi adults, the L1 varicosities contained extra cellular material, with more canaliculi and larger mitochondria (see also Table 3). Larger EM images are available in the supplement (Figure S3). (E) Quantification of EC diameters when exposed to RNAi at different points in development. Graph includes diameters measured using the P_nhr-31::gfp strain and confocal microscopy. The graph contains measurements of the EC of animals exposed to the following treatments: Measurement of L1 larvae starved for 12 hours (starved-L1), measurement of L3 ECs when exposed to control RNAi (L3-control) or nhr-31 RNAi (L3+nhr-31 RNAi) from the L1 to the L3 stage of development. Measurement of L4/young adult ECs when worms are exposed to control (L4/YAd control) or nhr-31 RNAi (L4/YAd+nhr-31 RNAi) from the L1 to the L4 stage. Animals exposed to control RNAi (Day 2Ad Control) or NHR-31 RNAi (Day2 Ad+larval nhr-31 only) from L1 to 2 day old adults, and then switched to control RNAi, and animals exposed to nhr-31 RNAi from L1 until day 2 of adulthood (day 2Ad+nhr-31 RNAi). This data shows that exposure to nhr-31 RNAi from the L1 stage of development to the L3 stage of development does not impact EC size in L3 worms, but that varicosities appear in late L4 development and continue to grow into adulthood.