Fig. 4

a Pre-embedding silver-enhanced immunogold staining for Dr-Vsp in (I) LREs and (II) IECs of 14-dpf wild-type zebrafish larva. The right two images are the same as the middle images but were highlighted with red and blue for microvilli and subapical region, respectively. In LREs, immunoparticles for Dr-Vsp are preferentially distributed at the subapical region while rarely detectable at microvilli, consistent with results of Dr-Vsp immunofluorescence in Fig. 3. In IECs, immunoparticles for Dr-Vsp are rarely detectable at both subapical region and microvilli, consistent with Dr-Vsp immunofluorescence and RNA-seq analysis in Fig. 2. Scale bar = 2 µm. b MDCKII cells co-expressing Dr-Vsp-mCherry and (I) Rab5-EGFP for early endosomes; or (II) Rab11-EGFP for recycling endosomes. Colocalized fluorescent signals (circles) represent Dr-Vsp expression at the endosomal membranes of early and recycling endosomes. Note that non-colocalized Dr-Vsp signals (arrowheads) are also present in both images. Magenta, Dr-Vsp. Green, Rab5 or Rab11. Scale bar = 20 µm.