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FIGURE 2
Knocking down TMEM14A mRNA translation causes proteinuria. Knocking down mRNA translation of the zebrafish homologue of TMEM14A through morpholino injection results in proteinuria. (a–f) Representative immunofluorescence images of transversal sections of zebrafish proximal tubule cells after injection of a mixture of red labeled 3 kDa dextran tracer (a, c, e) and green labeled 70 kDa dextran tracer (b, d, f) in controls (a,b), TMEM14A knockdowns (C and d), and PAN injected positive controls (e,f). Dextran tracers that passed the GFB are reabsorbed by proximal tubule epithelial cells in endosomes. Thus, reabsorbed dextran tracer appears as fluorescent droplets. The number of proximal tubule reabsorption droplets was counted in a blinded manner in sections as those shown here. The arrowheads in B point out examples of counted droplets. The circled areas show high fluorescence due to dextran present in the peritubular capillaries. These areas are not counted as reabsorption droplets. The sharpness of the images in panels A through F has been enhanced by overlaying them with a digital high pass filter. (g and h) Uptake of the red 3 kDa marker (g) was used to assess tubular reabsorption function, which was intact in both TMEM14A knockdown animals and controls. In the knockdown model, significantly more 70 kDa droplets (h) have passed the GFB and were subsequently reabsorbed. Puromycin aminonucleoside (PAN) injected zebrafish were used as positive controls. Students