“Zebrafishing” for Novel Genes Relevant to the Glomerular Filtration Barrier

Figure 2

Tubular detection of proteinuria. The normal glomerular filter in a zebrafish embryo has a similar size selectivity compared to the glomerular filter in a mammalian kidney. Excessive amounts of high-molecular-weight proteins in the tubules would indicate a loss of this size selectivity and damage to the filter unit. To examine this we inject a 70 kD rhodamine-red-fluorescent labelled dextran (a) at 48 hours after fertilization into the cardinal vein of the control and morpholino-injected wt1b-transgenic fish. These fish express a green-fluorescent protein (b) in the glomerulus (asterisk in (b)) and in the proximal tubular part of the pronephros (white arrows in (b)) ((b) fluorescence view of a normal pronephros; (b′) fluorescent view merged with brightfield picture indicating the localization of the center of the pronephros in the pectoral fin region). The combination of both ((c)–(c′′), merged view enlarged in (d)) can be used to visualize reuptake of filtered high-molecular-weight dextran in the proximal tubular region (white arrowheads in (d)). Examinations can be performed in living, anaesthetized fish larvae allowing for serial examinations of the same animal over time.