Zebrafish Fat1 genetically interacts with zebrafish Scribble. (A) MO-induced knockdown of zFat1 was compared with the knockdown of zebrafish Prickle 2 (zPk2), zebrafish Daam1 (zDaam1), zebrafish Protocadherin 8 (zPcdh8), zebrafish Fuzzy (zfuzzy), and zScrib. White arrowheads indicate examples of cyst formation. (B) Pronephric cyst formation, caused by the depletion of these molecules, was scored at 55 h post fertilization (h.p.f), using the transgenic zebrafish line Wt1b:gfp. A reproducible degree of cyst formation (30%–40%) was noted in zFat1-depleted embryos without significant reduction in larval survival. (C) Epistasis assays between components of the PCP pathway revealed a strong synergism between zFat1 MO (0.125 pmol) and zScrib MO (0.125 pmol) injections. Transverse sections at the level of glomerulus and proximal tubules revealed bilateral pronephric cyst formation adjacent to the glomerulus in combined knockdown of Fat1 and Scribble in zebrafish embryos. (D) The presence of pronephric cysts was scored at 50–55 h.p.f. in zebrafish embryos injected with low MO concentrations. Note that pronephric cysts are hardly detectable after single injections of either 0.125 pmol zFat1 MO or 0.125 pmol zScrib MO, whereas the combination causes pronephric cysts in > 10% of microinjected embryos. (*, P < 0.05; **, P < 0.0001).
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