Polycystic kidney disease (PKD) causes internal epithelial cysts and afflicts patients with hernias, aneurysms and cardiac valve defects. Mangos et al. describe a zebrafish model of autosomal dominant PKD, in which the fish are deficient in the polycystin genes, pkd1a/b and pkd2, linked to human PKD. The main structural element, the tail, is disrupted in mutant fish owing to over-abundant collagen deposition. This suggests that polycystins influence tissue formation and demonstrates a regulatory role for the extracellular matrix in PKD.

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