HDAC inhibition with TSA and VPA corrected body curvature (pkd2−/− [hi4166]) and reduced cyst formation (pkd2 morphants) in zebrafish; results verified by treating Pkd1fl/fl, Pkhd1-cre mice with VPA (reduced %KW/BW, CI, and BUN). This evidence concerns the gene HDAC9 and cyst.