The PKD/Mhm(cy/+) rat is a widely used animal model for the study of human autosomal dominant polycystic kidney disease, one of the most common genetic disorders, affecting one in 1000 individuals. We identified a new gene, Anks6, which is mutated (Anks6((p.R823W))) in PKD/Mhm(cy/+) rats. The evidence for a causal link between Anks6((p.R823W)) and cystogenesis is still lacking, and the function of Anks6 is presently unknown. This study presents a novel transgenic rat model that overexpresses the mutated 2.8-kb Anks6((p.R823W)) cDNA in the renal tubular epithelium. The transgenic Anks6((p.R823W)) acts in a dominant-negative fashion and causes a predictable polycystic phenotype that largely mimics the general characteristics of the PKD/Mhm(cy/+) rats. Cyst development is accompanied by enhanced c-myc expression and continuous proliferation, apoptosis, and de-differentiation of the renal tubular epithelium as well as by a lack of translational up-regulation of p21 during aging. Using Northern blot analysis and in situ hybridization studies, we identified the first 10 days of age as the period during which transgene expression precedes and initiates cystic growth. Thus, we not only provide the first in vivo evidence for a causal link between the novel Anks6((p.R823W)) gene mutation and polycystic kidney disease, but we also developed a new transgenic rat model that will serve as an important resource for further exploration of the still unknown function of Anks6.