renalcyst

Polycystic Kidney Disease (PKD) is the most common genetic disease that leads to kidney failure in humans. Two genes, PKD1 and PKD2 account for the vast majority of cases of ADPKD. Although potential therapies are been tested in clinical trials, no prevention or causal treatment exists at the present time. We have shown that renal cyst development in the PKD/Mhm(cy/+) rat is caused by a missense mutation in the Pkdr1 gene. Pkdr1 encodes a novel protein, Anks6, which contains ankyrin repeats (ANK) and a sterile alpha motif (SAM) where the cy mutation lies. Recently, we established a mouse model that carries a mutation in this protein, 5 amino-acids away from the cy mutation, which also leads to cyst formation in kidney. As Anks6 is expressed in primary cilia in kidney epithelial cells and does not share structural similarities with known polycystins or other proteins that are known to be involved in cystic kidney diseases, its functional analysis will provide new perspectives to elucidate the pathophysiology of renal cyst development in patients. This multidisciplinary proposal uses complementary approaches including immunomorphology, molecular biology and genetics. As no functional annotations of Anks6 are defined in public databases, we will firstly prioritise our research to a comprehensive genetic and phenotypic analysis of our newly derived mouse model. Genetic inheritance of the disease will be verified (Partner 2 and 3). Phenotypic investigations (Partner 1) will focus on renal development and cyst formation. Anks6 tissue expression patterns and cellular distribution will be investigated in human and in normal mouse kidney during development. The SAM and ANK domains of Anks6 suggest that the protein is involved in protein-protein interactions. We will focus on the discovery of Anks6 partner by Tandem Affinity Purification, (Partner 1) and Yeast-two-Hybrids methods (Partner 2). Preliminary experiments already identified an interaction disrupted by the mutation with a new protein sharing structural similarities with Anks6. The expression of the new partner proteins will be systematically analyzed in normal and Anks6 mutant mice (Partner 1). The role of these Anks6 partner proteins in cyst development will be investigated by an in vitro model of organotypic culture of embryonic kidney (Partner 1) and an in vivo approach (Partner 2) by injecting mice with interfering RNA of the Anks6 partner. The implication of Anks6 and its partners in the aetiology of cyst disorders will be evaluated in patients using a strategy which will test Anks6 as either a PKD susceptibility gene or an ADPKD modifier gene (Partner 3). As no effective treatment is currently available for any form of PKD, the consortium will take advantage of the Anks6 mouse model to test the efficiency of available drug treatment in ENU-mutagenized mice for Anks6 in order to shed light on molecular pathways that Anks6 and its interacting partners are involved in. Research will lead to the characterisation of the role of Anks6 through extensive physiological, genetic and genomic investigations in the Anks6 ENU-mutageneised mutant mouse model of polycystic kidney disease. Results from our investigations into the biological function of Anks6 and the effects of the mutation on cyst development will define new pathways and molecular mechanisms contributing to renal cyst formation. Preliminary results already identified a protein partner of Anks6 and we anticipate further evidence of interactions with other partners of this protein. Interaction analyses should uncover unknown factors contributing to cyst formation. The role of these new molecules involved in cystic disease will first be tested in mouse. Anks6 and its partners will also be assessed for their etiological role in PKD through candidate gene sequence analysis in patients with cystic diseases.