PKD1 and autosomal dominant polycystic kidney disease: However, as BicC is thought to act downstream of PKD1 in ADPKD patients, and as a PKD1 homologue has not been identified in D. melanogaster, potential differences in the signaling pathways implicated in the development of the renal cystic phenotype between human ADPKD patients and the BicC fly model might limit its relevance, both as a model for the human disease and for drugs screening.