The role of cilia in the pathogenesis of cystic kidney disease

PURPOSE OF REVIEW: Primary (immotile) cilia are specialized organelles present on most cell types. Almost all of proteins associated with a broad spectrum of human cystic kidney diseases have been localized to the region in or around the cilia. Abnormal cilia structure and function have both been reported in animal models and human cystic kidneys. The goal of this review is to discuss current understanding of the mechanisms by which abnormal genes/proteins and cilia interact to potentially influence renal cystogenesis. RECENT FINDINGS: Novel direct recording of cilia calcium levels/channel activity suggests that cilia form a calcium-mediated signaling microenvironment separate from the cytoplasm, which could provide a mechanism for cilia-specific downstream signaling. Genetic-based studies confirm that cilia are not required for cystogenesis, but modulate cystic kidney disease severity through a novel, undefined mechanism. Mechanisms by which both cilia-associated and noncilia-associated proteins can alter cilia structure/function have also been identified. SUMMARY: Considerable progress has been made in defining the mechanisms by which abnormal genes and proteins affect cilia structure and function. However, the exact mechanisms by which these interactions cause renal cyst formation and progression of cystic kidney disease are still unknown.