Abstract: TH-PO588

Cardiac Valvulogenesis Is Cilia Dependent and Exocyst-Mediated Ciliogenic Programs Are Conserved across Species and Organs

Session Information

Category: Genetic Diseases of the Kidney

  • 801 Cystic Kidney Diseases

Authors

  • Fulmer, Diana B., Medical University of South Carolina, Charleston, South Carolina, United States
  • Fogelgren, Ben, University of Hawaii, Honolulu, Hawaii, United States
  • Toomer, Katelynn A, Medical University of South Carolina, Charleston, South Carolina, United States
  • Norris, Russell A, Medical University of South Carolina, Charleston, South Carolina, United States
  • Lipschutz, Joshua H., Medical University of South Carolina, Charleston, South Carolina, United States
Background

Polycystic kidney diseases such as ADPKD, Joubert, and Meckel’s syndromes are associated with cardiac valve abnormalities. Our recent data show that primary cilia are expressed on developing, but not adult, cardiac valves and are required for normal valvulogenesis. Mutations in the highly-conserved, octameric exocyst complex disrupt ciliogenesis, and result in Joubert and Meckel’s syndromes. Exoc5 is a central component of the exocyst, and shRNA-induced knockdown in Madin Darby canine kidney cells inhibits ciliogenesis, increases cell proliferation, and results in low intracellular calcium levels that do not increase in response to fluid flow, all without grossly affecting cell polarity. Conversely, Exoc5 overexpression, results in longer cilia with normal intracellular calcium levels and enhanced response to fluid flow. The exocyst participates in cilogenesis by trafficking vesicles carrying ciliogenic cargo proteins, such as polycystin-2, from the Trans-Golgi network to the membrane. The exocyst and its cargo are localized to the nascent cilium by interactions with Cdc42 and other docking proteins. We have shown altered cilogenesis and nephrogenesis, in both exoc5 zebrafish morphants and Exoc5fl/fl mice bred with a kidney-specific Cre. Cdc42fl/fl kidney-specific Cre mice also displayed a cystic phenotype.

Methods

Exoc5 zebrafish mutants, along with cardiac-valve specific knockout in mice were used.

Results

Zebrafish morphants and two distinct lines of exoc5-/- mutant zebrafish have cardiac edema and severe outflow tract stenosis, and we demonstrate rescue of these phenotypes with human EXOC5 mRNA. We also found significant activation of the Hippo pathway in the exoc5 mutant zebrafish, which has been previously linked by us and others to PKD. Furthermore, Exoc5fl/fl mice bred with cardiac valve-specific NfatC1 Cre, have highly penetrant bicuspid aortic valve disease.

Conclusion

These data show that ciliogenic programs are conserved across species and organs, which helps to explain the association of cardiac valve abnormalities and PKD, and offer new animal models for future testing of therapeutic compounds.

Funding

  • Other NIH Support