Research

We used an extensive set of early and adult inducible inactivation models to inactivate Pkd1 or Pkd2 either alone or together with cilia to show the surprising finding that concomitant loss of cilia suppressed cyst formation in both kidney and liver. These in vivo studies provide genetic definition of a pathway that actively promotes cystic tissue remodeling only when polycystins are removed and cilia are left intact. We have termed this the ‘cilia dependent cyst activating (CDCA)’ pathway. We developed a strategy to define transcriptional changes specifically in Pkd-only knockout kidney tissues that are not changed in either Pkd+cilia double knockout and control kidneys, neither of which form cysts. The data from these studies is available on the MAGICK website we have established (https://pkdgenesandmetabolism.org/). From this, we have identified Glis2 and Anks3 as targets of polycystin signaling and effectors of CDCA dependent cyst growth. We have shown that Glis2 is a therapeutic target for therapy in ADPKD.

Our current studies focus on defining the additional molecular components of CDCA and defining the detailed functional relationships of Glis2, Anks3 and the other elements of CDCA.

We constructed mouse models in which adult inactivation of either Pkd1 or Pkd2 using inducible Cre/loxP can be followed by reactivation of the same gene later using inducible Flp/FRT. Using these models, we showed that re-expression of Pkd genes in cystic kidneys results in rapid reversal of ADPKD. Re-expression of polycystin results in reduced cyst cell proliferation, increased autophagy, and remodeling of the expanded lumens lined by squamoid cells in cystic tubules to normal kidney tubules with normal lumens lined by cuboidal cells. Increases in inflammation, extracellular matrix deposition and myofibroblast activation in the polycystic state are reversed and the kidneys become smaller when polycystins are re-expressed. These data show that phenotypic features of ADPKD are reversible, and that the kidney has an unexpected capacity for plasticity controlled at least in part by ADPKD gene function.

Our current studies are focused on defining the molecular events in the kidney tubule cells that underlie the phenotypic reversion from a polycystic dysfunctional state back to normalized kidney structure and function.

We have generated cell-based platform to study the role of regulation for the ciliary trafficking of polycystin complex underlying the pathogenesis of ADPKD: We have established comprehensive sets of cell lines expressing various PC1 and PC2 mutants with different fluorescent protein tag in the context of various genetically modified backgrounds. The ciliary expression of polycystin-1 and -2 in this system can be examined in confocal microscopy in live cells, which would allow us to study ciliary trafficking of polycystins and downstream signaling.