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Bicaudal‐C in Drosophila as a model of polycystic kidney disease (PKD) and intersection of oxalate nephrolithiasis
Author(s) -
Knier Catherine Grace,
Landry Greg M.,
Romero Michael F.
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.1224.27
Subject(s) - gene knockdown , medicine , secretion , calcium oxalate , gene , biology , urinary system , genetics
Background Autosomal Dominant Polycystic Kidney Disease (ADPKD) is a leading cause of end‐stage renal disease in adults affecting 1 in 800 people in the US. Knocking down bicaudal‐C (BicC) in zebrafish and Xenopus has been reported as a method used to model the cystic changes in ADPKD. Gamberi and colleagues [JASN 25: 538A, 2014] recently presented a similar knockdown in Drosophila melanogaster resulting in cystic Malpighian Tubules (MTs) homologous to the human kidney. Additionally, calcium oxalate (CaOx) kidney stones affect ~1 in 10 people in the US, with the incidence increasing ~2‐fold in PKD patients. Methods Our group has investigated the PKD phenotype in Drosophila using a Gal4/UAS‐RNAi system to knockdown the expression of BicC in MTs. We initiated CaOx crystal formation by feeding Na‐oxalate or adding to tubule bathing solution [Hirata, AJP 2012]. Results Penetrance of Uro, CapaR, and c724 drivers in the MTs were compared using UAS‐YFP, resulting in Uro::BicC expression in ~50% of cells with CapaR::BicC approaching 100% and c724 expression specific to MT stellate cells only. MT morphology was analyzed: controls [WT (0%); parental (18%)] occurrence v BicC knockdowns [Uro::BicC (25%); CapaR::BicC (15%); c724::BicC (6.3%)]. Functional tests using Ramsay secretion assays reveal a slower secretion rate in Uro::BicC, CapaR::BicC, and c724::BicC knockdowns compared to WT MTs. In CapaR::BicC knockdowns, slower secretion rates are observed even after stimulation with Drosophila ‐kinin. Since there is an increased risk for ADPKD‐related kidney stones, MT calcium oxalate (CaOx) crystallization experiments were performed to quantify crystal formation in BicC knockdown vs WT MTs. While crystals are present in all oxalate exposed MTs, BicC knockdowns using Uro::BicC and c724::BicC form more CaOx crystals than CapaR::BicC and WT. However, crystals formed by Uro::BicC and c724::BicC knockdowns have a significantly smaller total crystal area and average area/individual crystal compared to both CapaR::BicC and WT. Conclusions These results suggest that BicC knockdown parallels kidney stone increases associated with human PKD, but does not yet consistently mimic morphologic ADPKD‐induced cystic phenotypes usually observed in PKD models. Support or Funding Information DK90278, DK101405, DK101405