ODP651 Abnormal Primary Ciliogenesis in the Developing Mouse Kidney of Glucocorticoid Receptor-Deficient Mice

Glucocorticoid (GC) hormones have well characterised regulatory roles for the development and maturation of several fetal organs, however, specific developmental roles of GCs in the fetal kidney have not been described (1). We have explored both the expression and localisation of the glucocorticoid receptor (GR) within the developing fetal mouse kidney during organogenesis and the effect on the transcriptome of eliminating GR expression in gene-targeted GR-deficient mice. Staining for the GR by immunohistochemistry at E14.5, E16.5 and E18.5 demonstrated widespread expression of the GR in the renal tubule and the interstitial renal mesenchyme, with strong staining in collecting ducts and increasing expression in mesenchyme up to E18.5. Loss of GR expression in GR-null mice had a profound effect on the renal transcriptome with altered expression (at an FDR of 0.5 and fold change >2. 0) for 454 genes in the GR-null mouse kidney at E18.5, with a greater number of genes showing significantly reduced mRNA levels (305) than increased mRNA levels (99) relative to wild-type controls. Interestingly these deregulated genes included key primary cilia-associated genes, such as centrosomal protein 290 (Cep290), with the largest fold change of -3.6, Cep97, Ccp110, and the primary cilia-associated kinesin Kif3A. In addition, two renal tubule markers, Kidney androgen regulated protein (Kap) (proximal tubule marker) and S100 calcium binding protein G (S100g) (distal tubule marker) were also strongly downregulated with fold changes of -8.61 and -2.5 respectively. Analysis of primary cilia in sections of E18.5 kidney using multicolour confocal microscopy demonstrated that primary cilium length was significantly decreased and abnormally projected from kidney proximal tubule cells in E18.5 GR-null mice (5.23 + 0.12, µm + SEM) compared with wild type controls (6.27+ 0.15, µm + SEM). Finally, in cultured IMCD3 mouse collecting duct cells dexamethasone treatment was shown to increase the length of primary cilia compared to vehicle-treated control cells (vehicle 2.49 + 0. 03, µm + SEM vs dexamethasone 3.17 + 0. 05 µm + SEM), an effect that could be blocked by pre-treatment with the GR antagonist RU486. Taken together these results indicate that GC signalling mediated via the GR contributes either directly or indirectly to the normal formation of primary cilia in the proximal tubule and is therefore required for normal kidney development. This also suggests that abnormalities in GR-regulation of ciliogenesis may underpin or contribute to causes of human ciliopathy conditions. 1. Cole TJ, Short KL, Hooper SB (2019) The Science of Steroids. Sem. Fetal and Neonatal Med. 24: 170-175. Presentation: No date and time listed