Abstract 099: Akr1b7 CreERT2 Mice, A New Time And Renin Cell-specific Cre Inducible Model

Abstract

Gene targeting in renin cells has relied on either non-inducible Cre lines that can introduce developmental effects of gene deletion or BAC transgene-based inducible lines that may be prone to spurious and/or ectopic gene expression. To circumvent these problems, we generated an inducible mouse in which CreERT2 is under the control of the Akr1b7 locus. Akr1b7 , an established marker of renin cells, is co-expressed with renin under different developmental, physiological, and pathological conditions. To study the pattern of Cre expression, we generated Akr1b7 CreERT2/+ ; R26R mTmG/+ mice in which Cre -expressing cells are labeled with GFP upon tamoxifen (Tmx) administration. At E18.5 and P5, GFP was found in Juxtaglomerular (JG) cells, along the arterioles, and in the glomerular mesangium. In adult kidneys, GFP expression was present mainly in JG cells. We did not observe any GFP + cells in vehicle-treated mice, indicating that Cre expression is tightly regulated in this model. In mice given 0.5 g/L captopril in the drinking water and a low-NaCl (0.1%) diet to induce recruitment of renin cells, GFP expression extended along the afferent arterioles and in the mesangium. To study the response to Ren1 deletion in JG cells in the mice, we generated Akr1b7 CreERT2/+ ;Ren1 cFl/- ;R26R mTmG/+ ( Ren1 c cKO) mice. Compared to control mice, Ren1 c cKO mice exhibited a marked reduction in Ren1+ cells by immunostaining and a 80.1% reduction of Ren1 mRNA levels by RT-qPCR (0.19 ± 0.04 vs 0.92 ± 0.26, p= 0.0003). Plasma renin levels were significantly decreased in Ren1 c cKO versus control mice (12,5 ± 7,0 ng/ml vs 53,7 ± 27,9 ng/ml, p= 0.003). In addition, Ren1 c cKO mice had lower mean arterial pressures (68.91 ± 5.27 mmHg vs 82.74 ± 2.63 mmHg, p= 0.0001). When subjected to a low NaCl diet + captopril, Ren1 c cKO mice were able to recruit renin GFP+ cells along arterioles, mesangial cells, and large kidney arteries, suggesting that Ren1 expression in JG cells is dispensable for recruitment. More importantly, the cells can be monitored/tracked by the expression of GFP even when they are unable to express renin.In summary, Akr1b7 CreERT2 mice constitute a suitable model for the spatial and temporal control of gene expression in renin cells and the tracking of cells even when they are not expressing renin.