Global gene expression profiling in early-stage polycystic kidney disease in the Han:SPRD Cy rat identifies a role for RXR signaling

Abstract

Han:SPRD Cy is a spontaneous rat model of polycystic kidney disease (PKD) caused by a missense mutation in Pkdr1. Cystogenesis in this model is not clearly understood. In the current study, we performed global gene expression profiling in early-stage PKD cyst development in Cy/Cy kidneys and normal (+/+) kidneys at 3 and 7 days of postnatal age. Expression profiles were determined by microarray analysis, followed by validation with real-time RT-PCR. Genes were selected with over 1.5-fold expression changes compared with age-matched +/+ kidneys for canonical pathway analysis. We found nine pathways in common between 3- and 7-day Cy/Cy kidneys. Three significantly changed pathways were designated "Vitamin D Receptor (VDR)/Retinoid X Receptor (RXR) Activation," "LPS/IL-1-Mediated Inhibition of RXR Function," and "Liver X Receptor (LXR)/RXR Activation." These results suggest that RXR-mediated signaling is significantly altered in developing kidneys with mutated Pkdr1. In gene ontology analysis, the functions of these RXR-related genes were found to be involved in regulating cell proliferation and organ morphogenesis. With real-time RT-PCR analysis, the upregulation of Ptx2, Alox15b, OSP, and PCNA, major markers of cell proliferation associated with the RXR pathway, were confirmed in 3- and 7-day Cy/Cy kidneys compared with 3-day +/+ kidneys. The increased RXR protein was observed in both the nucleus and cytoplasm of cystic epithelial cells in early-stage Cy/Cy kidneys, and the RXR-positive cells were strongly positive for PCNA staining. Taken together, cell proliferation and organ morphogenesis signals transduced by RXR-mediated pathways may have important roles for cystogenesis in early-stage PKD in this Pkdr1-mutated Cy rat.

Global Gene Expression Profiling in PPAR-γAgonist-Treated Kidneys in an Orthologous Rat Model of Human Autosomal Recessive Polycystic Kidney Disease

“…The quality and concentration of each sample was confirmed by spectrophotometry (NanoDrop ND-1000; Asahi glass Co. Ltd., Tokyo, Japan). Total RNA obtained from three females was pooled in each PIO-treated or control vehicle-treated (CONT) group in accordance with our previous report [11]. …”

Animal Models for Human Polycystic Kidney Disease

“…Retinoid X receptor (RXR): recently, we reported that the rXr-mediated pathway is upregulated in the cy rat model [22]. This finding suggests that the regulation of this pathway may control PKD progression through cell proliferation mechanisms in this model.…”

Systems biology of polycystic kidney disease: a critical review

“…Differential expression was confirmed in only 74 genes, 12 of which showed discordant (opposite) results with the SAGE patterns. Other studies are less straightforward in the description of their methods, and in a few cases the number of samples is not even reported 20, 21, 22 .Analysis: while one should be able to assume that the data were properly analyzed, it is not necessarily realistic to expect that the reviewers for every publication re-analyzed the data and confirmed the results. In fact, it is not safe to assume that data are available, nor that, if available, the results can be reproduced, as a repeatability study by Ioannidis et al showed 23 .…”

“…Differential expression was confirmed in only 74 genes, 12 of which showed discordant (opposite) results with the SAGE patterns. Other studies are less straightforward in the description of their methods, and in a few cases the number of samples is not even reported 20, 21, 22 .…”