GSE99084
A Snapshot of RNA Expression in a Single Segment of the Kidney Reveals Stimulus Specific Responses
The identification of acute kidney disease at the time of patient encounter remains a central problem in clinical medicine. A single analyte, the serum creatinine (sCr) is currently in use as a surrogate for tubular, vascular, or interstitial cellular damage. Nonetheless the sCr test is not specific to kidney injury, but rather might reflect physiological responses to a the primary disease in a distant organ. In addition, while cellular events occur over minutes or hours, sCr requires 24 hours or more to reach a worrisome clinical threshold or demonstrate further deterioration of tissue function and architecture. Here we have adapted the method of Gay et al, Genes Dev. 2013 27(1):98-115. doi: 10.1101/gad.205278.112. to allow cell specific labelling of RNA at the time of our choosing after an injury. The technique involves the cell specific expression of a uracil phosphoribosyltransferase (Uprt) and the subsequent purification of 4-thio-uracil labelled nascent RNAs. Using this technique focused on the collecting duct, we found that a model of volume depletion and a model of ischemic damage, both of which raise the sCr do not activate the same cohort of genes nor the same pathways of gene expression. Hence, a snapshot of newly synthesized RNA reveals the complexity subsumed by diagnostic classifications dependent on sCr (called 'AKI'). We suggest that the Uprt technique will allow characterization of each cell type in the nephron at multiple time points after the onset of injury. These data will replace our current diagnostic strategies with Precision Medicine. Overall design: Examining transcriptional profiles of two models of "acute kidney injury" (iAKI and vAKI), compared to controls, in a single segment of the kidney using cre mediated 4-thio-Uracil tagging of RNA.