Project description:During kidney development segmented epithelia of the nephron derive from progenitor cells in the metanephric mesenchyme after induction by secreted molecules from the ureteric bud. We have identified three distinct inductive activities from a ureteric bud cell line. These include leukemia inhibitory factor (LIF), neutrophil gelatinase-associated lipocalin (NGAL) and an active fraction currently referred to as ANX. Each of these activities induces segmented nephron epithelia in isolated rat metanephric mesenchyme over a time period of 7 days. This study was designed to characterize the temporal sequence of gene expression in the course of the conversion process induced by each of the distinct inducers. Keywords: time course
Project description:During kidney development segmented epithelia of the nephron derive from progenitor cells in the metanephric mesenchyme after induction by secreted molecules from the ureteric bud. We have identified three distinct inductive activities from a ureteric bud cell line. These include leukemia inhibitory factor (LIF), neutrophil gelatinase-associated lipocalin (NGAL) and an active fraction currently referred to as ANX. Each of these activities induces segmented nephron epithelia in isolated rat metanephric mesenchyme over a time period of 7 days. This study was designed to characterize the temporal sequence of gene expression in the course of the conversion process induced by each of the distinct inducers. Experiment Overall Design: Metanephric mesenchymes were microdissected from rat E13.5 embryos. Mesenchymes were cultured on transwells in the presence of either LIF, NGAL or the ANX fraction and RNA was harvested after 1, 2, 3, 4, 5, and 7 days for RNA extraction. Freshly dissected mesenchymes and mesenchymes cultured in the absence of inducers for 1 and 2 days, respectively, served as controls. Each condition was analyzed in duplicate (biological replicates). Biotinylated cRNA was prepared and hybridized to Affymetrix Rat Genome 230 2.0 Microarrays. Expression values were obtained by robust multichip analysis.
Project description:BACKGROUND: Lim1 is a homeobox gene that is essential for nephrogenesis. During metanephric kidney development, Lim1 is expressed in the nephric duct, ureteric buds, and the induced metanephric mesenchyme. Conditional ablation of Lim1 in the metanephric mesenchyme blocks the formation of nephrons at the nephric vesicle stage, leading to the production of small, non-functional kidneys that lack nephrons. METHODS: In the present study, we used Affymetrix probe arrays to screen for nephron-specific genes by comparing the expression profiles of control and Lim1 conditional mutant kidneys. Kidneys from two developmental stages, embryonic day 14.5 (E14.5) and 18.5 (E18.5), were examined. RESULTS: Comparison of E18.5 kidney expression profiles generated a list of 465 nephron-specific gene candidates that showed a more than 2-fold increase in their expression level in control kidney versus the Lim1 conditional mutant kidney. Computational analysis confirmed that this screen enriched for kidney-specific genes. Furthermore, at least twenty-eight of the top fifty (56%) candidates (or their vertebrate orthologs) were previously reported to have a nephron-specific expression pattern. Our analysis of E14.5 expression data yielded 41 candidate genes that are up-regulated in the control kidneys compared to the conditional mutants. Three of them are related to the Notch signaling pathway that is known to be important in cell fate determination and nephron patterning. CONCLUSIONS: Therefore, we demonstrate that Lim1 conditional mutant kidneys serve as a novel tissue source for comprehensive expression studies and provide a means to identify nephron-specific genes. Keywords: tissue specificity, time course, development, kidney, metanephric mesenchyme, nephron, Lim1, knockout mice, conditional knockout