MicroRNAs (miRNAs) are a large and growing class of small, non-coding, regulatory RNAs that control gene expression predominantly at the post-transcriptional level. The production of most functional miRNAs depends on the enzymatic activity of Dicer, an RNase III class enzyme. To address the potential action of Dicer-dependent miRNAs in mammalian kidney development, we conditionally ablated Dicer function within cells of nephron lineage and the ureteric bud-derived collecting duct system. Six2Cre-mediated removal of Dicer activity from the progenitors of the nephron epithelium led to elevated apoptosis and premature termination of nephrogenesis. Thus, Dicer action is important for maintaining the viability of this critical self-renewing progenitor pool and, consequently, development of a normal nephron complement. HoxB7Cre-mediated removal of Dicer function from the ureteric bud epithelium led to the development of renal cysts. This was preceded by excessive cell proliferation and apoptosis, and accompanied by disrupted ciliogenesis within the ureteric bud epithelium. Dicer removal also disrupted branching morphogenesis with the phenotype correlating with downregulation of Wnt11 and c-Ret expression at ureteric tips. Thus Dicer, and by inference Dicer-dependent miRNA activity, have distinct regulatory roles within different components of the developing mouse kidney. Furthermore, an understanding of miRNA action may provide new insights into the etiology and pathogenesis of renal cyst-based kidney disease.

Congenital obstructive nephropathy is a major cause of chronic kidney disease in children. The contribution of changes in the identity of renal cells to the pathology of obstructive nephropathy is poorly understood. Using a partial unilateral ureteral obstruction model in genetically modified neonatal mice, we traced the fate of cells derived from the renal stroma, cap mesenchyme, ureteric bud epithelium and podocytes using Foxd1Cre, Six2Cre, HoxB7Cre and Podocyte.Cre mice respectively, crossed with double fluorescent reporter (mT/mG) mice. Persistent obstruction leads to a significant loss of tubular epithelium, rarefaction of the renal vasculature and decreased renal blood flow. In addition, Foxd1-derived pericytes significantly expanded in the interstitial space, acquiring a myofibroblast phenotype. Degeneration of Six2 and HoxB7-derived cells resulted in significant loss of glomeruli, nephron tubules and collecting ducts. Surgical release of obstruction resulted in striking regeneration of tubules, arterioles, interstitium accompanied by an increase in blood flow to the level of sham animals. Contra-lateral kidneys with remarkable compensatory response to kidney injury showed an increase in density of arteriolar branches. Deciphering the mechanisms involved in kidney repair and regeneration post relief of obstruction has potential therapeutic implications for infants and children and the growing number of adults suffering from chronic kidney disease.

-Renin, the key regulated enzyme of the renin-angiotensin system regulates blood pressure, fluid-electrolyte homeostasis, and renal morphogenesis. Whole body deletion of the renin gene results in severe morphological and functional derangements, including thickening of renal arterioles, hydronephrosis, and inability to concentrate the urine. Because renin is found in vascular and tubular cells, it has been impossible to discern the relative contribution of tubular versus vascular renin to such a complex phenotype. Therefore, we deleted renin independently in the vascular and tubular compartments by crossing Ren1 c fl/fl mice to Foxd1-cre and Hoxb7-cre mice, respectively. Deletion of renin in the vasculature resulted in neonatal mortality that could be rescued with daily injections of saline. The kidneys of surviving mice showed the absence of renin, hypertrophic arteries, hydronephrosis, and negligible levels of plasma renin. In contrast, lack of renin in the collecting ducts did not affect kidney morphology, intra-renal renin, or circulating renin in basal conditions or in response to a homeostatic stress, such as sodium depletion. We conclude that renin generated in the renal vasculature is fundamental for the development and integrity of the kidney, whereas renin in the collecting ducts is dispensable for normal kidney development and cannot compensate for the lack of renin in the vascular compartment. Further, the main source of circulating renin is the kidney vasculature.arterioles; conditional knockout; medulla; renin angiotensin system RENIN IS CRITICAL FOR THE control of blood pressure and fluid/ electrolyte homeostasis. In adult mammals, renin is synthesized and released from juxtaglomerular (JG) cells located in the wall of the afferent arterioles at the entrance to the glomeruli. However, within the embryonic (E) kidney, renin precursors appear before arteriolar development is discernible around E12.5-E14.5 days of gestation (22). JG cells descend from a group of stromal cells, which express the forkhead transcription factor Foxd1 and, in turn, differentiate into all the mural cells of the renal arterioles, pericytes, and glomerular mesangium (23). During this developmental process, renin cells regulate elongation and branching of the renal vasculature, where they are distributed broadly along large intrarenal arteries, in each tip of newly appearing arteriolar branches and inside glomerular cells, which differentiate into mesangial cells (7,8,18,21). Thus, during fetal and postnatal life, there is a widespread distribution and progressive shifting pattern of renin throughout the renal vasculature, and it is not until arteriolar development is finalized that these cells are circumscribed to their "classical" JG location, as typically seen in the adult mammal. Interestingly, Ren1 c KO mice display abnormal renal vascular development, with fewer, shorter, and prominently thicker renal interlobular arteries and afferent arterioles (28). In addition to the vascular abnormalities, the kidneys of Ren1 c KO ...

Insect males produce accessory gland (MAG) factors that are transferred in the seminal fluid to females during copulation, and elicit changes in the mated female's behavior and physiology. Our previous studies showed that the injection of synthetic Drosophila melanogaster sex-peptide (DrmSP) into virgin females of the moth Helicoverpa armigera causes a significant inhibition of pheromone production. In this and other moth species, pheromone production, correlated with female receptivity, is under neuroendocrine control due to the circadian release of the neuropeptide PBAN. In this study, we show that PBAN, present in the hemolymph during the scotophase in females, is drastically reduced after mating. We also identify 4 DrmSP-like HPLC peaks (Peaks A, S1, S2, and B) in MAGs, with increasing levels of DrmSP immunoreactivity during the scotophase, when compared to their levels observed during the photophase. In H. armigera MAGs, a significant reduction in the pheromonostatic peak (Peak B) was already evident after 15 min of copulation, and depletion of an additional peak (Peak S2) was evident after complete mating. Peak A is also detected in female brains, increasing significantly 1 h after mating, at which time inhibition of pheromone biosynthesis also occurs. However, changes corresponding to the other MAG peaks were not detected in mated female tissues.

No abstract