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Cxcl12a/cxcr4b and myca signaling override collective cell migration to repair zebrafish pronephros injuries

ABSTRACT: Injuries of the zebrafish kidney are rapidly repaired by a migratory response in two to three day-old embryos. While this migratory repair process re-establishes the integrity of the pronephric tubules independently of proliferation, fluid flow, intact cilia, or Wnt signaling, pronephros injuries before 36 hours post fertilization were repaired by a purse string-like mechanism that irreversibly occluded the pronephric tubules. Comparing the gene expression profiles between these two developmental stages and focusing on up-regulated zebrafish pronephros genes, we identified cxcl12a and myca as potential candidates orchestrating the migratory repair process. Zebrafish lines with either cxcl12a or cxcr4b mutations displayed striking repair abnormalities, confirming the requirement for cxc12a/cxcr4b signaling to override the ongoing collective cell migration and repair the pronephros injury. However, in contrast to the collective cell migration of the posterior lateral line primordium, cxc12a/cxcr4b signaling was dispensable for normal pronephros development. Zebrafish myca, the pronephros-specific homologue of human MYC, was also increased in cells participating in the repair response. The defective repair response caused by knockdown of myca resembled the abnormalities observed in cxcx12a/cxcr4b-deficient zebrafish, and was partially rescued by cxcr4b mRNA, suggesting that myca acts in part through up-regulating cxcr4b expression during the migration-based repair process. Kidney-specific knockout of Cxcl12 and Myc suppressed mitochondrial functions, reduced retinoic acid receptor signaling, and delayed the recovery after ischemic/reperfusion injury in mice. Tretinoin, known to stimulate Cxcr4 expression and mitochondrial metabolism, accelerated renal recovery. Thus, the zebrafish pronephros injury mode provides a systematic approach to identify molecules involved in the immediate repair response after kidney injury, and to design strategies to ameliorate this severe complication of human disease.

ORGANISM(S): Mus musculus

PROVIDER: GSE102044 | GEO | 2018/07/20

REPOSITORIES: GEO

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Project description:The goal of this study is to investigate the molecular mechanism of lhx1 on regulation of pronephros formation during the early embryonic development. In the vertebrate embryo the kidney is derived from the intermediate mesoderm. The LIM-class homeobox transcription factor lhx1 is expressed early in the intermediate mesoderm and is one of the first genes to be expressed in the nephric mesenchyme. The animal cap cells can be induced by treatment of activin and retinoic acid to differentiate into pronephros tissue. In this study we investigated the role of Lhx1 in differentiation of pronephros by depleting lhx1 in the organ culture system. We generated the gene expression profile of early pronephros tissue, and demonstrated that expression of genes from all the kidney domains is affected by the absence of lhx1. Taken together our results highlight an essential role for Lhx1 in pronephros formation. lhx1 is involved in driving specification of intermediate mesoderm into nephrogenic mesenchyme. Lhx1 is initially expressed throughout the entire intermediate mesoderm. To determine the role of lhx1 pronephros formation, we performed a microarray analysis using an explant culture system. Xenopus tissue explants can be surgically isolated and cultured under specific conditions to be driven towards many distinct tissue types. Formation of pronephric cell fates is induced by culturing isolated explants in the presence of Activin and RA (AcRA). Treatment of dissected explants of stage 9 blastulae embryos with 10ng/ml Activin and 1x10-4 M retinoic acid can induce differentiation of the pluripotent ectoderm into pan-kidney tissue. For this experiment, both blastomeres of 2-cell embryos were injected with a total of 800pg lhx1 DEED-AS. Explants were dissected and treated with AcRA and expression of pax8 at stage 15 (based on timing of paired control whole embryos) was analyzed. We observed a lack of induction of pax8 expression in lhx1-depleted explants under AcRA treatment conditions in which expression of this gene is normally induced. Based on this observation, microarray analysis was carried out to identify genes whose expression is affected by the absence of lhx1. Explants of injected embryos with 800pg of lhx1 DEED-AS were dissected, treated with pronephric tissue inductive conditions (AcRA) and harvested after 24 hours incubation at 14C (Fig. S5B). The sibling control embryos reached stage 12.5. Explants from uninjected embryos +AcRA and -AcRA as well as explants from DEED injected embryos -AcRA were also harvested. Approximately 12 caps were pooled for each RNA preparation and the analysis was performed using triplicates.

Project description:Microarray analysis of human kidneys with acute kidney injury (AKI) has been limited because such kidneys are seldom biopsied. However, all kidney transplants experience AKI, and early kidney transplants without rejection are an excellent model for human AKI: they are screened to exclude chronic kidney disease, frequently biopsied, and have extensive follow-up. We used histopathology and microarrays to compare indication biopsies from 28 transplants with AKI to 11 pristine protocol biopsies of stable transplants. Kidneys with AKI showed increased expression of 394 injury-repair response associated transcripts, including many known epithelial injury molecules (e.g. ITGB6, LCN2), tissue remodeling molecules (e.g. VCAN), and inflammation molecules (S100A8, ITGB3). Many other genes also predict the phenotype, depending on statistical filtering rules, including AKI biomarkers as HAVCR1 and IL18. Most mouse orthologs of the top injury-repair transcripts were increased in published mouse AKI models. Pathway analysis of the injury-repair transcripts revealed similarities to cancer, development, and cell movement. The injury-repair transcript score AKI kidneys correlated with reduced function, future recovery, brain death, and need for dialysis, but not future graft loss. In contrast, histologic features of "acute tubular injury" did not correlate with function or with the molecular changes. Thus the injury-repair associated transcripts represent a massive coordinate injury-repair response of kidney parenchyma to AKI, similar to mouse AKI models, and provide an objective measure for assessing the severity of AKI in kidney biopsies and validation for the use of many AKI biomarkers. AKI biopsies sample names and CEL files are from GSE21374. All consenting renal transplant patients undergoing biopsies for cause as standard of care between 09/2004 and 10/2007 at the university of Alberta or between 11/2006 and 02/2007 at the University of Illinois were included in the analysis. In addition to the cores required for standard histopathology, we collected one core for gene expression studies. the relationship between gene expression in the biopsy and subsequent graft loss was analyzed. This dataset is part of the TransQST collection.

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Cxcl12a/cxcr4b and myca signaling override collective cell migration to repair zebrafish pronephros injuries

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