Regulation Of Kidney Development Research Articles

The extracellular matrix protein fibronectin promotes metanephric kidney development

Complex interactions of the branching ureteric bud (UB) and surrounding mesenchymal cells during metanephric kidney development determine the final number of nephrons. Impaired nephron endowment predisposes to arterial hypertension and chronic kidney disease. In the kidney, extracellular matrix (ECM) proteins are usually regarded as acellular scaffolds or as the common histological end-point of chronic kidney diseases. Since only little is known about their physiological role in kidney development, we aimed for analyzing the expression and role of fibronectin. In mouse, fibronectin was expressed during all stages of kidney development with significant changes over time. At embryonic day (E) 12.5 and E13.5, fibronectin lined the UB epithelium, which became less pronounced at E16.5 and then switched to a glomerular expression in the postnatal and adult kidneys. Similar results were obtained in human kidneys. Deletion of fibronectin at E13.5 in cultured metanephric mouse kidneys resulted in reduced kidney sizes and impaired glomerulogenesis following reduced cell proliferation and branching of the UB epithelium. Fibronectin colocalized with alpha 8 integrin and fibronectin loss caused a reduction in alpha 8 integrin expression, release of glial-derived neurotrophic factor and expression of Wnt11, both of which are promoters of UB branching. In conclusion, the ECM protein fibronectin acts as a regulator of kidney development and is a determinant of the final nephron number.

Data driven analysis reveals prognostic genes and immunological targets in human sepsis-associated acute kidney injury.

The molecular mechanism of sepsis-associated acute kidney injury (SA-AKI) is unclear. We analyzed co-differentially expressed genes (co-DEGs) to elucidate the underlying mechanism and intervention targets of SA-AKI. The microarray datasets GSE65682, GSE30718, and GSE174220 were downloaded from the Gene Expression Omnibus (GEO) database. We identified the co-DEGs and constructed a gene co-expression network to screen the hub genes. We analyzed immune correlations and disease correlations and performed functional annotation of the hub genes. We also performed single-cell and microenvironment analyses and investigated the enrichment pathways and the main transcription factors. Finally, we conducted a correlation analysis to evaluate the role of the hub genes. Interleukin 32 (IL32) was identified as the hub gene in SA-AKI, and the main enriched signaling pathways were associated with hemopoiesis, cellular response to cytokine stimulus, inflammatory response, and regulation of kidney development. Additionally, IL32 was significantly associated with mortality in SA-AKI patients. Monocytes, macrophages, T cells, and NK cells were closely related to IL32 and were involved in the immune microenvironment in SA-AKI patients. IL32 expression increased significantly in the kidney of septic mouse. Toll-like receptor 2 (TLR2) was significantly and negatively correlated with IL32. IL32 is the key gene involved in SA-AKI and is significantly associated with prognosis. TLR2 and relevant immune cells are closely related to key genes.

Regulation of kidney development by the Mdm2/Mdm4-p53 axis.

While p53 activity is required for tumour suppression, unconstrained p53 activity on the other hand is detrimental to the organism, resulting in inappropriate cellular death or proliferation defects. Unimpeded p53 activity is lethal in the developing embryo, underlining the need for maintaining a tight control on p53 activity during this period. The critical role of the negative regulators of p53, Mdm2 and Mdm4, in vertebrate development came to light by fatal disruption of embryogenesis that was observed with Mdm2 and Mdm4 gene deletions in mice. Embryonic lethality was rescued only by superimposing p53 removal. Here we summarize the contribution of the Mdm2/Mdm4–p53 axis that occurs at multiple steps of kidney development. Conditional, cell type-specific deletions reveal distinct functions of these proteins in renal morphogenesis. The severe impact on the renal phenotype from targeted gene deletions underscores the critical role played by the Mdm2/Mdm4–p53 nexus on nephrogenesis, and emphasizes the need to monitor patients with aberrations in this pathway for kidney function defects and associated cardiovascular dysfunction.

Hepatocyte nuclear factor-1β: A regulator of kidney development and cystogenesis.

The understanding of the genomics of the renal tissue has gathered a considerable interest and is making rapid progress. The molecular mechanisms as well as the precise function of the associated molecular components toward renal pathophysiology have recently been realized. For the cystic kidney disease, the regulation of gene expression affecting epithelial cells proliferation, apoptosis as well as process of differentiation/de-differentiation represent key molecular targets. For the cystic disorders, molecular targets have been identified, which besides lending heterogeneity to cysts may also provide tools to unravel their functional importance to understand the renal tissue homeostasis. This review focuses on providing comprehensive information about the transcriptional regulatory role of hepatocyte nuclear factor-1β, a homeoprotein, as well as its interacting partners in renal tissue development and pathophysiology.

Comparative proteomic analysis of kidney development-related proteins in the pig

The development of the kidney is a complex process that serves as a model organ system for understanding many basic developmental mechanisms, and the pig kidney provides a useful and relevant model of kidney development and function. However, the molecular cascades involved in kidney development during embryonic development in the pig have not been elucidated fully. To better understand the molecular events associated with kidney development, we evaluated changes in gene expression during kidney development (days E40, E70, and E93) and compared these expressions with adults using two-dimensional gel electrophoresis. The functionally regulated proteins were identified by comparing differentially expressed proteins in embryonic kidneys vs. adult kidney. In addition, a representative set of the proteins was subjected to liquid chromatography tandem mass spectrometry analysis. Furthermore, the identified proteins were categorized according to their biological processes and molecular functions. Interestingly, 10 of the 25 proteins identified were apoptosis and actin cytoskeleton-related proteins, such as GRP75, α-fetoprotein, ANXA2, ANXA4, DDAH2, DJ-1, SOD2, cofilin1, vil1, and calbindin1. Based on these results, the proteomic approach was applied to identify specific protein expression changes in kidney tissues during development, and the expressional changes of these embryonic kidney proteins were found to be closely associated with the regulation of kidney development.

The role of <I>Pax2</I> in regulation of kidney development and kidney disease

Paired box2 (Pax2) gene plays a crucial role in kidney development and is expressed in the nephric duct, mesenchyme of pronephrons, mesonephrons, and metanephrons with special spatial and temporal characteristic. Research in animals indicate that Pax2 can interact with many important transcription factors such as Gdnf, Ret, SHH, Wnt4, and Fgf to organize the nephric linage specification, pro/mesonephric tubule formation and descent, emergence of the ureteric bud, branching morphogenesis, and nephron induction. Pax2 is associated with various congenital renal and ureter malformations, and the mutation is easist to detected in Renal-coloboma syndrome. In renal cell carcinoma, Wilms tumor and many acquired kidney diseases Pax2 is expressed abnormally, whose diagnose and therapy value will be the focus of further research. This paper reviews the molecular structure, expression and regulation of Pax2 in kidney development and diseases.

Regulation of kidney development by histone deacetylases

There is accumulating evidence that gene expression can be regulated independently of DNA sequence changes, also called epigenetic modifications. Histone deacetylases (HDACs), a specific epigenetic group of enzymes, dynamically and reversibly removes acetyl groups from histone tails projecting from the nucleosome. Clinically, valproic acid fetopathy sheds some insight into the effects of altered HDACs on human embryonic development, since valproic acid is an antiepileptic drug and an HDAC inhibitor. The fetal anomalies include severe renal dysgenesis, supporting the role played by HDACs in human kidney development. Our recent studies have shown that HDACs regulate the transcriptional networks required for controlling the cell cycle, Wnt signaling, and the pathway upstream of the GDNF/RET signaling pathway in the developing kidney. Here, we describe novel HDAC target genes not previously implicated in renal development based on studies using genome-wide microarrays. These genes can be divided into transcription factors, modulators of matrix biology, chromatin remodelers, and DNA repair genes. We also report that HDACs are requisite for tissue-specific gene expression.

Regulation of Kidney Development by Shp2: An Unbiased Stereological Analysis

Genes that regulate renal branching morphogenesis are likely to indirectly regulate nephron endowment, but few have been validated to do so in vivo. PTPN11, which encodes the nonreceptor protein tyrosine phosphatase Shp2, acts downstream of receptor tyrosine kinases to modulate the Ras-MAPK pathway and has been implicated in branching morphogenesis in vitro and in invertebrates, and is therefore a candidate in vivo regulator of nephron number. In this work, heterozygous null mutant Shp2(+/-) mice at postnatal days 30-35 were compared with their wild-type (WT) littermates using unbiased stereology to determine if, indeed, the former had decreased nephron number due to their 50% decrease in gene/protein dosage. Although there was a trend toward decreases in total glomerular (nephron) number and kidney volume in Shp2(+/-) mice compared with WT, neither difference was statistically significant (11310 vs. 12198 glomeruli, P = 0.22; 62.8 mm(3) vs. 66.0 mm(3) renal volume; P = 0.40). We conclude that loss of 50% gene/protein dosage of PTPN11/Shp2 is insufficient to affect glomerular (and thereby nephron) number in mouse kidneys in vivo.

Abstract A54: CnABP, a novel modulator of the Calcineurin-NFAT signaling pathway, is overexpressed in Wilms' tumors and promotes cell migration

Abstract Wilms' tumor (WT) is a classical cancer type that arises from abnormal differentiation of kidney progenitor cells, and occurs at a frequency of 1 in 10,000 live births, accounting for approx. 90% of childhood kidney cancer. Abnormally high levels of Pax2 (paired-box protein 2), a key regulator of kidney development, have been observed in both WT and renal cell carcinoma, which correlate with proliferation and increased invasiveness. Therefore the misexpression of Pax2 and its target genes may play an important role in tumor initiation and/or progression. To test this, we screened for target genes of Pax2 by cDNA microarray in the embryonic kidney. We identified CnABP (Calcineurin A Binding Protein), a novel gene under Pax2 regulation. In situ hybridization indicates that CnABP coexpresses with Pax2 in the condensing mesenchyme, the abnormal differentiation of which gives rise to WT. Furthermore, expression analysis by quantitative PCR indicates that CnABP is overexpressed in more than 70% of Wilms' tumors. Interestingly, in the proportion of tumors with upregulated PAX2 expression, more than 80% also overexpress CnABP. We characterized CnABP as a membrane-anchored protein that primarily promotes cell proliferation and migration. Mediators of these activities were investigated by Yeast-two-hybrid and immunoprecipitation, which identified an interaction between CnABP and Calcineurin A, the catalytic subunit of a calcium-responsive serine/threonine phosphatase Calcineurin. We showed that CnABP modulates phosphatase activities of Calcineurin, which consequently inhibits calcium/Calcineurin-dependent NFAT nuclear translocation. We further demonstrated that the inhibition of NFAT nuclear localization results in reduced NFAT-specific transcriptional activity. Components of the Calcineurin complex have been reported as differentially expressed genes distinguishing recurrent from non-recurrent Wilms' tumors. This is in line with the evidence we presented, as CnABP is upregulated in Wilms' tumors and is shown to promote proliferation and migration. Citation Information: Cancer Res 2009;69(23 Suppl):A54.

Discoidin domain receptor 1 activation suppresses α2β1 integrin‐dependent cell spreading through inhibition of Cdc42 activity

Upregulation and overexpression of discoidin domain receptor 1 (DDR1) have been implied in the regulation of kidney development and progression of cancers. Our previous studies with Mardin-Darby canine kidney (MDCK) cells showed that overexpression of DDR1 inhibited cell spreading, whereas dominant negative DDR1 promoted cell spreading on collagen-coated dish. Cell spreading is an important characteristic for cell differentiation and survival. However, little is known about the molecular mechanisms underlying the role of DDR1 in cell spreading. We have found here a novel signaling pathway of DDR1 consisting of Cdc42 that regulates the assembly and disassembly of cytoskeleton and cell spreading in MDCK cells. Cell spreading involves the organization of cytoskeleton that is mainly regulated by Rho-family GTPases. We assessed the activity of Rho-family GTPases and transfected MDCK cells with constitutively active or dominant negative GTPases, and quantified the extent of cell spreading. These results showed that DDR1 decreased the filamentous actin ratio and Rac1/Cdc42 activities, but had no effects on RhoA activity. Neither constitutively active nor dominant negative Rac1 altered DDR1-inhibited cell spreading. Constitutively active Cdc42 could rescue the DDR1-inhibited cell spreading, whereas dominant negative Cdc42 inhibited cell spreading, indicating that DDR1-inhibited cell spreading is Cdc42 dependent. With the use of alpha(2)beta(1) integrin blocking antibody, we showed that collagen-induced Cdc42 activation was mediated by alpha(2)beta(1) integrin. Moreover, ectopic FAK expression enhanced the Cdc42 activity. Reducing FAK activity by dominant negative FAK (FRNK) markedly abolished the Cdc42 activity. These findings show that DDR1a/b activation inhibits cell spreading through suppressing alpha(2)beta(1) integrin-mediated Cdc42 activation.

Novel Regulators of Kidney Development from the Tips of the Ureteric Bud

Mammalian nephrogenesis depends on the interaction between the ureteric bud and the metanephric mesenchyme. As the ureteric bud undergoes branching and segmentation, the stalks differentiate into the collecting system of the mature kidney, while the tip cells interact with the adjacent cells of the metanephric mesenchyme, inducing their conversion into nephrons. This induction is mediated by secreted factors. For identifying novel mediators, the tips of the ureteric tree were isolated and microarray analyses were performed using manually refined, multistep gene ontology annotations. For identifying conserved factors, two databases were developed, one from mouse E12.5 and one from rat E13.5 ureteric buds. The overlap of mouse and rat data sets yielded 20 different transcripts that were enriched in the ureteric bud compared with metanephric mesenchyme and predicted to code for secreted proteins. Real-time reverse transcriptase-PCR and in situ hybridization confirmed these identifications. One of the genes that was highly specific to the ureteric bud tip was cytokine-like factor 1 (CLF-1). Recombinant CLF-1 in complex with its physiologic ligand, cardiotrophin-like cytokine (CLC), triggered phosphorylation of signal transducer and activator of transcription 3 in mesenchyme, a pathway characteristic of mesenchymal-to-epithelial conversion. Indeed, when applied to isolated rat metanephric mesenchyme, CLF-1/CLC (3 nM) induced mature nephron structures expressing glomerular and tubular markers. These results underline the power of this first comprehensive gene expression analysis of the ureteric bud tip to identify bioactive molecules.

Midkine is involved in kidney development and in its regulation by retinoids.

In the kidney, in which development depends on epithelial-mesenchymal interactions, it has been shown that retinoids modulate nephrogenesis in a dose-dependent manner in vivo and in vitro. Midkine (MK) is a retinoic acid responsive gene for a heparin-binding growth factor. The aim of the present study was therefore to quantify the expression of MK mRNA during renal development in the rat, to analyze the regulation of MK expression by retinoids in vivo and in vitro, and, finally, to study the role of MK in rat metanephric organ cultures. The spatiotemporal expression of MK in fetal kidney was studied. In control rats, MK expression is ubiquitous at gestational day 14, i.e., at the onset of nephrogenesis. On day 16, MK is expressed in the condensed mesenchyme and in early epithelialized mesenchymal derivatives. On gestational day 21, MK is rather localized in the nonmature glomeruli of the renal cortex. In utero exposure to vitamin A deficiency did not modify the specific spatial and temporal expression pattern of MK gene in the metanephros, although a decrease in mRNA expression occurred. In metanephroi explanted from 14-d-old fetuses and cultured in a defined medium, expression of MK mRNA was found to be stimulated when retinoic acid (100 nM) was added in the culture medium. Finally, in vitro nephrogenesis was strongly inhibited in the presence of neutralizing antibodies for MK: the number of nephrons formed in vitro was reduced by approximately 50% without changes in ureteric bud branching morphogenesis. These results indicated that MK is implicated in the regulation of kidney development by retinoids. These results also suggested that MK plays an important role in the molecular cascade of the epithelial conversion of the metanephric blastema.

Introduction: Pediatric End-Stage Renal Disease

The field of pediatric nephrology requires an understanding of fetal physiology, developmental biology of the kidney, pharmacotherapeutics tailored to an altered metabolism, and the biophysical and psychological effects of normal growth and developmental processes that occur through young adulthood and are often superimposed on the course of chronic kidney disease. In addition, practitioners in this field must be acutely aware of how chronic kidney disease alters the normal course of sexual differentiation during adolescence. We believe that this issue of Advances in Renal Replacement Therapy, which is dedicated to the pediatric patient on maintenance dialysis, represents a state-of-the-art approach as it pertains to several of these important issues for children with kidney failure. Fully one third of children developing kidney failure have an anatomic lesion of the urinary tract, often developmentally acquired. Professor Adrian W 001£ and Nikesh Thiruchelvam present a coherent story of the regulation of kidney development, as but part of an emerging area of translational science about obstructive uropathy. Their review clearly shows how, in the future, both better diagnostic criteria for such lesions and perhaps even genetic modulation of developmental anomalies may be a component of the therapeutic armamentarium of the pediatric nephrologist and urologist. The extrarenal morbidity associated with end-stage renal disease (ESRD) in pediatrics is a topic that demands the utmost attention because of the impact it has on the long-term outcome of this young population. Drs Blanche Chavers and H.William Schnaper collaborate to discuss the recent clinical evidence of and scientific basis for the dramatic alterations of the cardiovascular system that can characterize the child with kidney failure. Dr Uri Alon follows with a comprehensive analysis of the profound effects that chronic kidney disease produces on the growing skeleton. He provides a theoretical and practical framework on which he proposes relevant clinical questions that can be answered only in the setting of multicenter studies. Both discussions are intended to stimulate innovative strategies to

Development of the embryonic kidney

The kidney is a favorite subject of developmental biologists. In the past decade, we have gained a great deal of knowledge about the regulation of kidney development. This review describes the organization of the kidney, the molecules involved in the regulation of kidney development, and a unique protocol for kidney culture. The pronephros, mesonephros, and metanephros represent three distinct renal organs which function, in succession, as the vertebrate excretory system.1 All three such kidneys are derived from the intermediate mesoderm and develop in a well defined temporal and spatial sequence. The pronephros, which consists of a tubule and excretory organ, is established earliest and functions as the simplest of the excretory organs in vertebrates. The amphibian pronephros, a simple organ which provides renal function in the early embryo, is conceptualized in the present study as a model system for devising experimental strategies for the in-vitro cultivation of donor organs and tissues for subsequent transplantation into vertebrate hosts. Combined activin and retinoic acid treatment of blastula-stage ectoderm cultured for 3 days yielded a pronephros-like structure. Its functional capacity was confirmed by transplanting it into late neurula-stage host embryos from which the natural pronephros rudiments had been removed. The donor tissue differentiated into a pronephros-like structure, and the host embryos were able to suppress the edema ordinarily caused by removal of the natural pronephric rudiments. Thus, this provides a model system for analyzing the experimental conditions and relevant principles for the cultivation of functional vertebrate organs for transplantation.

The regulation of kidney development: new insights from an old model

The embryonic kidney is an excellent model system in which to address many fundamental issues in developmental biology. Inductive interactions are required for proliferation and differentiation of the ureter epithelium and kidney mesenchyme. Recent studies implicate a receptor-type tyrosine kinase as a target of inductive signals in the developing ureter. In the mesenchyme, the early induction response requires at least two transcription factors, WT1 and Pax-2. Through the integrated application of in vitro culture models and gene targeting methods, the molecular mechanisms underlying kidney morphogenesis are becoming clearer.