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Clearman KR, Timpratoom N, Patel D, Rains AB, Haycraft CJ, Croyle MJ, Reiter JF, Yoder BK. Rab35 Is Required for Embryonic Development and Kidney and Ureter Homeostasis through Regulation of Epithelial Cell Junctions. J Am Soc Nephrol 2024; 35:719-732. [PMID: 38530365 PMCID: PMC11164122 DOI: 10.1681/asn.0000000000000335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2023] [Accepted: 03/12/2024] [Indexed: 03/28/2024] Open
Abstract
Key Points Loss of Rab35 leads to nonobstructive hydronephrosis because of loss of ureter epithelium. Rab35 regulates kidney and ureter epithelial cell adhesion and polarity. Rab35 is required for embryonic development. Background Rab35 is a member of a GTPase family of endocytic trafficking proteins. Studies in cell lines have indicated that Rab35 participates in cell adhesion, polarity, cytokinesis, and primary cilia length and composition. In addition, sea urchin Rab35 regulates actin organization and is required for gastrulation. In mice, loss of Rab35 in the central nervous system disrupts hippocampal development and neuronal organization. Outside of the central nervous system, the functions of mammalian Rab35 in vivo are unknown. Methods We generated and analyzed the consequences of both congenital and conditional null Rab35 mutations in mice. Using a LacZ reporter allele, we assessed Rab35 expression during development and postnatally. We assessed Rab35 loss in the kidney and ureter using histology, immunofluorescence microscopy, and western blotting. Results Congenital Rab35 loss of function caused embryonic lethality: homozygous mutants arrested at E7.5 with cardiac edema. Conditional loss of Rab35, either during gestation or postnatally, caused hydronephrosis. The kidney and ureter phenotype were associated with disrupted actin cytoskeletal architecture, altered Arf6 epithelial polarity, reduced adherens junctions, loss of tight junction formation, defects in epithelial growth factor receptor expression and localization, disrupted cell differentiation, and shortened primary cilia. Conclusions Rab35 may be essential for mammalian development and the maintenance of kidney and ureter architecture. Loss of Rab35 leads to nonobstructive hydronephrosis, making the Rab35 mutant mouse a novel mammalian model to study mechanisms underlying this disease.
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Song R, Yosypiv IV. Deletion of the prorenin receptor in the ureteric bud in mice inhibits Dot1/H3K79 pathway. Pediatr Res 2024; 95:1754-1757. [PMID: 38287105 PMCID: PMC11245383 DOI: 10.1038/s41390-024-03026-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Revised: 11/29/2023] [Accepted: 12/26/2023] [Indexed: 01/31/2024]
Abstract
BACKGROUND The prorenin receptor (PRR) plays a critical role in ureteric bud (UB) branching morphogenesis. DOT1 Like (DOT1L), a histone methyltransferase specific for Histone 3 lysine 79 (H3K79), is important for differentiation of the UB-derived renal collecting duct cells. In this study, we tested whether DOT1L/H3 dimethyl K79 (H3m2K79) are regulated by PRR deletion in the UB and UB-derived collecting ducts in the embryonic mouse kidneys. METHODS Mutant Hoxb7Cre+/PRRflox/flox (PRRUB-/-) and control PRRUB+/+, mice were studied on embryonic (E) day E17.5. DOT1L mRNA and protein expression in the kidney was examined by real-time qRT-PCR and immunohistochemistry, respectively. H3m2K79 protein expression was determined by immunohistochemistry and Western blot analysis. RESULTS DOT1L mRNA levels were decreased in mutant compared to control mice (0.68 ± 0.06 vs. 1.0 ± 0.01, p < 0.01). DOT1L and H3m2K79 immunostaining was reduced in the mutant vs. control kidneys (Dot1: 0.62 ± 0.03 vs. 1.0 ± 0.01, p < 0.05; H3m2K79: 0.64 ± 0.04 vs.1.1 ± 0.01. p < 0.05.). Western blot analysis revealed decreased H3m2K79 protein levels in mutant compared to control kidneys (1.0 ± 0.06 vs. 1.5 ± 0.02, p < 0.05). CONCLUSION Targeted deletion of the PRR in the UB and UB-derived collecting ducts results in reduced DOT1L gene/protein and H3m2K79 protein expression in the embryonic mouse metanephroi in vivo. IMPACT The role of histone methylation in mediating the effect of the prorenin receptor on the ureteric bud branching (UB) morphogenesis and urine acidification during kidney development is unknown. We demonstrate that histone H3 lysine (K) 79 dimethylation by methyltransferase Dot1 is reduced in the embryonic kidney of mice that lack the prorenin receptor in the UB lineage.
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Guan N, Kobayashi H, Ishii K, Davidoff O, Sha F, Ikizler TA, Hao CM, Chandel NS, Haase VH. Disruption of mitochondrial complex III in cap mesenchyme but not in ureteric progenitors results in defective nephrogenesis associated with amino acid deficiency. Kidney Int 2022; 102:108-120. [PMID: 35341793 PMCID: PMC9232975 DOI: 10.1016/j.kint.2022.02.030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Revised: 01/14/2022] [Accepted: 02/16/2022] [Indexed: 11/21/2022]
Abstract
Oxidative metabolism in mitochondria regulates cellular differentiation and gene expression through intermediary metabolites and reactive oxygen species. Its role in kidney development and pathogenesis is not completely understood. Here we inactivated ubiquinone-binding protein QPC, a subunit of mitochondrial complex III, in two types of kidney progenitor cells to investigate the role of mitochondrial electron transport in kidney homeostasis. Inactivation of QPC in sine oculis-related homeobox 2 (SIX2)-expressing cap mesenchyme progenitors, which give rise to podocytes and all nephron segments except collecting ducts, resulted in perinatal death from severe kidney dysplasia. This was characterized by decreased proliferation of SIX2 progenitors and their failure to differentiate into kidney epithelium. QPC inactivation in cap mesenchyme progenitors induced activating transcription factor 4-mediated nutritional stress responses and was associated with a reduction in kidney tricarboxylic acid cycle metabolites and amino acid levels, which negatively impacted purine and pyrimidine synthesis. In contrast, QPC inactivation in ureteric tree epithelial cells, which give rise to the kidney collecting system, did not inhibit ureteric differentiation, and resulted in the development of functional kidneys that were smaller in size. Thus, our data demonstrate that mitochondrial oxidative metabolism is critical for the formation of cap mesenchyme-derived nephron segments but dispensable for formation of the kidney collecting system. Hence, our studies reveal compartment-specific needs for metabolic reprogramming during kidney development.
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Gupta✉ N, Dilmen E, Morizane R. 3D kidney organoids for bench-to-bedside translation. J Mol Med (Berl) 2020; 99:477-487. [PMID: 33034708 PMCID: PMC8026465 DOI: 10.1007/s00109-020-01983-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 06/30/2020] [Accepted: 09/22/2020] [Indexed: 12/23/2022]
Abstract
The kidneys are essential organs that filter the blood, removing urinary waste while maintaining fluid and electrolyte homeostasis. Current conventional research models such as static cell cultures and animal models are insufficient to grasp the complex human in vivo situation or lack translational value. To accelerate kidney research, novel research tools are required. Recent developments have allowed the directed differentiation of induced pluripotent stem cells to generate kidney organoids. Kidney organoids resemble the human kidney in vitro and can be applied in regenerative medicine and as developmental, toxicity, and disease models. Although current studies have shown great promise, challenges remain including the immaturity, limited reproducibility, and lack of perfusable vascular and collecting duct systems. This review gives an overview of our current understanding of nephrogenesis that enabled the generation of kidney organoids. Next, the potential applications of kidney organoids are discussed followed by future perspectives. This review proposes that advancement in kidney organoid research will be facilitated through our increasing knowledge on nephrogenesis and combining promising techniques such as organ-on-a-chip models.
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Rutledge EA, Lindström NO, Michos O, McMahon AP. Genetic manipulation of ureteric bud tip progenitors in the mammalian kidney through an Adamts18 enhancer driven tet-on inducible system. Dev Biol 2020; 458:164-176. [PMID: 31734175 PMCID: PMC6995766 DOI: 10.1016/j.ydbio.2019.11.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Revised: 11/13/2019] [Accepted: 11/13/2019] [Indexed: 11/22/2022]
Abstract
The ureteric epithelial progenitor (UEP) population within the embryonic kidney generates the arborized epithelial network of the kidney's collecting system and plays a critical role in the expansion and induction of the surrounding nephron progenitor pool. Adamts18 shows UEP- restricted expression in the kidney and progenitor tip-restricted expression in several other organs undergoing branching epithelial growth. Adamts18 is encoded by 23 exons. Genetic removal of genomic sequence spanning exons 1 to 3 led to a specific loss of Adamts18 expression in UEPs, suggesting this region may encode a UEP-specific enhancer. Intron 2 (3 kb) was shown to have enhancer activity driving expression of the doxycycline inducible tet-on transcriptional regulator (rtTA) in an Adamts18en-rtTA transgenic mouse strain. Crossing Adamts18en-rtTA mice to a doxycycline dependent GFP reporter mouse enabled the live imaging of embryonic kidney explants. This facilitated the analysis of ureteric epithelial branching events at the cellular level. Ablation of UEPs at the initiation of ureteric bud outgrowth through the doxycycline-mediated induction of Diphtheria Toxin A (DTA) generated a range of phenotypes from complete kidneys agenesis, to duplex kidneys with double ureters. The latter outcome points to the potential of regulative processes to restore UEPs. In contrast, overexpression of YAP prior to ureteric bud outgrowth led to a complete failure of kidney development. Elevating YAP levels at later stages retarded branching growth. A similar phenotype was observed with the overexpression of MYC within the branch-tip localized UEP population. These experiments showcase the utility of the Adamts18en-rtTA transgenic model to the investigation of cellular and molecular events specific to branch tip progenitors within the mammalian kidney complementing existing CRE-dependent genetic tools. Further, the illustrative examples point to areas where new insight may be gained into the regulation of UEP programs.
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Isaacson D, Shen J, McCreedy D, Calvert M, McDevitt T, Cunha G, Baskin L. Lightsheet fluorescence microscopy of branching human fetal kidney. Kidney Int 2018; 93:525. [PMID: 29389399 DOI: 10.1016/j.kint.2017.09.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Accepted: 09/14/2017] [Indexed: 11/18/2022]
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Costa S, Carriço A, Valente F. Prenatal diagnosis of left isomerism with normal heart. BMJ Case Rep 2017; 2017:bcr-2017-223097. [PMID: 29133586 PMCID: PMC5695494 DOI: 10.1136/bcr-2017-223097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/27/2017] [Indexed: 11/03/2022] Open
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Myroshnychenko M, Sherstiuk S, Zubova Y, Nakonechna S. [PATHOGENICALLY INDUCED APOPTOSIS CAUSED BY HYPOXIC EFFECTS IN THE URINARY SYSTEM ORGANS OF FETUSES AND NEWBORNS (EXPERIMENTAL STUDY)]. GEORGIAN MEDICAL NEWS 2017:94-99. [PMID: 28972491] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The purpose of the study was to identify the characteristics of apoptosis in the kidneys, ureters and bladder of fetuses and newborns in the modeling of chronic intrauterine hypoxia, acute postnatal hypoxia and mixed hypoxia. An experiment was conducted on WAG rats for modeling high altitude hypoxia. Experimental animals were divided into four groups: I - control - fetuses and newborns from healthy rats; II - modeling of chronic intrauterine hypoxia; III - modeling of acute postnatal hypoxia; IV - modeling of mixed hypoxia. The material of the study was the tissue of the kidneys, ureters and bladder of fetuses and newborns. In group I in the kidneys of fetuses the mean value of the number of p53-positive cells was 7.83±0.31, newborns - 5.40±0.28; in the ureters and bladder of fetuses - 5.77±0.29 and 6.97±0.32, newborns - 3.58±0.21 and 5.36±0.28. In the kidneys in group II the mean value of the number of p53-expressing cells in fetuses was 1.43±0.50, in newborns - 21.72±0.58; in group III in newborns - 15.03±0.63; in group IV in newborns - 33.33±0.72. The mean value of the number of p53-expressing cells in the ureters and bladder in group II in fetuses was 13.17±0.49 and 11.83±0.43, in newborns - 16.24±0.37 and 15.38±0.37; in group III in newborns - 7.25±0.27 and 8.68±0.32; in group IV in newborns - 19.63±0.31and 21.03±0.40. As the result of the study it was found that experimental hypoxia induced apoptotic processes in the kidneys, ureters and bladder of fetuses and newborns, the severity of which was moderate in the modeling of acute postnatal hypoxia, expressed in the modeling of chronic intrauterine hypoxia and strongly expressed in the modeling of mixed hypoxia. Under the influence of acute postnatal hypoxia, chronic intrauterine hypoxia and mixed hypoxia in the ureters and bladder of fetuses and newborns p53-positive cells were located evenly in all layers of the wall of these organs, whereas in the kidneys p53-positive cells prevailed in the tubular component. In the modeling of chronic intrauterine hypoxia apoptotic processes in the kidneys, ureters and bladder increased in newborns in comparison with fetuses.
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Bohnenpoll T, Wittern AB, Mamo TM, Weiss AC, Rudat C, Kleppa MJ, Schuster-Gossler K, Wojahn I, Lüdtke THW, Trowe MO, Kispert A. A SHH-FOXF1-BMP4 signaling axis regulating growth and differentiation of epithelial and mesenchymal tissues in ureter development. PLoS Genet 2017; 13:e1006951. [PMID: 28797033 PMCID: PMC5567910 DOI: 10.1371/journal.pgen.1006951] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Revised: 08/22/2017] [Accepted: 08/01/2017] [Indexed: 12/19/2022] Open
Abstract
The differentiated cell types of the epithelial and mesenchymal tissue compartments of the mature ureter of the mouse arise in a precise temporal and spatial sequence from uncommitted precursor cells of the distal ureteric bud epithelium and its surrounding mesenchyme. Previous genetic efforts identified a member of the Hedgehog (HH) family of secreted proteins, Sonic hedgehog (SHH) as a crucial epithelial signal for growth and differentiation of the ureteric mesenchyme. Here, we used conditional loss- and gain-of-function experiments of the unique HH signal transducer Smoothened (SMO) to further characterize the cellular functions and unravel the effector genes of HH signaling in ureter development. We showed that HH signaling is not only required for proliferation and SMC differentiation of cells of the inner mesenchymal region but also for survival of cells of the outer mesenchymal region, and for epithelial proliferation and differentiation. We identified the Forkhead transcription factor gene Foxf1 as a target of HH signaling in the ureteric mesenchyme. Expression of a repressor version of FOXF1 in this tissue completely recapitulated the mesenchymal and epithelial proliferation and differentiation defects associated with loss of HH signaling while re-expression of a wildtype version of FOXF1 in the inner mesenchymal layer restored these cellular programs when HH signaling was inhibited. We further showed that expression of Bmp4 in the ureteric mesenchyme depends on HH signaling and Foxf1, and that exogenous BMP4 rescued cell proliferation and epithelial differentiation in ureters with abrogated HH signaling or FOXF1 function. We conclude that SHH uses a FOXF1-BMP4 module to coordinate the cellular programs for ureter elongation and differentiation, and suggest that deregulation of this signaling axis occurs in human congenital anomalies of the kidney and urinary tract (CAKUT). The mammalian ureter is a simple tube with a specialized multi-layered epithelium, the urothelium, and a surrounding coat of fibroblasts and peristaltically active smooth muscle cells. Besides its important function in urinary drainage, the ureter represents a simple model system to study epithelial and mesenchymal tissue interactions in organ development. The differentiated cell types of the ureter coordinately arise from precursor cells of the distal ureteric bud and its surrounding mesenchyme. How their survival, growth and differentiation is regulated and coordinated within and between the epithelial and mesenchymal tissue compartments is largely unknown. Previous work identified Sonic hedgehog (SHH) as a crucial epithelial signal for growth and differentiation of the ureteric mesenchyme, but the entirety of the cellular functions and the molecular mediators of its mesenchymal signaling pathway have remained obscure. Here we showed that epithelial SHH acts in a paracrine fashion onto the ureteric mesenchyme to activate a FOXF1-BMP4 regulatory module that directs growth and differentiation of both ureteric tissue compartments. HH signaling additionally acts in outer mesenchymal cells as a survival factor. Thus, SHH is an epithelial signal that coordinates various cellular programs in early ureter development.
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Xu J, Liu H, Chai OH, Lan Y, Jiang R. Osr1 Interacts Synergistically with Wt1 to Regulate Kidney Organogenesis. PLoS One 2016; 11:e0159597. [PMID: 27442016 PMCID: PMC4956120 DOI: 10.1371/journal.pone.0159597] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2016] [Accepted: 06/01/2016] [Indexed: 12/29/2022] Open
Abstract
Renal hypoplasia is a common cause of pediatric renal failure and several adult-onset diseases. Recent studies have associated a variant of the OSR1 gene with reduction of newborn kidney size and function in heterozygotes and neonatal lethality with kidney defects in homozygotes. How OSR1 regulates kidney development and nephron endowment is not well understood, however. In this study, by using the recently developed CRISPR genome editing technology, we genetically labeled the endogenous Osr1 protein and show that Osr1 interacts with Wt1 in the developing kidney. Whereas mice heterozygous for either an Osr1 or Wt1 null allele have normal kidneys at birth, most mice heterozygous for both Osr1 and Wt1 exhibit defects in metanephric kidney development, including unilateral or bilateral kidney agenesis or hypoplasia. The developmental defects in the Osr1+/-Wt1+/- mouse embryos were detected as early as E10.5, during specification of the metanephric mesenchyme, with the Osr1+/-Wt1+/- mouse embryos exhibiting significantly reduced Pax2-positive and Six2-positive nephron progenitor cells. Moreover, expression of Gdnf, the major nephrogenic signal for inducing ureteric bud outgrowth, was significantly reduced in the metanephric mesenchyme in Osr1+/-Wt1+/- embryos in comparison with the Osr1+/- or Wt1+/- littermates. By E11.5, as the ureteric buds invade the metanephric mesenchyme and initiate branching morphogenesis, kidney morphogenesis was significantly impaired in the Osr1+/-Wt1+/- embryos in comparison with the Osr1+/- or Wt1+/- embryos. These results indicate that Osr1 and Wt1 act synergistically to regulate nephron endowment by controlling metanephric mesenchyme specification during early nephrogenesis.
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Pietilä I, Prunskaite-Hyyryläinen R, Kaisto S, Tika E, van Eerde AM, Salo AM, Garma L, Miinalainen I, Feitz WF, Bongers EMHF, Juffer A, Knoers NVAM, Renkema KY, Myllyharju J, Vainio SJ. Wnt5a Deficiency Leads to Anomalies in Ureteric Tree Development, Tubular Epithelial Cell Organization and Basement Membrane Integrity Pointing to a Role in Kidney Collecting Duct Patterning. PLoS One 2016; 11:e0147171. [PMID: 26794322 PMCID: PMC4721645 DOI: 10.1371/journal.pone.0147171] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Accepted: 12/30/2015] [Indexed: 11/26/2022] Open
Abstract
The Wnts can be considered as candidates for the Congenital Anomaly of Kidney and Urinary Tract, CAKUT diseases since they take part in the control of kidney organogenesis. Of them Wnt5a is expressed in ureteric bud (UB) and its deficiency leads to duplex collecting system (13/90) uni- or bilateral kidney agenesis (10/90), hypoplasia with altered pattern of ureteric tree organization (42/90) and lobularization defects with partly fused ureter trunks (25/90) unlike in controls. The UB had also notably less tips due to Wnt5a deficiency being at E15.5 306 and at E16.5 765 corresponding to 428 and 1022 in control (p<0.02; p<0.03) respectively. These changes due to Wnt5a knock out associated with anomalies in the ultrastructure of the UB daughter epithelial cells. The basement membrane (BM) was malformed so that the BM thickness increased from 46.3 nm to 71.2 nm (p<0.01) at E16.5 in the Wnt5a knock out when compared to control. Expression of a panel of BM components such as laminin and of type IV collagen was also reduced due to the Wnt5a knock out. The P4ha1 gene that encodes a catalytic subunit of collagen prolyl 4-hydroxylase I (C-P4H-I) in collagen synthesis expression and the overall C-P4H enzyme activity were elevated by around 26% due to impairment in Wnt5a function from control. The compound Wnt5a+/-;P4ha1+/- embryos demonstrated Wnt5a-/- related defects, for example local hyperplasia in the UB tree. A R260H WNT5A variant was identified from renal human disease cohort. Functional studies of the consequence of the corresponding mouse variant in comparison to normal ligand reduced Wnt5a-signalling in vitro. Together Wnt5a has a novel function in kidney organogenesis by contributing to patterning of UB derived collecting duct development contributing putatively to congenital disease.
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Vivante A, Kleppa MJ, Schulz J, Kohl S, Sharma A, Chen J, Shril S, Hwang DY, Weiss AC, Kaminski MM, Shukrun R, Kemper MJ, Lehnhardt A, Beetz R, Sanna-Cherchi S, Verbitsky M, Gharavi AG, Stuart HM, Feather SA, Goodship JA, Goodship THJ, Woolf AS, Westra SJ, Doody DP, Bauer SB, Lee RS, Adam RM, Lu W, Reutter HM, Kehinde EO, Mancini EJ, Lifton RP, Tasic V, Lienkamp SS, Jüppner H, Kispert A, Hildebrandt F. Mutations in TBX18 Cause Dominant Urinary Tract Malformations via Transcriptional Dysregulation of Ureter Development. Am J Hum Genet 2015; 97:291-301. [PMID: 26235987 DOI: 10.1016/j.ajhg.2015.07.001] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Accepted: 07/07/2015] [Indexed: 12/22/2022] Open
Abstract
Congenital anomalies of the kidneys and urinary tract (CAKUT) are the most common cause of chronic kidney disease in the first three decades of life. Identification of single-gene mutations that cause CAKUT permits the first insights into related disease mechanisms. However, for most cases the underlying defect remains elusive. We identified a kindred with an autosomal-dominant form of CAKUT with predominant ureteropelvic junction obstruction. By whole exome sequencing, we identified a heterozygous truncating mutation (c.1010delG) of T-Box transcription factor 18 (TBX18) in seven affected members of the large kindred. A screen of additional families with CAKUT identified three families harboring two heterozygous TBX18 mutations (c.1570C>T and c.487A>G). TBX18 is essential for developmental specification of the ureteric mesenchyme and ureteric smooth muscle cells. We found that all three TBX18 altered proteins still dimerized with the wild-type protein but had prolonged protein half life and exhibited reduced transcriptional repression activity compared to wild-type TBX18. The p.Lys163Glu substitution altered an amino acid residue critical for TBX18-DNA interaction, resulting in impaired TBX18-DNA binding. These data indicate that dominant-negative TBX18 mutations cause human CAKUT by interference with TBX18 transcriptional repression, thus implicating ureter smooth muscle cell development in the pathogenesis of human CAKUT.
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Guo Q, Tripathi P, Manson SR, Austin PF, Chen F. Transcriptional dysregulation in the ureteric bud causes multicystic dysplastic kidney by branching morphogenesis defect. J Urol 2015; 193:1784-90. [PMID: 25301096 PMCID: PMC4504205 DOI: 10.1016/j.juro.2014.08.122] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/22/2014] [Indexed: 11/25/2022]
Abstract
PURPOSE The calcineurin-NFAT signaling pathway regulates the transcription of genes important for development. It is impacted by various genetic and environmental factors. We investigated the potential role of NFAT induced transcriptional dysregulation in the pathogenesis of congenital abnormalities of the kidneys and urinary tract. MATERIALS AND METHODS A murine model of conditional NFATc1 activation in the ureteric bud was generated and examined for histopathological changes. Metanephroi were also cultured in vitro to analyze branching morphogenesis in real time. RESULTS NFATc1 activation led to defects resembling multicystic dysplastic kidney. These mutants showed severe disorganization of branching morphogenesis characterized by decreased ureteric bud branching and the disconnection of ureteric bud derivatives from the main collecting system. The orphan ureteric bud derivatives may have continued to induce nephrogenesis and likely contributed to the subsequent formation of blunt ended filtration units and cysts. The ureter also showed irregularities consistent with impaired epithelial-mesenchymal interaction. CONCLUSIONS This study reveals the profound effects of NFAT signaling dysregulation on the ureteric bud and provides insight into the pathogenesis of multicystic dysplastic kidney. Our results suggest that the obstruction hypothesis and the bud theory may not be mutually exclusive to explain the pathogenesis of multicystic dysplastic kidney. Ureteric bud dysfunction such as that induced by NFAT activation can disrupt ureteric bud-metanephric mesenchyma interaction, causing primary defects in branching morphogenesis, subsequent dysplasia and cyst formation. Obstruction of the main collecting system can further enhance these defects, producing the pathological changes associated with multicystic dysplastic kidney.
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Tanigawa S, Nishinakamura R. [Advances in kidney development and application for regenerative medicine]. NIHON JINZO GAKKAI SHI 2015; 57:233-240. [PMID: 25735082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
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Jain S, Noordam MJ, Hoshi M, Vallania FL, Conrad DF. Validating single-cell genomics for the study of renal development. Kidney Int 2014; 86:1049-55. [PMID: 24759149 PMCID: PMC4207726 DOI: 10.1038/ki.2014.104] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Revised: 01/17/2014] [Accepted: 02/13/2014] [Indexed: 11/08/2022]
Abstract
Single-cell genomics will enable studies of the earliest events in kidney development, although it is unclear if existing technologies are mature enough to generate accurate and reproducible data on kidney progenitors. Here we designed a pilot study to validate a high-throughput assay to measure the expression levels of key regulators of kidney development in single cells isolated from embryonic mice. Our experiment produced 4608 expression measurements of 22 genes, made in small cell pools, and 28 single cells purified from the RET-positive ureteric bud. There were remarkable levels of concordance with expression data generated by traditional microarray analysis on bulk ureteric bud tissue with the correlation between our average single-cell measurements and GUDMAP measurements for each gene of 0.82-0.85. Nonetheless, a major motivation for single-cell technology is to uncover dynamic biology hidden in population means. There was evidence for extensive and surprising variation in expression of Wnt11 and Etv5, both downstream targets of activated RET. The variation for all genes in the study was strongly consistent with burst-like promoter kinetics. Thus, our results can inform the design of future single-cell experiments, which are poised to provide important insights into kidney development and disease.
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Cullen-McEwen LA, Young RJ, Fricout G, Jeulin D, Harper IS, Costantini F, Bertram JF. Imaging tools for analysis of the ureteric tree in the developing mouse kidney. Methods Mol Biol 2014; 1075:305-320. [PMID: 24052360 DOI: 10.1007/978-1-60761-847-8_16] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The structure of the ureteric tree in developing mouse and rat kidneys has previously been quantified in two dimensions. While this type of analysis may provide evidence of changes in ureteric growth, these measurements are effectively inaccurate, as the ureteric tree is a three-dimensional (3D) object. Here we describe a method for measuring the ureteric tree in three dimensions. This technique involves (1) culture of the metanephric kidney at embryonic day 12 (mouse) or 14 (rat), (2) whole-mount immunofluorescence to selectively stain ureteric tree epithelium, (3) confocal microscopy to obtain a complete Z series through the ureteric tree, and (4) image analysis algorithms to binarize, skeletonize, and measure individual branch lengths in 3D. This method has been extended to analysis of the same ureteric tree over time (4D). The results obtained provide accurate and precise quantitation of ureteric tree growth in the developing mouse or rat kidney.
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Paroly SS, Wang F, Spraggon L, Merregaert J, Batourina E, Tycko B, Schmidt-Ott KM, Grimmond S, Little M, Mendelsohn C. Stromal protein Ecm1 regulates ureteric bud patterning and branching. PLoS One 2013; 8:e84155. [PMID: 24391906 PMCID: PMC3877229 DOI: 10.1371/journal.pone.0084155] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Accepted: 11/12/2013] [Indexed: 01/28/2023] Open
Abstract
The interactions between the nephrogenic mesenchyme and the ureteric bud during kidney development are well documented. While recent studies have shed some light on the importance of the stroma during renal development, many of the signals generated in the stroma, the genetic pathways and interaction networks involving the stroma are yet to be identified. Our previous studies demonstrate that retinoids are crucial for branching of the ureteric bud and for patterning of the cortical stroma. In the present study we demonstrate that autocrine retinoic acid (RA) signaling in stromal cells is critical for their survival and patterning, and show that Extracellular matrix 1, Ecm1, a gene that in humans causes irritable bowel syndrome and lipoid proteinosis, is a novel RA-regulated target in the developing kidney, which is secreted from the cortical stromal cells surrounding the cap mesenchyme and ureteric bud. Our studies suggest that Ecm1 is required in the ureteric bud for regulating the distribution of Ret which is normally restricted to the tips, as inhibition of Ecm1 results in an expanded domain of Ret expression and reduced numbers of branches. We propose a model in which retinoid signaling in the stroma activates expression of Ecm1, which in turn down-regulates Ret expression in the ureteric bud cleft, where bifurcation normally occurs and normal branching progresses.
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Hokke SN, Armitage JA, Puelles VG, Short KM, Jones L, Smyth IM, Bertram JF, Cullen-McEwen LA. Altered ureteric branching morphogenesis and nephron endowment in offspring of diabetic and insulin-treated pregnancy. PLoS One 2013; 8:e58243. [PMID: 23516451 PMCID: PMC3596403 DOI: 10.1371/journal.pone.0058243] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Accepted: 01/31/2013] [Indexed: 12/11/2022] Open
Abstract
There is strong evidence from human and animal models that exposure to maternal hyperglycemia during in utero development can detrimentally affect fetal kidney development. Notwithstanding this knowledge, the precise effects of diabetic pregnancy on the key processes of kidney development are unclear due to a paucity of studies and limitations in previously used methodologies. The purpose of the present study was to elucidate the effects of hyperglycemia on ureteric branching morphogenesis and nephrogenesis using unbiased techniques. Diabetes was induced in pregnant C57Bl/6J mice using multiple doses of streptozotocin (STZ) on embryonic days (E) 6.5-8.5. Branching morphogenesis was quantified ex vivo using Optical Projection Tomography, and nephrons were counted using unbiased stereology. Maternal hyperglycemia was recognised from E12.5. At E14.5, offspring of diabetic mice demonstrated fetal growth restriction and a marked deficit in ureteric tip number (control 283.7±23.3 vs. STZ 153.2±24.6, mean±SEM, p<0.01) and ureteric tree length (control 33.1±2.6 mm vs. STZ 17.6±2.7 mm, p = 0.001) vs. controls. At E18.5, fetal growth restriction was still present in offspring of STZ dams and a deficit in nephron endowment was observed (control 1246.2±64.9 vs. STZ 822.4±74.0, p<0.001). Kidney malformations in the form of duplex ureter and hydroureter were a common observation (26%) in embryos of diabetic pregnancy compared with controls (0%). Maternal insulin treatment from E13.5 normalised maternal glycaemia but did not normalise fetal weight nor prevent the nephron deficit. The detrimental effect of hyperglycemia on ureteric branching morphogenesis and, in turn, nephron endowment in the growth-restricted fetus highlights the importance of glycemic control in early gestation and during the initial stages of renal development.
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Walker KA, Sims-Lucas S, Di Giovanni VE, Schaefer C, Sunseri WM, Novitskaya T, de Caestecker MP, Chen F, Bates CM. Deletion of fibroblast growth factor receptor 2 from the peri-wolffian duct stroma leads to ureteric induction abnormalities and vesicoureteral reflux. PLoS One 2013; 8:e56062. [PMID: 23409123 PMCID: PMC3567073 DOI: 10.1371/journal.pone.0056062] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2012] [Accepted: 01/03/2013] [Indexed: 11/18/2022] Open
Abstract
Purpose Pax3cre-mediated deletion of fibroblast growth factor receptor 2 (Fgfr2) broadly in renal and urinary tract mesenchyme led to ureteric bud (UB) induction defects and vesicoureteral reflux (VUR), although the mechanisms were unclear. Here, we investigated whether Fgfr2 acts specifically in peri-Wolffian duct stroma (ST) to regulate UB induction and development of VUR and the mechanisms of Fgfr2 activity. Methods We conditionally deleted Fgfr2 in ST (Fgfr2ST−/−) using Tbx18cre mice. To look for ureteric bud induction defects in young embryos, we assessed length and apoptosis of common nephric ducts (CNDs). We performed 3D reconstructions and histological analyses of urinary tracts of embryos and postnatal mice and cystograms in postnatal mice to test for VUR. We performed in situ hybridization and real-time PCR in young embryos to determine mechanisms underlying UB induction defects. Results We confirmed that Fgfr2 is expressed in ST and that Fgfr2 was efficiently deleted in this tissue in Fgfr2ST−/− mice at embryonic day (E) 10.5. E11.5 Fgfr2ST−/− mice had randomized UB induction sites with approximately 1/3 arising too high and 1/3 too low from the Wolffian duct; however, apoptosis was unaltered in E12.5 mutant CNDs. While ureters were histologically normal, E15.5 Fgfr2ST−/− mice exhibit improper ureteral insertion sites into the bladder, consistent with the ureteric induction defects. While ureter and bladder histology appeared normal, postnatal day (P) 1 mutants had high rates of VUR versus controls (75% versus 3%, p = 0.001) and occasionally other defects including renal hypoplasia and duplex systems. P1 mutant mice also had improper ureteral bladder insertion sites and shortened intravesicular tunnel lengths that correlated with VUR. E10.5 Fgfr2ST−/− mice had decreases in Bmp4 mRNA in stromal tissues, suggesting a mechanism underlying the ureteric induction and VUR phenotypes. Conclusion Mutations in FGFR2 could possibly cause VUR in humans.
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Wong YF, Wilson PD, Unwin RJ, Norman JT, Arno M, Hendry BM, Xu Q. Retinoic acid receptor-dependent, cell-autonomous, endogenous retinoic acid signaling and its target genes in mouse collecting duct cells. PLoS One 2012; 7:e45725. [PMID: 23049847 PMCID: PMC3458940 DOI: 10.1371/journal.pone.0045725] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2012] [Accepted: 08/20/2012] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Vitamin A is necessary for kidney development and has also been linked to regulation of solute and water homeostasis and to protection against kidney stone disease, infection, inflammation, and scarring. Most functions of vitamin A are mediated by its main active form, all-trans retinoic acid (tRA), which binds retinoic acid receptors (RARs) to modulate gene expression. We and others have recently reported that renal tRA/RAR activity is confined to the ureteric bud (UB) and collecting duct (CD) cell lineage, suggesting that endogenous tRA/RARs primarily act through regulating gene expression in these cells in embryonic and adult kidney, respectively. METHODOLOGY/PRINCIPAL FINDINGS To explore target genes of endogenous tRA/RARs, we employed the mIMCD-3 mouse inner medullary CD cell line, which is a model of CD principal cells and exhibits constitutive tRA/RAR activity as CD principal cells do in vivo. Combining antagonism of RARs, inhibition of tRA synthesis, exposure to exogenous tRA, and gene expression profiling techniques, we have identified 125 genes as candidate targets and validated 20 genes that were highly regulated (Dhrs3, Sprr1a, and Ppbp were the top three). Endogenous tRA/RARs were more important in maintaining, rather than suppressing, constitutive gene expression. Although many identified genes were expressed in UBs and/or CDs, their exact functions in this cell lineage are still poorly defined. Nevertheless, gene ontology analysis suggests that these genes are involved in kidney development, renal functioning, and regulation of tRA signaling. CONCLUSIONS/SIGNIFICANCE A rigorous approach to defining target genes for endogenous tRA/RARs has been established. At the pan-genomic level, genes regulated by endogenous tRA/RARs in a CD cell line have been catalogued for the first time. Such a catalogue will guide further studies on molecular mediators of endogenous tRA/RARs during kidney development and in relation to renal defects associated with vitamin A deficiency.
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Tsukahara Y, Tanaka M, Miyajima A. TROP2 expressed in the trunk of the ureteric duct regulates branching morphogenesis during kidney development. PLoS One 2011; 6:e28607. [PMID: 22194864 PMCID: PMC3237457 DOI: 10.1371/journal.pone.0028607] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Accepted: 11/11/2011] [Indexed: 11/18/2022] Open
Abstract
TROP2, a cell surface protein structurally related to EpCAM, is expressed in various carcinomas, though its function remains largely unknown. We examined the expression of TROP2 and EpCAM in fetal mouse tissues, and found distinct patterns in the ureteric bud of the fetal kidney, which forms a tree-like structure. The tip cells in the ureteric bud proliferate to form branches, whereas the trunk cells differentiate to form a polarized ductal structure. EpCAM was expressed throughout the ureteric bud, whereas TROP2 expression was strongest at the trunk but diminished towards the tips, indicating the distinct cell populations in the ureteric bud. The cells highly expressing TROP2 (TROP2(high)) were negative for Ki67, a proliferating cell marker, and TROP2 and collagen-I were co-localized to the basal membrane of the trunk cells. TROP2(high) cells isolated from the fetal kidney failed to attach and spread on collagen-coated plates. Using MDCK cells, a well-established model for studying the branching morphogenesis of the ureteric bud, TROP2 was shown to inhibit cell spreading and motility on collagen-coated plates, and also branching in collagen-gel cultures, which mimic the ureteric bud's microenvironment. These results together suggest that TROP2 modulates the interaction between the cells and matrix and regulates the formation of the ureteric duct by suppressing branching from the trunk during kidney development.
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Chi L, Saarela U, Railo A, Prunskaite-Hyyryläinen R, Skovorodkin I, Anthony S, Katsu K, Liu Y, Shan J, Salgueiro AM, Belo JA, Davies J, Yokouchi Y, Vainio SJ. A secreted BMP antagonist, Cer1, fine tunes the spatial organization of the ureteric bud tree during mouse kidney development. PLoS One 2011; 6:e27676. [PMID: 22114682 PMCID: PMC3219680 DOI: 10.1371/journal.pone.0027676] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2011] [Accepted: 10/21/2011] [Indexed: 01/02/2023] Open
Abstract
The epithelial ureteric bud is critical for mammalian kidney development as it generates the ureter and the collecting duct system that induces nephrogenesis in dicrete locations in the kidney mesenchyme during its emergence. We show that a secreted Bmp antagonist Cerberus homologue (Cer1) fine tunes the organization of the ureteric tree during organogenesis in the mouse embryo. Both enhanced ureteric expression of Cer1 and Cer1 knock out enlarge kidney size, and these changes are associated with an altered three-dimensional structure of the ureteric tree as revealed by optical projection tomography. Enhanced Cer1 expression changes the ureteric bud branching programme so that more trifid and lateral branches rather than bifid ones develop, as seen in time-lapse organ culture. These changes may be the reasons for the modified spatial arrangement of the ureteric tree in the kidneys of Cer1+ embryos. Cer1 gain of function is associated with moderately elevated expression of Gdnf and Wnt11, which is also induced in the case of Cer1 deficiency, where Bmp4 expression is reduced, indicating the dependence of Bmp expression on Cer1. Cer1 binds at least Bmp2/4 and antagonizes Bmp signalling in cell culture. In line with this, supplementation of Bmp4 restored the ureteric bud tip number, which was reduced by Cer1+ to bring it closer to the normal, consistent with models suggesting that Bmp signalling inhibits ureteric bud development. Genetic reduction of Wnt11 inhibited the Cer1-stimulated kidney development, but Cer1 did not influence Wnt11 signalling in cell culture, although it did inhibit the Wnt3a-induced canonical Top Flash reporter to some extent. We conclude that Cer1 fine tunes the spatial organization of the ureteric tree by coordinating the activities of the growth-promoting ureteric bud signals Gndf and Wnt11 via Bmp-mediated antagonism and to some degree via the canonical Wnt signalling involved in branching.
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Reidy K, Tufro A. Semaphorins in kidney development and disease: modulators of ureteric bud branching, vascular morphogenesis, and podocyte-endothelial crosstalk. Pediatr Nephrol 2011; 26:1407-12. [PMID: 21336944 PMCID: PMC3397149 DOI: 10.1007/s00467-011-1769-1] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2010] [Revised: 12/12/2010] [Accepted: 01/06/2011] [Indexed: 12/14/2022]
Abstract
Semaphorins are guidance proteins that play important roles in organogenesis and disease. Expression of class 3 semaphorins and their receptors is regulated during kidney development. Gain- and loss-of-function experiments demonstrated that tight semaphorin3a gene dosage is required for podocyte differentiation, and for the establishment of a normal glomerular filtration barrier. Sema3a modulates kidney vascular patterning acting as a negative regulator of endothelial cell migration and survival. Excess podocyte semaphorin3a expression causes glomerular disease in mice. In addition, Sema3a is a negative regulator of ureteric bud branching, whereas Sema3c is a positive regulator of ureteric bud and endothelial cell branching morphogenesis. In summary, secreted semaphorins modulate ureteric bud branching, vascular patterning, and podocyte-endothelial crosstalk, suggesting that they play a role in renal disease. Understanding the signaling pathways downstream from semaphorin receptors will provide insight into the mechanism of action of semaphorins in renal pathology.
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Yosypiv IV. Renin-angiotensin system in ureteric bud branching morphogenesis: insights into the mechanisms. Pediatr Nephrol 2011; 26:1499-512. [PMID: 21359618 DOI: 10.1007/s00467-011-1820-2] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/09/2010] [Revised: 01/24/2011] [Accepted: 02/01/2011] [Indexed: 12/31/2022]
Abstract
Branching morphogenesis of the ureteric bud (UB) is a key developmental process that controls organogenesis of the entire metanephros. Notably, aberrant UB branching may result in a spectrum of congenital anomalies of the kidney and urinary tract (CAKUT). Genetic, biochemical and physiological studies have demonstrated that the renin-angiotensin system (RAS), a key regulator of the blood pressure and fluid/electrolyte homeostasis, also plays a critical role in kidney development. All the components of the RAS are expressed in the metanephros. Moreover, mutations in the genes encoding components of the RAS in mice or humans cause diverse types of CAKUT which include renal papillary hypoplasia, hydronephrosis, duplicated collecting system, renal tubular dysgenesis, renal vascular abnormalities, abnormal glomerulogenesis and urinary concentrating defect. Despite widely accepted role of the RAS in metanephric kidney and renal collecting system (ureter, pelvis, calyces and collecting ducts) development, the mechanisms by which an intact RAS exerts its morphogenetic actions are incompletely defined. Emerging evidence indicates that defects in UB branching morphogenesis may be causally linked to the pathogenesis of renal collecting system anomalies observed under conditions of aberrant RAS signaling. This review describes the role of the RAS in UB branching morphogenesis and highlights emerging insights into the cellular and molecular mechanisms whereby RAS regulates this critical morphogenetic process.
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Boualia SK, Gaitan Y, Murawski I, Nadon R, Gupta IR, Bouchard M. Vesicoureteral reflux and other urinary tract malformations in mice compound heterozygous for Pax2 and Emx2. PLoS One 2011; 6:e21529. [PMID: 21731775 PMCID: PMC3123351 DOI: 10.1371/journal.pone.0021529] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2011] [Accepted: 05/31/2011] [Indexed: 12/19/2022] Open
Abstract
Congenital anomalies of the kidney and urinary tract (CAKUT) are the most common cause of chronic kidney disease in children. This disease group includes a spectrum of urinary tract defects including vesicoureteral reflux, duplex kidneys and other developmental defects that can be found alone or in combination. To identify new regulators of CAKUT, we tested the genetic cooperativity between several key regulators of urogenital system development in mice. We found a high incidence of urinary tract anomalies in Pax2;Emx2 compound heterozygous mice that are not found in single heterozygous mice. Pax2+/−;Emx2+/− mice harbor duplex systems associated with urinary tract obstruction, bifid ureter and a high penetrance of vesicoureteral reflux. Remarkably, most compound heterozygous mice refluxed at low intravesical pressure. Early analysis of Pax2+/−;Emx2+/− embryos point to ureter budding defects as the primary cause of urinary tract anomalies. We additionally establish Pax2 as a direct regulator of Emx2 expression in the Wolffian duct. Together, these results identify a haploinsufficient genetic combination resulting in CAKUT-like phenotype, including a high sensitivity to vesicoureteral reflux. As both genes are located on human chromosome 10q, which is lost in a proportion of VUR patients, these findings may help understand VUR and CAKUT in humans.
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