Impairment of Wnt11 function leads to kidney tubular abnormalities and secondary glomerular cystogenesis

Collagen XVIII regulates extracellular matrix integrity in the developing nephrons and impacts nephron progenitor cell behavior

Renal development is a complex process in which two major processes, tubular branching and nephron development, regulate each other reciprocally. Our previous findings have indicated that collagen XVIII (ColXVIII), an extracellular matrix protein, affects the renal branching morphogenesis. We investigate here the role of ColXVIII in nephron formation and the behavior of nephron progenitor cells (NPCs) using isoform-specific ColXVIII knockout mice. The results show that the short ColXVIII isoform predominates in the early epithelialized nephron structures whereas the two longer isoforms are expressed only in the later phases of glomerular formation. Meanwhile, electron microscopy showed that the ColXVIII mutant embryonic kidneys have ultrastructural defects at least from embryonic day 16.5 onwards. Similar structural defects had previously been observed in adult ColXVIII-deficient mice, indicating a congenital origin. The lack of ColXVIII led to a reduced NPC population in which changes in NPC proliferation and maintenance and in macrophage influx were perceived to play a role. The changes in NPC behavior in turn led to notably reduced overall nephron formation. In conclusion, the results show that ColXVIII has multiple roles in renal development, both in ureteric branching and in NPC behavior.

Spaceflight causes strain dependent gene expression changes associated with lipid and extracellular matrix dysregulation in the mouse kidney in vivo

To explore new worlds we must ensure humans can survive and thrive in the space environment. Incidence of kidney stones in astronauts is a major risk factor associated with long term missions, caused by increased blood calcium levels due to bone demineralisation triggered by microgravity and space radiation. Transcriptomic changes have been observed in other tissues during spaceflight, including the kidney. We analysed kidney transcriptome patterns in two different strains of mice flown on the International Space Station, C57BL/6J and BALB/c. Here we show a link between spaceflight and transcriptome patterns associated with dysregulation of lipid and extracellular matrix metabolism and altered transforming growth factor-beta signalling. A stronger response was seen in C57BL/6J mice than BALB/c. Genetic differences in hyaluronan metabolism between strains may confer protection against extracellular matrix remodelling through downregulation of epithelial-mesenchymal transition. We intend for our findings to contribute to development of new countermeasures against kidney disease in astronauts and people here on Earth.

Calcium signaling induces partial EMT and renal fibrosis in a Wnt4mCherry knock-in mouse model

The renal tubular epithelial cells (TEC) have a strong capacity for repair after acute injury, but when this mechanism becomes uncontrollable, it leads to chronic kidney diseases (CKD). Indeed, in progress toward CKDs, the TECs may dedifferentiate, undergo epithelial-to-mesenchyme transition (EMT), and promote inflammation and fibrosis. Given the critical role of Wnt4 signaling in kidney ontogenesis, we addressed whether changes in this signaling are connected to renal inflammation and fibrosis by taking advantage of a knock-in Wnt4mCh/mCh mouse. While the Wnt4mCh/mCh embryos appeared normal, the corresponding mice, within one month, developed CKD-related phenotypes, such as pro-inflammatory responses including T-cell/macrophage influx, expression of fibrotic markers, and epithelial cell damage with a partial EMT. The Wnt signal transduction component β-catenin remained unchanged, while calcium signaling is induced in the injured TECs involving Nfat and Tfeb transcription factors. We propose that the Wnt4 signaling pathway is involved in repairing the renal injury, and when the signal is overdriven, CKD is established.

Temporally and spatially regulated collagen XVIII isoforms are involved in ureteric tree development via the TSP1-like domain

Collagen XVIII (ColXVIII) is a component of the extracellular matrix implicated in embryogenesis and control of tissue homoeostasis. We now provide evidence that ColXVIII has a specific role in renal branching morphogenesis as observed in analyses of total and isoform-specific knockout embryos and mice. The expression of the short and the two longer isoforms differ temporally and spatially during renal development. The lack of ColXVIII or its specific isoforms lead to congenital defects in the 3D patterning of the ureteric tree where the short isoform plays a prominent role. Moreover, the ex vivo data suggests that ColXVIII is involved in the kidney epithelial tree patterning via its N-terminal domains, and especially the Thrombospondin-1-like domain common to all isoforms. This morphogenetic function likely involves integrins expressed in the ureteric epithelium. Altogether, the results point to an important role for ColXVIII in the matrix-integrin-mediated functions regulating renal development.

Modeling development of genitourinary birth defects to understand disruption due to changes in gene dosage

Genitourinary development is a delicately orchestrated process that begins in the embryo. Once complete, the genitourinary system is a collection of functionally disparate organs spread throughout the abdominal and pelvic regions. These distinct organs are interconnected through an elaborate duct system which aggregates the organs' products to a common exit point. The complicated nature of the genitourinary system makes it highly susceptible to developmental disruptions that produce anomalies. In fact, genitourinary anomalies are among the most common class of human birth defects. Aside from congenital anomalies of the kidney and urinary tract (CAKUT), for males, these birth defects can also occur in the penis (hypospadias) and testis (cryptorchism), which impact male fertility and male mental health. As genetic technology has advanced, it has become clear that a subset of cases of genitourinary birth defects are due to gene variation causing dosage changes in critical regulatory genes. Here we first review the parallels between human and mouse genitourinary development. We then demonstrate how translational research leverages mouse models of human gene variation cases to advance mechanistic understanding of causation in genitourinary birth defects. We close with a view to the future highlighting upcoming technologies that will provide a deeper understanding of gene variation affecting regulation of genitourinary development, which should ultimately advance treatment options for patients.

Wnt11 in regulation of physiological and pathological cardiac growth

Wnt11 regulates early cardiac development and left ventricular compaction in the heart, but it is not known how Wnt11 regulates postnatal cardiac maturation and response to cardiac stress in the adult heart. We studied cell proliferation/maturation in postnatal and adolescent Wnt11 deficient (Wnt11-/-) heart and subjected adult mice with partial (Wnt11+/-) and complete Wnt11 (Wnt11-/-) deficiency to cardiac pressure overload. In addition, we subjected primary cardiomyocytes to recombinant Wnt proteins to study their effect on cardiomyocyte growth. Wnt11 deficiency did not affect cardiomyocyte proliferation or maturation in the postnatal or adolescent heart. However, Wnt11 deficiency led to enlarged heart phenotype that was not accompanied by significant hypertrophy of individual cardiomyocytes. Analysis of stressed adult hearts from wild-type mice showed a progressive decrease in Wnt11 expression in response to pressure overload. When studied in experimental cardiac pressure overload, Wnt11 deficiency did not exacerbate cardiac hypertrophy or remodeling and cardiac function remained identical between the genotypes. When subjecting cardiomyocytes to hypertrophic stimulus, the presence of recombinant Wnt11 together with Wnt5a reduced protein synthesis. In conclusion, Wnt11 deficiency does not affect postnatal cardiomyocyte proliferation but leads to cardiac growth. Interestingly, Wnt11 deficiency alone does not substantially modulate hypertrophic response to pressure overload in vivo. Wnt11 may require cooperation with other noncanonical Wnt proteins to regulate hypertrophic response under stress.

The Wnt/PCP formin Daam1 drives cell-cell adhesion during nephron development

E-cadherin junctions facilitate assembly and disassembly of cell contacts that drive development and homeostasis of epithelial tissues. In this study, using Xenopus embryonic kidney and Madin-Darby canine kidney (MDCK) cells, we investigate the role of the Wnt/planar cell polarity (PCP) formin Daam1 (Dishevelled-associated activator of morphogenesis 1) in regulating E-cadherin-based intercellular adhesion. Using live imaging, we show that Daam1 localizes to newly formed cell contacts in the developing nephron. Furthermore, analyses of junctional filamentous actin (F-actin) upon Daam1 depletion indicate decreased microfilament localization and slowed turnover. We also show that Daam1 is necessary for efficient and timely localization of junctional E-cadherin, mediated by Daam1’s formin homology domain 2 (FH2). Finally, we establish that Daam1 signaling promotes organized movement of renal cells. This study demonstrates that Daam1 formin junctional activity is critical for epithelial tissue organization.

How cells remodel their adhesions through cell-surface proteins such as E-cadherin is a central question in epithelial tissue biology. Krneta-Stankic et al. show that the Wnt/PCP formin Daam1 regulates cytoskeletal membrane dynamics and E-cadherin localization within developing nephrons. These findings provide a new framework for studying cell-cell adhesion and nephron morphogenesis.

Postnatal prolongation of mammalian nephrogenesis by excess fetal GDNF

Nephron endowment, defined during the fetal period, dictates renal and related cardiovascular health throughout life. We show here that, despite its negative effects on kidney growth, genetic increase of GDNF prolongs the nephrogenic program beyond its normal cessation. Multi-stage mechanistic analysis revealed that excess GDNF maintains nephron progenitors and nephrogenesis through increased expression of its secreted targets and augmented WNT signaling, leading to a two-part effect on nephron progenitor maintenance. Abnormally high GDNF in embryonic kidneys upregulates its known targets but also Wnt9b and Axin2, with concomitant deceleration of nephron progenitor proliferation. Decline of GDNF levels in postnatal kidneys normalizes the ureteric bud and creates a permissive environment for continuation of the nephrogenic program, as demonstrated by morphologically and molecularly normal postnatal nephron progenitor self-renewal and differentiation. These results establish that excess GDNF has a bi-phasic effect on nephron progenitors in mice, which can faithfully respond to GDNF dosage manipulation during the fetal and postnatal period. Our results suggest that sensing the signaling activity level is an important mechanism through which GDNF and other molecules contribute to nephron progenitor lifespan specification.

Summary: Dosage of neurotropic factor GDNF regulates nephron progenitors and in utero growth factor augmentation can extend postnatal lifespan and differentiation of nephron progenitors.

Copy Number Variations Analysis Identifies QPRT as a Candidate Gene Associated With Susceptibility for Solitary Functioning Kidney

Background

The lack of understanding of molecular pathologies of the solitary functioning kidney makes improving and strengthening the continuity of care between pediatric and adult nephrological patients difficult. Copy number variations (CNVs) account for a molecular cause of solitary functioning kidney, but characterization of the pathogenic genes remains challenging.

Methods

In our prospective cohort study, 99 fetuses clinically diagnosed with a solitary functioning kidney were enrolled and evaluated using chromosomal microarray analysis (CMA). The genetic drivers for the pathogenic CNVs were analyzed. We characterized QPRT localization in fetal kidneys using immunohistochemistry and its expression in adult kidneys using quantitative RT-PCR. Further, QPRT was knocked down using siRNA in human embryonic kidney (HEK293T) cells, and the cell cycle and proliferation were tested.

Results

Besides one Triple X syndrome and one Down syndrome, we identified a total of 45 CNVs out of 34 subjects. Among the 14 pathogenic CNVs, CNV 16p11.2 reached the highest number of records with the phenotype of kidney anomalies in the Decipher database. Among the 26 genes within the 16p11.2 region, as a key enzyme for nicotinamide adenine dinucleotide (NAD+) biosynthesis, QPRT was distinctly localized in renal tubules but was barely observed in renal interstitial and glomeruli in fetal kidneys. The loss of QPRT prevented cells’ efficient transition into S phase, affected cell-cycle progression, and abrogated proliferation of human embryonic kidney cells.

Conclusion

Our data suggest that QPRT is a candidate gene associated with susceptibility for solitary functioning kidney. The CNVs discovered in our study exhibit great potential for future applications in genetic counseling and pregnancy management.

The Role of Wnt Signalling in Chronic Kidney Disease (CKD)

Chronic kidney disease (CKD) encompasses a group of diverse diseases that are associated with accumulating kidney damage and a decline in glomerular filtration rate (GFR). These conditions can be of an acquired or genetic nature and, in many cases, interactions between genetics and the environment also play a role in disease manifestation and severity. In this review, we focus on genetically inherited chronic kidney diseases and dissect the links between canonical and non-canonical Wnt signalling, and this umbrella of conditions that result in kidney damage. Most of the current evidence on the role of Wnt signalling in CKD is gathered from studies in polycystic kidney disease (PKD) and nephronophthisis (NPHP) and reveals the involvement of β-catenin. Nevertheless, recent findings have also linked planar cell polarity (PCP) signalling to CKD, with further studies being required to fully understand the links and molecular mechanisms.

Evolutionary Origin and Nomenclature of Vertebrate Wnt11-Family Genes

To adequately connect zebrafish medical models to human biology, it is essential that gene nomenclature reflects gene orthology. Analysis of gene phylogenies and conserved syntenies shows that the zebrafish gene currently called wnt11 (ENSDARG00000004256, ZFIN ID: ZDB-GENE-990603-12) is not the ortholog of the human gene called WNT11 (ENSG00000085741); instead, the gene currently called wnt11r (ENSDARG00000014796, ZFIN ID: ZDB-GENE-980526-249) is the zebrafish ortholog of human WNT11. Genomic analysis of Wnt11-family genes suggests a model for the birth of Wnt11-family gene ohnologs in genome duplication events, provides a mechanism for the death of a Wnt11-family ohnolog in mammals after they diverged from birds, and suggests revised nomenclature to better connect teleost disease models to human biology.

Wnt11 directs nephron progenitor polarity and motile behavior ultimately determining nephron endowment

A normal endowment of nephrons in the mammalian kidney requires a balance of nephron progenitor self-renewal and differentiation throughout development. Here, we provide evidence for a novel action of ureteric branch tip-derived Wnt11 in progenitor cell organization and interactions within the nephrogenic niche, ultimately determining nephron endowment. In Wnt11 mutants, nephron progenitors dispersed from their restricted niche, intermixing with interstitial progenitors. Nephron progenitor differentiation was accelerated, kidneys were significantly smaller, and the nephron progenitor pool was prematurely exhausted, halving the final nephron count. Interestingly, RNA-seq revealed no significant differences in gene expression. Live imaging of nephron progenitors showed that in the absence of Wnt11 they lose stable attachments to the ureteric branch tips, continuously detaching and reattaching. Further, the polarized distribution of several markers within nephron progenitors is disrupted. Together these data highlight the importance of Wnt11 signaling in directing nephron progenitor behavior which determines a normal nephrogenic program.

Prolonged prenatal hypoxia selectively disrupts collecting duct patterning and postnatal function in male mouse offspring

KEY POINTS

In the present study, we investigated whether hypoxia during late pregnancy impairs kidney development in mouse offspring, and also whether this has long-lasting consequences affecting kidney function in adulthood. Hypoxia disrupted growth of the kidney, particularly the collecting duct network, in juvenile male offspring. By mid-late adulthood, these mice developed early signs of kidney disease, notably a compromised response to water deprivation. Female offspring showed no obvious signs of impaired kidney development and did not develop kidney disease, suggesting an underlying protection mechanism from the hypoxia insult. These results help us better understand the long-lasting impact of gestational hypoxia on kidney development and the increased risk of chronic kidney disease.

ABSTRACT

Prenatal hypoxia is a common perturbation to arise during pregnancy, and can lead to adverse health outcomes in later life. The long-lasting impact of prenatal hypoxia on postnatal kidney development and maturation of the renal tubules, particularly the collecting duct system, is relatively unknown. In the present study, we used a model of moderate chronic maternal hypoxia throughout late gestation (12% O₂ exposure from embryonic day 14.5 until birth). Histological analyses revealed marked changes in the tubular architecture of male hypoxia-exposed neonates as early as postnatal day 7, with disrupted medullary development and altered expression of Ctnnb1 and Crabp2 (encoding a retinoic acid binding protein). Kidneys of the RARElacZ line offspring exposed to hypoxia showed reduced β-galactosidase activity, indicating reduced retinoic acid-directed transcriptional activation. Wild-type male mice exposed to hypoxia had an early decline in urine concentrating capacity, evident at 4 months of age. At 12 months of age, hypoxia-exposed male mice displayed a compromised response to a water deprivation challenge, which was was correlated with an altered cellular composition of the collecting duct and diminished expression of aquaporin 2. There were no differences in the tubular structures or urine concentrating capacity between the control and hypoxia-exposed female offspring at any age. The findings of the present study suggest that prenatal hypoxia selectively disrupts collecting duct patterning through altered Wnt/β-catenin and retinoic acid signalling and this results in impaired function in male mouse offspring in later life.

The multisystemic functions of FOXD1 in development and disease

Transcription factors (TFs) participate in a wide range of cellular processes due to their inherent function as essential regulatory proteins. Their dysfunction has been linked to numerous human diseases. The forkhead box (FOX) family of TFs belongs to the "winged helix" superfamily, consisting of proteins sharing a related winged helix-turn-helix DNA-binding motif. FOX genes have been extensively present during vertebrates and invertebrates' evolution, participating in numerous molecular cascades and biological functions, such as embryonic development and organogenesis, cell cycle regulation, metabolism control, stem cell niche maintenance, signal transduction, and many others. FOXD1, a forkhead TF, has been related to different key biological processes such as kidney and retina development and embryo implantation. FOXD1 dysfunction has been linked to different pathologies, thereby constituting a diagnostic biomarker and a promising target for future therapies. This paper aims to present, for the first time, a comprehensive review of FOXD1's role in mouse development and human disease. Molecular, structural, and functional aspects of FOXD1 are presented in light of physiological and pathogenic conditions, including its role in human disease aetiology, such as cancer and recurrent pregnancy loss. Taken together, the information given here should enable a better understanding of FOXD1 function for basic science researchers and clinicians.

16p11.2 transcription factor MAZ is a dosage-sensitive regulator of genitourinary development

Genitourinary (GU) birth defects are among the most common yet least studied congenital malformations. Congenital anomalies of the kidney and urinary tract (CAKUTs) have high morbidity and mortality rates and account for ∼30% of structural birth defects. Copy number variation (CNV) mapping revealed that 16p11.2 is a hotspot for GU development. The only gene covered collectively by all of the mapped GU-patient CNVs was MYC-associated zinc finger transcription factor (MAZ), and MAZ CNV frequency is enriched in nonsyndromic GU-abnormal patients. Knockdown of MAZ in HEK293 cells results in differential expression of several WNT morphogens required for normal GU development, including Wnt11 and Wnt4. MAZ knockdown also prevents efficient transition into S phase, affects transcription of cell-cycle regulators, and abrogates growth of human embryonic kidney cells. Murine Maz is ubiquitously expressed, and a CRISPR-Cas9 mouse model of Maz deletion results in perinatal lethality with survival rates dependent on Maz copy number. Homozygous loss of Maz results in high penetrance of CAKUTs, and Maz is haploinsufficient for normal bladder development. MAZ, once thought to be a simple housekeeping gene, encodes a dosage-sensitive transcription factor that regulates urogenital development and contributes to both nonsyndromic congenital malformations of the GU tract as well as the 16p11.2 phenotype.

Wnt Signaling in Kidney Development and Disease

Wnt signal cascade is an evolutionarily conserved, developmental pathway that regulates embryogenesis, injury repair, and pathogenesis of human diseases. It is well established that Wnt ligands transmit their signal via canonical, β-catenin-dependent and noncanonical, β-catenin-independent mechanisms. Mounting evidence has revealed that Wnt signaling plays a key role in controlling early nephrogenesis and is implicated in the development of various kidney disorders. Dysregulations of Wnt expression cause a variety of developmental abnormalities and human diseases, such as congenital anomalies of the kidney and urinary tract, cystic kidney, and renal carcinoma. Multiple Wnt ligands, their receptors, and transcriptional targets are upregulated during nephron formation, which is crucial for mediating the reciprocal interaction between primordial tissues of ureteric bud and metanephric mesenchyme. Renal cysts are also associated with disrupted Wnt signaling. In addition, Wnt components are important players in renal tumorigenesis. Activation of Wnt/β-catenin is instrumental for tubular repair and regeneration after acute kidney injury. However, sustained activation of this signal cascade is linked to chronic kidney diseases and renal fibrosis in patients and experimental animal models. Mechanistically, Wnt signaling controls a diverse array of biologic processes, such as cell cycle progression, cell polarity and migration, cilia biology, and activation of renin-angiotensin system. In this chapter, we have reviewed recent findings that implicate Wnt signaling in kidney development and diseases. Targeting this signaling may hold promise for future treatment of kidney disorders in patients.

Disruption of Core Planar Cell Polarity Signaling Regulates Renal Tubule Morphogenesis but Is Not Cystogenic

Oriented cell division (OCD) and convergent extension (CE) shape developing renal tubules, and their disruption has been associated with polycystic kidney disease (PKD) genes, the majority of which encode proteins that localize to primary cilia. Core planar cell polarity (PCP) signaling controls OCD and CE in other contexts, leading to the hypothesis that disruption of PCP signaling interferes with CE and/or OCD to produce PKD. Nonetheless, the contribution of PCP to tubulogenesis and cystogenesis is uncertain, and two major questions remain unanswered. Specifically, the inference that mutation of PKD genes interferes with PCP signaling is untested, and the importance of PCP signaling for cystogenic PKD phenotypes has not been examined. We show that, during proliferative stages, PCP signaling polarizes renal tubules to control OCD. However, we find that, contrary to the prevailing model, PKD mutations do not disrupt PCP signaling but instead act independently and in parallel with PCP signaling to affect OCD. Indeed, PCP signaling that is normally downregulated once development is completed is retained in cystic adult kidneys. Disrupting PCP signaling results in inaccurate control of tubule diameter, a tightly regulated parameter with important physiological ramifications. However, we show that disruption of PCP signaling is not cystogenic. Our results suggest that regulating tubule diameter is a key function of PCP signaling but that loss of this control does not induce cysts.