Muscle-Invasive Bladder Cancer With Hydronephrosis Exhibits a High Frequency of Mutations in Fibroblast Growth Factor Receptor 3 Gene.

BACKGROUND/AIM: Recent studies have reported conflicting findings regarding the significance of hydronephrosis (HN) in muscle-invasive bladder cancer (MIBC). The molecular characteristics of MIBC with HN are unclear, therefore, we aimed to address the gaps in previous research and elucidate HN's molecular significance in patients with MIBC. MATERIALS AND METHODS: Clinical, genetic, and imaging information on bladder cancer patients enrolled in The Cancer Genome Atlas were obtained from public databases to analyze the association between the presence of hydronephrosis and genetic alterations and molecular subtyping. A total of 108 patients who underwent total cystectomy for MIBC at the Hiroshima University Hospital were enrolled in the study to verify the association between HN and renal function with patient prognosis. RESULTS: We observed a statistically significant difference in the distribution of molecular subtypes (p=0.0146). The proportion of patients with the luminal papillary subtype was approximately twice as high in patients with HN (48.8%) than in those without HN (25.0%). The mutation frequency of fibroblast growth factor receptor (FGFR) 3 was approximately three-fold higher in patients with HN (20.9%) than in those without HN (7.1%). Multivariate analysis, which considered HN and estimated glomerular filtration rate as confounding factors in our MIBC cohort, revealed that reduced renal function, but not HN, was an independent predictor for overall survival. CONCLUSION: MIBC presenting HN exhibits a high frequency of mutations in the FGFR3 gene. In addition, not HN itself, but reduced renal function due to HN may worsen the prognosis for MIBC.

Prenatal Detection of a FOXF1 Deletion in a Fetus with ACDMPV and Hydronephrosis.

Alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV) is a lethal lung developmental disorder caused by the arrest of fetal lung formation, resulting in neonatal death due to acute respiratory failure and pulmonary arterial hypertension. Heterozygous single-nucleotide variants or copy-number variant (CNV) deletions involving the FOXF1 gene and/or its lung-specific enhancer are found in the vast majority of ACDMPV patients. ACDMPV is often accompanied by extrapulmonary malformations, including the gastrointestinal, cardiac, or genitourinary systems. Thus far, most of the described ACDMPV patients have been diagnosed post mortem, based on histologic evaluation of the lung tissue and/or genetic testing. Here, we report a case of a prenatally detected de novo CNV deletion (~0.74 Mb) involving the FOXF1 gene in a fetus with ACDMPV and hydronephrosis. Since ACDMPV is challenging to detect by ultrasound examination, the more widespread implementation of prenatal genetic testing can facilitate early diagnosis, improve appropriate genetic counselling, and further management.

Consistent alteration of chain length-specific ceramides in human and mouse fibrotic kidneys.

BACKGROUND: Several studies revealed alterations of single sphingolipid species, such as chain length-specific ceramides, in plasma and serum of patients with kidney diseases. Here, we investigated whether such alterations occur in kidney tissue from patients and mice suffering from renal fibrosis, the common endpoint of chronic kidney diseases. METHODS: Human fibrotic kidney samples were collected from nephrectomy specimens with hydronephrosis and/or pyelonephritis. Healthy parts from tumor nephrectomies served as nonfibrotic controls. Mouse fibrotic kidney samples were collected from male C57BL/6J mice treated with an adenine-rich diet for 14 days or were subjected to 7 days of unilateral ureteral obstruction (UUO). Kidneys of untreated mice and contralateral kidneys (UUO) served as respective controls. Sphingolipid levels were detected by LC-MS/MS. Fibrotic markers were analyzed by TaqMan® analysis and immunohistology. RESULTS: Very long-chain ceramides Cer d18:1/24:0 and Cer d18:1/24:1 were significantly downregulated in both fibrotic human kidney cortex and fibrotic murine kidney compared to respective control samples. These effects correlate with upregulation of COL1α1, COL3α1 and αSMA expression in fibrotic human kidney cortex and fibrotic mouse kidney. CONCLUSION: We have shown that very long-chain ceramides Cer d18:1/24:0 and Cer d18:1/24:1 are consistently downregulated in fibrotic kidney samples from human and mouse. Our findings support the use of in vivo murine models as appropriate translational means to understand the involvement of ceramides in human kidney diseases. In addition, our study raises interesting questions about the possible manipulation of ceramide metabolism to prevent progression of fibrosis and the use of ceramides as potential biomarkers of chronic kidney disease.

Prenatal diagnosis and management of monozygotic twins discordant for severe fetal abnormalities.

OBJECTIVE: We present prenatal diagnosis and management of monozygotic (MZ) twins discordant for severe fetal abnormalities. CASE REPORT: A 36-year-old woman underwent amniocentesis at 18 weeks of gestation because of advanced maternal age, and hydrops fetalis, a giant cystic hygroma of 5 × 3.5 cm and left hydronephrosis in a co-twin. The other co-twin was structurally normal. Amniocentesis revealed a karyotype of 46,XY in both co-twins. Simultaneous polymorphic DNA marker analysis using the DNAs extracted from maternal blood and uncultured amniocytes confirmed MZ twinning. The woman underwent a successful selective fetal reduction by radiofrequency ablation at 22 weeks of gestation. At 28 weeks of gestation, premature rupture of membranes occurred, and a 1280-g normal male baby and a 275-g dead malformed co-twin were delivered. The normal co-twin was phenotypically normal and was doing well at age seven weeks. CONCLUSIONS: Prenatal diagnosis of MZ twins discordant for structural abnormalities should include a differential diagnosis of MZ twinning, and a zygosity test is necessary under such a circumstance.

Pathogenic copy number variants are detected in a subset of patients with gastrointestinal malformations.

BACKGROUND: Gastrointestinal atresias and urological defects are main causes of pediatric surgery in infants. As copy number variants (CNVs) have been shown to be involved in the development of congenital malformations, the aim of our study was to investigate the presence of CNVs in patients with gastrointestinal and urological malformations as well as the possibility of tissue-specific mosaicism for CNVs in the cohort. METHODS: We have collected tissue and/or blood samples from 25 patients with anorectal malformations, esophageal atresia, or hydronephrosis, and screened for pathogenic CNVs using array comparative genomic hybridization (array-CGH). RESULTS: We detected pathogenic aberrations in 2/25 patients (8%) and report a novel possible susceptibility region for esophageal atresia on 15q26.3. CNV analysis in different tissues from the same patients did not reveal evidence of tissue-specific mosaicism. CONCLUSION: Our study shows that it is important to perform clinical genetic investigations, including CNV analysis, in patients with congenital gastrointestinal malformations since this leads to improved information to families as well as an increased understanding of the pathogenesis.

Cathepsin S regulates renal fibrosis in mouse models of mild and severe hydronephrosis.

As a member of the cysteine protease family, cathepsin S (CTSS) serves an important role in diseases such as cancer, arthritis and atherosclerosis. Nevertheless, its role in renal fibrosis is unknown. In the present study, the effects of CTSS on renal fibrosis in mild (group M) and severe (group S) hydronephrosis were studied by reverse transcription­-quantitative PCR (RT­qPCR), western blot analysis (WB), Masson's trichrome staining and immunohistochemical staining in mouse models. The effects of CTSS on extracellular matrix (ECM) deposition and epithelial­mesenchymal transition (EMT) and the potential mechanisms were further studied by RT­qPCR and WB in transforming growth factor (TGF­ß1)­stimulated TCMK­1 cells. Compared with group N (no hydronephrosis), the expression levels of CTSS in the M and S groups were significantly higher, and a significant increase in ECM deposition was observed in the S group. In addition, compared with group N, the expression levels of TGF­ß1, α­smooth muscle actin (α­SMA), SMAD2, SMAD3, phosphorylated (p)SMAD2 and pSMAD3 in groups M and S were significantly higher, whereas the expression of E­cadherin was significantly lower. Inhibition of CTSS expression increased the expression levels of TGF­ß1, α­SMA, fibronectin, collagen­I, SMAD2, SMAD3, pSMAD2 and pSMAD3, whereas E­cadherin expression decreased. A significant increase in CTSS was observed in the TGF­ß1­stimulated TCMK­1 cell line. ECM deposition and EMT were also intensified. The opposite outcomes occurred after intervention with small interfering RNA targeting CTSS. In conclusion, CTSS affected EMT and the deposition of ECM. CTSS may mediate the regulation of fibrosis by the TGF­ß/SMAD signaling pathway. CTSS may serve an important role in the treatment of renal fibrosis.

Silencing of SOCS-1 and SOCS-3 suppresses renal interstitial fibrosis by alleviating renal tubular damage in a rat model of hydronephrosis.

Our study was performed to elucidate how SOCS-1/3 silencing suppresses renal interstitial fibrosis (RIF) by alleviating renal tubular damage in rat models affected by hydronephrosis. Male Wistar rats were randomly selected to establish hydronephrosis rat model, after which all rats were classified into normal, model, negative control (NC), siRNA-SOCS-1, siRNA-SOCS-3, and siRNA-SOCS-1 + siRNA-SOCS-3 groups. The levels of urine protein, serum creatinine (Scr), and blood urea nitrogen (BUN) were detected. ELISA was performed to determine levels of cystatin (CysC), ß2-microglobulin (ß2-MG), interleukin (IL)-6, and tumor necrosis factor (TNF)-α. RT-qPCR and Western blotting were used for mRNA and protein expressions of SOCS-1, SOCS-3, α-smooth muscle actin (α-SMA), and transforming Growth Factor (TGF)-ß1. Compared with the normal group, the levels of Scr, BUN, urine protein, NAG, CysC, ß2-MG, IL-6, and TNF-α were increased in other groups, as well as elevated mRNA and protein expressions of SOCS-1, SOCS-3, α-SMA, and TGF-ß1. The siRNA-SOCS-1, siRNA-SOCS-3, and siRNA-SOCS-1 + siRNA-SOCS-3 groups were found with decreased levels of Scr, BUN, urine protein, NAG, CysC, ß2-MG, IL-6, and TNF-α, as well as mRNA and protein expressions of SOCS-1, SOCS-3, α-SMA, and TGF-ß1, including positive rates of SOCS-1 and SOCS-3 proteins in comparison with the model and NC groups. In comparison with the siRNA-SOCS-1 and siRNA-SOCS-3 groups, the siRNA-SOCS-1 + siRNA-SOCS-3 group exhibited decreased levels of Scr, BUN, urine protein, NAG, CysC, ß2-MG, IL-6, and TNF-α. Our study demonstrated that silencing of SOCS-1/3 may suppress RIF by alleviating the renal tubular damage in rat models affected by hydronephrosis.

Activated Hedgehog-GLI Signaling Causes Congenital Ureteropelvic Junction Obstruction.

Intrinsic ureteropelvic junction obstruction is the most common cause of congenital hydronephrosis, yet the underlying pathogenesis is undefined. Hedgehog proteins control morphogenesis by promoting GLI-dependent transcriptional activation and inhibiting the formation of the GLI3 transcriptional repressor. Hedgehog regulates differentiation and proliferation of ureteric smooth muscle progenitor cells during murine kidney-ureter development. Histopathologic findings of smooth muscle cell hypertrophy and stroma-like cells, consistently observed in obstructing tissue at the time of surgical correction, suggest that Hedgehog signaling is abnormally regulated during the genesis of congenital intrinsic ureteropelvic junction obstruction. Here, we demonstrate that constitutively active Hedgehog signaling in murine intermediate mesoderm-derived renal progenitors results in hydronephrosis and failure to develop a patent pelvic-ureteric junction. Tissue obstructing the ureteropelvic junction was marked as early as E13.5 by an ectopic population of cells expressing Ptch2, a Hedgehog signaling target. Constitutive expression of GLI3 repressor in Ptch1-deficient mice rescued ectopic Ptch2 expression and obstructive hydronephrosis. Whole transcriptome analysis of isolated Ptch2+ cells revealed coexpression of genes characteristic of stromal progenitor cells. Genetic lineage tracing indicated that stromal cells blocking the ureteropelvic junction were derived from intermediate mesoderm-derived renal progenitors and were distinct from the smooth muscle or epithelial lineages. Analysis of obstructive ureteric tissue resected from children with congenital intrinsic ureteropelvic junction obstruction revealed a molecular signature similar to that observed in Ptch1-deficient mice. Together, these results demonstrate a Hedgehog-dependent mechanism underlying mammalian intrinsic ureteropelvic junction obstruction.

The molecular biology of pelvi-ureteric junction obstruction.

Over recent years routine ultrasound scanning has identified increasing numbers of neonates as having hydronephrosis and pelvi-ureteric junction obstruction (PUJO). This patient group presents a diagnostic and management challenge for paediatric nephrologists and urologists. In this review we consider the known molecular mechanisms underpinning PUJO and review the potential of utilising this information to develop novel therapeutics and diagnostic biomarkers to improve the care of children with this disorder.

Constitutive Activation of Smoothened in the Renal Collecting Ducts Leads to Renal Hypoplasia, Hydronephrosis, and Hydroureter.

Sonic Hedgehog (Shh) signaling plays a major role in and is essential for regulation, patterning, and proliferation during renal development. Smoothened (Smo) plays a pivot role in transducing the Shh-glioma-associated oncogene Kruppel family member. However, the cellular and molecular mechanism underlying the role of sustained Smo activation in postnatal kidney development is still not clearly understood. Using a conditional knockin mouse model that expresses a constitutively activated form of Smo (SmoM2) upon Homeobox-B7-mediated recombination (Hoxb7-Cre), the effects of Shh signaling were determined in postnatal kidney development. SmoM2;Hoxb7-Cre mutant mice showed growth retardation with a reduction of body weight. Constitutive activation of Smo in the renal collecting ducts caused renal hypoplasia, hydronephrosis, and hydroureter. The parenchymal area and glomerular numbers were reduced, but the glomerular density was increased in SmoM2;Hoxb7-Cre mutant mice. The expression of Patched 1, the receptor of Shh and a downstream target gene of the Shh signaling pathway, was highly restricted and it was upregulated in the inner medullary collecting ducts of the kidney. The proliferative cells in the mesenchyme and collecting ducts were decreased in SmoM2;Hoxb7-Cre mutant mice. This study showed for the first time that sustained Smo inhibits postnatal kidney development by suppressing the proliferation of the mesenchyme and medullary collecting ducts in mice.

The SWI/SNF Protein PBRM1 Restrains VHL-Loss-Driven Clear Cell Renal Cell Carcinoma.

PBRM1 is the second most commonly mutated gene after VHL in clear cell renal cell carcinoma (ccRCC). However, the biological consequences of PBRM1 mutations for kidney tumorigenesis are unknown. Here, we find that kidney-specific deletion of Vhl and Pbrm1, but not either gene alone, results in bilateral, multifocal, transplantable clear cell kidney cancers. PBRM1 loss amplified the transcriptional outputs of HIF1 and STAT3 incurred by Vhl deficiency. Analysis of mouse and human ccRCC revealed convergence on mTOR activation, representing the third driver event after genetic inactivation of VHL and PBRM1. Our study reports a physiological preclinical ccRCC mouse model that recapitulates somatic mutations in human ccRCC and provides mechanistic and therapeutic insights into PBRM1 mutated subtypes of human ccRCC.

ACE serum level and I/D gene polymorphism in children with obstructive uropathies and other congenital anomalies of the kidney and urinary tract.

AIM: The aim of this study was to investigate the association of an insertion/deletion (I/D) polymorphism in angiotensin-converting enzyme (ACE) gene with serum ACE level in relation to the type and severity of malformations from congenital anomalies of the kidney and urinary tract (CAKUT) spectrum. METHODS: A group of 134 Bulgarian children with CAKUT divided into four subgroups according to the leading malformation and 109 controls were genotyped by classical polymerase chain reaction. The quantitative determination of serum ACE was performed by ELISA method. RESULTS: A significant elevation of DD-genotype was observed in high-grade hydronephrosis compared to low-grade (43% vs. 9%). The carrying of DD-genotype was associated with higher risk for severe hydronephrosis with OR = 7.5 (95% CI: 1.242÷45.278; P = 0.028). Also, elevated serum ACE concentrations in patients with high-grade compared to low-grade hydronephrosis (237.4 ± 45 ng/mL vs 180.5 ± 64 ng/mL; P = 0.0065) were found. ACE level was significantly lower in patients with unilateral renal agenesis; hypo/dysplasia and multicystic dysplastic kidney (156.6 ± 54 ng/mL) than controls (200.6 ± 56.7 ng/mL; P = 0.005) and the remaining CAKUT subgroups. CONCLUSION: The DD genotype of I/D ACE polymorphism encodes the highest serum ACE level may be an additional genetic risk factor contributing to the severe hydronephrosis in Bulgarian patients with obstructive uropathies in contrast to other investigated categories of CAKUT malformations.

ATP5B and ETFB metabolic markers in children with congenital hydronephrosis.

Congenital obstructive nephropathy is the primary cause of chronic renal failure in children. Disorders of mitochondrial energy metabolism may be a primary factor underlying tubular cell apoptosis in hydronephrosis. The ß-F1-ATPase (ATP5B) and electron transfer flavoprotein ß subunit (ETFB) metabolic markers are involved in mitochondrial energy metabolism in other diseases. The aim of the present study was to evaluate whether ATP5B and ETFB are represented in the hydronephrotic kidney, and whether they are associated with the progression of hydronephrosis. The cohort examined consisted of 20 children with hydronephrosis, graded III and IV using the Society for Fetal Urology grading system, and a control group consisting of 20 patients with nephroblastoma. Reverse transcription­quantitative polymerase chain reaction and immunoblot analyses were used to investigate the differential expression of genes and proteins in the two groups. The gene and protein expression levels of ATP5B and ETFB were upregulated in the hydronephrosis group. Correlation analyses revealed negative correlations between ATP5B, ETFB protein and split renal function (SRF). Receiver­operator curve analysis found a diagnostic profile of the ETFB protein in identifying children with hydronephrosis with abnormal SRF (<45%). These results suggested that increasing levels of ATP5B and ETFB were associated with worsening renal injury. ATP5B and ETFB may be novel markers in hydronephrosis and require further detailed investigation.

Genetic link between renal birth defects and congenital heart disease.

Structural birth defects in the kidney and urinary tract are observed in 0.5% of live births and are a major cause of end-stage renal disease, but their genetic aetiology is not well understood. Here we analyse 135 lines of mice identified in large-scale mouse mutagenesis screen and show that 29% of mutations causing congenital heart disease (CHD) also cause renal anomalies. The renal anomalies included duplex and multiplex kidneys, renal agenesis, hydronephrosis and cystic kidney disease. To assess the clinical relevance of these findings, we examined patients with CHD and observed a 30% co-occurrence of renal anomalies of a similar spectrum. Together, these findings demonstrate a common shared genetic aetiology for CHD and renal anomalies, indicating that CHD patients are at increased risk for complications from renal anomalies. This collection of mutant mouse models provides a resource for further studies to elucidate the developmental link between renal anomalies and CHD.

Uroplakin 1b is critical in urinary tract development and urothelial differentiation and homeostasis.

Proper development and maintenance of urothelium is critical to its function. Uroplakins are expressed in developing and mature urothelium where they establish plaques associated with the permeability barrier. Their precise functional role in development and disease is unknown. Here, we disrupted Upk1b in vivo where its loss resulted in urothelial plaque disruption in the bladder and kidney. Upk1b(RFP/RFP) bladder urothelium appeared dysplastic with expansion of the progenitor cell markers, Krt14 and Krt5, increased Shh expression, and loss of terminal differentiation markers Krt20 and uroplakins. Upk1b(RFP/RFP) renal urothelium became stratified with altered cellular composition. Upk1b(RFP/RFP) mice developed age-dependent progressive hydronephrosis. Interestingly, 16% of Upk1b(RFP/RFP) mice possessed unilateral duplex kidneys. Our study expands the role of uroplakins, mechanistically links plaque formation to urinary tract development and function, and provides a tantalizing connection between congenital anomalies of the kidney and urinary tract along with functional deficits observed in a variety of urinary tract diseases. Thus, kidney and bladder urothelium are regionally distinct and remain highly plastic, capable of expansion through tissue-specific progenitor populations. Furthermore, Upk1b plays a previously unknown role in early kidney development representing a novel genetic target for congenital anomalies of the kidney and urinary tract.

Renal denervation attenuates NADPH oxidase-mediated oxidative stress and hypertension in rats with hydronephrosis.

Hydronephrosis is associated with the development of salt-sensitive hypertension. Studies have suggested that increased sympathetic nerve activity and oxidative stress play important roles in hypertension and the modulation of salt sensitivity. The present study primarily aimed to examine the role of renal sympathetic nerve activity in the development of hypertension in rats with hydronephrosis. In addition, we aimed to investigate if NADPH oxidase (NOX) function could be affected by renal denervation. Partial unilateral ureteral obstruction (PUUO) was created in 3-wk-old rats to induce hydronephrosis. Sham surgery or renal denervation was performed at the same time. Blood pressure was measured during normal, high-, and low-salt diets. The renal excretion pattern, NOX activity, and expression as well as components of the renin-angiotensin-aldosterone system were characterized after treatment with the normal salt diet. On the normal salt diet, rats in the PUUO group had elevated blood pressure compared with control rats (115 ± 3 vs. 87 ± 1 mmHg, P < 0.05) and displayed increased urine production and lower urine osmolality. The blood pressure change in response to salt loading (salt sensitivity) was more pronounced in the PUUO group compared with the control group (15 ± 2 vs. 5 ± 1 mmHg, P < 0.05). Renal denervation in PUUO rats attenuated both hypertension (97 ± 3 mmHg) and salt sensitivity (5 ± 1 mmHg, P < 0.05) and normalized the renal excretion pattern, whereas the degree of renal fibrosis and inflammation was not changed. NOX activity and expression as well as renin and ANG II type 1A receptor expression were increased in the renal cortex from PUUO rats and normalized by denervation. Plasma Na(+) and K(+) levels were elevated in PUUO rats and normalized after renal denervation. Finally, denervation in PUUO rats was also associated with reduced NOX expression, superoxide production, and fibrosis in the heart. In conclusion, renal denervation attenuates hypertension and restores the renal excretion pattern, which is associated with reduced renal NOX and components of the renin-angiotensin-aldosterone system. This study emphasizes a link between renal nerves, the development of hypertension, and modulation of NOX function.

Urogenital development in Pallister-Hall syndrome is disrupted in a cell-lineage-specific manner by constitutive expression of GLI3 repressor.

Pallister-Hall syndrome (PHS) is a rare disorder caused by mutations in GLI3 that produce a transcriptional repressor (GLI3R). Individuals with PHS present with a variably penetrant variety of urogenital system malformations, including renal aplasia or hypoplasia, hydroureter, hydronephrosis or a common urogenital sinus. The embryologic mechanisms controlled by GLI3R that result in these pathologic phenotypes are undefined. We demonstrate that germline expression of GLI3R causes renal hypoplasia, associated with decreased nephron number, and hydroureter and hydronephrosis, caused by blind-ending ureters. Mice with obligate GLI3R expression also displayed duplication of the ureters that was caused by aberrant common nephric duct patterning and ureteric stalk outgrowth. These developmental abnormalities are associated with suppressed Hedgehog signaling activity in the cloaca and adjacent vesicular mesenchyme. Mice with conditional expression of GLI3R were utilized to identify lineage-specific effects of GLI3R. In the ureteric bud, GLI3R expression decreased branching morphogenesis. In Six2-positive nephrogenic progenitors, GLI3R decreased progenitor cell proliferation reducing the number of nephrogenic precursor structures. Using mutant mice with Gli3R and Gli3 null alleles, we demonstrate that urogenital system patterning and development is controlled by the levels of GLI3R and not by an absence of full-length GLI3. We conclude that the urogenital system phenotypes observed in PHS are caused by GLI3R-dependent perturbations in nephric duct patterning, renal branching morphogenesis and nephrogenic progenitor self-renewal.

Rho GAP myosin IXa is a regulator of kidney tubule function.

Mammalian class IX myosin Myo9a is a single-headed, actin-dependent motor protein with Rho GTPase-activating protein activity that negatively regulates Rho GTPase signaling. Myo9a is abundantly expressed in ciliated epithelial cells of several organs. In mice, genetic deletion of Myo9a leads to the formation of hydrocephalus. Whether Myo9a also has essential functions in the epithelia of other organs of the body has not been explored. In the present study, we report that Myo9a-deficient mice develop bilateral renal disease, characterized by dilation of proximal tubules, calyceal dilation, and thinning of the parenchyma and fibrosis. These structural changes are accompanied by polyuria (with normal vasopressin levels) and low-molecular-weight proteinuria. Immunohistochemistry revealed that Myo9a is localized to the circumferential F-actin belt of proximal tubule cells. In kidneys lacking Myo9a, the multiligand binding receptor megalin and its ligand albumin accumulated at the luminal surface of Myo9a-deficient proximal tubular cells, suggesting that endocytosis is dysregulated. In addition, we found, surprisingly, that levels of murine diaphanous-related formin-1, a Rho effector, were decreased in Myo9a-deficient kidneys as well as in Myo9a knockdown LLC-PK1 cells. In summary, deletion of the Rho GTPase-activating protein Myo9a in mice causes proximal tubular dilation and fibrosis, and we speculate that downregulation of murine diaphanous-related formin-1 and impaired protein reabsorption contribute to the pathophysiology.

Loss of Dgcr8-mediated microRNA expression in the kidney results in hydronephrosis and renal malformation.

BACKGROUND: Small non-coding RNA molecules (miRNAs) play a pivotal role in regulating gene expression in development. miRNAs regulate key processes at the cellular level and thereby influence organismal and tissue development including kidney morphogenesis. A miRNA molecule is initially synthesized as a longer hairneedle-shaped RNA transcript and then processed through an enzymatic complex that contains the RNA-processing enzyme Drosha and its essential interactor Dgcr8. Resulting pre-miRNAs are then cleaved by Dicer. Recent data showed that loss of Dicer resulted in severe developmental kidney phenotypes. However, as Dicer has multiple miRNA-independent functions, it was not entirely clear whether the observed renal phenotypes could be exclusively attributed to a lack of miRNA expression. METHODS: We analyzed the role of miRNAs in kidney development by conditional gene deletion of Dgcr8 in the developing kidney using a transgenic mouse line that expresses Cre recombinase in the distal nephron and derivatives of the ureteric bud in kidney development. RESULTS: Animals with a gene deletion of Dgcr8 in these tissues developed severe hydronephrosis, kidney cysts, progressive renal failure and premature death within the first two months after birth, a phenotype strongly resembling Dicer deletion. CONCLUSIONS: Here we show that conditional gene deletion of the essential miRNA-processing enzyme Dgcr8 in the developing renal tubular system results in severe developmental defects and kidney failure. These data confirm earlier findings obtained in Dicer knock-out animals and clearly illustrate the essential role of miRNAs in kidney development. The data suggests that miRNA dysregulation may play an important, yet ill-defined role in the pathogenesis of inborn defects of the genitourinary system and indicate that miRNA defects may be causative in the development of human disease.