Peri-Operative Patient Safety - An Interactive Workshop for Section 3 CPD Credits Developed in Collaboration with the CMPA.

BACKGROUND: The Royal College of Physicians and Surgeons of Canada requires physicians to collect credit in continuing professional development courses including Section 3 credits which require feedback and self-assessment. This study aims to examine the effectiveness of offering Section 3 credits in a conference setting using an interactive workshop on peri-operative patient safety developed in collaboration with the Canadian Medical Protective Association (CMPA). Both the knowledge gained and the attitudes towards the conference were analysed. METHODS: This was a pre/post-test study design. An interactive case studies workshop was implemented on medicolegal issues for patient care, before, during, and after surgery at the Canadian Society of Otolaryngology Head and Neck Surgery annual meeting. The workshop used small group and large interactive group educational strategies to gauge knowledge of both pre and post cases. Participants completed a questionnaire at the end of the workshop comparing their attitudes before and after the workshop. RESULTS: There were 22 participants in the workshop. A little over half knew the requirements for Section 3 CPD credits (58%) but only 36% knew how to obtain them. The data demonstrated with 95% confidence intervals, statistically significant improvement in how participants felt about their ability to identify at-risk behaviours in surgical practice (2.10 to 2.90, 3-point Likert, p<0.001), to analyze the impact of at-risk behaviour on patient care (1.95 to 2.65, p<0.001), and to develop strategies to address at-risk behaviours in surgical practice and improve patient care (1.95 to 2.80, p<0.001). One hundred percent of participants felt similar workshops should be included in future annual meetings, and 94% felt that future meetings should include more opportunities to obtain Section 3 credits. CONCLUSION: This study demonstrates the effectiveness of an interactive workshop in a conference setting to fulfill the need for Section 3 continuing professional development credits.

Implementing Obstetrics Quality Improvement, Driven by Medico-legal Risk, is Associated With Improved Workplace Culture.

OBJECTIVE: This study implemented a quality improvement program based on knowledge of medico-legal risk in obstetrics and sought to evaluate the impact of this program on workplace culture. METHODS: The study conducted needs assessments with front-line providers working in the obstetrical unit of the Queensway Carleton Hospital, an urban community hospital in Ottawa, Ontario, and included the safety, communication, operational reliability, and engagement (SCORE) survey. The study investigators delivered training in quality improvement science and co-developed three projects that were based on their alignment with local needs and aggregate medico-legal risk data: an organized team response to the need for an immediate cesarean section, a protocol for managing patients who present at term with pre-labour rupture of membranes, and regular morning team briefings. Outcome measures were determined for each project from a quality improvement indicator framework, and coaching was provided to project leads. Participants completed the SCORE survey and a program effectiveness tool after the intervention. RESULTS: The majority of participants (75.2% of 153 pre-intervention and 63.1% of 157 post-intervention participants) completed the SCORE surveys. Post-intervention improvements were found in teamwork, learning environment, and safety climate, whereas levels of provider burnout remained high. Program effectiveness was highly rated, and most projects showed qualitative improvements. CONCLUSION: This study showed positive workplace culture change associated with the quality improvement intervention. Lessons learned from the implementation of this program can inform future quality improvement initiatives.

Characterization of a novel disease-associated mutation within NPHS1 and its effects on nephrin phosphorylation and signaling.

Mutations in the transmembrane protein nephrin (encoded by NPHS1) underlie nearly half of all cases of congenital nephrotic syndrome (CNS), which is caused by aberrations in the blood filtering function of glomerular podocytes. Nephrin directly contributes to the structure of the filtration barrier, and it also serves as a signaling scaffold in podocytes, undergoing tyrosine phosphorylation on its cytoplasmic tail to recruit intracellular effector proteins. Nephrin phosphorylation is lost in several human and experimental models of glomerular disease, and genetic studies have confirmed its importance in maintenance of the filtration barrier. To date, however, the effect of CNS-associated NPHS1 variants on nephrin phosphorylation remains to be determined, which hampers genotype-phenotype correlations. Here, we have characterized a novel nephrin sequence variant, A419T, which is expressed along with C623F in a patient presenting with CNS. Nephrin localization is altered in kidney biopsies, and we further demonstrate reduced surface expression and ER retention of A419T and C623F in cultured cells. Moreover, we show that both mutations impair nephrin tyrosine phosphorylation, and they exert dominant negative effects on wildtype nephrin signaling. Our findings thus reveal that missense mutations in the nephrin extracellular region can impact nephrin signaling, and they uncover a potential pathomechanism to explain the spectrum of clinical severity seen with mild NPHS1 mutations.

Parental Health Literacy and Outcomes of Childhood Nephrotic Syndrome.

OBJECTIVE: Determine the association of parental health literacy with treatment response among children with nephrotic syndrome. METHODS: This was a cohort study of children aged 1-18 with nephrotic syndrome and their parent. Health literacy was measured using the validated Short Test of Functional Health Literacy in Adults assessing reading comprehension and numeracy. Outcomes included initial relapse-free period, frequently relapsing disease, relapse rate, second-line medication use, and complete remission after therapy. RESULTS: Of 190 parents, 80% had adequate health literacy (score >67 of 100), and higher scores were not correlated with higher education. Almost all achieved perfect numeracy scores (>86%); numeracy was not associated with outcomes. After adjusting for immigration, education, and income, higher reading comprehension scores (tertile 3) compared with lower scores (tertile 1) were significantly associated with lower risk of first relapse (hazard ratio 0.67, 95% confidence interval [CI] 0.48-0.94, P trend = .02), lower odds of frequently relapsing disease (odds ratio [OR] 0.38, 95% CI 0.21-0.70, P trend = .002), lower relapse rate (rate ratio 0.77, 95% CI 0.73-0.80, P trend < .001), and higher odds of complete remission after both initial steroids and cyclophosphamide (OR 2.07, 95% CI 1.36-3.16, P trend = .003; OR 5.97, 95% CI 2.42-14.7, P trend < .001). CONCLUSIONS: Lower parental health literacy, specifically reading comprehension, is associated with higher relapse rates among children with nephrotic syndrome and fewer achieving complete remission. This underscores the importance of assessing and targeting health literacy for chronic management of childhood-onset diseases.

Ethnic Differences in Incidence and Outcomes of Childhood Nephrotic Syndrome.

BACKGROUND AND OBJECTIVES: Ethnic differences in outcomes among children with nephrotic syndrome are unknown. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: We conducted a longitudinal study at a single regional pediatric center comparing ethnic differences in incidence from 2001 to 2011 census data and longitudinal outcomes, including relapse rates, time to first relapse, frequently relapsing disease, and use of cyclophosphamide. Among 711 children, 24% were European, 33% were South Asian, 10% were East/Southeast Asian, and 33% were of other origins. RESULTS: Over 10 years, the overall incidence increased from 1.99/100,000 to 4.71/100,000 among children ages 1-18 years old. In 2011, South Asians had a higher incidence rate ratio of 6.61 (95% confidence interval, 3.16 to 15.1) compared with Europeans. East/Southeast Asians had a similar incidence rate ratio (0.76; 95% confidence interval, 0.13 to 2.94) to Europeans. We determined outcomes in 455 children from the three largest ethnic groups with steroid-sensitive disease over a median of 4 years. South Asian and East/Southeast Asian children had significantly lower odds of frequently relapsing disease at 12 months (South Asian: adjusted odds ratio; 0.55; 95% confidence interval, 0.39 to 0.77; East/Southeast Asian: adjusted odds ratio; 0.42; 95% confidence interval, 0.34 to 0.51), fewer subsequent relapses (South Asian: adjusted odds ratio; 0.64; 95% confidence interval, 0.50 to 0.81; East/Southeast Asian: adjusted odds ratio; 0.47; 95% confidence interval, 0.24 to 0.91), lower risk of a first relapse (South Asian: adjusted hazard ratio, 0.74; 95% confidence interval, 0.67 to 0.83; East/Southeast Asian: adjusted hazard ratio, 0.65; 95% CI, 0.63 to 0.68), and lower use of cyclophosphamide (South Asian: adjusted hazard ratio, 0.82; 95% confidence interval, 0.53 to 1.28; East/Southeast Asian: adjusted hazard ratio, 0.54; 95% confidence interval, 0.41 to 0.71) compared with European children. CONCLUSIONS: Despite the higher incidence among South Asians, South and East/Southeast Asian children have significantly less complicated clinical outcomes compared with Europeans.

Parental attitudes to genetic testing differ by ethnicity and immigration in childhood nephrotic syndrome: a cross-sectional study.

BACKGROUND: Studies in the USA report differences in opinion among parents of different ethnic groups toward genetic testing for their child; however, there are no studies that address this issue in the diverse ethnic and immigrant population in Canada. OBJECTIVE: This study aims to determine whether ethnicity and immigration status influences parental interest in clinical genetic testing for a potentially progressive kidney disease. DESIGN: This is a cross-sectional study. SETTING: Participants were recruited from the Greater Toronto Area, Canada. PARTICIPANTS: The study included 320 parents of children ages 1-18 years with nephrotic syndrome enrolled in the Insight into Nephrotic Syndrome: Investigating Genes, Health and Therapeutics (INSIGHT) observational cohort study. MEASUREMENTS: Demographic, ethnicity, immigration, and child specific factors as well as interest in genetic testing were collected through self-reported questionnaires administered at baseline study visit. METHODS: Logistic regression models were used to examine association of ethnicity and immigration status with interest in genetic testing. RESULTS: The majority of parents (85 %) were interested in genetic testing for their child. South Asian and East/Southeast Asian parents had 74 and 76 % lower odds of agreeing to genetic testing when compared to Europeans (odds ratio (OR) 0.26, 95 % confidence interval (CI) 0.10-0.68; OR 0.24, 95 % CI 0.07-0.79, respectively) after controlling for age and sex of child, age and education level of parent, initial steroid resistance, and duration of time in Canada. Immigrants to Canada also had significantly lower odds (OR 0.29, 95 % CI 0.12-0.72) of agreeing to genetic testing after similar adjustment. Higher education level was not associated with greater interest in genetic testing (OR 1.24, 95 % CI 0.64-2.42). LIMITATIONS: Participants have already agreed to aggregate genetic testing for research purposes as part of enrolment in INSIGHT study. CONCLUSION: While majority of parents were interested in genetic testing for their child, immigrants, particularly South Asians and East/Southeast Asians, were more likely to decline genetic testing. Genetic counseling needs to be tailored to address specific concerns in these parental groups to maximize informed decision-making in the clinical setting. TRIAL REGISTRATION: ClinicalTrials.gov, NCT01605266.

MISE EN CONTEXTE: Des études aux États-Unis font état de différences d'opinions parmi les parents provenant de différentes origines ethniques quant à la possibilité de procéder à des tests de dépistage génétique sur leurs enfants. Toutefois il n'existe aucune étude qui traite de cette question au sein des différents groupes ethniques au Canada. OBJECTIFS DE L'ÉTUDE: L'étude avait pour but de vérifier si l'origine ethnique ou le statut d'immigrant des parents influençait leur façon d'aborder la question du dépistage génétique pour la détection d'une néphropathie potentiellement évolutive chez leur enfant. CADRE ET TYPE D'ÉTUDE: Cette étude transversale s'est tenue dans la grande région de Toronto au Canada. PARTICIPANTS: Il s'agit de 320 parents d'enfants âgés de 1 à 18 ans atteints d'un syndrome néphrotique qui participaient à l'étude de cohorte observationnelle INSIGHT (Insight into Nephrotic Syndrome: Investigating Genes Health and Therapeutics). MESURES: Les données soit la répartition démographique l'origine ethnique ou le statut d'immigrant des parents, les éléments propres à l'enfant ainsi que le niveau d'intérêt des parents à l'égard des tests de dépistage génétique, ont été colligées à partir d'un questionnaire remis aux parents lors de la première visite. MÉTHODOLOGIE: Des modèles de régression logistique ont été utilisés pour établir un parallèle entre l'origine ethnique ou le statut d'immigrant d'un parent et son intérêt à soumettre son enfant à un dépistage génétique. RÉSULTATS: La majorité des participants à l'étude (85 %) démontrait un intérêt envers la possibilité de soumettre leur enfant à un test de dépistage génétique. Toutefois dans le cas précis des gens originaires de l'Asie du Sud et de ceux provenant de l'Extrême-Orient ou de l'Asie du Sud-Est, les probabilités de consentir à un tel test étaient respectivement de 74 % et de 76 % plus faibles que pour les gens d'origine européenne. (Risque relatif [RR] : 0,26 à 95 % d'intervalle de confiance [IC] : 0.10-0.68; RR : 0,24 à 95 % IC : 0.07-0.79 respectivement). Ces résultats ont été obtenus après l'exclusion d'indicateurs relatifs à l'âge et au sexe de l'enfant, au sexe et au niveau d'éducation des parents, à la résistance de l'enfant au traitement initial par les stéroïdes et à la durée du séjour au Canada. Cette observation s'est également confirmée chez les immigrants reçus, pour qui la probabilité de consentir à un tel test pour leur enfant s'est aussi avérée significativement moins élevée après l'application des mêmes correctifs (RR : 0,29, à 95 % IC : 0.12-0.72). Aucune corrélation n'a pu être établie entre le niveau d'éducation élevé des parents et un intérêt accru à soumettre leur enfant à un test de dépistage génétique (RR : 1,24 à 95 % IC : 0.64-2.42). LIMITES DE L'ÉTUDE: Les résultats sont limités du fait que les participants avaient consenti à soumettre leur enfant à un test de dépistage génétique fà des fins de recherche dans le cadre de leur inclusion à l'étude INSIGHT. CONCLUSIONS: Alors que la majorité des parents ayant participé à l'étude voyait d'un bon œil la possibilité de soumettre leur enfant à un test de dépistage génétique les immigrants reçus ainsi que les participants originaires de l'Asie du Sud, de l'Extrême-Orient et de l'Asie du Sud-Est se sont avérés plus susceptibles de décliner l'offre. Par conséquent, le processus de consultation en génétique doit être adapté pour mieux répondre aux inquiétudes et aux préoccupations de ces groupes de parents; ceci afin de tirer le meilleur parti d'une prise de décision éclairée dans un contexte clinique.

A New Grading System for the Management of Antenatal Hydronephrosis.

BACKGROUND AND OBJECTIVES: Standard clinical assessments do not predict surgical intervention in patients with a moderate degree of upper tract hydronephrosis. This study investigated whether combined measures of renal calyceal dilation and anteroposterior diameter (APD) of the renal pelvis at the first postnatal ultrasound better predict surgical intervention beyond standard assessments of the APD or Society of Fetal Urology (SFU) grading system. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: A retrospective cohort of 348 children with antenatal hydronephrosis followed from 2003 to 2013 were studied. Using Cox regression, the risk for surgery by APD, SFU, and combined grading on the basis of the first postnatal ultrasound was calculated. The predictive capability of each grading system for surgery was determined by calculating the positive likelihood ratio (LR+). RESULTS: The combination of APD≥6-9 mm and diffuse caliectasis had a hazard ratio (HR) of 19.5 (95% confidence interval [95% CI], 3.94 to 96.9) versus 0.59 (95% CI, 0.05 to 6.53) for APD≥6-9 mm alone and a similar risk of 8.9 for SFU grade 3 (95% CI, 3.84 to 20.9). The combination of APD≥9-15 mm and diffuse caliectasis had an HR of 18.7 (95% CI, 4.36 to 80.4) versus 1.75 (95% CI, 0.29 to 10.5) for APD≥9-15 mm alone. The LR+ for surgery for diffuse caliectasis and APD≥6-9 mm was higher than for APD≥6-9 mm alone (HR=2.62; 95% CI, 0.87 to 7.94 versus HR=0.04; 95% CI, 0.01 to 0.32) and was higher for APD≥9-15 mm and diffuse caliectasis than APD≥9-15 mm alone (HR=2.0; 95% CI, 1.15 to 3.45 versus HR=0.14; 95% CI, 0.04 to 0.43). Both combined groups of moderate hydronephrosis (APD≥6-9 mm or ≥9-15 mm with diffuse caliectasis) had only slightly higher LR+ than SFU grade 3 (HR=1.89; 95% CI, 1.17 to 3.05). CONCLUSIONS: These results suggest a grading system combining APD and diffuse caliectasis distinguishes those children with moderate degrees of upper tract hydronephrosis that are at higher risk of surgery.

The rationale and design of Insight into Nephrotic Syndrome: Investigating Genes, Health and Therapeutics (INSIGHT): a prospective cohort study of childhood nephrotic syndrome.

BACKGROUND: Nephrotic syndrome is one of the most commonly diagnosed kidney diseases in childhood and its progressive forms can lead to chronic kidney disease (CKD) and/or end-stage renal disease (ESRD). There have been few longitudinal studies among a multi-ethnic cohort to determine potential risk factors influencing disease susceptibility, treatment response, and progression of nephrotic syndrome. Temporal relationships cannot be studied through cross-sectional study design. Understanding the interaction between various factors is critical to developing new strategies for treating children with kidney disease. We present the rationale and the study design of a longitudinal cohort study of children with nephrotic syndrome, the Insight into Nephrotic Syndrome: Investigating Genes, Health and Therapeutics (INSIGHT) study. The specific aims are to determine: 1) socio-demographic, environmental, and genetic factors that influence disease susceptibility; 2) rates of steroid treatment resistance and steroid treatment dependence, and identify factors that may modify treatment response; 3) clinical and genetic factors that influence disease susceptibility and progression to CKD and ESRD; and 4) the interaction between the course of illness and socio-demographic, environmental, and clinical risk factors. METHODS/DESIGN: INSIGHT is a disease-based observational longitudinal cohort study of children with nephrotic syndrome. At baseline, participants complete questionnaires and provide biological specimen samples (blood, urine, and toenail clippings). Follow-up questionnaires and repeat biological specimen collections are performed annually for up to five years. DISCUSSION: The proposed cohort will provide the structure to test various risk factors predicting or influencing disease susceptibility, treatment response, and progression to CKD among children with nephrotic syndrome. TRIAL REGISTRATION: ClinicalTrials.gov Identifier NCT01605266.

Notch promotes dynamin-dependent endocytosis of nephrin.

Notch signaling in podocytes causes proteinuria and glomerulosclerosis in humans and rodents, but the underlying mechanism remains unknown. Here, we analyzed morphologic, molecular, and cellular events before the onset of proteinuria in newborn transgenic mice that express activated Notch in podocytes. Immunohistochemistry revealed a loss of the slit diaphragm protein nephrin exclusively in podocytes expressing activated Notch. Podocyte-specific deletion of Rbpj, which is essential for canonical Notch signaling, prevented this loss of nephrin. Overexpression of activated Notch decreased cell surface nephrin and increased cytoplasmic nephrin in transfected HEK293T cells; pharmacologic inhibition of dynamin, but not depletion of cholesterol, blocked these effects on nephrin, suggesting that Notch promotes dynamin-dependent, raft-independent endocytosis of nephrin. Supporting an association between Notch signaling and nephrin trafficking, electron microscopy revealed shortened podocyte foot processes and fewer slit diaphragms among the transgenic mice compared with controls. These data suggest that Notch signaling induces endocytosis of nephrin, thereby triggering the onset of proteinuria.

Genetics of proteinuria: an overview of gene mutations associated with nonsyndromic proteinuric glomerulopathies.

Heritable causes of proteinuria are rare and account for a relatively small proportion of all cases of proteinuria affecting children and adults. Yet, significant contributions to understanding the mechanistic basis for proteinuria have been made through genetic and molecular analyses of a small group of syndromic and nonsyndromic proteinuric disorders which are caused by mutations encoding structural components of the glomerular filtration barrier. Technological advances in genomic analyses and improved accessibility to mutational screening at clinically approved laboratories have facilitated diagnosis of proteinuria in the clinical setting. From a clinical standpoint, it may be argued that a genetic diagnosis mitigates exposure to potentially ineffective and harmful treatments in instances where a clear genotype-phenotype correlation exists between a specific gene mutation and treatment nonresponsiveness. However, cautious interpretation of risk may be necessitated in cases with phenotypic heterogeneity (eg, variability in clinical or histological presentation). This review summarizes gene mutations which are known to be associated with proteinuric glomerulopathies in children and adults.

Lunatic Fringe-mediated Notch signaling is required for lung alveogenesis.

Distal lung development occurs through coordinated induction of myofibroblasts, epithelial cells, and capillaries. Lunatic Fringe (Lfng) is a beta(1-3) N-acetylglucosamine transferase that modifies Notch receptors to facilitate their activation by Delta-like (Dll1/4) ligands. Lfng is expressed in the distal lung during saccular development, and deletion of this gene impairs myofibroblast differentiation and alveogenesis in this context. A similar defect was observed in Notch2(beta-geo/+)Notch3(beta-geo/beta-geo) compound mutant mice but not in Notch2(beta-geo/+) or Notch3(beta-geo/beta-geo) single mutants. Finally, to directly test for the role of Notch signaling in myofibroblast differentiation in vivo, we used ROSA26-rtTA(/+);tetO-CRE(/+);RBPJkappa(flox/flox) inducible mutant mice to show that disruption of canonical Notch signaling during late embryonic development prevents induction of smooth muscle actin in mesenchymal cells of the distal lung. In sum, these results demonstrate that Lfng functions to enhance Notch signaling in myofibroblast precursor cells and thereby to coordinate differentiation and mobilization of myofibroblasts required for alveolar septation.

Remission of resistant MPGN type I with mycophenolate mofetil and steroids.

Very few studies have been published on how to treat children with membranoproliferative glomerulonephritis type I (MPGN I), and as yet there is only one report on the use of mycophenolate mofetil (MMF) in children with MPGN I. We report a 12-year-old boy who presented with edema, hypertension, nephrotic range proteinuria, and microscopic hematuria following an upper respiratory tract infection. Laboratory tests revealed a serum creatinine of 90 micromol/l, albumin of 20 g/l, and a C3 of 0.11 g/l (normal range: 0.7-1.4). Renal biopsy showed the presence of MPGN I. Upon failure to induce remission with prednisone, we started the patient on MMF at 500 mg/day (300 mg/m(2)), increasing up to a final dose of 2 g/day (1200 mg/m(2)), with a MMF metabolite mycophenolic acid (MPA) target range of 2-5 mg/l. Prednisone was subsequently reduced to alternate day therapy and gradually weaned to 7.5 mg on alternate days over 9 months. Within 4 months of starting MMF therapy, there was significant improvement in serum creatinine (decrease from 156 to 64 micromol/l), serum albumin (increase from 23 to 40 g/l), and proteinuria (decrease from 13 g/day to 40 mg/day). Twelve months following the introduction of MMF into his therapeutic regimen, he remains in remission with no further relapses. In summary, this case suggests that there may be potential benefit for use of MMF in children with refractory MPGN I, which supports the rationale for prospectively evaluating MMF treatment in a treatment trial of refractory MPGN I.

Ectopic notch activation in developing podocytes causes glomerulosclerosis.

Genetic evidence supports an early role for Notch signaling in the fate of podocytes during glomerular development. Decreased expression of Notch transcriptional targets in developing podocytes after the determination of cell fate suggests that constitutive Notch signaling may oppose podocyte differentiation. This study determined the effects of constitutive Notch signaling on podocyte differentiation by ectopically expressing Notch's intracellular domain (NOTCH-IC), the biologically active, intracellular product of proteolytic cleavage of the Notch receptor, in developing podocytes of transgenic mice. Histologic and molecular analyses revealed normal glomerular morphology and expression of podocyte markers in newborn NOTCH-IC-expressing mice; however, mice developed severe proteinuria and showed evidence of progressive glomerulosclerosis at 2 wk after birth. Features of mature podocytes were lost: Foot processes were effaced; expression of Wt1, Nphs1, and Nphs2 was downregulated; cell-cycle re-entry was induced; and the expression of Pax2 was increased. In contrast, mice with podocyte-specific inactivation of Rbpsuh, which encodes a protein essential for canonical Notch signaling, seemed normal. In addition, the damaging effects of NOTCH-IC expression were prevented in transgenic mice after simultaneous conditional inactivation of Rbpsuh in murine podocytes. These results suggest that Notch signaling is dispensable during terminal differentiation of podocytes but that constitutive (or inappropriate) Notch signaling is deleterious, leading to glomerulosclerosis.

Expression of Hairy/Enhancer of Split genes, Hes1 and Hes5, during murine nephron morphogenesis.

Hairy/Enhancer of Split (Hes) genes encode transcriptional repressors that function as downstream targets of activated Notch receptors in cell fate decisions during tissue development. During nephrogenesis, multiple Notch pathway genes are co-expressed in multi-potent epithelial progenitors (i.e. pre-tubular aggregates), but demonstrate distinct expression patterns in early nephrons (i.e. S-shaped bodies), suggesting that Notch signaling functions in patterning epithelial cell fate during nephron morphogenesis. To define the spatial activation of the Notch pathway in developing nephrons, we analyzed the expression of Hes1 and Hes5 by mRNA in situ hybridization in cryosections of developing kidneys, and compared their spatiotemporal expression with the expression of other Notch pathway genes in nephron progenitors. Hes1, and to a lesser extent Hes5, were expressed in pre-tubular aggregates and comma-shaped bodies of embryonic day (E) 13.5 and newborn kidneys. In S-shaped bodies, Hes1 expression was detected in the middle part which gives rise to the proximal tubule, but also extended into the lower and upper parts which give rise to the glomerulus and distal tubule, respectively, and was similar to the proximal-distal expression patterns for Notch1 and Jagged1 in these nephrogenic structures. In contrast, strong Hes5 expression was restricted to the middle segment of S-shaped bodies, and resembled Delta-like 1 expression. These data show that Hes1 and Hes5 expression are independently regulated along the proximal-distal axis of the developing nephron. Consequently, the differential, spatial regulation of Hes1 and Hes5 gene expression by the Notch signaling pathway in developing nephrons may be a mechanism for patterning cell fate decisions during nephron morphogenesis.

Elevated SMAD1/beta-catenin molecular complexes and renal medullary cystic dysplasia in ALK3 transgenic mice.

Renal dysplasia, the most frequent cause of childhood renal failure in humans, arises from perturbations in a complex series of morphogenetic events during embryonic renal development. The molecular pathogenesis of renal dysplasia is largely undefined. While investigating the role of a BMP-dependent pathway that inhibits branching morphogenesis in vitro, we generated a novel model of renal dysplasia in a transgenic (Tg) model of ALK3 receptor signaling. We report the renal phenotype, and our discovery of molecular interactions between effectors in the BMP and WNT signaling pathways in dysplastic kidney tissue. Expression of the constitutively active ALK3 receptor ALK3(QD), in two independent transgenic lines caused renal aplasia/severe dysgenesis in 1.5% and 8.4% of hemizygous and homozygous Tg mice, respectively, and renal medullary cystic dysplasia in 49% and 74% of hemizygous and homozygous Tg mice, respectively. The dysplastic phenotype, which included a decreased number of medullary collecting ducts, increased medullary mesenchyme, collecting duct cysts and decreased cortical thickness, was apparent by E18.5. We investigated the pathogenesis of dysplasia in these mice, and demonstrated a 30% decrease in branching morphogenesis at E13.5 before the appearance of histopathogical features of dysplasia, and the formation of beta-catenin/SMAD1/SMAD4 molecular complexes in dysplastic renal tissue. Increased transcriptional activity of a beta-catenin reporter gene in ALK3(QD);Tcf-gal mice demonstrated functional cooperativity between the ALK3 and beta-catenin-dependent signaling pathways in kidney tissue. Together with our results in the dysplastic mouse kidney, our findings that phospho-SMAD1 and beta-catenin are overexpressed in human fetal dysplastic renal tissue suggest that dysregulation of these signaling effectors is pathogenic in human renal dysplasia. Our work provides novel insights into the role that crucial developmental signaling pathways may play during the genesis of malformed renal tissue elements.

The molecular control of renal branching morphogenesis: current knowledge and emerging insights.

Mammalian kidney development requires the formation of a patterned, branched network of collecting ducts, a process termed renal branching morphogenesis. Disruption of renal branching morphogenesis during human kidney development results in renal dysplasia, the major cause of renal failure in young children. Genetic evidence, combined with in vitro data, have implicated transcription factors, secreted growth factors, and cell surface signaling peptides as critical regulators of renal branching morphogenesis. This review discusses the current knowledge regarding the regulation of renal branching morphogenesis in vivo provided by the analysis of genetic mutations in mice and humans which disrupt collecting duct system development. In addition, in vivo and in vitro evidence regarding the functions of several other gene families are considered, rendering new insight into emerging regulatory roles for these molecules in renal branching morphogenesis.