Modeling Pkd1 gene-targeted strategies for correction of polycystic kidney disease.

Autosomal dominant polycystic kidney disease (ADPKD) causes renal cysts and leads to end-stage renal disease in midlife due mainly to PKD1 gene mutations. Virtually no studies have explored gene therapeutic strategies for long-term effective treatment of PKD. Toward this aim, the severely cystic Pkd1-null mouse model was targeted with a series of transgene transfers using genomic Pkd1 under its regulatory elements (Pkd1wt), a kidney-targeted Pkd1 gene (SBPkd1), or Pkd1Minigene. The introduced Pkd1wt gene constructs with ∼8-fold overexpression display similar endogenous cellular profiles and full complementation of Pkd1-/- phenotype and establish the referral Pkd1 genomic length for proper regulation. SBPkd1 transgene transfer expressing 0.6- or 7-fold Pkd1 endogenous levels is sufficient to correct glomerular and proximal tubular cysts and to markedly postpone cysts in other tubular segments as well, showing that the small SB elements appreciably overlap with Pkd1 promoter/5' UTR regulation. Renal-targeted Pkd1Minigene at high copy numbers conveys an expression level similar to that of the endogenous Pkd1 gene, with widespread and homogeneous weak Pkd1 cellular signal, partially rescuing all cystic tubular segments. These transgene transfers determine that Pkd1 intragenic sequences regulate not only expression levels but also spatiotemporal patterns. Importantly, our study demonstrates that Pkd1 re-expression from hybrid therapeutic constructs can ameliorate, with considerably extended lifespan, or eliminate PKD.

A Phase III, multicenter, randomized, double-blind, active comparator-controlled study to evaluate the safety, tolerability, and immunogenicity of V114 compared with PCV13 in healthy infants (PNEU-PED-EU-1).

BACKGROUND: V114 (15-valent pneumococcal conjugate vaccine [PCV]) contains all serotypes in 13-valent PCV (PCV13) and additional serotypes 22F and 33F. This study evaluated safety and immunogenicity of V114 compared with PCV13 in healthy infants, and concomitant administration with DTPa-HBV-IPV/Hib and rotavirus RV1 vaccines. METHODS: V114 and PCV13 were administered in a 2+1 schedule at 2, 4, and 11-15 months of age. Adverse events (AEs) were collected on Days 1-14 following each vaccination. Serotype-specific anti-pneumococcal immunoglobulin G (IgG) was measured 30 days post-primary series (PPS), immediately prior to a toddler dose, and 30 days post-toddler dose (PTD). Primary objectives included non-inferiority of V114 to PCV13 for 13 shared serotypes and superiority of V114 to PCV13 for the two additional serotypes. RESULTS: 1184 healthy infants 42-90 days of age were randomized 1:1 to V114 (n = 591) or PCV13 (n = 593). Proportions of participants with solicited AEs and serious AEs were comparable between vaccination groups. V114 met pre-specified non-inferiority criteria for all 13 shared serotypes, based on the difference in proportions of participants with serotype-specific IgG concentrations ≥0.35 µg/mL (response rate; lower bound of two-sided 95% confidence interval [CI] >-10.0) and IgG geometric mean concentration (GMC) ratios (lower bound of two-sided 95% CI >0.5), and pre-specified superiority criteria for serotypes 22F and 33F (lower bound of two-sided 95% CI >10.0 for response rates and >2.0 for GMC ratios). Antibody responses to DTPa-HBV-IPV/Hib and RV1 vaccines met pre-specified non-inferiority criteria, based on antigen-specific response rates to DTPa-HBV-IPV/Hib and anti-rotavirus IgA geometric mean titers. CONCLUSIONS: After a 2+1 schedule, V114 elicited non-inferior immune responses to 13 shared serotypes and superior responses to the two additional serotypes compared with PCV13, with comparable safety profile. These results support the routine use of V114 in infants. TRIAL REGISTRATION: ClinicalTrials.gov: NCT04031846; EudraCT: 2018-003787-31.

Assimilation of Medical Appointment Scheduling Systems and Their Impact on the Accessibility of Primary Care: Mixed Methods Study.

BACKGROUND: The COVID-19 pandemic has prompted the adoption of digital health technologies to maximize the accessibility of medical care in primary care settings. Medical appointment scheduling (MAS) systems are among the most essential technologies. Prior studies on MAS systems have taken either a user-oriented perspective, focusing on perceived outcomes such as patient satisfaction, or a technical perspective, focusing on optimizing medical scheduling algorithms. Less attention has been given to the extent to which family medicine practices have assimilated these systems into their daily operations and achieved impacts. OBJECTIVE: This study aimed to fill this gap and provide answers to the following questions: (1) to what extent have primary care practices assimilated MAS systems into their daily operations? (2) what are the impacts of assimilating MAS systems on the accessibility and availability of primary care? and (3) what are the organizational and managerial factors associated with greater assimilation of MAS systems in family medicine clinics? METHODS: A survey study targeting all family medicine clinics in Quebec, Canada, was conducted. The questionnaire was addressed to the individual responsible for managing medical schedules and appointments at these clinics. Following basic descriptive statistics, component-based structural equation modeling was used to empirically explore the causal paths implied in the conceptual framework. A cluster analysis was also performed to complement the causal analysis. As a final step, 6 experts in MAS systems were interviewed. Qualitative data were then coded and extracted using standard content analysis methods. RESULTS: A total of 70 valid questionnaires were collected and analyzed. A large majority of the surveyed clinics had implemented MAS systems, with an average use of 1 or 2 functionalities, mainly "automated appointment confirmation and reminders" and "online appointment confirmation, modification, or cancellation by the patient." More extensive use of MAS systems appears to contribute to improved availability of medical care in these clinics, notwithstanding the effect of their application of advanced access principles. Also, greater integration of MAS systems into the clinic's electronic medical record system led to more extensive use. Our study further indicated that smaller clinics were less likely to undertake such integration and therefore showed less availability of medical care for their patients. Finally, our findings indicated that those clinics that showed a greater adoption rate and that used the provincial MAS system tended to be the highest-performing ones in terms of accessibility and availability of care. CONCLUSIONS: The main contribution of this study lies in the empirical demonstration that greater integration and assimilation of MAS systems in family medicine clinics lead to greater accessibility and availability of care for their patients and the general population. Valuable insight has also been provided on how to identify the clinics that would benefit most from such digital health solutions.

Trpv1 and Trpa1 are not essential for Psickle-like activity in red cells of the SAD mouse model of sickle cell disease.

The molecular identity of Psickle, the deoxygenation-activated cation conductance of the human sickle erythrocyte, remains unknown. We observed in human sickle red cells that inhibitors of TRPA1 and TRPV1 inhibited Psickle, whereas a TRPV1 agonist activated a Psickle-like cation current. These observations prompted us to test the roles of TRPV1 and TRPA1 in Psickle in red cells of the SAD mouse model of sickle cell disease. We generated SAD mice genetically deficient in either TRPV1 or TRPA1. SAD;Trpv1-/- and SAD;Trpa1-/- mice were indistinguishable in appearance, hematological indices, and osmotic fragility from SAD mice. We found that deoxygenation-activated cation currents remained robust in SAD;Trpa1-/- and SAD;Trpv1-/- mice. In addition, 45Ca2+ influx into SAD mouse red cells during prolonged deoxygenation was not reduced in red cells from SAD;Trpa1-/- and SAD;Trpv1-/- mice. We conclude that the nonspecific cation channels TRPA1 and TRPV1 are not required for deoxygenation to stimulate Psickle-like activity in red cells of the SAD mouse model of sickle cell disease. (159).

Advancing laboratory medicine in hospitals through health information exchange: a survey of specialist physicians in Canada.

BACKGROUND: Laboratory testing occupies a prominent place in health care. Information technology systems have the potential to empower laboratory experts and to enhance the interpretation of test results in order to better support physicians in their quest for better and safer patient care. This study sought to develop a better understanding of which laboratory information exchange (LIE) systems and features specialist physicians are using in hospital settings to consult their patients' laboratory test results, and what benefit they derive from such use. METHODS: As part of a broader research program on the use of health information exchange systems for laboratory medicine in Quebec, Canada, this study was designed as on online survey. Our sample is composed of 566 specialist physicians working in hospital settings, out of the 1512 physicians who responded to the survey (response rate of 17%). Respondents are representative of the targeted population of specialist physicians in terms of gender, age and hospital location. RESULTS: We first observed that 80% of the surveyed physicians used the province-wide interoperable electronic health records (iEHR) system and 93% used a laboratory results viewer (LRV) to consult laboratory test results and most (72%) use both systems to retrieve lab results. Next, our findings reveal important differences in the capabilities available in each type of system and in the use of these capabilities. Third, there are differences in the nature of the perceived benefits obtained from the use of each of these two systems. Last, the extent of use of an LRV is strongly influenced by the IT artefact itself (i.e., the hospital's LRV available capabilities) while the use of the provincial iEHR system is influenced by its organizational context (i.e. the hospital's size and location). CONCLUSIONS: The main contribution of this study lies in its insights into the role played by context in shaping physicians' choices about which laboratory information exchange systems to adopt and which features to use, and the different perceptions they have about benefits arising from such use. One related implication for practice is that success of LIE initiatives should not be solely assessed with basic usage statistics.

The master regulators Myc and p53 cellular signaling and functions in polycystic kidney disease.

The transcription factors Myc and p53 associated with oncogenesis play determinant roles in a human genetic disorder, autosomal dominant polycystic kidney disease (ADPKD), that was coined early in ADPKD etiology a «neoplasia in disguise ¼. These factors are interdependent master cell regulators of major biological processes including proliferation, apoptosis, cell growth, metabolism, inflammation, fibrosis and differentiation that are all modulated in ADPKD. Myc and p53 proteins evolved to respond and carry out overlapping functions via opposing mechanisms of action. Studies in human ADPKD kidneys, caused by mutations in the PKD1 or PKD2 genes, reveal reduced p53 expression and high expression of Myc in the cystic tubular epithelium. Myc and p53 via direct interaction act respectively, as transcriptional activator and repressor of PKD1 gene expression, consistent with increased renal PKD1 levels in ADPKD. Mouse models generated by Pkd1 and Pkd2 gene dosage dysregulation reproduce renal cystogenesis with activation of Myc expression and numerous signaling pathways, strikingly similar to those determined in human ADPKD. In fact, upregulation of renal Myc expression is also detected in virtually all non-orthologous animal models of PKD. A definitive causal connection of Myc with cystogenesis was established by renal overexpression of Myc in transgenic mice that phenocopies human ADPKD. The network of activated signaling pathways in human and mouse cystogenesis individually or in combination can target Myc as a central node of PKD pathogenesis. One or many of the multiple functions of Myc upon activation can play a role in every phases of ADPKD development and lend credence to the notion of "Myc addiction" for cystogenesis. We propose that the residual p53 levels are conducive to an ADPKD biological program without cancerogenesis while a "p53 dependent annihilation" mechanism would be permissive to oncogenesis. Of major importance, Myc ablation in orthologous mouse models or direct inhibition in non-orthologous mouse model significantly delays cystogenesis consistent with pharmacologic or genetic inhibition of Myc upstream regulator or downstream targets in the mouse. Together, these studies on PKD proteins upon dysregulation not only converged on Myc as a focal point but also attribute to Myc upregulation a causal and « driver ¼ role in pathogenesis. This review will present and discuss our current knowledge on Myc and p53, focused on PKD mouse models and ADPKD.

Combined genetic disruption of K-Cl cotransporters and Gardos channel KCNN4 rescues erythrocyte dehydration in the SAD mouse model of sickle cell disease.

Excessive red cell dehydration contributes to the pathophysiology of sickle cell disease (SCD). The densest fraction of sickle red cells (with the highest corpuscular hemoglobin concentration) undergoes the most rapid polymerization of deoxy-hemoglobin S, leading to accelerated cell sickling and increased susceptibility to endothelial activation, red cell adhesion, and vaso-occlusion. Increasing red cell volume in order to decrease red cell density can thus serve as an adjunct therapeutic goal in SCD. Regulation of circulating mouse red cell volume and density is mediated largely by the Gardos channel, KCNN4, and the K-Cl cotransporters, KCC3 and KCC1. Whereas inhibition of the Gardos channel in subjects with sickle cell disease increased red cell volume, decreased red cell density, and improved other hematological indices in subjects with SCD, specific KCC inhibitors have not been available for testing. We therefore investigated the effect of genetic inactivation of KCC3 and KCC1 in the SAD mouse model of sickle red cell dehydration, finding decreased red cell density and improved hematological indices. We describe here generation of mice genetically deficient in the three major red cell volume regulatory gene products, KCNN4, KCC3, and KCC1 in C57BL6 non-sickle and SAD sickle backgrounds. We show that combined loss-of-function of all three gene products in SAD mice leads to incrementally increased MCV, decreased CHCM and % hyperchromic cells, decreased red cell density (phthalate method), increased resistance to hypo-osmotic lysis, and increased cell K content. The data show that combined genetic deletion of the Gardos channel and K-Cl cotransporters in a mouse SCD model decreases red cell density and improves several hematological parameters, supporting the strategy of combined pharmacological inhibition of these ion transport pathways in the adjunct treatment of human SCD.

c-Myc is a regulator of the PKD1 gene and PC1-induced pathogenesis.

Autosomal dominant polycystic kidney disease (ADPKD) is among the most common monogenic disorders mainly associated with PKD1/PC1 mutations. We show herein that renal regulation in Pc1 dosage-reduced and -increased mouse models converge toward stimulation of c-Myc expression along with ß-catenin, delineating c-Myc as a key Pkd1 node in cystogenesis. Enhanced renal c-Myc-induced ADPKD in SBM transgenic mice lead conversely to striking upregulation of Pkd1/Pc1 expression and ß-catenin activation, lending credence for reciprocal crosstalk between c-Myc and Pc1. In adult SBM kidneys, c-Myc is strongly enriched on Pkd1 promoter with RNA pol II, consistent with Pkd1 upregulation during cystogenesis. Similar c-Myc direct binding at birth uncovers an equivalent role on Pkd1 regulation during renal developmental program. Concurrent with enriched c-Myc binding, recruitment of active chromatin modifying co-factors by c-Myc at the Pkd1 regulatory region probably opens chromatin to stimulate transcription. A similar transcriptional activation by c-Myc is also likely operant on endogenous human PKD1 gene from our transactivation analysis in response to human c-MYC upregulation. Genetic ablation of c-Myc in Pc1-reduced and -increased mouse models significantly attenuates cyst growth, proliferation and PKD progression. Our study determined a dual role for c-Myc, as a major contributor in Pc1-induced cystogenesis and in a feed-forward regulatory Pkd1-c-Myc loop mechanism that may also prevail in human ADPKD.

Laboratory testing in primary care: A systematic review of health IT impacts.

INTRODUCTION: Laboratory testing in primary care is a fundamental process that supports patient management and care. Any breakdown in the process may alter clinical information gathering and decision-making activities and can lead to medical errors and potential adverse outcomes for patients. Various information technologies are being used in primary care with the goal to support the process, maximize patient benefits and reduce medical errors. However, the overall impact of health information technologies on laboratory testing processes has not been evaluated. OBJECTIVES: To synthesize the positive and negative impacts resulting from the use of health information technology in each phase of the laboratory 'total testing process' in primary care. METHODS: We conducted a systematic review. Databases including Medline, PubMed, CINAHL, Web of Science and Google Scholar were searched. Studies eligible for inclusion reported empirical data on: 1) the use of a specific IT system, 2) the impacts of the systems to support the laboratory testing process, and were conducted in 3) primary care settings (including ambulatory care and primary care offices). Our final sample consisted of 22 empirical studies which were mapped to a framework that outlines the phases of the laboratory total testing process, focusing on phases where medical errors may occur. RESULTS: Health information technology systems support several phases of the laboratory testing process, from ordering the test to following-up with patients. This is a growing field of research with most studies focusing on the use of information technology during the final phases of the laboratory total testing process. The findings were largely positive. Positive impacts included easier access to test results by primary care providers, reduced turnaround times, and increased prescribed tests based on best practice guidelines. Negative impacts were reported in several studies: paper-based processes employed in parallel to the electronic process increased the potential for medical errors due to clinicians' cognitive overload; systems deemed not reliable or user-friendly hampered clinicians' performance; and organizational issues arose when results tracking relied on the prescribers' memory. DISCUSSION: The potential of health information technology lies not only in the exchange of health information, but also in knowledge sharing among clinicians. This review has underscored the important role played by cognitive factors, which are critical in the clinician's decision-making, the selection of the most appropriate tests, correct interpretation of the results and efficient interventions. CONCLUSIONS: By providing the right information, at the right time to the right clinician, many IT solutions adequately support the laboratory testing process and help primary care clinicians make better decisions. However, several technological and organizational barriers require more attention to fully support the highly fragmented and error-prone process of laboratory testing.

Improving performance in the ED through laboratory information exchange systems.

BACKGROUND: The accessibility of laboratory test results is crucial to the performance of emergency departments and to the safety of patients. This study aims to develop a better understanding of which laboratory information exchange (LIE) systems emergency care physicians (ECPs) are using to consult their patients' laboratory test results and which benefits they derive from such use. METHODS: A survey of 163 (36%) ECPs in Quebec was conducted in collaboration with the Quebec's Department of Health and Social Services. Descriptive statistics, chi-square tests, cluster analyses, and ANOVAs were conducted. RESULTS: The great majority of respondents indicated that they use several LIE systems including interoperable electronic health record (iEHR) systems, laboratory results viewers (LRVs), and emergency department information systems (EDIS) to consult their patients' laboratory results. Three distinct profiles of LIE users were observed. The extent of LIE usage was found to be primarily determined by the functional design differences between LIE systems available in the EDs. Our findings also indicate that the more widespread LIE usage, the higher the perceived benefits. More specifically, physicians who make extensive use of iEHR systems and LRVs obtain the widest range of benefits in terms of efficiency, quality, and safety of emergency care. CONCLUSIONS: Extensive use of LIE systems allows ECPs to better determine and monitor the health status of their patients, verify their diagnostic assumptions, and apply evidence-based practices in laboratory medicine. But for such benefits to be possible, ECPs must be provided with LIE systems that produce accurate, up-to-date, complete, and easy-to-interpret information.

Casein kinase 1ε and 1α as novel players in polycystic kidney disease and mechanistic targets for (R)-roscovitine and (S)-CR8.

Following the discovery of (R)-roscovitine's beneficial effects in three polycystic kidney disease (PKD) mouse models, cyclin-dependent kinases (CDKs) inhibitors have been investigated as potential treatments. We have used various affinity chromatography approaches to identify the molecular targets of roscovitine and its more potent analog (S)-CR8 in human and murine polycystic kidneys. These methods revealed casein kinases 1 (CK1) as additional targets of the two drugs. CK1ε expression at the mRNA and protein levels is enhanced in polycystic kidneys of 11 different PKD mouse models as well as in human polycystic kidneys. A shift in the pattern of CK1α isoforms is observed in all PKD mouse models. Furthermore, the catalytic activities of both CK1ε and CK1α are increased in mouse polycystic kidneys. Inhibition of CK1ε and CK1α may thus contribute to the long-lasting attenuating effects of roscovitine and (S)-CR8 on cyst development. CDKs and CK1s may constitute a dual therapeutic target to develop kinase inhibitory PKD drug candidates.

Approaches for Analysis of Erythroid Cell Parameters and Hemoglobinopathies in Mouse Models.

Over the last decades several mouse models of human hemoglobin disorders have been and continue to be generated. This chapter aims at describing various approaches to evaluate the global red blood cell properties in mouse models of human hemoglobin disorders, in particular thalassemia and sickle cell disease. Analysis of erythroid parameters provides insights into the RBC physiologic or pathophysiologic status. Mice expressing both murine and human globin genes can be investigated using adapted protocols provided herein.

Cardiorespiratory pathogenesis of sickle cell disease in a mouse model.

The nature and development of cardiorespiratory impairments associated with sickle cell disease are poorly understood. Given that the mechanisms of these impairments cannot be addressed adequately in clinical studies, we characterized cardiorespiratory pathophysiology from birth to maturity in the sickle cell disease SAD mouse model. We identified two critical phases of respiratory dysfunction in SAD mice; the first prior to weaning and the second in adulthood. At postnatal day 3, 43% of SAD mice showed marked apneas, anemia, and pulmonary vascular congestion typical of acute chest syndrome; none of these mice survived to maturity. The remaining SAD mice had mild lung histological changes in room air with an altered respiratory pattern, seizures, and a high rate of death in response to hypoxia. Approximately half the SAD mice that survived to adulthood had an identifiable respiratory phenotype including baseline tachypnea at 7-8 months of age, restrictive lung disease, pulmonary hypertension, cardiac enlargement, lower total lung capacity, and pulmonary vascular congestion. All adult SAD mice demonstrated impairments in exercise capacity and response to hypoxia, with a more severe phenotype in the tachypneic mice. The model revealed distinguishable subgroups of SAD mice with cardiorespiratory pathophysiology mimicking the complications of human sickle cell disease.

Genome-wide association study of erythrocyte density in sickle cell disease patients.

Deoxy-hemoglobin S polymerization into rigid fibers is the direct cause of the clinical sequelae observed in sickle cell disease (SCD). The rate of polymerization of sickle hemoglobin is determined primarily by intracellular hemoglobin concentration, itself dependent on the amount of sickle hemoglobin and on red blood cell (RBC) volume. Dense, dehydrated RBC (DRBC) are observed in SCD patients, and their number correlates with hemolytic parameters and complications such as renal dysfunction, leg ulcers and priapism. To identify new genes involved in RBC hydration in SCD, we performed the first genome-wide association study for DRBC in 374 sickle cell anemia (HbSS) patients. We did not find genome-wide significant results, indicating that variants that modulate DRBC have modest-to-weak effects. A secondary analysis demonstrated a nominal association (P=0.003) between DRBC in SCD patients and a variant associated with mean corpuscular hemoglobin concentration (MCHC) in non-anemic individuals. This intronic variant controls the expression of ATP2B4, the main calcium pump in erythrocytes. Our study highlights ATP2B4 as a promising target for modulation of RBC hydration in SCD patients.

Ceiling effect in EMR system assimilation: a multiple case study in primary care family practices.

BACKGROUND: There has been indisputable growth in adoption of electronic medical record (EMR) systems in the recent years. However, physicians' progress in using these systems has stagnated when measured with maturity scales. While this so-called ceiling effect has been observed and its consequences described in previous studies, there is a paucity of research on the elements that could explain such an outcome. We first suggest that in the context of EMR systems we are in presence of a "tiered ceiling effect" and then we show why such phenomenon occurs. METHODS: We conducted in-depth case studies in three primary care medical practices in Canada where physicians had been using EMR systems for 3 years or more. A total of 37 semi-structured interviews were conducted with key informants: family physicians (about half of the interviews), nurses, secretaries, and administrative managers. Additional information was obtained through notes taken during observations of users interacting with their EMR systems and consultation of relevant documents at each site. We used abductive reasoning to infer explanations of the observed phenomenon by going back and forth between the case data and conceptual insights. RESULTS: Our analysis shows that a ceiling effect has taken place in the three clinics. We identified a set of conditions preventing the users from overcoming the ceiling. In adopting an EMR system, all three clinics essentially sought improved operational efficiency. This had an influence on the criteria used to assess the systems available on the market and eventually led to the adoption of a system that met the specified criteria without being optimal. Later, training sessions focussed on basic functionalities that minimally disturbed physicians' habits while helping their medical practices become more efficient. Satisfied with the outcome of their system use, physicians were likely to ignore more advanced EMR system functionalities. This was because their knowledge about EMR systems came almost exclusively from a single source of information: their EMR system vendors. This knowledge took the form of interpretations of what the innovation was (know-what), with little consideration of the rationales for innovation adoption (know-why) or hands-on strategies for adopting, implementing and assimilating the innovation in the organization (know-how). CONCLUSIONS: This paper provides a holistic view of the technological innovation process in primary care and contends that limited learning, satisficing behaviours and organizational inertia are important factors leading to the ceiling effect frequently experienced in the EMR system assimilation phase.

Bicaudal C mutation causes myc and TOR pathway up-regulation and polycystic kidney disease-like phenotypes in Drosophila.

Progressive cystic kidney degeneration underlies diverse renal diseases, including the most common cause of kidney failure, autosomal dominant Polycystic Kidney Disease (PKD). Genetic analyses of patients and animal models have identified several key drivers of this disease. The precise molecular and cellular changes underlying cystogenesis remain, however, elusive. Drosophila mutants lacking the translational regulator Bicaudal C (BicC, the fly ortholog of vertebrate BICC1 implicated in renal cystogenesis) exhibited progressive cystic degeneration of the renal tubules (so called "Malpighian" tubules) and reduced renal function. The BicC protein was shown to bind to Drosophila (d-) myc mRNA in tubules. Elevation of d-Myc protein levels was a cause of tubular degeneration in BicC mutants. Activation of the Target of Rapamycin (TOR) kinase pathway, another common feature of PKD, was found in BicC mutant flies. Rapamycin administration substantially reduced the cystic phenotype in flies. We present new mechanistic insight on BicC function and propose that Drosophila may serve as a genetically tractable model for dissecting the evolutionarily-conserved molecular mechanisms of renal cystogenesis.

microRNA-17 family promotes polycystic kidney disease progression through modulation of mitochondrial metabolism.

Autosomal dominant polycystic kidney disease (ADPKD) is the most frequent genetic cause of renal failure. Here we identify miR-17 as a target for the treatment of ADPKD. We report that miR-17 is induced in kidney cysts of mouse and human ADPKD. Genetic deletion of the miR-17∼92 cluster inhibits cyst proliferation and PKD progression in four orthologous, including two long-lived, mouse models of ADPKD. Anti-miR-17 treatment attenuates cyst growth in short-term and long-term PKD mouse models. miR-17 inhibition also suppresses proliferation and cyst growth of primary ADPKD cysts cultures derived from multiple human donors. Mechanistically, c-Myc upregulates miR-17∼92 in cystic kidneys, which in turn aggravates cyst growth by inhibiting oxidative phosphorylation and stimulating proliferation through direct repression of Pparα. Thus, miR-17 family is a promising drug target for ADPKD, and miR-17-mediated inhibition of mitochondrial metabolism represents a potential new mechanism for ADPKD progression.

Acute kidney injury induces hallmarks of polycystic kidney disease.

Acute kidney injury (AKI) and autosomal dominant polycystic kidney disease (ADPKD) are considered separate entities that both frequently cause renal failure. Since ADPKD appears to depend on a polycystin-1 (Pc1) or Pc2 dosage mechanism, we investigated whether slow progression of cystogenesis in two Pkd1 transgenic mouse models can be accelerated with moderate ischemia-reperfusion injury (IRI). Transient unilateral left ischemic kidneys in both nontransgenic and transgenic mice reproducibly develop tubular dilatations, cysts, and typical PKD cellular defects within 3 mo post-IRI. Similar onset and severity of IRI induced-cystogenesis independently of genotype revealed that IRI is sufficient to promote renal cyst formation; however, this response was not further amplified by the transgene in Pkd1 mouse models. The IRI nontransgenic and transgenic kidneys showed from 16 days post-IRI strikingly increased and sustained Pkd1/Pc1 (>3-fold) and Pc2 (>8-fold) expression that can individually be cystogenic in mice. In parallel, long-term and important stimulation of hypoxia-inducible factor 1α expression was induced as in polycystic kidney disease. While mammalian target of rapamycin signaling is activated, stimulation of the Wnt pathway, with markedly increased active ß-catenin and c-Myc expression in IRI renal epithelium, uncovered a similar regulatory cystogenic response shared by IRI and ADPKD. Our study demonstrates that long-term AKI induces cystogenesis and cross talk with ADPKD Pc1/Pc2 pathogenic signaling.

The Role of G-Protein-Coupled Receptor Proteolysis Site Cleavage of Polycystin-1 in Renal Physiology and Polycystic Kidney Disease.

Polycystin-1 (PC1) plays an essential role in renal tubular morphogenesis, and PC1 dysfunction causes human autosomal dominant polycystic kidney disease. A fundamental characteristic of PC1 is post-translational modification via cleavage at the juxtamembrane GPCR proteolysis site (GPS) motif that is part of the larger GAIN domain. Given the considerable biochemical complexity of PC1 molecules generated in vivo by this process, GPS cleavage has several profound implications on the intracellular trafficking and localization in association with their particular function. The critical nature of GPS cleavage is further emphasized by the increasing numbers of PKD1 mutations that significantly affect this cleavage process. The GAIN domain with the GPS motif therefore represents the key structural element with fundamental importance for PC1 and might be polycystic kidney disease's (PKD) Achilles' heel in a large spectrum of PKD1 missense mutations. We highlight the central roles of PC1 cleavage for the regulation of its biogenesis, intracellular trafficking and function, as well as its significance in polycystic kidney disease.