The Quebec Congenital Heart Disease Registry: A Model of Prospective Databank to Facilitate Research in Congenital Cardiology.

Background: A national registry of congenital heart disease (CHD) would facilitate project initiation, decrease costs, increase statistical power, and avoid duplication. Establishing such registries poses numerous challenges, but the current Canadian research ecosystem in CHD is well positioned to meet them. We assessed the feasibility of building a province-wide CHD registry by automatically identifying people with CHD and extracting their native cardiac anatomy from multiple clinical data sources, without the need for manual data entry. Methods: We designed a CHD registry of all fetuses and children with at least 1 echocardiographic report confirming CHD since 2000. We interfaced the registry with several clinical and echocardiography data sources from all paediatric cardiology programmes in Québec. Results: We extracted 885,287 echocardiogram reports and 70,121 clinical records. We identified CHD in 43,452 children and 4682 fetuses. There were 1128 (2.3%) cases with files in multiple institutions, and patients with more complex CHD were 3 times more likely to be seen in more than 1 institution. So far, the registry has been used to build and link CHD cohorts for 7 distinct projects. Conclusions: We demonstrated the feasibility of a baseline CHD registry in Québec without the need for manual data entry, in which other CHD research projects could be nested. This could serve as a blueprint to expand the registry and to develop an integrated approach where data gathered in caring for patients with CHD serve as data layers that incrementally contribute to a national cohort, for which data remain easily accessible and usable.

Contexte: Un registre national des cardiopathies congénitales (CC) pourrait faciliter le lancement de projets de recherche, en diminuer les coûts, en améliorer la puissance statistique tout en évitant les redondances. La mise en place de tels registres pose de nombreux défis, mais l'écosystème de recherche canadien dans le domaine de la CC est bien placé pour y répondre. Nous avons évalué la faisabilité de la mise en place d'un registre des CC à l'échelle provinciale par l'identification automatique des personnes atteintes de CC et l'extraction de leur anatomie cardiaque native à partir de plusieurs sources de données cliniques, sans nécessiter de saisie manuelle de données. Méthodologie: Nous avons conçu un registre des CC incluant tous les fœtus et les enfants pour qui au moins un rapport d'évaluation électrocardiographique confirmait la présence d'une CC depuis 2000. Le registre a été mis en relation avec plusieurs sources de données cliniques et échocardiographiques provenant de tous les programmes en cardiologie pédiatrique au Québec. Résultats: Nous avons extrait 885 287 rapports d'échocardiographie et 70 121 dossiers cliniques. La présence d'une CC a été établie chez 43 452 enfants et 4 682 fœtus. Dans 1 128 cas (2,3 %), un dossier existait dans plus d'un établissement. Les patients présentant des CC plus complexes étaient 3 fois plus susceptibles d'être suivis dans plus d'un établissement. Jusqu'à présent, le registre a été utilisé pour établir et mettre en relation des cohortes de patients atteints de CC pour sept projets de recherche distincts. Conclusions: Nous avons démontré la faisabilité de la mise en place d'un registre de référence des CC au Québec sans recours à la saisie manuelle de données, dans lequel peuvent se nicher d'autres projets de recherche sur les CC. Notre démarche pourrait servir de prototype pour une expansion du registre et pour une approche d'intégration des données recueillies dans la prestation de soins aux patients atteints de CC, afin de former des couches de données qui s'ajoutent au fur et à mesure à une cohorte nationale, avec des données faciles à obtenir et à utiliser.

Further evidence for functional recovery of AQP2 mutations associated with nephrogenic diabetes insipidus.

Aquaporin-2 (AQP2) is a homotetrameric water channel responsible for the final water reuptake in the kidney. Disease-causing AQP2 mutations induce nephrogenic diabetes insipidus (NDI), a condition that challenges the bodily water balance by producing large urinary volumes. In this study, we characterize three new AQP2 mutations identified in our lab from NDI patients (A120D, A130V, T179N) along the previously reported A47V variant. Using Xenopus oocytes, we compared the key functional and biochemical features of these mutations against classical recessive (R187C) and dominant (R254Q) forms, and once again found clear functional recovery features (increased protein stability and function) for all mutations under study. This behaviour, attributed to heteromerization to wt-AQP2, challenge the classical model to NDI which often depicts recessive mutations as ill-structured proteins unable to oligomerize. Consequently, we propose a revised model to the cell pathophysiology of AQP2-related NDI which accounts for the functional recovery of recessive AQP2 mutations.

Endothelial deletion of PKCδ prevents VEGF inhibition and restores blood flow reperfusion in diabetic ischemic limb.

AIMS: Peripheral artery disease is a complication of diabetes leading to critical hindlimb ischemia. Diabetes-induced inhibition of VEGF actions is associated with the activation of protein kinase Cδ (PKCδ). We aim to specifically investigate the role of PKCδ in endothelial cell (EC) function and VEGF signaling. METHODS: Nondiabetic and diabetic mice, with (ec-Prkcd-/-) or without (ec-Prkcdf/f) endothelial deletion of PKCδ, underwent femoral artery ligation. Blood flow reperfusion was assessed up to 4 weeks post-surgery. Capillary density, EC apoptosis and VEGF signaling were evaluated in the ischemic muscle. Src homology region 2 domain-containing phosphatase-1 (SHP-1) phosphatase activity was assessed in vitro using primary ECs. RESULTS: Ischemic muscle of diabetic ec-Prkcdf/f mice exhibited reduced blood flow reperfusion and capillary density while apoptosis increased as compared to nondiabetic ec-Prkcdf/f mice. In contrast, blood flow reperfusion and capillary density were significantly improved in diabetic ec-Prkcd-/- mice. VEGF signaling pathway was restored in diabetic ec-Prkcd-/- mice. The deletion of PKCδ in ECs prevented diabetes-induced VEGF unresponsiveness through a reduction of SHP-1 phosphatase activity. CONCLUSIONS: Our data provide new highlights in mechanisms by which PKCδ activation in EC contributed to poor collateral vessel formation, thus, offering novel therapeutic targets to improve angiogenesis in the diabetic limb.

New autosomal recessive mutations in aquaporin-2 causing nephrogenic diabetes insipidus through deficient targeting display normal expression in Xenopus oocytes.

Aquaporin-2 (AQP2), located at the luminal side of the collecting duct principal cells, is a water channel responsible for the final concentration of urine. Lack of function, often occurring through mistargeting of mutated proteins, induces nephrogenic diabetes insipidus (NDI), a condition characterized by large urinary volumes. In the present study, two new mutations (K228E and V24A) identified in NDI-affected individuals from distinct families along with the already reported R187C were analysed in comparison to the wild-type protein (AQP2-wt) using Xenopus laevis oocytes and a mouse collecting duct cell-line (mIMCD-3). Initial data in oocytes showed that all mutations were adequately expressed at reduced levels when compared to AQP2-wt. K228E and V24A were found to be properly targeted at the plasma membrane and exhibited adequate functionality similar to AQP2-wt, as opposed to R187C which was retained in internal stores and was thus inactive. In coexpression studies using oocytes, R187C impeded the functionality of all other AQP2 variants while combinations with K228E, V24A and AQP2-wt only showed additive functionalities. When expressed in mIMCD-3 cells, forskolin treatment efficiently promoted the targeting of AQP2-wt at the plasma membrane (>90%) while K228E only weakly responded to the same treatment (approximately 20%) and both V24A and R187C remained completely insensitive to the treatment. We concluded that both V24A and K228E are intrinsically functional water channels that lack a proper response to vasopressin, which leads to NDI as found in both compound mutations studied (K228E + R187C and V24A + R187C). The discrepancies in plasma membrane targeting response found in both expression systems stress the need to evaluate such data using mammalian cell systems.

Characterization of D150E and G196D aquaporin-2 mutations responsible for nephrogenic diabetes insipidus: importance of a mild phenotype.

Aquaporin-2 (AQP2) is a water channel responsible for the final water reabsorption in renal collecting ducts. Alterations in AQP2 function induce nephrogenic diabetes insipidus (NDI), a condition characterized by severe polyuria and polydipsia. Three patients affected with severe NDI, who were compound heterozygous for the AQP2 mutations D150E and G196D, are presented here along with a mildly affected D150E homozygous patient from another family. Using Xenopus oocytes as an expression system, these two mutations (G196D and D150E) were compared with the wild-type protein (AQP2-wt) for functional activity (water flux analysis), protein maturation, and plasma membrane targeting. AQP2-wt induces a major increase in water permeability (P(f) = 47.4 +/- 12.2 x 10(-4) cm/s) whereas D150E displays intermediate P(f) values (P(f) = 12.5 +/- 3.0 x 10(-4) cm/s) and G196D presents no specific water flux, similar to controls (P(f) = 2.1 +/- 0.8 x 10(-4) cm/s and 2.2 +/- 0.7 x 10(-4) cm/s, respectively). Western blot and immunocytochemical evaluations show protein targeting that parallels activity levels with AQP2-wt adequately targeted to the plasma membrane, partial targeting for D150E, and complete sequestration of G196D within intracellular compartments. When coinjecting AQP2-wt with mutants, no (AQP2-wt + D150E) or partial (AQP2-wt + G196D) reduction of water flux were observed compared with AQP2-wt alone, whereas complete loss of function was found when both mutants were coinjected. These results essentially recapitulate the clinical profiles of the family members, showing a typical dominant negative effect when G196D is coinjected with either AQP2-wt or D150E but not between AQP2-wt and D150E mutant.

Elaboration of a novel technique for purification of plasma membranes from Xenopus laevis oocytes.

Over the past two decades, Xenopus laevis oocytes have been widely used as an expression system to investigate both physiological and pathological properties of membrane proteins such as channels and transporters. Past studies have clearly shown the key implications of mistargeting in relation to the pathogenesis of these proteins. To unambiguously determine the plasma membrane targeting of a protein, a thorough purification technique becomes essential. Unfortunately, available techniques are either too cumbersome, technically demanding, or require large amounts of material, all of which are not adequate when using oocytes individually injected with cRNA or DNA. In this article, we present a new technique that permits excellent purification of plasma membranes from X. laevis oocytes. This technique is fast, does not require particular skills such as peeling of vitelline membrane, and permits purification of multiple samples from as few as 10 and up to >100 oocytes. The procedure combines partial digestion of the vitelline membrane, polymerization of the plasma membrane, and low-speed centrifugations. We have validated this technique essentially with Western blot assays on three plasma membrane proteins [aquaporin (AQP)2, Na(+)-glucose cotransporter (SGLT)1, and transient receptor potential vanilloid (TRPV)5], using both wild-type and mistargeted forms of the proteins. Purified plasma membrane fractions were easily collected, and samples were found to be adequate for Western blot identification.