Le canal sodique voltage-dependant des fibres nerveuses et musculaires du calmar Loligo forbesi. Purification, reconstitution fonctionnelle et approche en biologie moleculaire

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : T 81991 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

A204E mutation in Nav1.4 DIS3 exerts gain- and loss-of-function effects that lead to periodic paralysis combining hyper- with hypo-kalaemic signs

Abstract Periodic paralyses (PP) are characterized by episodic muscle weakness and are classified into the distinct hyperkalaemic (hyperPP) and hypokalaemic (hypoPP) forms. The dominantly-inherited form of hyperPP is caused by overactivity of Nav1.4 — the skeletal muscle voltage-gated sodium channel. Familial hypoPP results from a leaking gating pore current induced by dominant mutations in Nav1.4 or Cav1.1, the skeletal muscle voltage-gated calcium channel. Here, we report an individual with clinical signs of hyperPP and hypokalaemic episodes of muscle paralysis who was heterozygous for the novel p.Ala204Glu (A204E) substitution located in one region of Nav1.4 poor in disease-related variations. A204E induced a significant decrease of sodium current density, increased the window current, enhanced fast and slow inactivation of Nav1.4, and did not cause gating pore current in functional analyses. Interestingly, the negative impact of A204E on Nav1.4 activation was strengthened in low concentration of extracellular K+. Our data prove the existence of a phenotype combining signs of hyperPP and hypoPP due to dominant Nav1.4 mutations. The hyperPP component would result from gain-of-function effects on Nav1.4 and the hypokalemic episodes of paralysis from loss-of-function effects strengthened by low K+. Our data argue for a non-negligible role of Nav1.4 loss-of-function in familial hypoPP

Defining a Mutational Panel and Predicting the Prevalence of Cystic Fibrosis in Oman

Objectives: Cystic fibrosis transmembrane conductance regulator (CFTR) mutations form distinct mutational panels in different populations and subgroups. The frequency of cystic fibrosis (CF) mutations and prevalence are unknown in Oman. This study aimed to elucidate the mutational panel and prevalence of CF for the North Al Batinah (NAB) region in Oman and to estimate the national prevalence of CF based on the carrier screening of unrelated volunteers. Methods: The study included retrospective and prospective analyses of CF cases in the NAB region for 1998–2012. Genetic analysis of disease-causing mutations was conducted by screening of the entire coding sequence and exon-intron borders. The obtained mutational panel was used for the carrier screening of 408 alleles of unrelated and unaffected Omani individuals. Results: S549R and F508del were the major mutations, accounting for 89% of mutations in the patient population. Two private mutations, c.1733-1734delTA and c.1175T>G, were identified in the patient cohort. Two carriers, one for F508del and another for S549R, were identified by screening of the volunteer cohort, resulting in a predicted prevalence for Oman of 1 in 8,264. The estimated carrier frequency of CF in Oman was 1 in 94. The carrier frequency in the NAB region was 3.9 times higher. Conclusion: The mutational panel for the NAB region and the high proportion of S549R mutations emphasises the need for specific screening for CF in Oman. The different distribution of allele frequencies suggests a spatial clustering of CF in the NAB region

Functional and clinical characterization of KCNJ2 mutations associated with LQT7 (Andersen syndrome)

Andersen syndrome (AS) is a rare, inherited disorder characterized by periodic paralysis, long QT (LQT) with ventricular arrhythmias, and skeletal developmental abnormalities. We recently established that AS is caused by mutations in KCNJ2, which encodes the inward rectifier K(+) channel Kir2.1. In this report, we characterized the functional consequences of three novel and seven previously described KCNJ2 mutations using a two-microelectrode voltage-clamp technique and correlated the findings with the clinical phenotype. All mutations resulted in loss of function and dominant-negative suppression of Kir2.1 channel function. In mutation carriers, the frequency of periodic paralysis was 64% and dysmorphic features 78%. LQT was the primary cardiac manifestation, present in 71% of KCNJ2 mutation carriers, with ventricular arrhythmias present in 64%. While arrhythmias were common, none of our subjects suffered sudden cardiac death. To gain insight into the mechanism of arrhythmia susceptibility, we simulated the effect of reduced Kir2.1 using a ventricular myocyte model. A reduction in Kir2.1 prolonged the terminal phase of the cardiac action potential, and in the setting of reduced extracellular K(+), induced Na(+)/Ca(2+) exchanger–dependent delayed afterdepolarizations and spontaneous arrhythmias. These findings suggest that the substrate for arrhythmia susceptibility in AS is distinct from the other forms of inherited LQT syndrome

A regionally based precision medicine implementation initiative in North Africa:The PerMediNA consortium

International audiencePrecision Medicine is being increasingly used in the developed world to improve health care. While several Precision Medicine (PM) initiatives have been launched worldwide, their implementations have proven to be more challenging particularly in low- and middle-income countries. To address this issue, the “Personalized Medicine in North Africa” initiative (PerMediNA) was launched in three North African countries namely Tunisia, Algeria and Morocco. PerMediNA is coordinated by Institut Pasteur de Tunis together with the French Ministry for Europe and Foreign Affairs, with the support of Institut Pasteur in France. The project is carried out along with Institut Pasteur d’Algérie and Institut Pasteur du Maroc in collaboration with national and international leading institutions in the field of PM including Institut Gustave Roussy in Paris. PerMediNA aims to assess the readiness level of PM implementation in North Africa, to strengthen PM infrastructure, to provide workforce training, to generate genomic data on North African populations, to implement cost effective, affordable and sustainable genetic testing for cancer patients and to inform policy makers on how to translate research knowledge into health products and services. Gender equity and involvement of young scientists in this implementation process are other key goals of the PerMediNA project.In this paper, we are describing PerMediNA as the first PM implementation initiative in North Africa. Such initiatives contribute significantly in shortening existing health disparities and inequities between developed and developing countries and accelerate access to innovative treatments for global health