Cardiac involvement in patient-specific induced pluripotent stem cells of myotonic dystrophy type 1: unveiling the impact of voltage-gated sodium channels

Myotonic dystrophy type 1 (DM1) is a genetic disorder that causes muscle weakness and myotonia. In DM1 patients, cardiac electrical manifestations include conduction defects and atrial fibrillation. DM1 results in the expansion of a CTG transcribed into CUG-containing transcripts that accumulate in the nucleus as RNA foci and alter the activity of several splicing regulators. The underlying pathological mechanism involves two key RNA-binding proteins (MBNL and CELF) with expanded CUG repeats that sequester MBNL and alter the activity of CELF resulting in spliceopathy and abnormal electrical activity. In the present study, we identified two DM1 patients with heart conduction abnormalities and characterized their hiPSC lines. Two differentiation protocols were used to investigate both the ventricular and the atrial electrophysiological aspects of DM1 and unveil the impact of the mutation on voltage-gated ion channels, electrical activity, and calcium homeostasis in DM1 cardiomyocytes derived from hiPSCs. Our analysis revealed the presence of molecular hallmarks of DM1, including the accumulation of RNA foci and sequestration of MBNL1 in DM1 hiPSC-CMs. We also observed mis-splicing of SCN5A and haploinsufficiency of DMPK. Furthermore, we conducted separate characterizations of atrial and ventricular electrical activity, conduction properties, and calcium homeostasis. Both DM1 cell lines exhibited reduced density of sodium and calcium currents, prolonged action potential duration, slower conduction velocity, and impaired calcium transient propagation in both ventricular and atrial cardiomyocytes. Notably, arrhythmogenic events were recorded, including both ventricular and atrial arrhythmias were observed in the two DM1 cell lines. These findings enhance our comprehension of the molecular mechanisms underlying DM1 and provide valuable insights into the pathophysiology of ventricular and atrial involvement

A Proton Leak Current through the Cardiac Sodium Channel Is Linked to Mixed Arrhythmia and the Dilated Cardiomyopathy Phenotype

Cardiac Na+ channels encoded by the SCN5A gene are essential for initiating heart beats and maintaining a regular heart rhythm. Mutations in these channels have recently been associated with atrial fibrillation, ventricular arrhythmias, conduction disorders, and dilated cardiomyopathy (DCM)

Réfléchir les pratiques face à l'urgence écologique

L’ergothérapie soutient la participation des personnes dans leurs occupations. Comment encourager ces activités dans un environnement de bouleversements écologiques ? La filière ergothérapie de la HETSL s’est emparée de cette question urgente

Effect of cream pasteurization, microfiltration and enzymatic proteolysis on in vitro cholesterol-lowering activity of buttermilk solids

The lipids and proteins of buttermilk solids have been associated with several potential health benefits. In this work, the effect of cream pasteurization, microfiltration (MF) and enzymatic proteolysis on the chemical composition and cholesterol-lowering activity of buttermilk solids was studied. Buttermilk was made from pasteurized or unpasteurized cream and fractionated using a 0.5-μm MF membrane or treated with pepsin or pepsin followed by trypsin. The cholesterol-lowering activity of the products obtained was measured as micellar solubility of cholesterol in vitro. This value was reduced significantly by 57.1% of the control in the presence of raw-cream buttermilk, while buttermilk from pasteurized cream had a much lower impact (reduction of 17.0%). These results suggest a strong inhibitory effect of components in raw-cream buttermilk on in vitro micellar solubility of cholesterol. MF retentate and permeate of buttermilks made from either cream had smaller effects on micellar solubility. Enzymatic hydrolysis of buttermilk made from pasteurized cream seemed to restore the lost cholesterol-lowering activity

Parcours de vie et parcours scolaires des jeunes décrocheurs âgés de 16 à 18 ans qui raccrochent dans un Centre d’éducation des adultes : retombées pour la pratique du travail social

De plus en plus de jeunes âgés entre 16 et 18 ans fréquentent les Centres d’éducation des adultes (CEA) afin d’obtenir un diplôme qualifiant. Le visage des CEA s’est donc grandement modifié au cours des dernières années, accueillant de plus en plus de jeunes dont les écoles du secteur régulier ne correspondaient pas à leurs besoins, à leur rythme et à leurs capacités d’apprentissage. Dans le but de mieux comprendre la réalité de ces jeunes et de documenter le portrait de leur parcours de vie et de leur parcours scolaire ainsi que des motifs qui les poussent à raccrocher dans une école de « seconde chance », une étude qualitative a été réalisée auprès de 27 jeunes âgés de moins de 18 ans (14 filles et 13 garçons). Cette étude, qui repose sur la technique des entrevues semi-dirigées, permet de constater que de nombreuses difficultés et embûches tant personnelles, académiques que sociales ont été vécues tout au long de leur parcours scolaire. Les données de cette étude permettent aussi de constater que les facteurs de risque à l’origine de l’abandon des études dans les écoles du secteur jeune varient en fonction du sexe des répondants et, qu’en général, l’apparition des difficultés académiques, le manque de motivation et les facteurs de risque tant intrinsèques (ex : difficultés d’apprentissage, troubles de comportement) qu’extrinsèques (ex : abus ou négligence familiale, intimidation) associés au décrochage scolaire sont apparus dès le deuxième cycle du primaire (vers l’âge de neuf ans). Cette communication permettra d’identifier des pistes d’intervention qui pourraient être mises en place par les intervenants sociaux travaillant en milieu scolaire, dont la mission est entre autre d’éviter le décrochage scolaire

Biophysical properties of NaV1.5 channels from atrial-like and ventricular-like cardiomyocytes derived from human induced pluripotent stem cells

Abstract Generating atrial-like cardiomyocytes derived from human induced pluripotent stem cells (hiPSCs) is crucial for modeling and treating atrial-related diseases, such as atrial arrythmias including atrial fibrillations. However, it is essential to obtain a comprehensive understanding of the electrophysiological properties of these cells. The objective of the present study was to investigate the molecular, electrical, and biophysical properties of several ion channels, especially NaV1.5 channels, in atrial hiPSC cardiomyocytes. Atrial cardiomyocytes were obtained by the differentiation of hiPSCs treated with retinoic acid (RA). The quality of the atrial specification was assessed by qPCR, immunocytofluorescence, and western blotting. The electrophysiological properties of action potentials (APs), Ca2+ dynamics, K+ and Na+ currents were investigated using patch-clamp and optical mapping approaches. We evaluated mRNA transcript and protein expressions to show that atrial cardiomyocytes expressed higher atrial- and sinoatrial-specific markers (MYL7, CACNA1D) and lower ventricular-specific markers (MYL2, CACNA1C, GJA1) than ventricular cardiomyocytes. The amplitude, duration, and steady-state phase of APs in atrial cardiomyocytes decreased, and had a shape similar to that of mature atrial cardiomyocytes. Interestingly, NaV1.5 channels in atrial cardiomyocytes exhibited lower mRNA transcripts and protein expression, which could explain the lower current densities recorded by patch-clamp. Moreover, Na+ currents exhibited differences in activation and inactivation parameters. These differences could be explained by an increase in SCN2B regulatory subunit expression and a decrease in SCN1B and SCN4B regulatory subunit expressions. Our results show that a RA treatment made it possible to obtain atrial cardiomyocytes and investigate differences in NaV1.5 channel properties between ventricular- and atrial-like cells

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

The variant hERG/R148W associated with LQTS is a mutation that reduces current density on co-expression with the WT

International audienceBackground: A variant of the ether-à-go-go related channel (hERG), p.Arg148Trp (R148W) was found at heterozygous state in two infants who died from sudden infant death syndrome (SIDS), one with documented prolonged QTc and Torsade de Pointes (TdP), and in an adult woman with QTc > 500 ms, atrio-ventricular block and TdP. This variant was previously reported in cases of severe ventricular arrhythmia but very rarely in control subjects. Its classification as mutation or polymorphism awaited electrophysiological characterization. Methods: The properties of this N-terminal, proximal domain, hERG variant were explored in Xenopus oocytes injected with the same amount of RNA encoding for either hERG/WT or hERG/R148W or their equimolar mixture. The human ventricular cell (TNNP) model was used to test the effects of changes in hERG current.Results: R148W alone produced a current similar to the WT (369±76 nA (mean±SEM), n=13 versus 342±55 nA in WT, n=13), while the coexpression of 1/2 WT + 1/2 R148W lowered the current by 29 % versus WT (243±35 nA, n=13, p<0.05). The voltage dependencies of steady-state activation and inactivation were not changed in the variant alone or in coexpression with the WT. The time constants of fast recovery from inactivation and of fast and slow deactivation analyzed between –120 and +20 mV were not changed. The voltage-dependent distribution of the current amplitudes among fast-, slow- and non-deactivating fractions was unaltered. A 6.6 % increase in APD90 from 323.5 ms to 345 ms was observed using the human cardiac ventricular myocyte model.Conclusions: Such a decrease in hERG current as evidenced here when co-expressing the hERG/R148W variant with the WT may have predisposed to the observed long QT syndrome and associated TdP. Therefore, the heterozygous carriers of hERG/R148W may be at risk of cardiac sudden death