Generation of a patient-specific induced pluripotent stem cell line carrying the DES p.R406W mutation, an isogenic control and a DES p.R406W knock-in line

Mutations in the DES gene, which encodes the intermediate filament desmin, lead to desminopathy, a rare disease characterized by skeletal muscle weakness and different forms of cardiomyopathies associated with cardiac conduction defects and arrhythmias. We generated human induced pluripotent stem cells (hiPSC) from a patient carrying the DES p.R406W mutation, and employed CRISPR/Cas9 to rectify the mutation in the patient's hiPSC line and introduced the mutation in an hiPSC line from a control individual unrelated to the patient. These hiPSC lines represent useful models for delving into the mechanisms of desminopathy and developing new therapeutic approaches.

Pathophysiological mechanisms of cardiomyopathies induced by desmin gene variants located in the C-Terminus of segment 2B

Desmin, the most abundant intermediate filament in cardiomyocytes, plays a key role in maintaining cardiomyocyte structure by interconnecting intracellular organelles, and facilitating cardiomyocyte interactions with the extracellular matrix and neighboring cardiomyocytes. As a consequence, mutations in the desmin gene (DES) can lead to desminopathies, a group of diseases characterized by variable and often severe cardiomyopathies along with skeletal muscle disorders. The basic desmin intermediate filament structure is composed of four segments separated by linkers that further assemble into dimers, tetramers and eventually unit-length filaments that compact radially to give the final form of the filament. Each step in this process is critical for proper filament formation and allow specific interactions within the cell. Mutations within the desmin gene can disrupt filament formation, as seen by aggregate formation, and thus have severe cardiac and skeletal outcomes, depending on the locus of the mutation. The focus of this review is to outline the cardiac molecular consequences of mutations located in the C-terminal part of segment 2B. This region is crucial for ensuring proper desmin filament formation and is a known hotspot for mutations that significantly impact cardiac function.

The G213D variant in Nav1.5 alters sodium current and causes an arrhythmogenic phenotype resulting in a multifocal ectopic Purkinje-related premature contraction phenotype in human-induced pluripotent stem cell-derived cardiomyocytes

AIMS

Variants in SCN5A encoding Nav1.5 are associated with cardiac arrhythmias. We aimed to determine the mechanism by which c.638G>A in SCNA5 resulting in p.Gly213Asp (G213D) in Nav1.5 altered Na+ channel function and how flecainide corrected the defect in a family with multifocal ectopic Purkinje-related premature contractions (MEPPC)-like syndrome.

METHODS AND RESULTS

Five patients carrying the G213D variant were treated with flecainide. Gating pore currents were evaluated in Xenopus laevis oocytes. The 638G>A SCN5A variant was introduced to human-induced pluripotent stem cell (hiPSC) by CRISPR-Cas9 gene editing and subsequently differentiated to cardiomyocytes (hiPSC-CM). Action potentials and sodium currents were measured in the absence and presence of flecainide. Ca2+ transients were measured by confocal microscopy. The five patients exhibited premature atrial and ventricular contractions which were suppressed by flecainide treatment. G213D induced gating pore current at potentials negative to -50 mV. Voltage-clamp analysis in hiPSC-CM revealed the activation threshold of INa was shifted in the hyperpolarizing direction resulting in a larger INa window current. The G213D hiPSC-CMs had faster beating rates compared with wild-type and frequently showed Ca2+ waves and alternans. Flecainide applied to G213D hiPSC-CMs decreased window current by shifting the steady-state inactivation curve and slowed the beating rate.

CONCLUSION

The G213D variant in Nav1.5 induced gating pore currents and increased window current. The changes in INa resulted in a faster beating rate and Ca2+ transient dysfunction. Flecainide decreased window current and inhibited INa, which is likely responsible for the therapeutic effectiveness of flecainide in MEPPC patients carrying the G213D variant.

Circulating Levels of WISP-1 (Wnt1-Inducible Signaling Pathway Protein 1) and Other Selected Adipokines in Children With Inflammatory Bowel Disease

Wnt1 inducible protein-1 signaling pathway (WISP-1) is a relatively new adipokine involved in many cellular processes, including epithelial mucosa healing. The aim of the study was to compare circulating levels of WISP-1 and other selected adipokines [adiponectin, resistin and retinol-binding protein 4 (RBP-4)] in children with inflammatory bowel disease (IBD) with healthy controls and to investigate possible differences between Crohn's disease patients. (CD) or ulcerative colitis (UC). The study was performed as a case-control study. In addition to adipokines, anthropometric, lipid parameters, markers of inflammation or disease activity were evaluated in all participants. Compared to healthy controls (n=20), significantly lower levels of adiponectin and higher levels of resistin and WISP-1 were found in patients with IBD (n=58). Elevation of WISP-1 was detected only in the CD group (n=31). There were no differences in RBP-4 levels between the groups. Adiponectin, WISP-1 and RBP-4 were independently associated with body mass index only, resistin levels were associated with C-reactive protein levels and leukocyte counts. Adverse adipokines production reflects presence of dysfunctional fat tissue in IBD patients. Higher levels of WISP-1 in CD compared to patients with UC may indicate a specific role for mesenteric adipose tissue in WISP-1 production.