Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a primary heart muscle disorder associated with sudden cardiac death. Its pathophysiology is still poorly understood. We aimed to produce an in vitro cellular model of ARVC using patient-specific induced pluripotent stem cell (iPSC)-derived cardiomyocytes and determine whether the model could recapitulate key features of the disease phenotype. Dermal fibroblasts were obtained from a 30-year-old man with a clinical diagnosis of ARVC, harbouring a plakophilin 2 (PKP2) gene mutation. Four stable iPSC lines were generated using retroviral reprogramming, and functional cardiomyocytes were derived. Gene expression levels of desmosomal proteins (PKP2 and plakoglobin) in cardiomyocytes from ARVC–iPSCs were significantly lower compared with cardiomyocytes from control iPSCs (P< 0.01); there were no significant differences in the expression of desmoplakin, N-cadherin, and connexin 43 between the two groups. Cardiomyocytes derived from ARVC–iPSCs exhibited markedly reduced immunofluorescence signals when stained for PKP2 and plakoglobin, but similar levels of staining for desmoplakin, N-cadherin, and connexin 43 compared with control cardiomyocytes. Transmission electron microscopy showed that ARVC–iPSC cardiomyocytes were larger and contained darker lipid droplets compared with control cardiomyocytes. After 2 weeks of cell exposure to adiopgenic differentiation medium, ARVC–iPSC cardiomyocytes were found to contain a significantly greater amount of lipid, calculated using Oil Red O staining, compared with controls (734 ± 35.6 vs. 8.1 ± 0.49 a.u., respectively; n = 7, P = 0.001). Patient-specific iPSC-derived cardiomyocytes display key features of ARVC, including reduced cell surface localization of desmosomal proteins and a more adipogenic phenotype.

Introduction: Type 1 long QT syndrome (LQT1) is a common type of cardiac channelopathy associated with loss-of-function mutations of KCNQ1. Currently there is a lack of drugs that target the defected slowly activating delayed rectifier potassium channel (IKs). With LQT1 patient-specific human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (hiPSC-CMs), we tested the effects of a selective IKs activator ML277 on reversing the disease phenotypes. Methods: A LQT1 family with a novel heterozygous exon 7 deletion in the KCNQ1 gene was identified. Dermal fibroblasts from the proband and her healthy father were reprogrammed to hiPSCs and subsequently differentiated into hiPSC-CMs. Results: Compared with the control, LQT1 patient hiPSC-CMs showed reduced levels of wild type KCNQ1 mRNA accompanied by multiple exon skipping mRNAs and a ~50% reduction of the full length Kv7.1 protein. Patient hiPSC-CMs showed reduced IKs current (tail current density at 30 mV: 0.33 ± 0.02 vs. 0.92 ± 0.21, P < 0.05) and prolonged action potential duration (APD) (APD 50 and APD90: 603.9 ± 39.2 vs. 319.3 ± 13.8 ms, P < 0.005; and 671.0 ± 41.1 vs. 372.9 ± 14.2 ms, P < 0.005). ML277, a small molecule recently identified to selectively activate K_V7.1, reversed the decreased IKs and partially restored APDs in patient hiPSC-CMs. Conclusions: From a LQT1 patient carrying a novel heterozygous exon7 deletion mutation of KCNQ1, we generated hiPSC-CMs that faithfully recapitulated the LQT1 phenotypes that are likely associated with haploinsufficiency and trafficking defect of KCNQ1/Kv7.1. The small molecule ML277 restored IKs function in hiPSC-CMs and could have therapeutic value for LQT1 patients.

Coiled-coil-helix-coiled-coil-helix domain containing protein 2 (CHCHD2) mutations were linked with autosomal dominant Parkinson’s disease (PD) and recently, Alzheimer’s disease/frontotemporal dementia. In the current study, we generated isogenic human embryonic stem cell (hESC) lines harboring PD-associated CHCHD2 mutation R145Q or Q126X via clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein 9 (Cas9) method, aiming to unravel pathophysiologic mechanism and seek potential intervention strategy against CHCHD2 mutant-caused defects. By engaging super-resolution microscopy, we identified a physical proximity and similar distribution pattern of CHCHD2 along mitochondria with mitochondrial contact site and cristae organizing system (MICOS), a large protein complex maintaining mitochondria cristae. Isogenic hESCs and differentiated neural progenitor cells (NPCs) harboring CHCHD2 R145Q or Q126X mutation showed impaired mitochondria function, reduced CHCHD2 and MICOS components and exhibited nearly hollow mitochondria with reduced cristae. Furthermore, PD-linked CHCHD2 mutations lost their interaction with coiled-coil-helix-coiled-coil-helix domain containing protein 10 (CHCHD10), while transient knockdown of either CHCHD2 or CHCHD10 reduced MICOS and mitochondria cristae. Importantly, a specific mitochondria-targeted peptide, Elamipretide/MTP-131, now tested in phase 3 clinical trials for mitochondrial diseases, was found to enhance CHCHD2 with MICOS and mitochondria oxidative phosphorylation enzymes in isogenic NPCs harboring heterozygous R145Q, suggesting that Elamipretide is able to attenuate CHCHD2 R145Q-induced mitochondria dysfunction. Taken together, our results suggested CHCHD2–CHCHD10 complex may be a novel therapeutic target for PD and related neurodegenerative disorders, and Elamipretide may benefit CHCHD2 mutation-linked PD.

Background: Parkinson’s disease (PD) is characterized by selective and progressive dopamine (DA) neuron loss in the substantia nigra and other brain regions, with the presence of Lewy body formation. Most PD cases are sporadic, whereas monogenic forms of PD have been linked to multiple genes, including Leucine kinase repeat 2 (LRRK2) and PTEN-induced kinase 1 (PINK1), two protein kinase genes involved in multiple signaling pathways. There is increasing evidence to suggest that endogenous DA and DA-dependent neurodegeneration have a pathophysiologic role in sporadic and familial PD. Methods: We generated patient-derived dopaminergic neurons and human midbrain-like organoids (hMLOs), transgenic (TG) mouse and Drosophila models, expressing both mutant and wild-type (WT) LRRK2 and PINK1. Using these models, we examined the effect of LRRK2 and PINK1 on tyrosine hydroxylase (TH)–DA pathway. Results: We demonstrated that PD-linked LRRK2 mutations were able to modulate TH–DA pathway, resulting in up-regulation of DA early in the disease which subsequently led to neurodegeneration. The LRRK2-induced DA toxicity and degeneration were abrogated by wild-type (WT) PINK1 (but not PINK1 mutations), and early treatment with a clinical-grade drug, α-methyl-L-tyrosine (α-MT), a TH inhibitor, was able to reverse the pathologies in human neurons and TG Drosophila models. We also identified opposing effects between LRRK2 and PINK1 on TH expression, suggesting that functional balance between these two genes may regulate the TH–DA pathway. Conclusions: Our findings highlight the vital role of the TH–DA pathway in PD pathogenesis. LRRK2 and PINK1 have opposing effects on the TH–DA pathway, and its balance affects DA neuron survival. LRRK2 or PINK1 mutations can disrupt this balance, promoting DA neuron demise. Our findings provide support for potential clinical trials using TH–DA pathway inhibitors in early or prodromic PD.