hiPSC-derived cardiac fibroblasts dynamically enhance the mechanical function of hiPSC-derived cardiomyocytes on an engineered substrate.

Introduction: Cardiac fibroblasts deposit and turnover the extracellular matrix in the heart, as well as secrete soluble factors that play critical roles in development, homeostasis, and disease. Coculture of CFs and human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (CMs) enhances CM mechanical output, yet the mechanism remains unclear.

Methods: Here, we use an engineered platform to compare the effects on CM mechanical function of direct CM-CF Coculture and soluble signaling alone through CF Conditioned Medium to a CM Only monoculture.

The role of iPSC research for insight into inherited arrhythmia conditions.

Human induced pluripotent stem cells (iPSCs) have emerged as a transformative platform for modeling inherited cardiac arrhythmia syndromes and uncovering human-specific disease mechanisms. However, the promise of iPSC-derived cardiomyocytes lies beyond the recapitulation of arrhythmogenic phenotypes and channelopathies. In this review, we explore recent works which have enabled mechanistic interrogation and therapeutic insight for inherited arrhythmia syndromes, beyond the capabilities of traditional animal models.

Atomic-level investigation of KCNJ2 mutations associated with ventricular arrhythmic syndrome phenotypes.

KCNJ2 encodes the inward rectifying potassium channel (Kir2.1) that underlies I which maintains the cardiac resting membrane potential and regulates excitability. Mutations in KCNJ2 have been linked to several clinical phenotypes associated with life-threatening ventricular arrhythmia and sudden death including Andersen-Tawil syndrome (ATS) from loss of function mutations, and Short QT Syndrome 3 from gain of function mutations.

Modeling Idiopathic Ventricular Fibrillation Using iPSC Cardiomyocytes and Computational Approaches: A Proof-of-Concept Study.

Idiopathic ventricular fibrillation (IVF) is an unrefined diagnosis representing a heterogeneous patient group without a structural or genetic definition. IVF treatment is not mechanistic-based due to the lack of experimental patient-models. We sought to create a methodology to assess cellular arrhythmia mechanisms for IVF as a proof-of-concept study.

Global Proteomic Analysis Reveals Alterations in Differentially Expressed Proteins between Cardiopathic Lamin A/C Mutations.

Lamin A/C (LMNA) is an important component of nuclear lamina. Mutations cause arrhythmia, heart failure, and sudden cardiac death. While LMNA-associated cardiomyopathy typically has an aggressive course that responds poorly to conventional heart failure therapies, there is variability in severity and age of penetrance between and even within specific mutations, which is poorly understood at the cellular level.

The impact of COVID-19 on healthcare coverage and access in racial and ethnic minority populations in the United States.

This study described spatiotemporal changes in health insurance coverage, healthcare access, and reasons for non-insurance among racial/ethnic minority populations in the United States during the COVID-19 pandemic using four national survey datasets. Getis-Ord Gi* statistic and scan statistics were used to analyze geospatial clusters of health insurance coverage by race/ethnicity. Logistic regression was used to estimate odds of reporting inability to access healthcare across two pandemic time periods by race/ethnicity.

How Functional Genomics Can Keep Pace With VUS Identification.

Over the last two decades, an exponentially expanding number of genetic variants have been identified associated with inherited cardiac conditions. These tremendous gains also present challenges in deciphering the clinical relevance of unclassified variants or variants of uncertain significance (VUS). This review provides an overview of the advancements (and challenges) in functional and computational approaches to characterize variants and help keep pace with VUS identification related to inherited heart diseases.

Mutation-Specific Differences in Kv7.1 () and Kv11.1 () Channel Dysfunction and Long QT Syndrome Phenotypes.

The electrocardiogram (ECG) empowered clinician scientists to measure the electrical activity of the heart noninvasively to identify arrhythmias and heart disease. Shortly after the standardization of the 12-lead ECG for the diagnosis of heart disease, several families with autosomal recessive (Jervell and Lange-Nielsen Syndrome) and dominant (Romano-Ward Syndrome) forms of long QT syndrome (LQTS) were identified. An abnormally long heart rate-corrected QT-interval was established as a biomarker for the risk of sudden cardiac death.

Hypoxia Inducible Factor-1α binds and activates γ-secretase for Aβ production under hypoxia and cerebral hypoperfusion.

Hypoxic-ischemic injury has been linked with increased risk for developing Alzheimer's disease (AD). The underlying mechanism of this association is poorly understood. Here, we report distinct roles for hypoxia-inducible factor-1α (Hif-1α) in the regulation of BACE1 and γ-secretase activity, two proteases involved in the production of amyloid-beta (Aβ).

Mutant CHCHD10 causes an extensive metabolic rewiring that precedes OXPHOS dysfunction in a murine model of mitochondrial cardiomyopathy.

Mitochondrial cardiomyopathies are fatal diseases, with no effective treatment. Alterations of heart mitochondrial function activate the mitochondrial integrated stress response (ISR), a transcriptional program affecting cell metabolism, mitochondrial biogenesis, and proteostasis. In humans, mutations in CHCHD10, a mitochondrial protein with unknown function, were recently associated with dominant multi-system mitochondrial diseases, whose pathogenic mechanisms remain to be elucidated.

The Predictive Accuracy of the CareMOSAIC Risk Assessment for Discharge Disposition in Medicare Bundle Patients After Total Joint Arthroplasty.

Background: This article evaluates the predictive accuracy of the CareMOSAIC Risk Assessment for discharge disposition in Medicare patients undergoing total joint arthroplasty.

Methods: Retrospectively collected data from a single institution on 499 consecutive Medicare patients who underwent primary total hip arthroplasty or total knee arthroplasty were reviewed. The CareMOSAIC Risk Assessment was completed by each patient during the preoperative period.

Most myopathic lamin variants aggregate: a functional genomics approach for assessing variants of uncertain significance.

Hundreds of LMNA variants have been associated with several distinct disease phenotypes. However, genotype-phenotype relationships remain largely undefined and the impact for most variants remains unknown. We performed a functional analysis for 178 variants across five structural domains using two different overexpression models.

Proteomic Analysis of the Functional Inward Rectifier Potassium Channel (Kir) 2.1 Reveals Several Novel Phosphorylation Sites.

Membrane proteins represent a large family of proteins that perform vital physiological roles and represent key drug targets. Despite their importance, bioanalytical methods aiming to comprehensively characterize the post-translational modification (PTM) of membrane proteins remain challenging compared to other classes of proteins in part because of their inherent low expression and hydrophobicity. The inward rectifier potassium channel (Kir) 2.

Long QT Syndrome Variant Induces hERG1a/1b Subunit Imbalance in Patient-Specific Induced Pluripotent Stem Cell-Derived Cardiomyocytes.

[Figure: see text].

Long QT Syndrome Type 2: Emerging Strategies for Correcting Class 2 () Mutations and Identifying New Patients.

Significant advances in our understanding of the molecular mechanisms that cause congenital long QT syndrome (LQTS) have been made. A wide variety of experimental approaches, including heterologous expression of mutant ion channel proteins and the use of inducible pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) from LQTS patients offer insights into etiology and new therapeutic strategies. This review briefly discusses the major molecular mechanisms underlying LQTS type 2 (LQT2), which is caused by loss-of-function (LOF) mutations in the gene (also known as the human ether-à-go-go-related gene or ).

A rapid solubility assay of protein domain misfolding for pathogenicity assessment of rare DNA sequence variants.

Purpose: DNA sequencing technology has unmasked a vast number of uncharacterized single-nucleotide variants in disease-associated genes, and efficient methods are needed to determine pathogenicity and enable clinical care.

Methods: We report an E. coli-based solubility assay for assessing the effects of variants on protein domain stability for three disease-associated proteins.

Prohibitin S-Nitrosylation Is Required for the Neuroprotective Effect of Nitric Oxide in Neuronal Cultures.

Prohibitin (PHB) is a critical protein involved in many cellular activities. In brain, PHB resides in mitochondria, where it forms a large protein complex with PHB2 in the inner TFmembrane, which serves as a scaffolding platform for proteins involved in mitochondrial structural and functional integrity. PHB overexpression at moderate levels provides neuroprotection in experimental brain injury models.

Prohibitin levels regulate OMA1 activity and turnover in neurons.

The GTPase OPA1 and the AAA-protease OMA1 serve well-established roles in mitochondrial stress responses and mitochondria-initiated cell death. In addition to its role in mitochondrial membrane fusion, cristae structure, and bioenergetic function, OPA1 controls apoptosis by sequestering cytochrome c (cyt c) in mitochondrial cristae. Cleavage of functional long OPA1 (L-OPA1) isoforms by OMA1 inactivates mitochondrial fusion and primes apoptosis.

AGO CLIP Reveals an Activated Network for Acute Regulation of Brain Glutamate Homeostasis in Ischemic Stroke.

Post-transcriptional regulation by microRNAs (miRNAs) is essential for complex molecular responses to physiological insult and disease. Although many disease-associated miRNAs are known, their global targets and culminating network effects on pathophysiology remain poorly understood. We applied Argonaute (AGO) crosslinking immunoprecipitation (CLIP) to systematically elucidate altered miRNA-target interactions in brain following ischemia and reperfusion (I/R) injury.

ALS/FTD mutant CHCHD10 mice reveal a tissue-specific toxic gain-of-function and mitochondrial stress response.

Mutations in coiled-coil-helix-coiled-coil-helix domain containing 10 (CHCHD10), a mitochondrial protein of unknown function, cause a disease spectrum with clinical features of motor neuron disease, dementia, myopathy and cardiomyopathy. To investigate the pathogenic mechanisms of CHCHD10, we generated mutant knock-in mice harboring the mouse-equivalent of a disease-associated human S59L mutation, S55L in the endogenous mouse gene. CHCHD10 mice develop progressive motor deficits, myopathy, cardiomyopathy and accelerated mortality.

Visualizing Mutation-Specific Differences in the Trafficking-Deficient Phenotype of Kv11.1 Proteins Linked to Long QT Syndrome Type 2.

encodes the Kv11.1 α-subunit that underlies the rapidly activating delayed-rectifier K current in the heart. Loss-of-function mutations cause long QT syndrome type 2 (LQT2), and most LQT2-linked missense mutations inhibit the trafficking of Kv11.

Prohibitin is a positive modulator of mitochondrial function in PC12 cells under oxidative stress.

Prohibitin (PHB) is a ubiquitously expressed and evolutionarily conserved mitochondrial protein with multiple functions. We have recently shown that PHB up-regulation offers robust protection against neuronal injury in models of cerebral ischemia in vitro and in vivo, but the mechanism by which PHB affords neuroprotection remains to be elucidated. Here, we manipulated PHB expression in PC12 neural cells to investigate its impact on mitochondrial function and the mechanisms whereby it protects cells exposed to oxidative stress.

Critical Role of Flavin and Glutathione in Complex I-Mediated Bioenergetic Failure in Brain Ischemia/Reperfusion Injury.

Background And Purpose: Ischemic brain injury is characterized by 2 temporally distinct but interrelated phases: ischemia (primary energy failure) and reperfusion (secondary energy failure). Loss of cerebral blood flow leads to decreased oxygen levels and energy crisis in the ischemic area, initiating a sequence of pathophysiological events that after reoxygenation lead to ischemia/reperfusion (I/R) brain damage. Mitochondrial impairment and oxidative stress are known to be early events in I/R injury.

Neuronal expression of the mitochondrial protein prohibitin confers profound neuroprotection in a mouse model of focal cerebral ischemia.

The mitochondrial protein prohibitin (PHB) has emerged as an important modulator of neuronal survival in different injury modalities . We previously showed that viral gene transfer of PHB protects CA1 neurons from delayed neurodegeneration following transient forebrain ischemia through mitochondrial mechanisms. However, since PHB is present in all cell types, it is not known if its selective expression in neurons is protective, and if the protection occurs also in acute focal ischemic brain injury, the most common stroke type in humans.