The nutrient sensor CRTC and Sarcalumenin/thinman represent an alternate pathway in cardiac hypertrophy.

CREB-regulated transcription co-activator (CRTC) is activated by Calcineurin (CaN) to regulate gluconeogenic genes. CaN also has roles in cardiac hypertrophy. Here, we explore a cardiac-autonomous role for CRTC in cardiac hypertrophy.

3D reconstruction of murine mitochondria reveals changes in structure during aging linked to the MICOS complex.

During aging, muscle gradually undergoes sarcopenia, the loss of function associated with loss of mass, strength, endurance, and oxidative capacity. However, the 3D structural alterations of mitochondria associated with aging in skeletal muscle and cardiac tissues are not well described. Although mitochondrial aging is associated with decreased mitochondrial capacity, the genes responsible for the morphological changes in mitochondria during aging are poorly characterized.

The nutrient sensor CRTC & Sarcalumenin / Thinman represent a new pathway in cardiac hypertrophy.

Obesity and type 2 diabetes are at epidemic levels and a significant proportion of these patients are diagnosed with left ventricular hypertrophy. egulated ranscription o-activator ( ) is a key regulator of metabolism in mammalian hepatocytes, where it is activated by calcineurin (CaN) to increase expression of gluconeogenic genes. CaN is known its role in pathological cardiac hypertrophy, however, a role for CRTC in the heart has not been identified.

Mitochondrial MICOS complex genes, implicated in hypoplastic left heart syndrome, maintain cardiac contractility and actomyosin integrity.

Hypoplastic left heart syndrome (HLHS) is a severe congenital heart disease (CHD) with a likely oligogenic etiology, but our understanding of the genetic complexities and pathogenic mechanisms leading to HLHS is limited. We performed whole genome sequencing (WGS) on 183 HLHS patient-parent trios to identify candidate genes, which were functionally tested in the heart model. Bioinformatic analysis of WGS data from an index family of a HLHS proband born to consanguineous parents prioritized 9 candidate genes with rare, predicted damaging homozygous variants.

Multiplatform modeling of atrial fibrillation identifies phospholamban as a central regulator of cardiac rhythm.

Atrial fibrillation (AF) is a common and genetically inheritable form of cardiac arrhythmia; however, it is currently not known how these genetic predispositions contribute to the initiation and/or maintenance of AF-associated phenotypes. One major barrier to progress is the lack of experimental systems to investigate the effects of gene function on rhythm parameters in models with human atrial and whole-organ relevance. Here, we assembled a multi-model platform enabling high-throughput characterization of the effects of gene function on action potential duration and rhythm parameters using human induced pluripotent stem cell-derived atrial-like cardiomyocytes and a Drosophila heart model, and validation of the findings using computational models of human adult atrial myocytes and tissue.

Deacetylase-dependent and -independent role of HDAC3 in cardiomyopathy.

Cardiomyopathy is a common disease of cardiac muscle that negatively affects cardiac function. HDAC3 commonly functions as corepressor by removing acetyl moieties from histone tails. However, a deacetylase-independent role of HDAC3 has also been described.

Atrial Fibrillation Genomics: Discovery and Translation.

Purpose Of Review: Our understanding of the fundamental cellular and molecular factors leading to atrial fibrillation (AF) remains stagnant despite significant advancement in ablation and device technologies. Diagnosis and prevention strategies fall behind that of treatment, but expanding knowledge in AF genetics holds the potential to drive progress. We aim to review how an understanding of the genetic contributions to AF can guide an approach to individualized risk stratification and novel avenues in drug discovery.

Conserved Role of the Large Conductance Calcium-Activated Potassium Channel, K1.1, in Sinus Node Function and Arrhythmia Risk.

Background: encodes the α-subunit of the large-conductance Ca-activated K channel, K1.1, and lies within a linkage interval for atrial fibrillation (AF). Insights into the cardiac functions of K1.

Prolonged Exposure to Microgravity Reduces Cardiac Contractility and Initiates Remodeling in Drosophila.

Understanding the effects of microgravity on human organs is crucial to exploration of low-earth orbit, the moon, and beyond. Drosophila can be sent to space in large numbers to examine the effects of microgravity on heart structure and function, which is fundamentally conserved from flies to humans. Flies reared in microgravity exhibit cardiac constriction with myofibrillar remodeling and diminished output.

Patient-specific genomics and cross-species functional analysis implicate LRP2 in hypoplastic left heart syndrome.

Congenital heart diseases (CHDs), including hypoplastic left heart syndrome (HLHS), are genetically complex and poorly understood. Here, a multidisciplinary platform was established to functionally evaluate novel CHD gene candidates, based on whole-genome and iPSC RNA sequencing of a HLHS family-trio. Filtering for rare variants and altered expression in proband iPSCs prioritized 10 candidates.

Systemic and heart autonomous effects of sphingosine Δ4 desaturase deficiency in lipotoxic cardiac pathophysiology.

Lipotoxic cardiomyopathy (LCM) is characterized by cardiac steatosis, including the accumulation of fatty acids, triglycerides and ceramides. Model systems have shown the inhibition of ceramide biosynthesis to antagonize obesity and improve insulin sensitivity. Sphingosine Δ4 desaturase (encoded by in ) enzymatically converts dihydroceramide into ceramide.

Overexpression of in the Developing Heart Causes Valvar and Contractility Defects: Implications for Human Congenital Heart Disease.

Left-sided congenital heart defects (CHDs) are among the most common forms of congenital heart disease, but a disease-causing gene has only been identified in a minority of cases. Here, we identified a candidate gene for CHDs, , that was associated with a chromosomal balanced translocation t(2;8)(q37;p11) in a patient with left-sided heart and aortic valve defects. The breakpoint was in the 5' untranslated region of the gene at 2q37, which suggested that the break affected the levels of gene expression.

Extracellular matrix induced by steroids and aging through a G-protein-coupled receptor in a model of renal fibrosis.

Aldosterone is produced by the mammalian adrenal cortex to modulate blood pressure and fluid balance; however, excessive, prolonged aldosterone promotes fibrosis and kidney failure. How aldosterone triggers disease may involve actions independent of its canonical mineralocorticoid receptor. Here, we present a model of renal pathology caused by excess extracellular matrix formation, stimulated by exogenous aldosterone and by insect ecdysone.

TGFB-INHB/activin signaling regulates age-dependent autophagy and cardiac health through inhibition of MTORC2.

Age-related impairment of macroautophagy/autophagy and loss of cardiac tissue homeostasis contribute significantly to cardiovascular diseases later in life. MTOR (mechanistic target of rapamycin kinase) signaling is the most well-known regulator of autophagy, cellular homeostasis, and longevity. The MTOR signaling consists of two structurally and functionally distinct multiprotein complexes, MTORC1 and MTORC2.

The Functional Polymorphism R129W in the Gene Is Associated with Sporadic Tetralogy of Fallot in the Han Chinese Population.

Tetralogy of Fallot (TOF) accounts for ∼10% of congenital heart disease cases. The blood vessel epicardial substance () gene has been reported to play a role in the function of adult hearts. However, whether allelic variants in contribute to the risk of TOF and its possible mechanism remains unknown.

Ceramide-Protein Interactions Modulate Ceramide-Associated Lipotoxic Cardiomyopathy.

Lipotoxic cardiomyopathy (LCM) is characterized by abnormal myocardial accumulation of lipids, including ceramide; however, the contribution of ceramide to the etiology of LCM is unclear. Here, we investigated the association of ceramide metabolism and ceramide-interacting proteins (CIPs) in LCM in the Drosophila heart model. We find that ceramide feeding or ceramide-elevating genetic manipulations are strongly associated with cardiac dilation and defects in contractility.

Reduced Cardiac Expression Mimics Long-Term Hypoxia-Induced Heart Defects in .

Background: Hypoxia is often associated with cardiopulmonary diseases, which represent some of the leading causes of mortality worldwide. Long-term hypoxia exposures, whether from disease or environmental condition, can cause cardiomyopathy and lead to heart failure. Indeed, hypoxia-induced heart failure is a hallmark feature of chronic mountain sickness in maladapted populations living at high altitude.

Transcriptomic analysis identifies a role of PI3K-Akt signalling in the responses of skeletal muscle to acute hypoxia in vivo.

Key Points: Changes in gene expression that occur within hours of exposure to hypoxia in in vivo skeletal muscles remain unexplored. Two hours of hypoxia caused significant down-regulation of extracellular matrix genes followed by a shift at 6 h to altered expression of genes associated with the nuclear lumen while respiratory and blood gases were stabilized. Enrichment analysis of mRNAs classified by stability rates suggests an attenuation of post-transcriptional regulation within hours of hypoxic exposure, where PI3K-Akt signalling was suggested to have a nodal role by pathway analysis.

Age-dependent electrical and morphological remodeling of the Drosophila heart caused by hERG/seizure mutations.

Understanding the cellular-molecular substrates of heart disease is key to the development of cardiac specific therapies and to the prevention of off-target effects by non-cardiac targeted drugs. One of the primary targets for therapeutic intervention has been the human ether a go-go (hERG) K+ channel that, together with the KCNQ channel, controls the rate and efficiency of repolarization in human myocardial cells. Neither of these channels plays a major role in adult mouse heart function; however, we show here that the hERG homolog seizure (sei), along with KCNQ, both contribute significantly to adult heart function as they do in humans.

Experimental Evolution and Heart Function in Drosophila.

Drosophila melanogaster is a good model species for the study of heart function. However, most previous work on D. melanogaster heart function has focused on the effects of large-effect genetic variants.

A Restrictive Cardiomyopathy Mutation in an Invariant Proline at the Myosin Head/Rod Junction Enhances Head Flexibility and Function, Yielding Muscle Defects in Drosophila.

An "invariant proline" separates the myosin S1 head from its S2 tail and is proposed to be critical for orienting S1 during its interaction with actin, a process that leads to muscle contraction. Mutation of the invariant proline to leucine (P838L) caused dominant restrictive cardiomyopathy in a pediatric patient (Karam et al., Congenit.

SPARC-Dependent Cardiomyopathy in Drosophila.

Background: The Drosophila heart is an important model for studying the genetics underpinning mammalian cardiac function. The system comprises contractile cardiomyocytes, adjacent to which are pairs of highly endocytic pericardial nephrocytes that modulate cardiac function by uncharacterized mechanisms. Identifying these mechanisms and the molecules involved is important because they may be relevant to human cardiac physiology.

Cardiac responses to hypoxia and reoxygenation in Drosophila.

An adequate supply of oxygen is important for the survival of all tissues, but it is especially critical for tissues with high-energy demands, such as the heart. Insufficient tissue oxygenation occurs under a variety of conditions, including high altitude, embryonic and fetal development, inflammation, and thrombotic diseases, often affecting multiple organ systems. Responses and adaptations of the heart to hypoxia are of particular relevance in human cardiovascular and pulmonary diseases, in which the effects of hypoxic exposure can range in severity from transient to long-lasting.