Rabphilin silencing causes dilated cardiomyopathy in a Drosophila model of nephrocyte damage

Diurnal expression of Dgat2 induced by time-restricted feeding maintains cardiac health in the Drosophila model of circadian disruption

Circadian disruption is associated with an increased risk of cardiometabolic disorders and cardiac diseases. Time-restricted feeding/eating (TRF/TRE), restricting food intake within a consistent window of the day, has shown improvements in heart function from flies and mice to humans. However, whether and how TRF still conveys cardiac benefits in the context of circadian disruption remains unclear. Here, we demonstrate that TRF sustains cardiac performance, myofibrillar organization, and regulates cardiac lipid accumulation in Drosophila when the circadian rhythm is disrupted by constant light. TRF induces oscillations in the expression of genes associated with triglyceride metabolism. In particular, TRF induces diurnal expression of diacylglycerol O-acyltransferase 2 (Dgat2), peaking during the feeding period. Heart-specific manipulation of Dgat2 modulates cardiac function and lipid droplet accumulation. Strikingly, heart-specific overexpression of human Dgat2 at ZT 0-10 significantly improves cardiac performance in flies exposed to constant light. We have demonstrated that TRF effectively attenuates cardiac decline induced by circadian disruption. Moreover, our data suggests that diurnal expression of Dgat2 induced by TRF is beneficial for heart health under circadian disruption. Overall, our findings have underscored the relevance of TRF in preserving heart health under circadian disruptions and provided potential targets, such as Dgat2, and strategies for therapeutic interventions in mitigating cardiac aging, metabolic disorders, and cardiac diseases in humans.

Obg-like ATPase 1 Genetic Deletion Leads to Dilated Cardiomyopathy in Mice and Structural Changes in Drosophila Heart

Cardiomyopathy, disease of the heart muscle, is a significant contributor to heart failure. The pathogenesis of cardiomyopathy is multifactorial and involves genetic, environmental, and lifestyle factors. Identifying and characterizing novel genes that contribute to cardiac pathophysiology are crucial for understanding cardiomyopathy and effective therapies. In this study, we investigated the role of a novel gene, Obg-like ATPase 1 ( Ola1 ), in cardiac pathophysiology using a cardiac-specific knockout mouse model as well as a Drosophila model. Our previous work demonstrated that OLA1 modulates the hypertrophic response of cardiomyocytes through the GSK-beta/beta-catenin signaling pathway. Furthermore, recent studies have suggested that OLA1 plays a critical role in organismal growth and development. For example, Ola1 null mice exhibit increased heart size and growth retardation. It is not known, however, if loss of function for Ola1 leads to dilated cardiomyopathy. We generated cardiac-specific Ola1 knockout mice (OLA1-cKO) to evaluate the role of OLA1 in cardiac pathophysiology. We found that Ola1 -cKO in mice leads to dilated cardiomyopathy (DCM) and left ventricular (LV) dysfunction. These mice developed severe LV dilatation, thinning of the LV wall, reduced LV function, and, in some cases, ventricular wall rupture and death. In Drosophila, RNAi-mediated knock-down specifically in developing heart cells led to the change in the structure of pericardial cells from round to elongated, and abnormal heart function. This also caused significant growth reduction and pupal lethality. Thus, our findings suggest that OLA1 is critical for cardiac homeostasis and that its deficiency leads to dilated cardiomyopathy and dysfunction. Furthermore, our study highlights the potential of the Ola1 gene as a therapeutic target for dilated cardiomyopathy and heart failure.

zDHHC9 Regulates Cardiomyocyte Rab3a Activity and Atrial Natriuretic Peptide Secretion Through Palmitoylation of Rab3gap1

Production and release of natriuretic peptides by the stressed heart reduce cardiac workload by promoting vasodilation, natriuresis, and diuresis, which has been leveraged in the recent development of novel heart-failure pharmacotherapies, yet the mechanisms regulating cardiomyocyte exocytosis and natriuretic peptide release remain ill defined. We found that the Golgi S-acyltransferase zDHHC9 palmitoylates Rab3gap1 resulting in its spatial segregation from Rab3a, elevation of Rab3a-GTP levels, formation of Rab3a-positive peripheral vesicles, and impairment of exocytosis that limits atrial natriuretic peptide release. This novel pathway potentially can be exploited for targeting natriuretic peptide signaling in the treatment of heart failure.

Inter-Species Rescue of Mutant Phenotype-The Standard for Genetic Analysis of Human Genetic Disorders in Drosophila melanogaster Model

Drosophila melanogaster (the fruit fly) is arguably a superstar of genetics, an astonishing versatile experimental model which fueled no less than six Nobel prizes in medicine. Nowadays, an evolving research endeavor is to simulate and investigate human genetic diseases in the powerful D. melanogaster platform. Such a translational experimental strategy is expected to allow scientists not only to understand the molecular mechanisms of the respective disorders but also to alleviate or even cure them. In this regard, functional gene orthology should be initially confirmed in vivo by transferring human or vertebrate orthologous transgenes in specific mutant backgrounds of D. melanogaster. If such a transgene rescues, at least partially, the mutant phenotype, then it qualifies as a strong candidate for modeling the respective genetic disorder in the fruit fly. Herein, we review various examples of inter-species rescue of relevant mutant phenotypes of the fruit fly and discuss how these results recommend several human genes as candidates to study and validate genetic variants associated with human diseases. We also consider that a wider implementation of this evolutionist exploratory approach as a standard for the medicine of genetic disorders would allow this particular field of human health to advance at a faster pace.

Drosophila Heart as a Model for Cardiac Development and Diseases

The Drosophila heart, also referred to as the dorsal vessel, pumps the insect blood, the hemolymph. The bilateral heart primordia develop from the most dorsally located mesodermal cells, migrate coordinately, and fuse to form the cardiac tube. Though much simpler, the fruit fly heart displays several developmental and functional similarities to the vertebrate heart and, as we discuss here, represents an attractive model system for dissecting mechanisms of cardiac aging and heart failure and identifying genes causing congenital heart diseases. Fast imaging technologies allow for the characterization of heartbeat parameters in the adult fly and there is growing evidence that cardiac dysfunction in human diseases could be reproduced and analyzed in Drosophila, as discussed here for heart defects associated with the myotonic dystrophy type 1. Overall, the power of genetics and unsuspected conservation of genes and pathways puts Drosophila at the heart of fundamental and applied cardiac research.