Modak, S. | bioRxiv Science

bioRxiv2026

Molecular and Cellular Determinants of Human Iron Overload Cardiomyopathy

Iron overload cardiomyopathy (IOC) is a serious heart condition that is caused by elevated levels of systemic iron. IOC is characterized by both systolic and diastolic dysfunction as well as arrhythmias. It has been challenging to isolate the cardiac-specific cellular and molecular mechanisms driving IOC because the disease affects multiple interconnected organ systems. Here, we leverage stem cell technologies, cardiac tissue engineering, and protein reconstitution assays to model key aspects of human IOC in vitro and to probe the cellular and molecular mechanisms driving cardiac dysfunction. We demonstrate that human engineered heart tissues consisting of both cardiomyocytes and cardiac fibroblasts faithfully recapitulate key aspects of the human disease, including reduced systolic function, impaired diastolic function, and increased prevalence of arrhythmogenic events. We demonstrate that while both cardiomyocytes and cardiac fibroblasts show increased intracellular iron levels, leading to reduced viability, cardiomyocytes show higher levels of iron accumulation and higher levels of reactive oxygen species production. Moreover, we show that in a tissue, iron overload has little effect on the action potential kinetics; however, it directly impacts the amplitude and kinetics of the calcium transient, potentially driving arrhythmogenesis. Finally, we demonstrate that iron overload decreases force production, in part, through oxidative damage of sarcomeric proteins and direct iron-based inhibition of myosin. In summary, our results reveal new insights into the cellular and molecular mechanisms of human IOC pathogenesis, and they establish new in vitro models that can be harnessed to faithfully recapitulate key aspects of the human disease phenotype. HighlightsO_LIContractile aspects of iron overload cardiomyopathy have been difficult to study in vitro. C_LIO_LIWe developed engineered heart tissues to model key aspects of the human disease. C_LIO_LIIn vitro iron overload reduces contractility and induces arrhythmogenesis. C_LIO_LIIron differentially affects cardiomyocytes and cardiac fibroblasts. C_LIO_LIIron overload directly impacts the actomyosin contractile apparatus. C_LI

biophysics↗

bioRxiv2022

Clonal evolution during metastatic spread in high-risk neuroblastoma

High-risk neuroblastoma is generally metastatic and often lethal. Using genomic profiling of 470 sequential and spatially separated samples from 283 patients, we characterize subtype-specific genetic evolutionary trajectories from diagnosis, through progression and end-stage metastatic disease. Clonal tracing timed disease initiation to embryogenesis. Continuous acquisition of structural variants at disease defining loci (MYCN, TERT, MDM2-CDK4) followed by convergent evolution of mutations targeting shared pathways emerged as the predominant feature of progression. At diagnosis metastatic clones were already established at distant sites where they could stay dormant, only to cause relapses years later and spread via metastasis-to-metastasis and polyclonal seeding after therapy.

genomics↗

bioRxiv2020

Baffling: A cheater strategy using self-made tools in tree crickets

Intense sexual selection in the form of mate choice can facilitate the evolution of different alternative reproductive strategies. These strategies can be condition-dependent, wherein genetically similar individuals express the strategy based on their condition. Our study shows that baffling, a mate attraction strategy using self-made acoustic amplifiers, employed by male tree crickets, is a classic example of a condition-dependent alternative strategy. We show that less preferred males, who are smaller or produce less loud calls, predominantly use this alternative strategy. Baffling allows these males to increase their call loudness and advertisement range, and attract a higher number of mates. Baffling also allows these males to deceive females into mating for longer durations with them. Our results suggest that the advantage of baffling in terms of sperm transfer is primarily limited to less preferred males, thus maintaining the polymorphism of calling strategies in the population. Impact statementThis study shows that less preferred tree cricket males use an alternative signaling strategy to call louder, thus attracting and mating with otherwise choosy females using deception.

evolutionary biology↗