Biology subjects

Dente, M.

Publications and source records attributed to Dente, M..

4 recordsLinked to original sources

bioRxiv2026

Species-Dependent Limitations of Murine Myocardium for Investigating the Combined Inotropic Effects of SERCA2a Stimulation and Myofilament Ca2+ Sensitization

Impaired sarcoplasmic reticulum Ca2+ handling and myofilament function both contribute to contractile dysfunction in heart failure. A previous study in failing human myocardium showed that combining the SERCA2a activator istaroxime (ISTA) with the Ca2+ sensitizer levosimendan (LEVO) produces greater positive inotropy than either drug alone. However, human multicellular preparations did not allow comprehensive investigation of the underlying cellular mechanisms. We therefore assessed contractile performance and Ca2+ dynamics in murine multicellular myocardial preparations and ventricular cardiomyocytes treated with ISTA (20 M), LEVO (0.5 M), or their combination. ISTA improved developed force, contraction-relaxation kinetics, and mechanical restitution. These effects were associated with increased Ca2+ transient amplitude, accelerated Ca2+ rise and decay, and enhanced sarcoplasmic reticulum reloading. Adding LEVO produced no further mechanical benefit and only minor changes in Ca2+ handling. LEVO alone elicited heterogeneous contractile responses and increased myofilament Ca2+ sensitivity in only a minority of cardiomyocytes, while consistently accelerating Ca2+ transient decay. This effect was reproduced by the phosphodiesterase-3 inhibitor cilostamide, after which LEVO caused no significant additional change, consistent with a contribution of downstream cAMP-PKA signaling to the acceleration of Ca2+ removal. Thus, limited murine responsiveness to LEVO-mediated myofilament sensitization prevented mechanistic reconstruction of the additive inotropic effect observed in human myocardium, highlighting a species-dependent limitation of the mouse model for studying this combined therapy.

physiology↗

bioRxiv2025

Molecular mechanisms of altered contraction with the β-myosin R403Q mutation in porcine ventricular muscle and a human stem cell-derived cardiomyocyte model.

I.The R403Q mutation in the sarcomere protein beta-myosin heavy chain ({beta}-MHC) is a known genetic cause of hypertrophic cardiomyopathy (HCM), associated with ventricular hypercontractility, impaired relaxation, and cardiac arrhythmias. Despite extensive research, the mutations impact on myosin contractile properties remains unclear, likely due, at least in part, to discrepancies cross different model systems. In this study, we used a multidisciplinary approach to explore mutational effects using two distinct heterozygous R403Q systems: a Yucatan minipig model and human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). X-ray diffraction of R403Q minipig ventricular muscle demonstrated reduced order of the thick filament, suggesting destabilization of the inhibited OFF (vs. ON) state of myosin in relaxed muscle, which correlated with elevated force at submaximal calcium. Super-resolution, single-molecule fluorescence microscopy indicated elevated ATPase activity in thick filament zones lacking cMyBP-C. Furthermore, R403Q myofibrils exhibited slower activation and relaxation kinetics, with reduced sensitivity to ADP. Molecular dynamics simulations suggested that altered interactions at the actomyosin interface contribute to these effects, rather than changes at the nucleotide binding pocket, typically associated with ADP release. Human engineered heterozygous R403Q hiPSC-CMs exhibited reduced maximal myofibril force, slowed contractile kinetics, and hypercontraction in engineered heart tissue constructs-consistent with HCM phenotypes observed in the heterozygous porcine model. Our results demonstrate that the R403Q mutation induces early and persistent contractile dysfunction, and that hypercontractility and slower contractile kinetics may result from a combination of an increased population of activated (ON) myosin heads and delayed detachment during cross-bridge cycling, respectively.

biophysics↗

bioRxiv2025

Probing relaxed myosin states in hypertrophic cardiomyopathy by second harmonic-generation microscopy

This study explores the use of polarized second-harmonic generation (pSHG) to investigate myosin conformation in the relaxed state, differentiating between the actin-available, disordered (ON) state and the energy-conserving, ordered (OFF) state. By shifting the ON/OFF equilibrium using both physical and chemical manipulations, we demonstrate the sensitivity of pSHG in quantifying the ON/OFF ratio in skeletal and cardiac tissues. Comparisons with X-ray diffraction measurements further validate our findings. Applying this approach to a sarcomeric mutation associated with hypertrophic cardiomyopathy, we show that R403Q/MYH7-mutated minipig ventricle tissue exhibits a higher ON fraction compared to controls. This difference is abolished under high concentrations of a myosin activator (2-deoxyATP) and an inhibitor (Mavacamten), indicating structural similarity between R403Q and controls in these two states. ATPase assays reveal increased resting ATPase activity in R403Q samples, which persists even in the presence of 2-deoxyATP, suggesting that the elevated energy consumption in the R403Q mutation is driven by both a population shift toward the ON state and enhanced myosin ATPase activity per motor head.

physiology↗

bioRxiv2022

Species interactions promote parallel evolution of global transcriptional regulators in a widespread Staphylococcus species

Experimental studies of microbial evolution have largely focused on monocultures of model organisms, but most microbes live in communities where interactions with other species may impact rates and modes of evolution. Using the cheese rind model microbial community, we determined how species interactions shape the evolution of the widespread food- and animal-associated bacterium Staphylococcus xylosus. We evolved S. xylosus for 450 generations alone or in co-culture with one of three microbes: the yeast Debaryomyces hansenii, the bacterium Brevibacterium aurantiacum, and the mold Penicillium solitum. We used the frequency of colony morphology mutants (pigment and colony texture phenotypes) and whole-genome sequencing of isolates to quantify phenotypic and genomic evolution after 15 weeks of the evolution. The yeast D. hansenii strongly promoted diversification of S. xylosus; by the end of the experiment, all populations co-cultured with the yeast were dominated by pigment and colony morphology mutant phenotypes. Populations of S. xylosus grown alone, with Brevibacterium, or with Penicillium did not evolve novel phenotypic diversity. Whole-genome sequencing of individual mutant isolates across all four treatments revealed numerous unique mutations in the operons for the SigB, Agr, and WalKR global regulators, but only in the D. hansenii treatment. Phenotyping and RNA-seq experiments demonstrated that these mutations altered pigment and biofilm production, spreading, stress tolerance, and metabolism of S. xylosus. Fitness experiments revealed trade-offs of these mutations across biotic environments caused by antagonistic pleiotropy, where beneficial mutations that evolved in the presence of the yeast Debaryomyces had strong negative fitness effects in other biotic environments. IMPORTANCESubstantial phenotypic and genomic variation exists within microbial species, but the ecological factors that shape this strain diversity are poorly characterized. We demonstrate that the biotic context of a widespread Staphylococcus species can impact the evolution of strain diversity. This work demonstrates the potential for microbes in food production environments to rapidly evolve to novel substrates and biotic environments. Our findings may also help understand how other Staphylococcus species may evolve in multispecies microbiomes.

microbiology↗