Biology subjects

Landim-Vieira, M.

Publications and source records attributed to Landim-Vieira, M..

7 recordsLinked to original sources

bioRxiv2026

CD14 Blockade Attenuates Arrhythmogenic Cardiomyopathy

Background: Arrhythmogenic cardiomyopathy (ACM) is a genetic and phenotypically heterogeneous myocardial disorder characterized by progressive cardiomyocyte loss, immune cell infiltration, and fibro-fatty replacement of the ventricular myocardium, with an increased risk of sudden cardiac death (SCD), predominantly caused by mutations in cardiac desmosomal genes including PKP2, DSP, and DSG2. We previously described the pivotal role of NF{kappa}B and CCR2+ cardiac macrophage-triggered inflammation in ACM pathogenesis. Methods: WT or Dsg2mut/mut mice were treated with either isotype control or anti-CD14 antibody once a week for the described treatment period (4 or 8 weeks). At the end of the treatment period, disease characteristics were assessed by echocardiography, electrocardiography, histology, immunofluorescence, positron emission tomography (PET) imaging and single-cell transcriptomics. Results: Here, we demonstrate the efficacy of neutralizing CD14 signaling, an important mediator of inflammatory macrophage activation, in attenuating ACM disease in vivo. Additionally, we elucidate shifts in the cellular and transcriptomic landscapes that occur following anti-CD14 antibody treatment in a well-established mouse model of ACM and identify substantial reductions in inflammatory macrophage and pro-fibrotic fibroblast populations. Conclusion: This study provides evidence that blockade of CD14 can attenuate the ACM disease phenotype. It may do so by inhibiting macrophage-based activation and inflammation, while also altering the transcriptional state of other important cell types. Collectively, these findings suggest that CD14 inhibition may be an effective option for ACM, which should be explored in early-phase clinical studies.

immunology↗

bioRxiv2026

Porcine Left Atrial and Ventricular Thick Filaments Exhibit Distinct Resting Structures and Calcium-dependent Responses

The heart maintains systemic perfusion through the coordinated function of its four chambers: the left and right atria and ventricles. Each chamber has distinct structural, functional, and molecular properties tailored to its role in circulation, which may result in chamber-specific differences in myofilament structure and regulation between atria and ventricles. To test this hypothesis, we employed muscle mechanics and X-ray diffraction to investigate functional and structural differences in porcine left atrial (LA) and left ventricular (LV) tissue. Here, we report the first X-ray diffraction study of atrial tissue, demonstrating that under resting conditions, myosin filaments in LA adopted a more ON-like, structurally distinct configuration compared with those in LV. Under contracting conditions, LV generated greater force and exhibited higher sinusoidal stiffness than LA across multiple calcium concentrations. LA showed faster kTR than in LV, with no calcium-dependence, in contrast to the calcium-dependence of kTR seen in LV. Structurally, the distinct myosin head configuration seen in the relaxed LA persisted during contraction. Furthermore, using the troponin inhibitor MYK-7660 to inhibit active contraction, we showed that, unlike LV, LA showed no direct calcium-dependent thick filament activation, reconciling discrepancies between fast rat and slow porcine ventricular myocardium regarding calciums role in thick filament regulation. Altogether, our study reveals that LA myosin filaments adopt a molecular architecture and regulatory mechanism distinct from their LV counterparts, suggesting that myosin filament structure and regulation have evolved differently to meet the unique functional demands of each cardiac chamber. Moreover, atrial disease is often associated with cardiomyopathy-related genetic variants, highlighting the atrial myocardium as an important therapeutic target and understanding atrial-specific regulatory mechanisms provides new insights into therapeutic strategies for atrial diseases.

physiology↗

bioRxiv2025

Desmoglein-2 deficiency results in cardiac dysfunction by compromising both Z-disc- and intercalated disc-mediated mechanotransduction

Desmoglein-2 (DSG2), a critical component of the cardiac desmosome and located at the cardiomyocyte-cardiomyocyte intercalated disc, is essential for cell-cell adhesion, cardiomyocyte mechanical stability, and electrical coupling between cells. However, its relative contribution in maintaining cardiac function at the sarcomere level remains unclear. Using 4-week-old (adolescent) and 16-week-old (adult) homozygous knock-in Dsg2-mutant (Dsg2mut/mut) mice, we found that loss of DSG2 leads to early onset chamber- and age-dependent cardiac dysfunction driven by Z-disc structural defects and increased myosin detachment rate. Interestingly, Ca{superscript 2}-activated force was markedly reduced in adolescent Dsg2mut/mut permeabilized left ventricular cardiac muscle bundles but preserved in permeabilized isolated cardiomyocytes. This disparity demonstrates that DSG2 is not only crucial for mechanical coupling between cardiomyocytes but also for force transmission within and between sarcomeres, revealing a novel role for DSG2 in maintaining contractile integrity at both the cellular and tissue levels.

biophysics↗

bioRxiv2023

Unlocking the Role of sMyBP-C: A Key Player in Skeletal Muscle Development and Growth

Skeletal muscle is the largest organ in the body, responsible for gross movement and metabolic regulation. Recently, variants in the MYBPC1 gene have been implicated in a variety of developmental muscle diseases, such as distal arthrogryposis. How MYBPC1 variants cause disease is not well understood. Here, through a collection of novel gene-edited mouse models, we define a critical role for slow myosin binding protein-C (sMyBP-C), encoded by MYBPC1, across muscle development, growth, and maintenance during prenatal, perinatal, postnatal and adult stages. Specifically, Mybpc1 knockout mice exhibited early postnatal lethality and impaired skeletal muscle formation and structure, skeletal deformity, and respiratory failure. Moreover, a conditional knockout of Mybpc1 in perinatal, postnatal and adult stages demonstrates impaired postnatal muscle growth and function secondary to disrupted actomyosin interaction and sarcomere structural integrity. These findings confirm the essential role of sMyBP-C in skeletal muscle and reveal specific functions in both prenatal embryonic musculoskeletal development and postnatal muscle growth and function.

physiology↗

bioRxiv2023

Mechanisms of Innate Immune Injury in Arrhythmogenic Cardiomyopathy

Inhibition of nuclear factor kappa-B (NF{kappa}B) signaling prevents disease in Dsg2mut/mut mice, a model of arrhythmogenic cardiomyopathy (ACM). Moreover, NF{kappa}B is activated in ACM patient-derived iPSC-cardiac myocytes under basal conditions in vitro. Here, we used genetic approaches and sequencing studies to define the relative pathogenic roles of immune signaling in cardiac myocytes vs. inflammatory cells in Dsg2mut/mutmice. We found that NF{kappa}B signaling in cardiac myocytes drives myocardial injury, contractile dysfunction, and arrhythmias in Dsg2mut/mut mice. It does this by mobilizing cells expressing C-C motif chemokine receptor-2 (CCR2+ cells) to the heart, where they mediate myocardial injury and arrhythmias. Contractile dysfunction in Dsg2mut/mut mice is caused both by loss of heart muscle and negative inotropic effects of inflammation in viable muscle. Single nucleus RNA sequencing and cellular indexing of transcriptomes and epitomes (CITE-seq) studies revealed marked pro-inflammatory changes in gene expression and the cellular landscape in hearts of Dsg2mut/mut mice involving cardiac myocytes, fibroblasts and CCR2+ cells. Changes in gene expression in cardiac myocytes and fibroblasts in Dsg2mut/mutmice were modulated by actions of CCR2+ cells. These results highlight complex mechanisms of immune injury and regulatory crosstalk between cardiac myocytes, inflammatory cells, and fibroblasts in the pathogenesis of ACM. BRIEF SUMMARYWe have uncovered a therapeutically targetable innate immune mechanism regulating myocardial injury and cardiac function in a clinically relevant mouse model of Arrhythmogenic Cardiomyopathy (ACM).

immunology↗

bioRxiv2021

Post-translational modification patterns on β-myosin heavy chain are altered in ischemic and non-ischemic human hearts

Phosphorylation and acetylation of sarcomeric proteins are important for fine-tuning myocardial contractility. Here, we used bottom-up proteomics and label-free quantification to identify novel post-translational modifications (PTMs) on beta-myosin heavy chain ({beta}-MHC) in normal and failing human heart tissues. We report six acetylated lysines and two phosphorylated residues: K34-Ac, K58-Ac, S210-P, K213-Ac, T215-P, K429-Ac, K951-Ac, and K1195-Ac. K951-Ac was significantly reduced in both ischemic and non-ischemic failing hearts compared to non-diseased hearts. Molecular dynamics simulations show that K951-Ac may impact stability of thick filament tail interactions and ultimately myosin head positioning. K58-Ac altered the solvent exposed SH3 domain surface - known for protein-protein interactions - but did not appreciably change motor domain conformation or dynamics under conditions studied. Together, K213-Ac/T215-P altered loop 1s structure and dynamics - known to regulate ADP-release, ATPase activity, and sliding velocity. Our study suggests that {beta}-MHC acetylation levels may be influenced more by the PTM location than the type of heart disease since less protected acetylation sites are reduced in both heart failure groups. Additionally, these PTMs have potential to modulate interactions between {beta}-MHC and other regulatory sarcomeric proteins, ADP-release rate of myosin, flexibility of the S2 region, and cardiac myofilament contractility in normal and heart failure hearts.

physiology↗

bioRxiv2021

Myofibril orientation as a metric for characterizing heart disease

Myocyte disarray is a hallmark of many cardiac disorders. However, the relationship between alterations in the orientation of individual myofibrils and myofilaments to disease progression has been largely underexplored. This oversight has predominantly been due to a paucity of methods for objective and quantitative analysis. Here we introduce a novel, less-biased approach to quantify myofibrillar and myofilament orientation in cardiac muscle under near physiological conditions and demonstrate its superiority as compared to conventional histological assessments. Using small-angle X-ray diffraction, we first investigated changes in myofibrillar orientation at increasing sarcomere lengths in permeabilized, relaxed, wildtype mouse myocardium by assessing the angular spread of the 1,0 equatorial reflection (angle {sigma}). At a sarcomere length (SL) of 1.9 m, the angle {sigma} was 0.23{+/-}0.01 rad, decreased to 0.19{+/-}0.01 rad at a SL of 2.1 m, and further decreased to 0.15{+/-}0.01 rad at a SL of 2.3 m (p<0.0001). Angle {sigma} was significantly larger in R403Q, a MYH7 hypertrophic cardiomyopathy (HCM) model, porcine myocardium (0.24{+/-}0.01 rad) compared to WT myocardium (0.14{+/-}0.005 rad, p<0.0001) as well as in human heart failure tissue (0.19{+/-}0.006 rad) when compared to non-failing samples (0.17{+/-}0.007 rad, p=0.01). These data indicate that diseased myocardium suffers from greater myofibrillar disorientation compared to healthy controls. Finally, we showed that conventional, histology-based analysis of disarray can be subject to user bias and/or sampling error and lead to false positives. Our method for directly assessing myofibrillar orientation avoids the artifacts introduced by conventional histological approaches that assess myocyte orientation and only indirectly evaluate myofibrillar orientation, and provides a precise and objective metric for phenotypically characterizing myocardium. The ability to obtain excellent X-ray diffraction patterns from frozen human myocardium provides a new tool for investigating structural anomalies associated with cardiac diseases. Statement of SignificanceWe introduce a precise and quantitative approach to directly measure myofibrillar and myofilament orientation in cardiac muscle under near physiological conditions as a novel tool for phenotypically characterizing striated muscle systems. We use this technique to demonstrate that myocardium from disease model organisms and failing human myocardium suffers from greater myofibrillar disorientation compared to healthy controls. We also demonstrate that excellent diffraction patterns can be obtained from frozen and thawed human myocardium. Given the ready availability of frozen human heart tissue in tissue banks, this capability opens up a large space of potential experiments relating sarcomere structure to dysfunction in cardiac disorders.

biophysics↗