Biology subjects

Garcia-Pavia, P.

Publications and source records attributed to Garcia-Pavia, P..

4 recordsLinked to original sources

bioRxiv2023

Amino acid substitutions hydrophilizing the core of titin domains cause dilated cardiomyopathy

The underlying genetic defect in most cases of dilated cardiomyopathy (DCM), a common inherited heart disease, remains unknown. Intriguingly, many patients carry single missense variants of uncertain pathogenicity targeting the giant protein titin, a fundamental sarcomere component. To explore the deleterious potential of these variants, we first solved the wild-type and mutant crystal structures of I21, the titin domain targeted by pathogenic variant p.C3575S. Although both structures are remarkably similar, the increase in hydrophilicity of deeply buried position 3575 strongly destabilizes the mutant domain, a scenario supported by molecular dynamics simulations and by biochemical assays that show no disulfide involving C3575. Prompted by these observations, we have found that thousands of similar hydrophilizing variants associate specifically with DCM. Hence, our results imply that titin domain destabilization causes DCM, a conceptual framework that not only informs pathogenicity assessment of gene variants but also points to therapeutic strategies counterbalancing protein destabilization.

biochemistry↗

bioRxiv2020

Nanomechanical phenotypes in cMyBP-C mutants that cause hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a disease of the myocardium caused by mutations in sarcomeric proteins with mechanical roles, such as the molecular motor myosin. Around half of the HCM-causing genetic variants target contraction modulator cardiac myosin-binding protein C (cMyBP-C), although the underlying pathogenic mechanisms remain unclear since many of these mutations cause no alterations in protein structure and stability. As an alternative pathomechanism, here we have examined whether pathogenic mutations perturb the nanomechanics of cMyBP-C, which would compromise its modulatory mechanical tethers across sliding actomyosin filaments. Using single-molecule atomic force spectroscopy, we have quantified mechanical folding and unfolding transitions in cMyBP-C mutant domains. Our results show that domains containing mutation R495W are mechanically weaker than wild-type at forces below 40 pN, and that R502Q mutant domains fold faster than wild-type. None of these alterations are found in control, non-pathogenic variants, suggesting that nanomechanical phenotypes induced by pathogenic cMyBP-C mutations contribute to HCM development. We propose that mutation-induced nanomechanical alterations may be common in mechanical proteins involved in human pathologies.

biophysics↗

bioRxiv2020

Conserved cysteines in titin sustain the mechanical function of cardiomyocytes

The protein titin determines cardiomyocyte contraction and truncating variants in the titin gene (TTN) are the most common cause of dilated cardiomyopathy (DCM). Different to truncations, missense variants in TTN are currently classified as variants of uncertain significance due to their high frequency in the population and the absence of functional annotation. Here, we report the regulatory role of conserved, mechanically active titin cysteines, which, contrary to current views, we uncover to be reversibly oxidized in basal conditions leading to isoform- and force-dependent modulation of titin stiffness and dynamics. Building on our functional studies, we demonstrate that missense mutations targeting a conserved titin cysteine alter myocyte contractile function and cause DCM in humans. Our findings have a direct impact on genetic counselling in clinical practice. One sentence summaryMutations targeting cysteines key to the mechanoredox control of titin cause human dilated cardiomyopathy

physiology↗

bioRxiv2020

Functional impact and regulation of global alternative splicing patterns in heart development and disease

Alternative splicing (AS) plays a major role in the generation of transcript diversity. In the heart, roles have been described for some AS variants and individual regulatory RNA binding proteins (RBPs); however, the global impact and regulation of AS patterns in cardiac pathophysiology is poorly understood. Here, we studied the AS profiles in heart disease, their relationship with heart development and the regulatory mechanisms control-ling AS dynamics in the mouse heart using a total of 136 RNA-seq samples. We found that AS and gene expression changes affect different genes, which are also involved in distinct biological functions. Developmental AS changes were more abundant and had stronger predicted impact on the encoded protein than those taking place during heart disease. However, AS changes in heart disease significantly modified protein interaction patterns and rewire the protein-protein interaction network. Using a database of experimentally determined binding sites of a large collection of RNA binding proteins, we studied the regulatory proteins associated to AS changes in each condition. Computational modelling revealed that developmental transitions were mainly driven by the up-regulation of MBNL1, whereas disease associated AS changes were driven by a more complex regulatory network, characterized by the interaction of different RNA binding proteins, with PTBP1 as the largest individual modulator. In adult mice, PTBP1 over-expression was sufficient to induce cardiac hypertrophy and diastolic dysfunction and significantly alter the AS profile. Overall, our study provides new in-sights into the functional impact of AS patterns in cardiac physiology and how computationally driven hypotheses can help to improve our understanding of RNA regulation and its contribution to heart disease.

bioinformatics↗