Biology subjects

Spiegelhalter, C.

Publications and source records attributed to Spiegelhalter, C..

5 recordsLinked to original sources

bioRxiv2025

BIN1 overexpression rescues cardiac but not skeletal muscle defects in a mouse model of caveolinopathy

BackgroundMutations in CAV3, encoding caveolin-3, cause caveolinopathies, rare genetic disorders affecting both skeletal and cardiac muscle. Caveolin-3 contributes to T-tubule formation and excitation-contraction coupling. BIN1 (amphiphysin 2), a membrane-shaping protein critical for T-tubule integrity, has shown therapeutic promise in congenital myopathies and heart dysfunction. To date, there are no therapy for caveolinopathies. MethodsWe evaluated the therapeutic impact of BIN1 overexpression in Cav-3 knockout mice, a model recapitulating key features of human caveolinopathy. We assessed skeletal and cardiac function, T-tubule morphology, mitochondria, and gene expression using histological, physiological, and molecular approaches. ResultsWe found Cav-3-/- mice displayed skeletal muscle weakness, T-tubule disorganization, and mitochondrial abnormalities, alongside cardiac diastolic dysfunction and myofibrillar disarray. While BIN1 overexpression failed to improve skeletal muscle strength, T-tubule structure, or fiber atrophy, it corrected nuclear positioning and partially restored mitochondrial markers. In contrast, BIN1 robustly rescued cardiac performance, restoring end-diastolic volume, cardiac output, and sarcomeric integrity. Expression profiling revealed greater dysregulation of excitation-contraction coupling and atrogene pathways in skeletal than in cardiac muscle. Cavin-4, a BIN1-interacting protein, was selectively dysregulated in Cav3-/- muscle, suggesting a mechanistic barrier to BIN1-mediated rescue in this tissue. ConclusionsThese findings identify tissue-specific differences in the molecular consequences of caveolin-3 loss and demonstrate that BIN1 overexpression effectively rescues cardiac, but not skeletal, manifestations of caveolinopathy. Our results support BIN1 as a promising gene therapy target for inherited cardiomyopathies, while highlighting the need for alternative strategies in skeletal muscle.

pathology↗

bioRxiv2024

Srs2/PARI DNA helicase mediates abscission inhibition in response to chromatin bridges in yeast and human cells

The coordination of chromosome segregation with cytokinesis is crucial for maintaining genomic stability. Chromatin bridges, arising from DNA replication stress or catenated chromosomes, can interfere with this process, leading to genomic instability if not properly managed. Here, we uncover that the budding yeast DNA helicase Srs2 and its human homolog PARI delay the timing of abscission events in the presence of chromatin bridges. We demonstrate that Srs2 is essential for delaying abscission in yeast cells with chromatin bridges, and preventing their damage by cytokinesis. In human cells, PARI similarly plays a key role in delaying abscission events, such as midbody severing and actin patch disassembly during cytokinesis, in response to chromatin bridges caused by topoisomerase II inhibition. Our results also show that PARI functions within the Aurora B-mediated abscission checkpoint pathway. These findings reveal an evolutionarily conserved role of the Srs2/PARI DNA helicase in maintaining genomic integrity by modulating abscission timing in response to chromatin bridge formation.

cell biology↗

bioRxiv2024

Myosin cluster dynamics determines epithelial wound ring constriction

Collection of myosin motors and actin filaments can self-assemble into submicrometric clusters under the regulation of RhoA. Emergent dynamics of these clusters have been reported in a variety of morphogenetic systems, ranging from Drosophila to acto-myosin assays in vitro. In single cell cytokinetic rings, acto-myosin clusters are associated with stress generation when radial and transport when tangential with respect to the ring closure. Here, we show that these phenomena hold true for acto-myosin multi-cellular rings during wound closure in epithelial monolayers. We assessed the activity of RhoA using FRET sensors, and we report that cluster dynamics does not correlate with RhoA activity. Nevertheless, we show that bursts of RhoA activation precede recruitment of myosin. Altogether myosin clusters dynamics is conserved between single and multi-cellular systems and this suggests that they could be used as generic read-outs for mapping and predicting stress generation and shape changes in morphogenesis.

biophysics↗

bioRxiv2023

Senescent cells deposit intracellular contents through adhesion-dependent fragmentation

Cellular senescence is a state of stable arrest and secretion linked to aging and disease. Here we identify that senescent cells dispose of large fragments of themselves through cell-to-cell adhesion, which we term senescent-cell adhesion fragments (SCAFs). Found across all senescent types examined, SCAFs lack nuclear material but contain organelles, including damaged mitochondria. Disrupting adherens junctions decreased SCAF formation but induced senescent-cell death, which was caused by an inability to shed damaged mitochondria. Dynamic analyses show that SCAFs ultimately rupture, releasing a complex proteome including damage-associated molecular patterns (DAMPs) and proteins linked to neurodegenerative disease. Functionally, SCAFs activate wound-healing and cancer-related programs, promoting migration and invasion. Altogether, these findings identify a new feature that facilitates senescent cell survival, but the consequence of which is external deposition of damaged intracellular contents, with implications for cancer and aging.

cell biology↗

bioRxiv2019

Functional analyses of STIM1 mutations reveal a common pathomechanism for tubular aggregate myopathy and Stormorken syndrome

Tubular aggregate myopathy (TAM) is a progressive disorder essentially involving muscle weakness, cramps, and myalgia. TAM clinically overlaps with Stormorken syndrome (STRMK), associating TAM with miosis, thrombocytopenia, hyposplenism, ichthyosis, short stature, and dyslexia. TAM and Stormorken syndrome arise from gain-of-function mutations in STIM1 or ORAI1, both encoding key regulators of Ca2+ homeostasis, and mutations in either gene results in excessive Ca2+ entry. The pathomechanistic similarities and differences of TAM and Stormorken syndrome are only partially understood. Here we provide functional in cellulo experiments demonstrating that STIM1 harboring the TAM D84G or the STRMK R304W mutation similarly cluster and exert a dominant effect on the wild-type protein. Both mutants recruit ORAI1 to the clusters, induce major nuclear import of the Ca2+-dependent transcription factor NFAT, and trigger the formation of circular membrane stacks. In conclusion, the analyzed TAM and STRMK mutations have a comparable impact on STIM1 protein function and downstream effects of excessive Ca2+ entry, highlighting that TAM and Stormorken syndrome involve a common pathomechanism.

molecular biology↗