Biology subjects

Ottenheijm, C.

Publications and source records attributed to Ottenheijm, C..

3 recordsLinked to original sources

bioRxiv2026

Integrated Single-Fiber Multi-Omics Links an Inflammatory-Associated Myofiber State to Altered Myosin Dynamics in Patients with ICU-acquired weakness

Skeletal muscle dysfunction is a pervasive complication of critical illness that worsens survival and recovery, yet remains poorly explained by current clinical or molecular markers. To directly connect disease-associated molecular states to the contractile machinery, this study combined sequential functional, transcriptomic, and proteomic profiling of the same single human skeletal myofibers from critically ill patients in the intensive care unit with acquired weakness (ICU-AW) and controls. Despite marked donor-level heterogeneity, integrated analysis revealed a subtle yet conserved myofiber state enriched in ICU-AW, characterized by inflammatory and chemotactic gene programs, intracellular structural remodeling, and bioenergetic adaptation. Nineteen features were significantly altered at both RNA and protein levels from the same myofiber, linking an inflammatory transcriptional landscape to a proteomic shift toward mitochondrial and translational machinery and away from membrane-associated signaling. Functionally, fibers in this state displayed selectively disrupted myosin dynamics, evidenced by prolonged ATP turnover time of myosin heads in their super-relaxed conformation, implicating altered myosin energetics as a contributor to muscle dysfunction. These findings define a discrete, disease-associated myofiber state and establish an integrative single-fiber framework for connecting multi-omic heterogeneity to molecular motor function in complex human disease. Graphical AbstractSingle-fiber multi-omic and functional analysis reveals a stress-adapted myofiber state in ICU-AW. Specifically, for the present study, myofibers from ICU-AW donors and control donors were isolated and functionally profiled for myosin dynamics before being split for simultaneous transcriptomic and proteomic analysis. Integrated analysis then identified a reproducible fiber phenotype enriched in ICU-AW, characterized by inflammatory transcriptional signatures coordinated with mitochondrial proteomic remodeling and altered myosin super-relaxed state energetics. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=95 SRC="FIGDIR/small/706099v1_ufig1.gif" ALT="Figure 1"> View larger version (23K): org.highwire.dtl.DTLVardef@95715forg.highwire.dtl.DTLVardef@1462ff8org.highwire.dtl.DTLVardef@f74996org.highwire.dtl.DTLVardef@10055ec_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2025

The titin N2A-MARP signalosome constrains muscle longitudinal hypertrophy in response to stretch

Titin-based mechanosensing is a key driver of trophic signaling in muscle, yet the downstream pathways linking titin sensing to muscle remodeling remain poorly understood. To investigate these signaling mechanisms, we utilized unilateral diaphragm denervation (UDD), an in vivo model that induces titin-stiffness-dependent hypertrophy via mechanical stretch. Using UDD in rats and mice, we characterized the longitudinal hypertrophic response and distinguished stretch-induced signaling from denervation effects by performing global transcriptomic and proteomic analyses following UDD and bilateral diaphragm denervation (BDD) in rats. Our findings identified upregulation of titin-associated muscle ankyrin repeat proteins (MARPs). Subsequent phosphorylation enrichment mass spectrometry in mouse diaphragm highlighted the involvement of the N2A-element. UDD in MARP knockout (KO) mice resulted in enhanced longitudinal hypertrophy, with Western blot analysis revealing activation of the mTOR pathway. Furthermore, pharmacological inhibition of mTORC1 with rapamycin suppressed longitudinal hypertrophy, demonstrating that mTOR signaling regulates titin-mediated hypertrophic growth in a MARP-dependent manner. These findings establish MARPs as key modulators of titin-based mechanotransduction and highlight mTORC1 as a central regulator of longitudinal muscle hypertrophy.

physiology↗

bioRxiv2023

Characterization of NEB mutations in patients reveals novel nemaline myopathy disease mechanisms and omecamtiv mecarbil force effects

Nebulin, a critical protein of the skeletal muscle thin filament, plays important roles in physiological processes such as regulating thin filament length (TFL), cross-bridge cycling, and myofibril alignment. Mutations in the nebulin gene (NEB) cause NEB-based nemaline myopathy (NEM2), a genetically heterogeneous disorder characterized by hypotonia and muscle weakness, currently lacking therapies targeting the underlying pathological mechanisms. In this study, we examined a cohort of ten NEM2 patients, each with unique mutations, aiming to understand their impact on mRNA, protein, and functional levels. Results show that truncation mutations affect NEB mRNA stability and lead to nonsense-mediated decay of the mutated transcript. Moreover, a high incidence of cryptic splice site activation was found in patients with splicing mutations which is expected to disrupt the actin-binding sites of nebulin. Determination of protein levels revealed patients with relatively normal nebulin levels and others with markedly reduced nebulin. We observed a positive relation between the reduction in nebulin and a reduction in TFL, and a positive relation between the reduction in nebulin level and the reduction in tension (both maximal and submaximal tension). Interestingly, our study revealed a duplication mutation in nebulin that resulted in a larger nebulin protein and longer TFL. Additionally, we investigated the effect of Omecamtiv mecarbil (OM), a small-molecule activator of cardiac myosin, on force production of type I muscle fibers of NEM2 patients. OM treatment substantially increased submaximal tension across all NEM2 patients ranging from 87-318%, with the largest effects in patients with the lowest level of nebulin. In summary, this study indicates that post-transcriptional or post-translational mechanisms regulate nebulin expression. Moreover, we propose that the pathomechanism of NEM2 involves not only shortened but also elongated thin filaments, along with the disruption of actin-binding sites resulting from splicing mutations. Significantly, our findings highlight the potential of OM treatment to improve skeletal muscle function in NEM2 patients, especially those with large reductions in nebulin levels.

genetics↗