Non-peripheral (displaced) myonuclei are characteristic of skeletal muscle pathology and severe injury but also appear after exercise and with aging. Displaced myonuclei are typically attributed to the activity of muscle stem cells, or satellite cells. We sought to address whether displaced myonuclei in adult skeletal muscle are exclusively from an exogenous source such as satellite cells or can result from resident myonuclear migration. To address this question, we used a murine recombination-independent muscle fibre-specific doxycycline-inducible fluorescent myonuclear labelling approach, EdU stem cell fate tracking, two durations of plantaris muscle mechanical overload (MOV, 3 days and 7 days), and fluorescent histology. Our findings show that: 1) displaced myonuclei emerge early during MOV in adult mice, 2) resident myonuclear movement occurs rapidly during MOV, and 3) the contribution of resident versus exogenous displaced myonuclei depends on the preferential effects of MOV for specific fibre types or fibre sizes with a given MOV duration. These observations provide fundamental insights on myonuclear motility in response to stress in vivo and reframe our understanding of how a recognized feature of mammalian skeletal muscle can emerge in response to stressors such as mechanical loading.
© 2025. The Author(s).

Detecting the proliferation of cells with copper(I)-catalyzed azide-alkyne cycloaddition (click chemistry) and the thymidine analogue, 5-ethynyl-2'-deoxyuridine (EdU), is a simpler and more versatile method than traditional antibody-based approaches. Instead of the harsh series of steps typically used for 5-bromo-2'-deoxyuridine (BrdU) detection, detecting EdU does not require DNA denaturation and is suitable for use with other applications. This approach was implemented in an animal model of ischemic stroke. The following protocol details how to use EdU to label, track, and visualize leukocyte recruitment for flow cytometry and fluorescence microscopy, including the processes for EdU injection and blood and tissue sample preparation. Considerations for timing, dosing, and cell viability are also outlined to tailor the protocol to experimental needs. This method could be applied to various models that require extended tracking periods, as the signal from EdU can last several cell divisions, depending on cell type and condition. Key features • EdU labeling is simple and compatible with routine laboratory methods. • This method is compatible with genetically encoded fluorophores, such as GFP and tdTomato. • EdU incorporation in circulating leukocytes varies depending on the specific cell subtype. • This technique can be adapted to track leukocyte recruitment, including when cells are recruited from the bloodstream.
©Copyright : © 2025 The Authors; This is an open access article under the CC BY-NC license.

Skeletal muscle satellite cells (SCs) reside between the myofiber sarcolemma and basal lamina, where extracellular matrix (ECM) interactions are essential for their maintenance and regenerative function. Here, we identify chondrolectin (CHODL), a type I transmembrane protein with a C-type lectin domain, as a critical regulator of SC biology. Single-cell RNA-seq analysis reveals that Chodl is highly enriched in quiescent SCs but downregulated in proliferating myoblasts. Using conditional knockout models, we show that deletion of Chodl in embryonic myoblasts ( Chodl MKO ) or adult SCs ( Chodl PKO ) does not affect muscle development but markedly impairs regeneration in both young and aged mice. Chodl -deficient SCs exhibit reduced self-renewal, diminish proliferation, and impair differentiation, leading to defective myofiber repair. In silico network perturbation further predicts disruption of ECM-ligand interactions and Notch signaling, consistent with our observation that a significant fraction of SCs in Chodl PKO mice localize outside the basal lamina and undergo precocious activation. Together, these findings establish CHODL as a key determinant of SC niche localization and regenerative function, uncovering a previously unrecognized mechanism linking ECM interactions to muscle stem cell maintenance and repair.

In mammals, olfactory sensory neurons (OSNs) are born throughout life, ostensibly solely to replace neurons lost via turnover or injury. This assumption follows from the hypothesis that olfactory neurogenesis is stochastic with respect to neuron subtype, as defined by the single odorant receptor that each neural precursor stochastically chooses out of hundreds of possibilities. This assumption is challenged, however, by recent findings that the birthrates of a fraction of OSN subtypes are selectively reduced by olfactory deprivation. These findings raise questions about how, and why, olfactory stimuli are required to accelerate the neurogenesis rates of some subtypes, including whether the stimuli are specific (e.g. discrete odorants) or generic (e.g. broadly activating odors or mechanical stimuli). Based on previous findings that the exposure of mice to sex-specific odors can increase the representations of subtypes responsive to those odors, we hypothesized that the neurogenic stimuli comprise discrete odorants that selectively stimulate OSNs of the same subtypes whose birthrates are accelerated. In support of this, we have found, using scRNA-seq and subtype-specific OSN birthdating, that exposure to male and exogenous musk odors can accelerate the birthrates of subtypes responsive to those odors. These findings reveal that certain odor experiences can selectively 'amplify' specific OSN subtypes and suggest that persistent OSN neurogenesis serves, in part, an adaptive function.
© 2024, Hossain et al.

Molecular subtypes of small cell lung cancer (SCLC) have been described based on differential expression of the transcription factors (TFs) ASCL1, NEUROD1, and POU2F3 and immune-related genes. We previously reported an additional subtype based on expression of the neurogenic TF ATOH1 within our SCLC circulating tumor cell-derived explant (CDX) model biobank. Here, we show that ATOH1 protein is detected in 7 of 81 preclinical models and 16 of 102 clinical samples of SCLC. In CDX models, ATOH1 directly regulates neurogenesis and differentiation programs, consistent with roles in normal tissues. In ex vivo cultures of ATOH1+ CDXs, ATOH1 is required for cell survival. In vivo, ATOH1 depletion slows tumor growth and suppresses liver metastasis. Our data validate ATOH1 as a bona fide lineage-defining TF of SCLC with cell survival and pro-metastatic functions. Further investigation exploring ATOH1-driven vulnerabilities for targeted treatment with predictive biomarkers is warranted.
Copyright © 2025 The Authors. Published by Elsevier Inc. All rights reserved.