Biology subjects

Ashby, N.

Publications and source records attributed to Ashby, N..

5 recordsLinked to original sources

bioRxiv2026

Deep-tissue mechanosensation emerges from the interaction of external force and internal tissue state

Muscle sensation is often considered in terms of proprioception, but muscle pain illustrates that other types of sensory neurons are also involved. Here, we show that trigeminal neurons innervating the masseter muscle fall into three classes: A{beta} low-threshold mechanoreceptors, A{delta} high-threshold mechanoreceptors (A{delta}-HTMRs), and peptidergic neurons (PEP). All three types are recruited by mechanical stimulation, with massage being a particularly effective stimulus. Chemogenetic activation of masseter A{delta}-HTMRs and PEP neurons results in pain-like symptoms. Moreover, acute and chronic inflammation sensitize nociceptors, altering behavioral tolerance in an animal model of massage. Taken together, our results provide a framework for understanding muscle somatosensation and how massage of sore muscles may be painful yet beneficial. SignificanceMuscle sensation is usually most prominent when something goes wrong: after overuse, injury, or inflammation, even ordinary pressure or movement can become painful. Yet how mechanical force is detected in muscle, and when a stimulus becomes painful, remain poorly understood. Here, we identify a simple cellular organization for muscle mechanosensation in which three sensory-neuron classes encode force through graded population recruitment. Massage effectively recruited all three classes, including the two nociceptive populations. We further show that these nociceptive neurons are sensitized by acute and chronic inflammation, leading to enhanced recruitment during massage. These findings show that the representation of mechanical force in muscle can be shaped by tissue state and provide a foundation for understanding muscle soreness, pain, and therapeutic touch.

neuroscience↗

bioRxiv2026

3D cortical microtissue with innate microglia for studying real-time cell behavior across maturation and inflammatory response

Microglia represent the immune component of the central nervous system (CNS) that displays dynamic responses to injury and disease. Across the developing and mature CNS, microglia emerge as immunocompetent cells that continuously survey their surroundings to maintain tissue homeostasis and respond to threats. There remains a gap in 3D in vitro models that contain microglia and can provide both developmental and mature functional hallmarks. Using a 3D neural multicellular model, cortical microtissues, derived from primary rat cortical cells, we conducted live imaging to monitor microglia dynamics from early, middle, and late stage microtissue maturation. We optimized a within-micromold imaging approach that allows for live microglia imaging without removing microtissues from their culturing environment. We confirm that microglia exhibit baseline surveillance characterized by relatively stationary somas and highly dynamic cell processes that continuously extend and retract. Following proinflammatory challenges, microglia engulf lipopolysaccharide particles, accompanied by dynamic shifts in motility patterns; and rapidly respond to laser-induced tissue damage through process extension, whole-cell displacement, and local recruitment. Lastly, we show that microtissue age in culture strongly influences both baseline and directed motility profiles. Collectively, these studies demonstrate that within a 3D microenvironment, microglia exhibit pronounced changes in morphology, surveillance area, motility, and injury response across microtissue maturation. Microtissues can serve as a valuable in vitro platform for both microglia developmental studies and investigations of brain inflammation related to CNS injuries, infections, and diseases.

neuroscience↗

bioRxiv2026

Log-linear scaling of TRPV4-KCNN4 transcripts tunes ROCK-dependent mechanotransduction in a DCIS progression model

Mechanotransduction converts mechanical stress into cellular responses, yet how transcript abundance sets mechanotransduction capacity remains unclear. Using an isogenic MCF10A breast epithelial progression series in which crowding functionally inhibits plasma-membrane TRPV4 and triggers pro-invasive motility, we quantified how pathway mRNA levels relate to stress-evoked single-cell motility. TRPV4 (Ca{superscript 2}-permeable mechanosensor) and KCNN4 (Ca{superscript 2}-activated K channel) mRNA levels scaled log-linearly with motility under hyperosmotic stress or pharmacologic TRPV4 inhibition (both engaging the crowding-induced pro-invasive motility program) across a [~]600-fold TRPV4 mRNA range including isogenic and patient-derived DCIS lines (TRPV4: R{superscript 2}=0.89-0.92; KCNN4: R{superscript 2}=0.81-0.94). In contrast, bulk TRPV4 protein did not correlate with motility. Mechanistically, ROCK inhibition abolished stress-induced cortical actin-myosin organization and associated motility gains, identifying ROCK-dependent cortical contractility as a downstream effector. Notably, log-linear scaling was restricted to membrane channels and did not extend to tested cytosolic effectors, suggesting hierarchical transcript regulation may shape heterogeneous DCIS stress responsiveness in this model system.

cell biology↗

bioRxiv2024

Cell crowding induces TRPV4 inhibition and its relocation to plasma membranes, implicating pro-invasive cell volume reduction mechanotransduction pathway

Cell crowding is a common microenvironmental factor influencing various disease processes, but its role in promoting cell invasiveness remains unclear. This study investigates the biomechanical changes induced by cell crowding, focusing on pro-invasive cell volume reduction in ductal carcinoma in situ (DCIS). Crowding specifically enhanced invasiveness in high-grade DCIS cells through significant volume reduction compared to hyperplasia-mimicking or normal cells. Mass spectrometry revealed that crowding selectively relocated ion channels, including TRPV4, to the plasma membrane in high-grade DCIS cells. TRPV4 inhibition triggered by crowding decreased intracellular calcium levels, reduced cell volume, and increased invasion and motility. During this process, TRPV4 membrane relocation primed the channel for later activation, compensating for calcium loss. Analyses of patient-derived breast cancer tissues confirmed that plasma membrane- associated TRPV4 is specific to high-grade DCIS and indicates the presence of a pro-invasive cell volume reduction mechanotransduction pathway. Hyperosmotic conditions and pharmacologic TRPV4 inhibition mimicked crowding-induced effects, while TRPV4 activation reversed them. Silencing TRPV4 diminished mechanotransduction in high-grade DCIS cells, reducing calcium depletion, volume reduction, and motility. This study uncovers a novel pro-invasive mechanotransduction pathway driven by cell crowding and identifies TRPV4 as a potential biomarker for predicting invasion risk in DCIS patients.

cell biology↗

bioRxiv2023

ATF2 phosphorylation is a key event in neuronal apoptosis, linking the DLK/LZK kinase cascade to JUN upregulation

Apoptotic neuron death is a key feature of neurodegenerative disease. Considerable efforts have been made to target this pathway but the molecular mechanisms remain incompletely understood. Here, we conducted an unbiased whole genome CRISPR inhibition screen in human neurons to discover genes required for their death and identified known targets including the kinase MAP3K12 (DLK) and the transcription factor JUN. In addition, this screen revealed a potential role for the transcription factor ATF2. We demonstrate that ATF2 phosphorylation by MAP3 kinases is the core driver of the pro-apoptotic transcriptional response. Surprisingly, JUN phosphorylation is not required for apoptosis. However, the phosphorylation of ATF2 and upregulation of JUN expression are crucial. ATF2 therefore converts the kinase signal into a transcriptional response. Inhibiting ATF2 in cultured human neurons prevents cell death. Notably we show that ATF2 knockdown is neuroprotective in injury models in vivo. Thus, ATF2 provides a promising new target for a wide range of neurodegenerative disorders.

neuroscience↗