Biology subjects

Nelson, C. M.

Publications and source records attributed to Nelson, C. M..

15 recordsLinked to original sources

bioRxiv2026

Individual traits shape hemispheric vlPFC sensitization to Cyberball exclusion: Evidence from single-trial fNIRS analyses

Ostracism (i.e., social exclusion) threatens social security and individuals who are hypersensitive to it may face long-term negative mental health consequences. Clarifying how self-reported distress and neural responses to ostracism unfold moment-by-moment and across varying levels of individual traits may help better understand what contributes to hypersensitivity. To this objective, the current study employed a functional near-infrared spectroscopy (fNIRS) adapted Cyberball task and single-trial analytic techniques in a sample of 53 college students (aged 18-22 years). Results confirmed that Cyberball induced ostracism increased self-reported distress and neural activity in the ventrolateral prefrontal cortex (vlPFC), a region associated with emotion regulation. Self-reported distress varied with differences in social anxiety and need for belonging. Moreover, vlPFC activity sensitized across exclusion-specific trials and this neural sensitization was differentially modulated by social anxiety, need for belonging, and personality growth mindset. The current study highlights the value of single-trial approaches for capturing the nuanced temporal dynamics of ostracism responses. Additionally, it underscores the importance of examining how individual differences shape immediate responses to ostracism to better understand their association with downstream, longer-term consequences.

neuroscience↗

bioRxiv2026

TGFβ determines epithelial tissue spacing by regulating mesenchymal condensation

The branched structure of the vertebrate lung provides a high surface area-to-volume ratio, which increases the efficiency of diffusion-driven gas exchange. Generating this structure requires that the epithelial branches avoid contacting each other as they elongate during development. Previous studies have suggested that the spacing between neighboring branches is intrinsic to growth of the epithelium, but the underlying physical mechanisms remain elusive. Here, we used the embryonic chicken lung as a model system and found that branch spacing is regulated primarily by signaling to the mesenchyme through transforming growth factor-beta (TGF{beta}). Although proliferation decreases in epithelial cells that are located in close proximity to an adjacent branch, these patterns surprisingly emerge after regular branch spacing has been established. Instead, we find that TGF{beta} promotes the directed migration of mesenchymal cells, which form a condensation that physically displaces the adjacent epithelium and tunes branch spacing. Continuous disruption of TGF{beta} signaling prevents mesenchymal condensation and eventually results in contact between adjacent branches. These data suggest that the spacing between epithelial branches results from mesenchymal cell dynamics rather than from epithelial-intrinsic self-avoidance.

developmental biology↗

bioRxiv2025

Mapping embryonic mouse lung development using enhanced spatial transcriptomics

The mature mammalian lung contains [~]50 different cell types that are located in precise positions along and around the airway epithelial tree. Here, we investigated how these spatial patterns are progressively established during development. Specifically, we optimized a microfluidics-enabled, deterministic barcoding-based sequencing (DBiT-seq) workflow to achieve highly sensitive spatial mapping of tissue sections from early embryonic mouse lungs. Spatial mapping of epithelial populations revealed that Sox9+ epithelial progenitors are located throughout the epithelial tree at early stages before becoming confined to the distal ends. Spatial mapping of mesenchymal populations revealed a previously unrecognized mesenchymal cluster that expresses high levels of extracellular matrix proteins and appears to promote embryonic lung innervation. These findings provide new insights into the spatial organization and cellular dynamics underlying early lung development, and demonstrate the power of spatial transcriptomics to uncover hidden patterns and populations of cells.

developmental biology↗

bioRxiv2025

Biophysical mechanisms of morphogenesis in lizard lungs

The lungs of squamate reptiles (lizards and snakes) are highly diverse, exhibiting single chambers, multiple chambers, transitional forms with two to three chambers, along with a suite of other anatomical features, including finger-like epithelial projections into the body cavity known as diverticulae. During embryonic development of the simple, sac-like lungs of anoles, the epithelium is pushed through the openings of a pulmonary smooth muscle mesh by the forces of luminal fluid pressure. This process of stress ball morphogenesis generates the faveolar epithelium typical of squamate lungs. Here, we compared embryonic lung development in brown anoles, leopard geckos, and veiled chameleons to determine if stress ball morphogenesis is conserved across squamates and to understand the physical processes that generate transitional-chambered lungs with diverticulae. We found that epithelial protrusion through the holes in a pulmonary smooth muscle mesh is conserved across squamates. Surprisingly, however, we found that luminal inflation is not conserved. Instead, leopard geckos and veiled chameleons appear to generate their faveolae via epithelial folding downstream of epithelial proliferation. We also found experimental and computational evidence suggesting that the transitional chambers and diverticulae of veiled chameleon lungs develop via apical constriction, a process known to be crucial for airway branching in the bird lung. Thus, distinct morphogenetic mechanisms generate epithelial diversity in squamate lungs, which may underpin their species-specific physiological and ecological adaptations.

developmental biology↗

bioRxiv2025

Patterns of Mitochondrial ATP Predict Tissue Folding

The construction of complex tissue shapes during embryonic development results from spatial patterns of gene expression and mechanical forces fueled by chemical energy from ATP hydrolysis. We find that chemical energy is similarly patterned during morphogenesis. Specifically, mitochondria are locally enriched at the apical sides of epithelial cells during apical constriction, which is widely used across the animal kingdom to fold epithelial tissues. Timelapse imaging, spatial transcriptomics, and measurements of oxygen consumption rate reveal that mitochondrial density, potential, and ATP increase in epithelial cells prior to actomyosin contraction and tissue folding, which is prevented by inhibiting oxidative phosphorylation. Mitochondrial enrichment and apicobasal patterning are conserved during apical constriction in flies, chicks, and mice, and these subcellular patterns can be used to predict computationally patterns of tissue folding. These findings highlight a spatial dimension of bioenergetics in embryonic development.

developmental biology↗

bioRxiv2025

High-fat circulating nutrients promote growth and invasion in a 3D microfluidic tumor model of triple-negative breast cancer

Diet influences the levels of small molecules that circulate in plasma and interstitial fluid, altering the biochemical composition of the tumor microenvironment (TME). These circulating nutrients have been associated with how tumors grow and respond to treatment, but it remains difficult to parse their direct effects on cancer cells. Here, we combine a three-dimensional (3D) microfluidic tumor model with physiologically relevant culture media to investigate how concentrations of circulating nutrients influence tumor growth, cancer cell invasion, and overall tumor metabolism. Human triple-negative breast cancer cells cultured in 2D under media conditions mimicking five different dietary states show no observable differences in proliferation or morphology. Nonetheless, those exposed to high-fat conditions exhibit increased metabolic activity and upregulate genes associated with motility and extracellular matrix remodeling. In the 3D microfluidic model, high-fat conditions accelerate tumor growth and invasion and induce the formation of hollow cavities. Surprisingly, the presence of these cavities does not correlate with an increase in apoptosis or ferroptosis. Instead, RNA-sequencing analysis revealed that high-fat conditions induce the expression of MMP1, consistent with cavitation via cell invasion. Mimicking the flow of circulating nutrients within the TME can thus be used to identify novel connections between metabolic states and tumor phenotype.

bioengineering↗

bioRxiv2023

Mesenchymal Vangl facilitates airway elongation and widening independently of the planar cell polarity complex

A hallmark of mammalian lungs is the fractal nature of the bronchial tree. In the adult, each successive generation of airways is a fraction of the size of the parental branch. This fractal structure is physiologically beneficial, as it minimizes the energy needed for breathing. Achieving this pattern likely requires precise control of airway length and diameter, as the branches of the embryonic airways initially lack the fractal scaling observed in those of the adult lung. In epithelial monolayers and tubes, directional growth can be regulated by the planar cell polarity (PCP) complex. Here, we comprehensively characterized the roles of PCP-complex components in airway initiation, elongation, and widening during branching morphogenesis of the murine lung. Using tissue-specific knockout mice, we surprisingly found that branching morphogenesis proceeds independently of PCP-component expression in the developing airway epithelium. Instead, we found a novel, Celsr1-independent role for the PCP component Vangl in the pulmonary mesenchyme. Specifically, mesenchymal loss of Vangl1/2 leads to defects in branch initiation, elongation, and widening. At the cellular level, we observe changes in the shape of smooth muscle cells that indicate a potential defect in collective mesenchymal rearrangements, which we hypothesize are necessary for lung morphogenesis. Our data thus reveal an explicit function for Vangl that is independent of the core PCP complex, suggesting a functional diversification of PCP components in vertebrate development. These data also reveal an essential role for the embryonic mesenchyme in generating the fractal structure of airways of the mature lung.

developmental biology↗

bioRxiv2023

An Anaplasma phagocytophilum T4SS effector, AteA, is essential for tick infection

Pathogens must adapt to disparate environments in permissive host species, a feat that is especially pronounced for vector-borne microbes, which transition between vertebrate hosts and arthropod vectors to complete their lifecycles. Most knowledge about arthropod-vectored bacterial pathogens centers on their life in the mammalian host, where disease occurs. However, disease outbreaks are driven by the arthropod vectors. Adapting to the arthropod is critical for obligate intracellular rickettsial pathogens, as they depend on eukaryotic cells for survival. To manipulate the intracellular environment, these bacteria use Type IV Secretion Systems (T4SS) to deliver effectors into the host cell. To date, few rickettsial T4SS translocated effectors have been identified and have only been examined in the context of mammalian infection. We identified an effector from the tick-borne rickettsial pathogen Anaplasma phagocytophilum, HGE1_02492, as critical for survival in tick cells and acquisition by ticks in vivo. Conversely, HGE1_02492 was dispensable during mammalian cell culture and murine infection. We show HGE1_02492 is translocatable in a T4SS-dependent manner to the host cell cytosol. In eukaryotic cells, the HGE1_02492 localized with cortical actin filaments, which is dependent on multiple sub-domains of the protein. HGE1_02492 is the first arthropod-vector specific T4SS translocated effector identified from a rickettsial pathogen. Moreover, the subcellular target of HGE1_02492 suggests that A. phagocytophilum is manipulating actin to enable arthropod colonization. Based on these findings, we propose the name AteA for Anaplasma (phagocytophilum) tick effector A. Altogether, we show that A. phagocytophilum uses distinct strategies to cycle between mammals and arthropods. ImportanceTicks are the number one vector of pathogens for livestock worldwide and for humans in the US. The biology of tick transmission is an understudied area. Understanding this critical interaction could provide opportunities to affect the course of disease spread. In this study we examined the zoonotic tick-borne agent Anaplasma phagocytophilum and identified a secreted protein, AteA, that is expressed in a tick-specific manner. These secreted proteins, termed effectors, are the first proteins to interact with the host environment. AteA is essential for survival in ticks and appears to interact with cortical actin. Most effector proteins are studied in the context of the mammalian host; however, understanding how this unique set of proteins affect tick transmission is critical to developing interventions.

microbiology↗

bioRxiv2022

Vangl facilitates mesenchymal thinning during lung sacculation independently of Celsr

The planar cell polarity (PCP) complex orients cytoskeletal and multicellular organization throughout vertebrate development. PCP is speculated to function in formation of the murine lung, where branching morphogenesis generates a complex tree of tubular epithelia whose distal tips expand dramatically during sacculation in preparation for gas exchange after birth. Here, using tissue-specific knockouts, we show that the PCP complex is dispensable in the airway epithelium for sacculation. Rather, we find a novel, Celsr1-independent role for the PCP component Vangl in the pulmonary mesenchyme: loss of Vangl1/2 inhibits mesenchymal thinning and expansion of the saccular epithelium. Further, loss of mesenchymal Wnt5a mimics the sacculation defects observed in Vangl2-mutant lungs, implicating mesenchymal Wnt5a/Vangl signaling as a key regulator of late lung morphogenesis. By mathematically modeling sacculation, we predict that the process of sacculation requires a fluid mesenchymal compartment. Finally, lineage-tracing and cell-shape analyses are consistent with the pulmonary mesenchyme acting as a fluid tissue, and suggest that loss of Vangl1/2 likely impacts the ability of mesenchymal cells to exchange neighbors. Our data thus uncover an explicit function for Vangl and the pulmonary mesenchyme during late lung morphogenesis to actively shape the saccular epithelium.

developmental biology↗

bioRxiv2022

pYtags enable spatiotemporal measurements of receptor tyrosine kinase signaling in living cells

Receptor tyrosine kinases (RTKs) are major signaling hubs in metazoans, playing crucial roles in cell proliferation, migration, and differentiation. However, few tools are available to measure the activity of a specific RTK in individual living cells. Here, we present pYtags, a modular approach for monitoring the activity of a user-defined RTK by live-cell microscopy. pYtags consist of an RTK modified with a tyrosine activation motif that, when phosphorylated, recruits a fluorescently labeled tandem SH2 domain with high specificity. We show that pYtags enable the monitoring of a specific RTK on seconds-to-minutes time scales and across subcellular and multicellular length scales. Using a pYtag biosensor for epidermal growth factor receptor (EGFR), we quantitively characterize how signaling dynamics vary with the identity and dose of activating ligand. We show that orthogonal pYtags can be used to monitor the dynamics of EGFR and ErbB2 activity in the same cell, revealing distinct phases of activation for each RTK. The specificity and modularity of pYtags opens the door to robust biosensors of multiple tyrosine kinases and may enable engineering of synthetic receptors with orthogonal response programs. HighlightsO_LIpYtags report on signaling of user-defined RTKs in living cells C_LIO_LIEGFR signaling dynamics depend on ligand identity and dimer strength C_LIO_LIrthogonal pYtags enable reporter multiplexing C_LIO_LIpYtags can report on signaling of endogenously expressed RTKs C_LI

cell biology↗

bioRxiv2022

Origins of smooth muscle and evolutionary specializations of the pulmonary mesenchyme in the vertebrate lung

Lungs exhibit strikingly diverse epithelial architectures - from the branched airways of mammals to the sac-like lungs of lizards and the looped airways of birds. Across lineages, the pulmonary mesenchyme gives rise to smooth muscle that interacts with and shapes the underlying pulmonary epithelium. In mammals and lizards, pulmonary smooth muscle forms early and drives epithelial branching, whereas in birds it appears only after morphogenesis is largely complete. The developmental basis for this delay has remained unclear. Using comparative single-cell RNA sequencing, ATAC-sequencing, and imaging of mouse, anole, and chicken embryos, we found that smooth muscle in the chicken lung is transcriptionally similar to vascular, rather than visceral, smooth muscle. Strikingly, imaging revealed smooth muscle cells extending between the pulmonary vasculature and the epithelium, and surgical removal of these vessels prevented the formation of smooth muscle around the airways. The vascular transcription factor PITX2 was highly expressed in these cells and its knockdown markedly reduced smooth muscle differentiation. Taken together, these findings identify vascular smooth muscle as the developmental source of pulmonary smooth muscle in birds and establish PITX2 as a key regulator of this lineage transition, revealing an unexpected developmental and evolutionary link between the circulatory and respiratory systems.

developmental biology↗

bioRxiv2022

Plasticity in airway smooth muscle differentiation during mouse lung development

Smooth muscle differentiation has been proposed to sculpt airway epithelial branches in mammalian lungs. Serum response factor (SRF) acts with its cofactor myocardin to promote the expression of contractile smooth muscle markers. However, smooth muscle cells exhibit a variety of phenotypes beyond contractile that are independent of SRF/myocardin-induced transcription. To determine whether airway smooth muscle exhibits phenotypic plasticity during embryonic development, we deleted Srf from the pulmonary mesenchyme. Srf-mutant lungs branch normally, and the mesenchyme exhibits normal cytoskeletal features and patterning. scRNA-seq revealed an Srf-null smooth muscle cluster wrapping the airways of mutant lungs that lacks contractile smooth muscle markers but retains many features of control smooth muscle. Srf-null airway smooth muscle exhibits a synthetic phenotype, compared to the contractile phenotype of mature wildtype airway smooth muscle. Our findings reveal plasticity in airway smooth muscle differentiation and demonstrate that a synthetic smooth muscle layer is sufficient for airway branching morphogenesis.

developmental biology↗

bioRxiv2020

Patterning the embryonic pulmonary mesenchyme

Smooth muscle guides morphogenesis of several epithelia during organogenesis, including the mammalian airways. However, it remains unclear how airway smooth muscle differentiation is spatiotemporally patterned and whether it originates from distinct mesenchymal progenitors. Using single-cell RNA-sequencing of embryonic mouse lungs, we show that the pulmonary mesenchyme contains a continuum of cell identities, but no distinct progenitors. Transcriptional variability correlates with sub-epithelial and sub-mesothelial mesenchymal compartments that are regulated by Wnt signaling. Live-imaging and tension-sensors reveal compartment-specific migratory behaviors and cortical forces, and show that sub-epithelial mesenchyme contributes to airway smooth muscle. Cytoskeletal and Wnt signaling pathways are activated early in reconstructed differentiation trajectories. Consistently, Wnt activation stimulates the earliest stages of smooth muscle differentiation and induces local accumulation of mesenchymal F-actin, which influences epithelial morphology. Our single-cell approach uncovers the principles of pulmonary mesenchymal patterning during branching morphogenesis and identifies a morphogenetically active mesenchymal layer that sculpts the airway epithelium.

developmental biology↗

bioRxiv2020

Serial sarcomere number is substantially decreased within the paretic biceps brachii in chronic hemiparetic stroke

A muscles structure, or architecture, is indicative of its function and is plastic; changes in input to or use of the muscle alter its architecture. Stroke-induced neural deficits substantially alter both input to and usage of individual muscles. Here, we combined novel in vivo imaging methods (second harmonic generation microendoscopy, extended field-of-view ultrasound, and fat-supression MRI) to quantify functionally meaningful muscle architecture parameters in the biceps brachii of both limbs of individuals with chronic hemiparetic stroke and in age-matched, unimpaired controls. Specifically, serial sarcomere number and physiological cross-sectional area were calculated from data collected at three anatomical scales: sarcomere length, fascicle length, and muscle volume. Our data indicate that the paretic biceps brachii had ~8,500 fewer serial sarcomeres compared to the contralateral limb (p=0.0044). In the single joint posture tested, the decreased serial sarcomere number was manifested by significantly shorter fascicles (10.7cm vs 13.6cm; p<0.0001) without significant differences in sarcomere lengths (3.58m vs. 3.54m; p=0.6787) in the paretic compared to the contralateral biceps. No interlimb differences were observed in unimpaired controls, suggesting we observed muscle adaptations associated with stroke rather than natural interlimb variability. This study provides the first direct evidence of the loss of serial sarcomeres in human muscle, observed in a population with neural impairments that lead to disuse and chronically place the affected muscle at a shortened position. This adaptation is consistent with functional consequences (increased passive resistance to elbow extension) that would amplify already problematic, neurally driven motor impairments. SIGNIFICANCE STATEMENTSerial sarcomere number determines a muscles length during maximum force production and its available length range for active force generation. Skeletal muscle length adapts to functional demands; for example, animal studies demonstrate that chronically shortened muscles decrease length by losing serial sarcomeres. This phenomenon has never been demonstrated in humans. Integrating multi-scale imaging techniques, including two photon microendoscopy, an innovative advance from traditional, invasive measurement methods at the sarcomere scale, we establish that chronic impairments that place a muscle in a shortened position are associated with the loss of serial sarcomeres in humans. Understanding how muscle adapts following impairment is critical to the design of more effective clinical interventions to mitigate such adaptations and to improve function following motor impairments.

bioengineering↗

bioRxiv2018

Glucocorticoid Regulation of Ependymal Glia and Regenerative Potential after Spinal Cord Injury

Following injury, the mammalian spinal cord forms a glial scar and fails to regenerate. In contrast, spinal cord tissue of vertebrate fish regenerates and restores function. Cord transection in zebrafish (Danio rerio) initially causes paralysis and neural cell death, with subsequent ependymal glial proliferation, extension of bipolar glia across the lesion, and neurogenesis. Axons extending from spared and nascent neurons along trans-lesional glial bridges restore functional connectivity. Here we report that glucocorticoids directly target the regeneration supporting changes in ependymal glia to inhibit neural repair. This effect is independent of hematogenic immune cells or microglia. Furthermore, glucocorticoid receptor signaling in ependymal glia is inversely regulated in rat models of spinal cord injury compared to zebrafish. The blockade of neural regeneration by glucocorticoids via a direct effect on ependymal glia has important clinical implications concerning the putative therapeutic benefit of corticosteroids in early management of spinal cord injury.

neuroscience↗