Biology subjects

Pham, T. T.

Publications and source records attributed to Pham, T. T..

15 recordsLinked to original sources

bioRxiv2026

The functional neuronal lipotype is specified by activity and PS synthesis using dietary and lysosomal inputs

Neurons maintain specialized membranes necessary for lifelong circuit function. While neuronal membranes thus contain unique lipidomes, how and why specific lipids become synaptically enriched remains mysterious. Here, we identify a conserved hallmark of mature neurons, phosphatidylserines containing omega-3 fatty acids (n-3 PS), which dynamically accumulate during synaptogenesis from Drosophila to humans. This neuronal lipotype depends on dietary n-3 and lysosomal catabolism mediated by Saposin, the phospholipase PLA2G15, and the lysophospholipid transporter spin/SPNS1. Reducing neuronal PS biosynthesis by targeting the PS synthase (Pss) caused lipidomic, synaptic, and behavioral deficits exacerbated by impaired glycerophospholipid catabolism. While dietary, lysosomal, and lipoprotein manipulations broadly altered n-3 levels, silencing developmental activity-templating neurons selectively reduced n-3 PS. Remarkably, pathogenic Pss variants lacking feedback inhibition similarly reduced n-3 PS and impaired circuit function. As n-3 PS is reduced during neurodegeneration but absent from iPSC-derived neurons, important relationships between lipotype and physiology may not be recapitulated in vitro.

neuroscience↗

bioRxiv2026

A self-organized signaling hierarchy patterns the cortex during cell repair

Cells generate dynamic patterns of Rho GTPase activation to direct the subsequent patterning of Rho GTPase effectors needed to remodel the cell cortex during processes ranging from cell division to cell repair. To understand how such patterns arise, we used live cell imaging, time-resolved Rho GTPase manipulations, and a novel computational tool to study the spatiotemporal dynamics of Rho, Cdc42 and several downstream Cdc42 targets in wounded Xenopus laevis oocytes. We find that the characteristic wound-induced segregation of Rho and Cdc42 activity into concentric zones is followed by polarization of the Cdc42 zone such that Toca-1 progressively concentrates at the back of the Cdc42 zone while Arp2/3, cofilin, cortactin, and the Rho GAP p190RhoGAP progressively concentrate at the front of the Cdc42 zone, where it overlaps the Rho zone. Remarkably, the juxtaposition of Rho activity to Cdc42 is required for the polarization of p190RhoGAP, while p190RhoGAP is responsible for establishing the boundary between the Cdc42 and Rho zones. The results indicate that the characteristic segregation of the Rho and Cdc42 zones, as well as the polarization of the Cdc42 zone, arise from cortical self-organization. Further, these findings reveal a simple mechanism for hierarchical establishment of cortical patterns: recruitment of new proteins to regions of signaling compartment overlap.

cell biology↗

bioRxiv2026

Assembly-pathway regulation dictates pH-responsive actuation in the R-body protein machinery

Refractile bodies (R-bodies) are protein assemblies that form tightly rolled morphologies in cells and undergo large-scale extension into long spirals in response to environmental stimuli. The type 51 R-body, the focus of this study, is assembled from four Reb proteins and undergoes a rapid repeatable [~]50-fold extension. Although R-bodies were first described more than 70 years ago, it has remained unclear how RebC and RebD contribute to the formation and function of this four-protein machinery even though RebA and RebB have been proposed as its major components. We characterized the wild-type R-body (Rb_WT) and a series of reb gene knockout mutants by combining in-cell, biochemical analyses, small-angle X-ray scattering (SAXS) and attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy. We found that RebD is incorporated into Rb_WT as a minor component, while RebC is not detectably incorporated into the final assembly. Mutants lacking either RebA or RebB still form roll-like assemblies but lack pH-dependent extension. In contrast, mutants lacking RebC and/or RebD exhibit a substantially lower propensity for roll formation and instead undergo off-pathway aggregation with increased {beta}-sheet content. SAXS analyses further indicate that roll-like morphology does not ensure formation of the ordered lamellar architecture characteristic of functional Rb_WT. Thus, pH-responsive R-body actuation is dictated not simply by the major proteins that constitute the final architecture, but by a regulated assembly pathway that builds the ordered lamellar architecture required for actuation. These findings establish assembly-pathway regulation as a key principle for constructing dynamic protein architectures capable of stimuli-responsive mechanical actuation.

biophysics↗

bioRxiv2026

The REFLEX system enables in vivo identification of perivascular angiogenic macrophages in the heart

Direct identification of physically interacting cells in vivo remains challenging because conventional interactome analyses infer signaling partners from transcriptomes and cannot reveal which cells are in direct contact. In pressure-overload induced cardiac remodeling, VEGF-A plays a central role in the maintenance of vascular integrity and cardiac function. However, the cell type which produces VEGF-A and how the VEGF-A peptide is delivered to vascular endothelial cells remains unclear. Here, we developed a genetically encoded platform that combines REFLEX mice with HUNTERuni-seq, enabling unbiased detection and transcriptional profiling of the cells that physically interact with vascular endothelial cells. The REFLEX and HUNTERuni-seq approach identified subpopulations of Vegfa positive macrophages which we named perivascular angiogenic macrophages (PVAMs). Although the amount of VEGF-A in PVAMs is small, loss of VEGF-A in PVAMs impaired angiogenesis and systolic function during pressure overload. We additionally show that direct contact between PVAMs and endothelial cells is critical for the delivery of VEGF-A to endothelial cells. Conventional interactome analysis predicted that cardiomyocytes as dominant sources of VEGF-A in the heart. However, cardiomyocyte Vegfa deletion had no effect on capillary density nor systolic function in a model of heart failure. These results suggest that VEGF-A signaling does not rely on free diffusion through the interstitium and that cellular proximity and physical contact between PVAMs and endothelial cells are the key determinants of effective signal delivery. Together, these findings establish REFLEX and HUNTERuni-seq as a versatile platform for uncovering biologically critical cell-to-cell interactions and provide new insight into intercellular communication in pathological tissue contexts.

cell biology↗

bioRxiv2025

Characterisation of the dual roles of senescent-like T cells that arise during healthy and unhealthy ageing

Ageing is accompanied by progressive remodelling of the immune system, but chronic metabolic disease may accelerate this process and drive qualitatively distinct forms of immune dysfunction. Here, we used type 2 diabetes (T2D) as a model of unhealthy immune ageing to identify a distinct population of CD8 TEMRA cells that accumulates in older individuals with T2D. These cells were highly differentiated, oligoclonally expanded and had shorter telomeres, consistent with an increased replicative history and premature senescence-like state. Unlike conventional TEMRA cells, which can preserve cytotoxic function through acquisition of NK-cell receptors, T2D-associated TEMRA cells showed reduced surface expression of KLRG1, NKG2D and NKG2A together with defective receptor recycling. TGF{beta}1 was elevated in T2D and reproduced several features of this phenotype in vitro, including increased TEMRA differentiation, reduced NK-receptor expression, altered receptor trafficking and induction of p21. Functionally, these cells displayed reduced TCR-triggered degranulation, correlating with impaired cytotoxicity and altered tissue distribution in individuals with T2D. Rather than providing effective immune surveillance, the accumulation of these highly differentiated TEMRA cells with diminished effector capacity may compromise immune function. Together, these findings identify a distinct senescent-like CD8 TEMRA state linking metabolic inflammation to dysregulated T cell differentiation.

immunology↗

bioRxiv2025

A Continuously Oxygenated Macroencapsulation System Enables High-Density Packing and Delivery of Insulin-Secreting Cells

The encapsulation of insulin-secreting cells within immuno-protective systems holds significant promise for curative treatment of type 1 diabetes without immunosuppression. A major challenge, however, remains the inadequate oxygen tension within the encapsulation systems, which compromises the survival and function of encapsulated cells and necessitates low packing density and impractically large systems to deliver a curative cell mass. In this study, we present a novel cell encapsulation system capable of generating oxygen via the electrolysis of tissue moisture to provide a continuous oxygen supply to densely packed insulin-secreting cells. Our system comprises a miniaturized implantable electrochemical oxygen generator (iEOG) and a scalable cylindrical cell encapsulation pouch, designed in a linear configuration to facilitate minimally invasive implantation and retrieval. The oxygen generation from the system was shown to be precisely controlled, stable, and capable of supporting clinically relevant doses of pancreatic islets. In vitro studies demonstrated that the oxygenated system effectively maintained the viability and function of insulinoma cell aggregates and human pancreatic islets at densities of 60,000 islet equivalents per mL (IEQ/mL) or 4,200 IEQ/cm{superscript 2} under a hypoxic cell culture condition (1% O ). In an allogeneic rat model, the oxygenated systems containing pancreatic islets implanted into the poorly vascularized but clinically attractive subcutaneous space at a density of 60,000 IEQ/mL successfully reversed diabetes for up to about 3 months without the need for immunosuppression, while animals implanted with non-oxygenated systems remained diabetic. Most ([~] 90%) of the pancreatic islets encapsulated in the continuously oxygenated systems were found viable and functional upon retrieval. These findings suggest the feasibility of using continuous oxygenation to support insulin-secreting cells at high loading densities in subcutaneous space, enabling the development of an encapsulation system with clinically practical dimensions.

bioengineering↗

bioRxiv2025

Bridging Prediction and Reality: Comprehensive Analysis of Experimental and AlphaFold 2 Full-Length Nuclear Receptor Structures

AlphaFold 2 has revolutionized protein structure prediction, yet systematic evaluations of its performance against experimental structures for specific protein families remain limited. Here we present the first comprehensive analysis comparing AlphaFold 2-predicted and experimental nuclear receptor structures, examining root-mean-square deviations, secondary structure elements, domain organization, and ligand-binding pocket geometry. While AlphaFold2 achieves high accuracy in predicting stable conformations with proper stereochemistry, it shows limitations in capturing the full spectrum of biologically relevant states, particularly in flexible regions and ligand-binding pockets. Statistical analysis reveals significant domain-specific variations, with ligand-binding domains showing higher structural variability (CV = 29.3%) compared to DNA-binding domains (CV = 17.7%). Notably, Alphafold 2 systematically underestimates ligand-binding pocket volumes and captures only single conformational states in homodimeric receptors where experimental structures show functionally important asymmetry. These findings provide critical insights for structure-based drug design targeting nuclear receptors and establish a framework for evaluating Alphafold 2 predictions across other protein families.

bioinformatics↗

bioRxiv2025

CSMA: an ImageJ Plugin for the Analysis of Wound Healing Assays

Accurate quantification of wound closure in cell migration assays is crucial yet challenging. Still, existing methods often underperform due to omitting cell detection within the wound area, resulting in biased outcomes. To overcome this limitation, we developed the CSMA plugin for ImageJ. CSMA utilizes advanced image processing techniques, including contrast enhancement, edge detection, and morphological operations, to precisely identify and quantify cells in the wound region. The plugin offers user-friendly features and adjustable parameters to accommodate different imaging conditions, ensuring robust performance across diverse experimental setups. Validation against conventional tools confirms CSMAs superior ability to delineate wound boundaries and provide accurate estimations of area and width at every time point. As applied to SW480-ADH colon cancer cells treated with various compounds, CSMA proves valuable in biomedical research. It represents a significant advancement in wound healing assay analysis, providing researchers with a simple and reliable tool for studying cell migration dynamics with enhanced precision and reproducibility. CSMA is available as an ImageJ plugin and source code at https://github.com/AminaSagymbayeva/CSMA_WoundHealing.

bioinformatics↗

bioRxiv2024

Stable and robust Xi and Y transcriptomes drive cell-type-specific autosomal and Xa responses in vivo and in vitro in four human cell types

Recent in vitro studies of human sex chromosome aneuploidy showed that the Xi ("inactive" X) and Y chromosomes broadly modulate autosomal and Xa ("active" X) gene expression in two cell types. We tested these findings in vivo in two additional cell types. Using linear modeling in CD4+ T cells and monocytes from individuals with one to three X chromosomes and zero to two Y chromosomes, we identified 82 sex-chromosomal and 344 autosomal genes whose expression changed significantly with Xi and/or Y dosage in vivo. Changes in sex-chromosomal expression were remarkably constant in vivo and in vitro across all four cell types examined. In contrast, autosomal responses to Xi and/or Y dosage were largely cell-type-specific, with up to 2.6-fold more variation than sex-chromosomal responses. Targets of the X- and Y-encoded transcription factors ZFX and ZFY accounted for a significant fraction of these autosomal responses both in vivo and in vitro. We conclude that the human Xi and Y transcriptomes are surprisingly robust and stable across the four cell types examined, yet they modulate autosomal and Xa genes - and cell function - in a cell-type-specific fashion. These emerging principles offer a foundation for exploring the wide-ranging regulatory roles of the sex chromosomes across the human body.

genomics↗

bioRxiv2022

Cardiovascular Hemodynamics in Mice with Tumor Necrosis Factor Receptor - Associated Factor 2 Mediated Cytoprotection in the Heart

Many studies in mice have demonstrated that cardiac-specific innate immune signaling pathways can be reprogrammed to modulate inflammation in response to myocardial injury and improve outcomes. While the echocardiography standard parameters of left ventricular (LV) ejection fraction, fractional shortening, and end-diastolic diameter, and others, are used to assess cardiac function, their dependency on loading conditions somewhat limit their utility in completely reflecting the contractile function and global cardiovascular efficiency of the heart. A true measure of global cardiovascular efficiency should include of the interaction between the ventricle and the aorta (ventriculo-vascular coupling, VVC) as well as measures of aortic impedance and pulse wave velocity. We measured cardiac Doppler velocities, blood pressures, along with VVC, aortic impedance, and pulse wave velocity to evaluate global cardiac function in mouse model of cardiac-restricted low levels TRAF2 overexpression that conferred cytoprotection in the heart. While previous studies reported that response to myocardial infraction and reperfusion was improved in the TRAF2 overexpressed mice, we found that TRAF2 mice had significantly lower cardiac systolic velocities and accelerations, diastolic atrial velocity, lower aortic pressures and rate-pressure product, lower LV contractility and relaxation, and lower stroke work when compared to littermate control mice. Also, we found significantly longer aortic ejection time, isovolumic contraction and relaxation times, and significantly higher mitral early/atrial ratio, myocardial performance index, and ventricular vascular coupling in the TRAF2 overexpression mice compared to their littermate controls. We found no significant differences in the aortic impedance and pulse wave velocity. While the reported tolerance to ischemic insults in TRAF2 overexpression mice may suggest enhanced cardiac reserve, our results indicate a diminished cardiac function in these mice.

biophysics↗

bioRxiv2022

Myoscaffolds reveal laminin scarring is detrimental for stem cell function while sarcospan induces compensatory fibrosis

We developed an on-slide decellularization approach to generate acellular extracellular matrix (ECM) scaffolds that can be repopulated with various cell types to interrogate cell-ECM interactions. Using this platform, we investigated whether fibrotic ECM scarring affected human skeletal muscle progenitor cell (SMPC) functions that are essential for myoregeneration. SMPCs exhibited robust adhesion, motility, and differentiation on healthy muscle-derived myoscaffolds. All SPMC interactions with fibrotic myoscaffolds from dystrophic muscle were severely blunted including reduced motility rate and migration. Furthermore, SMPCs were unable to remodel laminin dense fibrotic scars within diseased myoscaffolds. Proteomics and structural analysis revealed that excessive collagen deposition alone is not pathological, and can be compensatory, as revealed by overexpression of sarcospan and its associated ECM receptors in dystrophic muscle. Our in vivo data also supported that ECM remodeling is important for SMPC engraftment and that fibrotic scars may represent one barrier to efficient cell therapy.

cell biology↗

bioRxiv2018

Drosophila scribble mutant tumors undergo a transition from a growth arrest state to a proliferative state over time

The Drosophila neoplastic tumor suppressor gene (nTSG) mutant tumors have successfully modeled many aspects of human tumor progression. However, the fly nTSG mutant tumors progress rapidly over days. This is in contrast with most human tumors which develop slowly, harbor heterogeneous cell populations for selection and undergo an evolution-like process. Whether the fast-growing fly nTSG mutant tumors have capacity for evolution remains unclear. Through quantitative analysis of the scrib mutant tumor growth, we found that the scrib mutant tumors evolve to display different growth rates and cell cycle profiles over time. Multiple growth-regulatory signaling pathways show quantitative differences in early versus late scrib mutant tumors. These data suggest that the scrib mutant tumors undergo a transition from a growth arrest state to a proliferative state. Through longitudinal single cell RNA (scRNA) data analysis we found that the scrib mutant tumors harbor heterogeneous cell populations likely of distinct proliferative states, which are available for potential selection. This study raises the possibility of studying tumor evolution in a genetically accessible and fast-growing invertebrate tumor model.

developmental biology↗

bioRxiv2018

Spatiotemporally controlled Myosin relocalization and internal pressure cause biased cortical extension to generate sibling cell size asymmetry

Metazoan cells can generate unequal sized sibling cells during cell division. This form of asymmetric cell division depends on spindle geometry and Myosin distribution but the underlying mechanics are unclear. Here, we use atomic force microscopy and live cell imaging to elucidate the biophysical forces involved in the establishment of physical asymmetry in Drosophila neural stem cells. We show that the force driving initial apical membrane expansion is provided by hydrostatic pressure, peaking shortly after anaphase onset, and enabled by a relieve of actomyosin contractile tension on the apical cell cortex. The subsequent increase in contractile forces at the cleavage furrow, combined with the relocalization of basally located Myosin results in basal membrane extension and sustained apical expansion. We propose that spatiotemporally controlled actomyosin contractile tension and hydrostatic pressure enables stereotypic biased membrane expansion to generate sibling cell size asymmetry.

cell biology↗

bioRxiv2017

Drones count wildlife more accurately and precisely than humans

Ecologists are increasingly using technology to improve the quality of data collected on wildlife, particularly for assessing the environmental impacts of human activities. Remotely Piloted Aircraft Systems (RPAS; commonly known as drones) are widely touted as a cost-effective way to collect high quality wildlife population data, however, the validity of these claims is unclear. Using life-sized seabird colonies containing a known number of replica birds, we show that RPAS-derived data are, on average, between 43% and 96% more accurate than data from the traditional ground-based collection method. We also demonstrate that counts from this remotely sensed imagery can be semi-automated with a high degree of accuracy. The increased accuracy and precision of RPAS-derived wildlife monitoring data provides greater statistical power to detect fine-scale population fluctuations allowing for more informed and proactive ecological management.

ecology↗

bioRxiv2017

Proteomic Analysis Defines Kinase Taxonomies Specific For Subtypes Of Breast Cancer

Multiplexed small molecule inhibitors covalently bound to Sepharose beads (MIBs) were used to capture functional kinases in luminal, HER2-enriched and triple negative, basal-like and claudin-low breast cancer cell lines and tumors. Kinase MIB-binding profiles at baseline without perturbation proteomically distinguished the four breast cancer subtypes. Kinases lacking defined functions in breast cancer were highly represented in the MIB-binding taxonomies. We show that these understudied kinases, whose disease associations and pharmacology are generally unexplored, are integrated in kinase signaling subnetworks with kinases that have been previously well characterized in breast cancer. Computationally it was possible to define subtypes using profiles of less than 50 of the more than 300 kinases bound to MIBs that included understudied as well as metabolic and lipid kinases. Furthermore, analysis of MIB-binding profiles established potential functional annotations for these understudied kinases. Thus, comprehensive MIBs-based capture of kinases provides a unique proteomics-based method for integration of poorly characterized kinases of the understudied kinome into functional subnetworks in breast cancer cells and tumors that is not possible using genomic strategies. The MIB-binding profiles readily defined subtype-selective differential adaptive kinome reprogramming in response to targeted kinase inhibition, demonstrating how MIB profiles can be used in determining dynamic kinome changes that result in subtype selective phenotypic state changes.

cancer biology↗