Biology subjects

Lim, M.

Publications and source records attributed to Lim, M..

At least 37 records · Page 2Linked to original sources

bioRxiv2024

SEX-SPECIFIC IMPACTS OF EARLY LIFE SLEEP DISRUPTION: ETHANOL SEEKING, SOCIAL INTERACTION, AND ANXIETY ARE DIFFERENTIALLY ALTERED IN ADOLESCENT PRAIRIE VOLES

Early life sleep is important for neuronal development and maturation. Using the highly social prairie vole rodent model, we have previously reported that early-life sleep disruption (ELSD) during the pre-weaning period postnatal day (P)14 to 21 results in adult interference with social bonding and increases ethanol consumption following a stressor. Furthermore, we have reported increased parvalbumin expression and reduced glutamatergic neurotransmission in cortical regions in adult prairie voles that experienced this paradigm. To understand the impact of ELSD on the lifespan, examination of an earlier time in life is necessary. Thus, the aim of the present study was to examine the behavioral outcomes of ELSD on adolescent prairie voles. Here we hypothesized that anxiety and reward related behaviors, as measured by light/dark box, 2-bottle choice and social interactions, would be negatively impacted by ELSD in adolescent male and female prairie voles. Male ELSD voles were no different from control voles in measures of anxiety and ethanol preference or consumption, but affiliative social interactions were significantly reduced. ELSD differentially impacted female prairie voles, with increased anxiety-like behavior and reductions in ethanol consumption compared to Controls, but no impact on ethanol preference or social interactions. Together, these results suggest both male and female prairie voles experience differential changes to reward seeking behaviors, but only female prairie voles showed increases in anxiety-like behavior. These results further suggest that early-life sleep is critically important for neurotypical behaviors in adolescence, a time where reward-seeking and risky behaviors are adaptive for learning and promoting survival.

animal behavior and cognition↗

bioRxiv2023

The role of positively charged small biomolecules in the aggregation of hyperphosphorylated tau in Alzheimer's disease

Tau proteins have recently drawn attention as a possible cause of Alzheimers disease (AD)-associated neuronal dementia. Hyperphosphorylated tau proteins detach from microtubules, impairing their stability and leading to neuronal degeneration. The present study focuses on understanding the molecular mechanisms behind the aggregation of hyperphosphorylated tau. Since hyperphosphorylated proteins are highly negatively charged, it is implausible that they create the damaging aggregates in the absence of some counteracting positive charge. This study found such an electrostatic (charge-charge) interaction between tau proteins and polyamines, identifying this interaction as crucial to promoting tau aggregation. In this study, we also directly observed the transition over time from tau protein aggregates to fibril structures. These findings challenge existing theories and offer insights into potential therapeutic targets for AD.

biophysics↗

bioRxiv2023

Honokiol decreases alpha-synuclein mRNA levels and reveals novel targets for modulating alpha-synuclein expression.

Neuronal inclusions comprised of aggregated alpha-synuclein (syn) represent a key histopathological feature of neurological disorders collectively termed "synucleinopathies", which includes Parkinsons disease (PD). Mutations and amplifications in the SNCA gene encoding syn cause familial forms of PD and a large body of evidence indicate a correlation between syn accumulation and disease. Decreasing syn expression is recognized as a valid target for PD therapeutics, with down-regulation of SNCA expression potentially attenuating downstream cascades of pathologic events. Honokiol (HKL) is a polyphenolic compound derived from magnolia tree bark that has demonstrated neuroprotective properties. Here, we describe potential beneficial effects of HKL on syn levels in multiple experimental models. Using human neuroglioma cells stably overexpressing syn and mouse primary neurons, we demonstrate that HKL treatment results in a significant decrease in syn expression at both the protein and mRNA levels. Our data support a mechanism whereby HKL acts by post-transcriptional modulation of SNCA rather than modulating syn protein degradation. Additionally, transcriptional profiling of mouse cortical neurons treated with HKL identified several differentially expressed genes (DEG) as potential targets to modulate SNCA expression. Overall, these data highlight a viable strategy to reduce syn levels, which represents a promising target to modify disease progression in PD and other synucleinopathies. In addition, HKL acts as a powerful tool for investigating SNCA gene modulation and its downstream effects.

neuroscience↗

bioRxiv2023

Chronic stress triggers seeking of a starvation-like state in anxiety-prone female mice

Elevated anxiety often precedes anorexia nervosa and persists after weight restoration. Patients with anorexia nervosa often describe hunger as pleasant, potentially because food restriction can be anxiolytic. Here, we tested whether chronic stress can cause animals to prefer a starvation-like state. We developed a virtual reality place preference paradigm in which head-fixed mice can voluntarily seek a starvation-like state induced by optogenetic stimulation of hypothalamic agouti-related peptide (AgRP) neurons. Prior to stress induction, male but not female mice showed mild aversion to AgRP stimulation. Strikingly, following chronic stress, a subset of females developed a strong preference for AgRP stimulation that was predicted by high baseline anxiety. Such stress-induced changes in preference were reflected in changes in facial expressions during AgRP stimulation. Our study suggests that stress may cause females predisposed to anxiety to seek a starvation state, and provides a powerful experimental framework for investigating the underlying neural mechanisms.

neuroscience↗

bioRxiv2023

Distinct Myeloid Derived Suppressor Cell Populations Promote Tumor Aggression in Glioblastoma

The diversity of genetic programs and cellular plasticity of glioma-associated myeloid cells, and thus their contribution to tumor growth and immune evasion, is poorly understood. We performed single cell RNA-sequencing of immune and tumor cells from 33 glioma patients of varying tumor grades. We identified two populations characteristic of myeloid derived suppressor cells (MDSC), unique to glioblastoma (GBM) and absent in grades II and III tumors: i) an early progenitor population (E-MDSC) characterized by strong upregulation of multiple catabolic, anabolic, oxidative stress, and hypoxia pathways typically observed within tumor cells themselves, and ii) a monocytic MDSC (M-MDSC) population. The E-MDSCs geographically co-localize with a subset of highly metabolic glioma stem-like tumor cells with a mesenchymal program in the pseudopalisading region, a pathognomonic feature of GBMs associated with poor prognosis. Ligand-receptor interaction analysis revealed symbiotic cross-talk between the stemlike tumor cells and E-MDSCs in GBM, whereby glioma stem cells produce chemokines attracting E-MDSCs, which in turn produce growth and survival factors for the tumor cells. Our large-scale single-cell analysis elucidated unique MDSC populations as key facilitators of GBM progression and mediators of tumor immunosuppression, suggesting that targeting these specific myeloid compartments, including their metabolic programs, may be a promising therapeutic intervention in this deadly cancer. One-Sentence SummaryAggressive glioblastoma harbors two unique myeloid populations capable of promoting stem-like properties of tumor cells and suppressing T cell function in the tumor microenvironment.

immunology↗

bioRxiv2023

Clinically relevant concurrent BRAF and MEK inhibition alters differentiation states and sensitizes BRAF V600E-mutated high-grade gliomas to immune checkpoint blockade

Resistance to BRAF plus MEK inhibition (BRAFi+MEKi) in BRAFV600E-mutant gliomas drives rebound, progression, and high mortality, yet it remains poorly understood. This study addresses the urgent need to develop treatments for BRAFi+MEKi-resistant glioma in novel mouse models and patient-derived materials. BRAFi+MEKi reveals glioma plasticity by heightening cell state transitions along glial differentiation trajectories, giving rise to astrocyte- and immunomodulatory oligodendrocyte (OL)-like states. PD-L1 upregulation in OL-like cells links cell state transitions to tumor evasion, possibly orchestrated by Galectin-3. BRAFi+MEKi induces interferon response signatures, tumor infiltration, and suppression of T cells. Combining BRAFi+MEKi with immune checkpoint inhibition enhances survival in a T cell-dependent manner, reinvigorates T cells, and outperforms individual or sequential therapies in mice. Elevated PD-L1 expression in BRAF-mutant versus BRAF-wildtype glioblastoma supports the rationale for PD-1 inhibition in patients. These findings underscore the potential of targeting glioma plasticity and highlight combination strategies to overcome therapy resistance in BRAFV600E-mutant HGG. In briefXing et al. show that combined BRAF and MEK inhibitor (BRAFi+MEKi) treatment induces cell state transitions in BRAFV600E-mutant high-grade glioma cells linked with programmed death-ligand (PD-L1) upregulation and T cell suppression, potentially orchestrated through the secretion of galectin-3. These tumor-intrinsic adaptations may be overcome by concurrent immune checkpoint inhibition (ICI), as demonstrated in murine studies, offering novel therapeutic opportunities. HighlightsO_LIBRAFV600E-mutant HGG exhibits cell plasticity induced by BRAFi+MEKi, which links cell state transitions towards glial differentiation with immune evasion C_LIO_LIBRAFi+MEKi enhances anti-tumor immunity and simultaneously suppresses T cells via PD-L1 upregulation C_LIO_LIBRAF-mutant glioblastoma has elevated PD-L1 expression compared to BRAF-wildtype counterparts, providing a criterion for PD-1 inhibition therapy C_LIO_LIConcurrent BRAFi+MEKi and immune checkpoint inhibition enhance T cell-mediated anti-tumor activity and boost survival more effectively than sequential treatment in mice, guiding clinical translation C_LI

cancer biology↗

bioRxiv2022

Programmed cell death-1 receptor mediated regulation of Tbet+ NK1.1- Innate Lymphoid Cells within the Tumor Microenvironment

Innate Lymphoid Cells (ILCs) play a key role in tissue mediated immunity and can be controlled by co-receptor signaling. Here we define a subset of ILCs that are Tbet+NK1.1- and are present within the tumor microenvironment (TME). We show programmed death-1 receptor (PD-1) expression on ILCs within TME is found in Tbet+NK1.1-ILCs. PD-1 significantly controlled the proliferation and function of Tbet+NK1.1-ILCs in multiple murine and human tumors. We found tumor derived lactate enhanced PD-1 expression on Tbet+NK1.1-ILCs within the TME, which resulted in dampened mTOR signaling along with increased fatty acid uptake. In line with these metabolic changes, PD-1 deficient Tbet+NK1.1-ILCs expressed significantly increased IFN{gamma}, granzyme B and K. Furthermore, PD1 deficient Tbet+NK1.1- ILCs contributed towards diminished tumor growth in an experimental murine model of melanoma. These data demonstrate that PD-1 can regulate anti-tumor responses of Tbet+NK1.1-ILCs within the tumor microenvironment. HighlightsO_LITbet+NK1.1- ILCs are found in WT and PD1 ko mice C_LIO_LIPD-1 is expressed on Tbet+NK1.1- ILC1s within multiple TME C_LIO_LIPD-1 controls the proliferation and function of Tbet+NK1.1- ILCs within the tumor microenvironment by modulating fatty acid metabolism. C_LIO_LIPD-1 regulates the proliferation of human Tbet+ ILC1s in human cutaneous squamous cell carcinoma (cSCC) and melanoma tumor microenvironment. C_LI

immunology↗

bioRxiv2022

Systematic Elucidation and Pharmacological Targeting of Tumor-Infiltrating Regulatory T Cell Master Regulators

Due to their immunosuppressive role, tumor-infiltrating regulatory T cells (TI-Tregs) represent attractive therapeutic targets. Analysis of TI vs. peripheral Tregs (P-Tregs) from 36 patients, across four malignancies, identified 17 candidate Master Regulators (MRs), predicted to mechanistically regulate TI-Tregs transcriptional state. In vivo, pooled CRISPR-KO screening, using a hematopoietic stem cell transplant model, confirmed essentiality of 7 of 17 MRs in TI-Treg recruitment and/or retention to the TME, without affecting other T cell subtypes, while individual knockout of the most significant MR (TRPS1) significantly reduced tumor allograft growth. TI-Treg drug perturbation profile analysis identified drugs capable of inverting the TI-Treg-specific MR activity signature at low concentration. Low dose treatment with gemcitabine (top prediction) inhibited tumor growth in immunocompetent but not immunocompromised allografts, increased PD-1 inhibitor efficacy, and depleted TI-Tregs in vivo. The study provides key insight into Treg infiltration mechanism and a gene reporter assay to identify additional small molecule inhibitors. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=140 HEIGHT=200 SRC="FIGDIR/small/481404v1_ufig1.gif" ALT="Figure 1"> View larger version (26K): org.highwire.dtl.DTLVardef@1cca60borg.highwire.dtl.DTLVardef@a93ce6org.highwire.dtl.DTLVardef@dd2aa2org.highwire.dtl.DTLVardef@1a2c98_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2021

EEG-Based Focus Estimation Using Neurable's Enten Headphones and Analytics Platform

We introduce Neurables research on focus using our recently developed Enten EEG headphones. First we quantify Entens performance on standard EEG protocols, including eyes-closed alpha rhythms, auditory evoked response and the P300 event-related potential paradigm. We show that Entens performance is on-par with established industry-standard hardware. We then introduce a series of experimental tasks designed to mimic how focus might be maintained or disrupted in a real-world office setting. We show that (A) these tasks induce behavioral changes that reflect underlying changes in focus levels and (B) our proprietary algorithm detects these changes across a large number of sessions without needing to adjust the model per participant or recording session. Through manipulation of our experimental protocol, we show that our algorithm is not dependent on gross EMG artifacts and it is driven by changes in EEG. Finally, we evaluated the models performance on the same subject across several days, and show that performance remained consistent over time. Our model correctly captured 80% {+/-} 4.1% of distractions present in our experiments with statistical significance. This indicates that our model generalizes across subjects, time points, and conditions. Our findings are based on EEG data collected from 132 participants across 337 sessions and 45 different experiments.

neuroscience↗

bioRxiv2021

Epigenome erosion drives neural crest-like phenotypic mimicry in triple-negative breast cancer and other SOX10+ malignancies

AO_SCPLOWBSTRACTC_SCPLOWO_ST_ABSBackgroundC_ST_ABSIntratumoural heterogeneity is a poor prognostic feature in triple-negative breast cancer (TNBC) and other high-grade malignancies. It is caused by genomic instability and phenotypic plasticity, but how these features co-evolve during tumour development remains unclear. SOX10 is a transcription factor, neural crest stem cell (NCSC) specifier and candidate mediator of cancer-associated phenotypic plasticity. MethodsUsing immunophenotyping, we investigated the expression of SOX10 in normal human breast tissue and breast cancer (n=21 cosmetic breast reduction and 1,860 tumour samples with clinical annotation). We then defined the context and evolution of its expression in TNBC compared to 21 other malignancies using systems-level transcriptomics. ResultsSOX10 was detected in nuclei of normal mammary luminal progenitor cells, the histogenic origin of most TNBCs. In breast cancer, nuclear SOX10 predicted poor outcome amongst cross-sectional (log-rank p=0.0015, hazard ratio 2.02, n=224) and metaplastic (log-rank p=0.04, n=66) TNBCs. Systems-level transcriptional network analysis identified a core module in SOX10s normal mammary epithelial transcription program that is rewired to NCSC genes in TNBC. Reprogramming was proportional to DNA damage and genome-wide promoter hypomethylation, particularly at CpG island shores. Using a novel network analysis pipeline, we found that NCSC-like transcriptional reprogramming is also strongly associated with promoter hypomethylation in other SOX10+ malignancies: glioma and melanoma. ConclusionsWe propose that cancer-associated genome hypomethylation simulates the open chromatin landscape of more primitive cell states, and that on this relatively unrestricted background, SOX10 recreates its ancestral gene regulatory circuits by default. These findings provide new insights about the basis of intratumoural heterogeneity and resurrection of developmental phenotypes in cancer; and highlight the potential for therapeutics that limit chromatin remodelling.

cancer biology↗

bioRxiv2021

Characterisation of immune cell subsets of tumour infiltrating lymphocytes in brain metastases

The heterogeneity of tumor infiltrating lymphocytes is not well characterized in brain metastasis. To address this, we performed a targeted analysis of immune cell subsets in brain metastasis tissues to test which immunosuppressive routes are involved in brain metastasis. We performed multiplex immunofluorescence (mIF), using commercially available validated antibodies on twenty formalin-fixed paraffin embedded whole sections. We quantitated the subsets of immune cells utilizing a targeted panel of proteins including PanCK, CD8, CD4, VISTA and Iba1, and analyzed an average of 15000 cells per sample. We classified tumours as either high (>30%) or low (<30%) tumour infiltrating lymphocytes (TILs) and found that increased TILs density correlated with survival. We next sought out to phenotype these TILs using mIF. The tumours with low TILs (n=9) had significantly higher expression of the immune-checkpoint molecule VISTA in tumor cells (p<0.01) as well as in their microenvironment (p<0.001). Contrastingly, the brain metastatic tumours with high TILs (n=8) displayed higher levels of activated microglia, as measured by Iba1 expression. Low TILs-tumours displayed CD8+ T-cells that co-express VISTA (p<0.01) significantly more compared to high TILs group, where CD8+ T-cells significantly co-express Iba1 (p<0.05). Interestingly, no definite phenotypes of CD4+ subsets were observed. These results were supported by RNA analysis of a publicly available, independent cohort. In conclusion, our work contributes to a growing understanding of the immune surveillance escape routes active in brain metastasis. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=190 SRC="FIGDIR/small/430531v1_ufig1.gif" ALT="Figure 1"> View larger version (57K): org.highwire.dtl.DTLVardef@11b6cd8org.highwire.dtl.DTLVardef@186ff6dorg.highwire.dtl.DTLVardef@1eb8962org.highwire.dtl.DTLVardef@88bb5c_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical abstract:C_FLOATNO Brain metastasis patients with low TILs have high VISTA expression and patients with high TILs have significantly more activated microglia C_FIG

pathology↗

bioRxiv2020

Designing Sub-20 nm Nanocarriers for Small Molecule Delivery: Interplay among Structural Geometry, Assembly Energetics, and Cargo Release Kinetics

Biological constraints in diseased tissues have motivated the need for small nanocarriers (10-30 nm) to achieve sufficient vascular extravasation and pervasive tumor penetration. This particle size limit is only an order of magnitude larger than small molecules, such that cargo loading is better described by co-assembly processes rather than simple encapsulation. Understanding the structural, kinetic, and energetic contributions of carrier-cargo co-assembly is thus critical to achieve molecular-level control and predictable in vivo behavior. These interconnected set of properties were systematically examined using sub-20 nm self-assembled nanocarriers known as three-helix micelles (3HM). Both hydrophobicity and the "geometric packing parameter" dictate small molecule compatibility with 3HMs alkyl tail core. Planar obelisk-like apomorphine and doxorubicin (DOX) molecules intercalated well within the 3HM core and near the core-shell interface, forming an integral component to the co-assembly, as corroborated by small angle X-ray and neutron-scattering structural studies. DOX promoted crystalline alkyl tail ordering, which significantly increased (+63%) the activation energy of 3HM subunit exchange. Subsequently, 3HM-DOX displayed slow-release kinetics (t1/2=40 h) at physiological temperatures, with ~50x greater cargo preference for the micelle core as described by two drug partitioning coefficients (micellar core/shell Kp1 ~24, and shell/bulk solvent Kp2 ~2). The geometric and energetic insights between nanocarrier and their small molecule cargos developed here will aid in broader efforts to deconvolute the interconnected properties of carrier-drug co-assemblies, and to understand nanomedicine behavior throughout all the physical and in vivo processes they are intended to encounter.

bioengineering↗

bioRxiv2020

Design of 18 nm Doxorubicin-loaded 3-helix Micelles: Cellular Uptake and Cytotoxicity in Patient-derived GBM6 Cells

The fate of nanocarrier materials at the cellular level constitutes a critical checkpoint in the development of effective nanomedicines, determining whether tissue level accumulation results in therapeutic benefit. The cytotoxicity and cell internalization of ~18 nm 3-helix micelle (3HM) loaded with doxorubicin (DOX) was analyzed in patient-derived glioblastoma (GBM) cells in vitro. The inhibitory concentration (IC50) of 3HM-DOX increased to 6.2 {micro}g/mL from < 0.5 {micro}g/mL for free DOX in patient derived GBM6 cells, 15.0 {micro}g/mL from 6.5 {micro}g/mL in U87MG cells, and 21.5 {micro}g/mL from ~0.5 {micro}g/mL in LN229 cells. Modeling analysis of previous 3HM biodistribution results predict these cytotoxic concentrations are achievable with intravenous injection in rodent GBM models. 3HM-DOX formulations were internalized intact and underwent intracellular trafficking distinct from free DOX. 3HM was quantified to have an internalization half-life of 12.6 h in GBM6 cells, significantly longer than comparable reported liposome and polymer systems. 3HM was found to traffic through active endocytic processes, with clathrin-mediated endocytosis being the most involved of the pathways studied. Inhibition studies suggest substantial involvement of low density lipoprotein receptor (LDLR) in initiating 3HM uptake. Since 3HM surface is polyethylene glycol (PEG)-ylated with no targeting functionalities, protein corona involvement in 3HM recognition is expected. The present work develops insights of the cytotoxicity, pharmacodynamics and cellular interactions of 3HM and 3HM-DOX relevant for ongoing pre-clinical studies. This work also contributes to efforts to develop predictive mathematical models tracking accumulation and biodistribution kinetics at a systemic level. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=81 SRC="FIGDIR/small/072892v1_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@99c9a4org.highwire.dtl.DTLVardef@8540c1org.highwire.dtl.DTLVardef@5e7690org.highwire.dtl.DTLVardef@1b9f88a_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2020

Immunophenotyping of HER4/YAP axis in breast cancer brain metastasis

Brain metastasis (BrM) is a devastating diagnosis for patients with breast cancer. Identification of immunophenotypical features specific to BrM is crucial for developing effective new therapeutic interventions. Yes-associated protein (YAP) mediates downstream effects of the neuregulin receptor, HER4, on breast cancer cell proliferation in vitro. HER4 is frequently over-expressed in BrM, but the relationship with YAP has not been investigated. This study examined the HER4/YAP axis in patient samples (n=41) from matched primary breast and metastatic brain tumours. Immunohistochemistry analysis revealed HER4 was highly phosphorylated in BrM compared to matched primary tumours (p=0.0022), and this was strongly associated with expression and phosphorylation of dimerization partners HER2 and HER3 (p<0.0001). When compared to a general breast cancer cohort (n=373), we found HER4 activation to be brain metastasis specific (p<0.0001). However, YAP was frequently phosphorylated in both HER4-activated primary breast tumours and brain metastases, suggesting that pro-proliferative YAP signaling is not a major consequence of HER4 activation in these tumours. These results display the complexity of expression of the HER family receptors and the downstream pathways in BrM and suggest simultaneous targeting of multiple receptors might be more advantageous.

pathology↗

bioRxiv2020

Tyrosine phosphorylation of ACLY regulates lipid metabolism and oncogenesis in ALK positive Anaplastic Large Cell Lymphoma

A fundamental requirement for growth of rapidly proliferating cells is metabolic adaptation to promote synthesis of biomass1. ATP citrate lyase (ACLY) is a critical enzyme responsible for synthesis of cytosolic acetyl-CoA, the key building component for de novo fatty acid synthesis and links vital pathways such as carbohydrate and lipid metabolism2. The mechanisms of ACLY regulation are not completely understood and the regulation of ACLY function by tyrosine phosphorylation is unknown. Here we show using mass-spectrometry-driven phosphoproteomics and metabolomics that ACLY is phosphorylated and functionally regulated at an evolutionary conserved residue, Y682. Physiologic signals promoting rapid cell growth such as epidermal growth factor stimulation in epithelial cells and T-cell receptor activation in primary human T-cells result in rapid phosphorylation of ACLY at Y682. In vitro kinase assays demonstrate that Y682 is directly phosphorylated by multiple tyrosine kinases, including ALK, ROS1, SRC, JAK2 and LTK. Oncogenically activating structural alterations such as gene-fusions, amplification or point mutations of ALK tyrosine kinase result in constitutive phosphorylation of ACLY in diverse forms of primary human cancer such as lung cancer, anaplastic large cell lymphoma (ALCL) and neuroblastoma. Expression of a phosphorylation-defective ACLY-Y682F mutant in NPM-ALK+ ALCL decreases ACLY activity and attenuates lipid synthesis. Metabolomic analyses reveal that ACLY-Y682F expression results in increased {beta}-oxidation of 13C-oleic acid-labeled fatty acid with increased labeling of +2-citrate (p<0.01) and +18-oleyol carnitine (p<0.001). Similarly, oxygen consumption rate (OCR) is significantly increased in cells expressing ACLY-Y682F (p<0.001). Moreover, expression of ACLY-Y682F dramatically decreases cell proliferation, impairs clonogenicity and abrogates tumor growth in vivo. Our results reveal a novel mechanism for direct ACLY regulation that is subverted by multiple oncogenically-activated tyrosine kinases in diverse human cancers. These findings have significant implications for novel therapies targeting ACLY in cancer and metabolism.

cancer biology↗

bioRxiv2019

Corollary Discharge Promotes a Sustained Motor State in a Neural Circuit for Navigation

Animals exhibit behavioral and neural responses that persist on longer time scales than transient or fluctuating stimulus inputs. Here, we report that C. elegans uses feedback from the motor circuit to a sensory processing interneuron to sustain its motor state during thermotactic navigation. By imaging circuit activity in behaving animals, we show that a principal postsynaptic partner of the AFD thermosensory neuron, the AIY interneuron, encodes both temperature and motor state information. By optogenetic and genetic manipulation of this circuit, we demonstrate that the motor state representation in AIY is a corollary discharge signal. RIM, an interneuron that is connected with premotor interneurons, is required for this corollary discharge. Ablation of RIM eliminates the motor representation in AIY, allows thermosensory representations to reach downstream premotor interneurons, and reduces the animals ability to sustain forward movements during thermotaxis. We propose that feedback from the motor circuit to the sensory processing circuit underlies a positive feedback mechanism to generate persistent neural activity and sustained behavioral patterns in a sensorimotor transformation.

neuroscience↗

bioRxiv2019

Development and evaluation of a rapid on-site water pathogen detection system for water quality monitoring

Timely response to outbreak of water-borne diseases caused by bacteria requires efficient monitoring and rapid detection strategies. Herein, we report a rapid DNA-based on-site detection system for specific detection of Pseudomonas aeruginosa. To evaluate the test performance of our method against spiked water samples, parallel tests based on real-time PCR and standard culture methods were concurrently performed. Test sensitivities of between 96.7% and 92.3% were obtained, based on the calculation obtained from qPCR and culture test, respectively, with a corresponding level of specificity of 92.9% and 83.3%. Time-to-result is around 45 min, with a detection limit of 1 CFU/100 mL. Here, a fully-deployable detection method where bacteria of-interest can be detected rapidly with high accuracy was described. This test method can be modified to detect other bacteria of-interest and can also be used in different applications. The test results can be obtained on-site and can therefore be particularly useful in public facilities health surveillance, where regulators can quickly determine if a site is safe or if other emergency response measures are required.\n\nIMPORTANCEPseudomonas aeruginosa is a well-established water quality biomarker, known to be associated to humans health risks. To ascertain the presence of this pathogen, relevant stakeholders currently rely on standard quantitative ISO methods (APHA 9213E) which require 6 days from sampling to results. This window could potentially lead to waterborne outbreaks if the contaminated water features are not shut down for proper and urgent mitigation. This manuscript describes a method to detect this disease-causing microorganism in its viable forms under 1 hour, with a sensitivity of 1 CFU/100mL. Besides providing valuable information of the quality of water system, this direct monitoring of pathogens can reduce substantial time needed from sampling to reporting. This method can be established as a platform technology for other pathogenic microorganisms. On-going work to develop economic point-of-care prototypes could facilitate quick screening of targeted waterborne pathogens and results in better assessment of public health risk and quick in devising emergency response measures and other management strategies.

microbiology↗

bioRxiv2019

Diffusive Flux Analysis of Tumor Vascular Permeability for 3-Helix-Micelles in Comparison to Other Nanoparticles

Understanding the complex interplay of factors affecting nanoparticle accumulation in solid tumors is a challenge that must be surmounted to develop effective cancer nanomedicine. The tumor microenvironment is unique in comparison to healthy tissue, possessing elevated interstitial pressure that limits convective transport, hence leaving diffusive processes to predominate especially in the tumors necrotic core. Certain tumor types such as glioblastoma multiforme and pancreatic tumor are known to be poorly permeable, making them less accessible for nanoparticle drug delivery. Evidence indicates that small and long-circulating nanoparticles are ideal for taking advantage of the enhanced permeability and retention effect, even in such intractable tumor models. Three-helix-micelle (3HM) self-assembled nanoparticles possess these characteristics, and previous studies have shown that 3HM can achieve more favorable tumor accumulation and penetration than liposomes in several tumor models. The reason for its superior performance had yet to be determined, and thus we sought to examine its passive transport into tumors. In this paper we present a simple mathematical model based on diffusive flux to describe particle accumulation in tumors with respect to particle plasma pharmacokinetics. Fitting the diffusive flux equation to in vivo particle tumor concentration yields the particle effective permeability value, which for 3HM is 2.31 {+/-} 0.18 x 10-8 cm/s in U87MG glioblastoma and 4.25 {+/-} 0.91 x 10-8 cm/s in HT29 colon cancer murine models. Applying this diffusive flux model to other nanoparticles reported in literature enables the effect of plasma half-life to be decoupled from particle permeability in influencing tumor accumulation, reinforced trends reported in the field regarding the impact of particle size, and provided a semi-quantitative means of comparing various tumor models. This work is also the first demonstration, to the best our knowledge, of extracting particle permeability values from bulk biodistribution data obtained via positron emission tomography, as opposed to laborious tumor optical window intravital microscopy experiments. As such the analysis provided here presents a simple and accessible tool to further enhance nanomedicine development.\n\n\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=87 SRC=\"FIGDIR/small/708263v1_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (26K):\norg.highwire.dtl.DTLVardef@5981e5org.highwire.dtl.DTLVardef@5ef928org.highwire.dtl.DTLVardef@137edceorg.highwire.dtl.DTLVardef@dd9b17_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical abstractC_FLOATNO C_FIG

bioengineering↗