Biology subjects

Choi, S.

Publications and source records attributed to Choi, S..

At least 91 records · Page 5Linked to original sources

bioRxiv2024

Collagen mineralization decreases NK cell-mediated cytotoxicity of breast cancer cells via increased glycocalyx thickness

Skeletal metastasis is common in patients with advanced breast cancer, and often caused by immune evasion of disseminated tumor cells (DTCs). In the skeleton, tumor cells not only disseminate to the bone marrow, but also to osteogenic niches in which they interact with newly mineralizing bone extracellular matrix (ECM). However, it remains unclear how mineralization of collagen type I, the primary component of bone ECM, regulates tumor-immune cell interactions. Here, we have utilized a combination of synthetic bone matrix models with controlled mineral content, nanoscale optical imaging, and flow cytometry to evaluate how collagen type I mineralization affects the biochemical and biophysical properties of the tumor cell glycocalyx, a dense layer of glycosylated proteins and lipids decorating their cell surface. Our results suggest that collagen mineralization upregulates mucin-type O-glycosylation and sialylation by tumor cells, which increased their glycocalyx thickness while enhancing resistance to attack by Natural Killer (NK) cells. These changes were functionally linked as treatment with a sialylation inhibitor decreased mineralization-dependent glycocalyx thickness and made tumor cells more susceptible to NK cell attack. Together, our results suggest that interference with glycocalyx sialylation may represent a therapeutic strategy to enhance cancer immunotherapies targeting bone-metastatic breast cancer.

cancer biology↗

bioRxiv2024

IN SILICO DESIGN AND BINDING MECHANISM OF E3 LIGASE UBR1 RECRUITERS

Proteolysis Targeting Chimeric Molecules (PROTACs) represent a promising avenue in drug discovery, as they can induce the targeted degradation of disease-relevant proteins within the cellular machinery. These compounds comprise a ligand tailored to bind the specific targeted protein connected to a recruiter molecule that engages with the E3 ligase. Despite their promise as therapeutic agents, their clinical advancement has encountered substantial challenges, primarily due to the limited availability of suitable E3 ligases. Additionally, cell permeability and proteolytic stability due to their peptide nature often hamper their application. In this study, we focus on the development of recruiters for the E3 ligase UBR1. This widely expressed protein has recently been demonstrated to be efficient in driving the degradation of oncogenic proteins. Our computational approach leverages a fragment-based peptidomimetics strategy, integrating pharmacophore filtering, docking, and fragment-linking optimization. Finally, we subject the wild-type peptide and the most promising combined fragments to advanced binding free energy calculations, unveiling insights into their dynamic water-mediated binding mechanisms and their potential as robust E3 ligase UBR1 recruiters, ultimately leading to the identification of promising compounds. This computational workflow is readily applicable to the development of related PROTACs and also to model protein-protein interactions with similar characteristics.

biophysics↗

bioRxiv2024

Candidatus Nitrosocosmicus members are the dominant archaea associated with pepper (Capsicum annuum L.) and ginseng (Panax ginseng C.A. Mey.) plants rhizospheres

BackgroundAlthough archaea are widespread in terrestrial environments, little is known about the selection forces that shape their composition, functions, survival, and proliferation strategies in the rhizosphere. The ammonia-oxidizing archaea (AOA), which are abundant in soil environments, catalyze the first step of nitrification and have the potential to influence plant growth and development significantly. ResultsBased on archaeal 16S rRNA and amoA gene (encoding the ammonia monooxygenase subunit A) amplicon sequencing analysis, distinct archaeal communities dominated by AOA were found to be associated with the root systems of pepper (Capsicum annuum L.) and ginseng (Panax ginseng C.A. Mey.) plants compared to bulk soil not penetrated by roots. AOA related to "Candidatus Nitrosocosmicus", which, unlike most other AOA, harbor genes encoding manganese catalase (MnKat), dominated rhizosphere soils, and thus contributed to the development of distinct archaeal communities in rhizospheres. Accordingly, for both plant species, the copy number ratios of AOA MnKat genes to amoA genes were significantly higher in rhizosphere soils than in bulk soils. In contrast to MnKat-negative strains from other AOA clades, the catalase activity of a representative isolate of "Ca. Nitrosocosmicus" was demonstrated. Members of this clade were enriched in H2O2-amended bulk soils, and constitutive expression of their MnKat gene was observed in both bulk and rhizosphere soils. ConclusionsDue to their abundance, "Ca. Nitrosocosmicus" members can be considered key players mediating the nitrification process in rhizospheres. The selection of this MnKat-containing AOA in rhizospheres of several agriculturally important plants hints at a previously overlooked AOA-plant interaction. For additional mechanistic analyses of the interaction, this key clade of AOA with cultured representatives can be employed.

microbiology↗

bioRxiv2023

General Anesthesia Activates a Central Anxiolytic Center in the BNST

Low doses of general anesthetics like ketamine and dexmedetomidine have anxiolytic properties independent of their sedative effects. How these different drugs exert these anxiolytic effects is not well understood. We discovered a population of GABAergic neurons in the oval division of the bed nucleus of the stria terminalis that is activated by multiple anesthetics and the anxiolytic drug diazepam (ovBNSTGA). A majority of ovBNSTGA neurons express neurotensin receptor 1 (Ntsr1) and innervate brain regions known to regulate anxiety and stress responses. Optogenetic activation ovBNSTGA or ovBNSTNtsr1 neurons significantly attenuated anxiety-like behaviors in both naive animals and mice with inflammatory pain, while inhibition of these cells increased anxiety. Notably, activation of these neurons decreased heart rate and increased heart rate variability, suggesting that they reduce anxiety through modulation of the autonomic nervous system. Our study identifies ovBNSTGA/ovBNSTNtsr1 neurons as one of the brains endogenous anxiolytic centers and a potential therapeutic target for treating anxiety-related disorders. HIGHLIGHTSO_LIGeneral anesthetics and anxiolytics activate a population of neurons in the ovBNST C_LIO_LIAnesthesia-activated ovBNST neurons bidirectionally modulate anxiety-like behavior C_LIO_LIMost anesthesia-activated ovBNST neurons express neurotensin receptor 1 C_LIO_LIovBNSTNtsr1 neuron activation shifts autonomic responses to an anxiolytic state C_LI

neuroscience↗

bioRxiv2023

Mapping the bioimaging marker of Alzheimer's disease based on pupillary light response-driven brain-wide fMRI in awake mice

Pupil dynamics has emerged as a critical non-invasive indicator of brain state changes. In particular, pupillary-light-responses (PLR) in Alzheimers disease (AD) patients may be used as biomarkers of brain degeneration. To characterize AD-specific PLR and its underlying neuromodulatory sources, we combined high-resolution awake mouse fMRI with real-time pupillometry to map brain-wide event-related correlation patterns based on illumination-driven pupil constriction (Pc) and post-illumination pupil dilation recovery (amplitude, Pd, and time, T). The Pc-driven differential analysis revealed altered visual signal processing coupled with reduced thalamocortical activation in AD mice compared with the wild-type normal mice. In contrast, the post-illumination pupil dilation recovery-based fMRI highlighted multiple brain areas related to AD brain degeneration, including the cingulate cortex, hippocampus, septal area of the basal forebrain, medial raphe nucleus, and pontine reticular nuclei (PRN). Also, brain-wide functional connectivity analysis highlighted the most significant changes in PRN of AD mice, which serves as the major subcortical relay nuclei underlying oculomotor function. This work combined non-invasive pupil-fMRI measurements in preclinical models to identify pupillary biomarkers based on neuromodulatory dysfunction coupled with AD brain degeneration.

neuroscience↗

bioRxiv2023

High-resolution awake mouse fMRI at 14 Tesla

High-resolution awake mouse fMRI remains challenging despite extensive efforts to address motion-induced artifacts and stress. This study introduces an implantable radiofrequency (RF) surface coil design that minimizes image distortion caused by the air/tissue interface of mouse brains while simultaneously serving as a headpost for fixation during scanning. Furthermore, this study provides a thorough acclimation method used to accustom animals to the MRI environment minimizing motion induced artifacts. Using a 14T scanner, high-resolution fMRI enabled brain- wide functional mapping of visual and vibrissa stimulation at 100x100x200{micro}m resolution with a 2s per frame sampling rate. Besides activated ascending visual and vibrissa pathways, robust BOLD responses were detected in the anterior cingulate cortex upon visual stimulation and spread through the ventral retrosplenial area (VRA) with vibrissa air-puff stimulation, demonstrating higher-order sensory processing in association cortices of awake mice. In particular, the rapid hemodynamic responses in VRA upon vibrissa stimulation showed a strong correlation with the hippocampus, thalamus, and prefrontal cortical areas. Cross-correlation analysis with designated VRA responses revealed early positive BOLD signals at the contralateral barrel cortex (BC) occurring 2 seconds prior to the air-puff in awake mice with repetitive stimulation, which was not detected using a randomized stimulation paradigm. This early BC activation indicated a learned anticipation through the vibrissa system and association cortices in awake mice under continuous training of repetitive air-puff stimulation. This work establishes a high-resolution awake mouse fMRI platform, enabling brain-wide functional mapping of sensory signal processing in higher association cortical areas. Significance StatementThis awake mouse fMRI platform was developed by implementing an advanced implantable radiofrequency (RF) coil scheme, which simultaneously served as a headpost to secure the mouse head during scanning. A thorough acclimation method was used to accustom animals to the MRI environment minimizing motion induced artifacts. The ultra-high spatial resolution (100x100x200{micro}m) BOLD fMRI enabled the brain-wide mapping of activated visual and vibrissa systems during sensory stimulation in awake mice, including association cortices, e.g. anterior cingulate cortex and retrosplenial cortex, for high order sensory processing. Also, the activation of barrel cortex at 2 s prior to the air-puff indicated a learned anticipation of awake mice under continuous training of the repetitive vibrissa stimulation.

neuroscience↗

bioRxiv2023

Restoring AIBP deficiency in the retina provides neuroprotection in glaucoma

Glaucoma is a neurodegenerative disease manifested in retinal ganglion cell (RGC) death and irreversible blindness. While lowering intraocular pressure (IOP) is the only proven therapeutic strategy in glaucoma, it is insufficient for preventing disease progression, thus justifying the recent focus on targeting retinal neuroinflammation and preserving RGCs. We have identified apolipoprotein A-I binding protein (AIBP) as the protein regulating several mechanisms of retinal neurodegeneration. AIBP controls excessive cholesterol accumulation via upregulating the cholesterol transporter ATP-binding cassette transporter 1 (ABCA1) and reduces inflammatory signaling via toll-like receptor 4 (TLR4) and mitochondrial dysfunction. ABCA1, TLR4 and oxidative phosphorylation components are genetically linked to primary open-angle glaucoma. Here we demonstrated that AIBP and ABCA1 expression was decreased, while TLR4, interleukin 1 {beta} (IL-1{beta}), and the cholesterol content increased in the retina of patients with glaucoma and in mouse models of glaucoma. Restoring AIBP expression by a single intravitreal injection of adeno-associated virus (AAV)-AIBP protected RGCs in glaucomatous DBA/2J mice, in mice with microbead-induced chronic IOP elevation, and optic nerve crush. In addition, AIBP expression attenuated TLR4 and IL-1{beta} expression, localization of TLR4 to lipid rafts, reduced cholesterol accumulation, and ameliorated visual dysfunction. These studies collectively indicate that restoring AIBP expression in the glaucomatous retina reduces neuroinflammation and protects RGCs and Muller glia, suggesting the therapeutic potential of AAV-AIBP in human glaucoma. Significance StatementLowering intraocular pressure is insufficient to prevent progressive neuroinflammation, retinal ganglion cell (RGC) death and vision loss in glaucoma. We show that reduced expression of AIBP is associated with increased markers of neuroinflammation, TLR4 and IL-1{beta}, in human glaucomatous retina and mouse models of glaucoma. Restoring AIBP expression by an intravitreal injection of AAV-AIBP protects RGCs and preserves visual function in mouse models of glaucoma. Mechanistically, we demonstrate that AAV-AIBP disrupts TLR4-lipid raft formation and attenuates phosphorylation of AMPK, ERK1/2 and p38 and expression of TLR4 and IL-1{beta} in vivo. Collectively, our findings suggest that AIBP-mediated disruption of retinal TLR4-lipid rafts can prevent RGC loss and demonstrate the therapeutic potential of AAV-AIBP in treatment of human glaucoma.

neuroscience↗

bioRxiv2023

Brainstem premotor mechanisms underlying vocal production and vocal-respiratory coordination

Speech generation critically depends on precise controls of laryngeal muscles and coordination with ongoing respiratory activity. However, the neural mechanisms governing these processes remain unknown. Here, we mapped laryngeal premotor circuitry in adult mice and viral-genetically identified excitatory vocal premotor neurons located in the retroambiguus nucleus (RAmVOC) as both necessary and sufficient for driving vocal-cord closure and eliciting mouse ultrasonic vocalizations (USVs). The duration of RAmVOC activation determines the lengths of USV syllables and post-inspiration phases. RAmVOC-neurons receive inhibitory inputs from the preBotzinger complex, and inspiration needs can override RAmVOC-mediated vocal-cord closure. Ablating inhibitory synapses in RAmVOC-neurons compromised this inspiration gating of laryngeal adduction, resulting in de-coupling of vocalization and respiration. Our study revealed the hitherto unknown circuits for vocal pattern generation and vocal-respiratory coupling. One-Sentence SummaryIdentification of RAmVOC neurons as the critical node for vocal pattern generation and vocal-respiratory coupling.

neuroscience↗

bioRxiv2023

Neither alpha-synuclein-preformed fibrils derived from patients with GBA1 mutations nor the host murine genotype significantly influence seeding efficacy in the mouse olfactory bulb.

Parkinsons disease (PD) is a neurodegenerative disease characterized by progressive motor symptoms and alpha-synuclein (syn) aggregation in the nervous system. For unclear reasons, PD patients with certain GBA mutations (GBA-PD) have a more aggressive clinical progression. Two testable hypotheses that can potentially account for this phenomenon are that GBA1 mutations promote syn spread or drive the generation of highly pathogenic syn polymorphs (i.e., strains). We tested these hypotheses by treating homozygous GBA1 D409V knockin (KI) mice with human -syn-preformed fibrils (PFFs) and treating wild-type mice (WT) with several syn-PFF polymorphs amplified from brain autopsy samples collected from patients with idiopathic PD and GBA-PD patients with either homozygous or heterozygous GBA1 mutations. Robust phosphorylated-syn (PSER129) positive pathology was observed at the injection site (i.e., the olfactory bulb granular layer) and throughout the brain six months following PFF injection. The PFF seeding efficiency and degree of spread were similar regardless of the mouse genotype or PFF polymorphs. We found that PFFs amplified from the human brain, regardless of patient genotype, were generally more effective seeders than wholly synthetic PFFs (i.e., non-amplified); however, PFF concentration differed between these two studies, and this might also account for the observed differences. To investigate whether the molecular composition of pathology differed between different seeding conditions, we permed Biotinylation by Antibody Recognition on PSER129 (BAR-PSER129). We found that for BAR-PSER129, the endogenous PSER129 pool dominated identified interactions, and thus, very few potential interactions were explicitly identified for seeded pathology. However, we found Dctn2 interaction was shared across all PFF conditions, and Nckap1 and Ap3b2 were unique to PFFs amplified from GBA-PD brains of heterozygous mutation carriers. In conclusion, both the genotype and syn strain had little effect on overall seeding efficacy and global PSER129-interactions.

neuroscience↗

bioRxiv2023

Enhanced functionalities of immune cells separated by microfludic lattice: assessment based on holotomography

The isolation of white blood cells (WBCs) from whole blood constitutes a pivotal process for immunological studies, diagnosis of hematologic disorders, and the facilitation of immunotherapy. Despite the ubiquity of density gradient centrifugation in WBC isolation, its influence on WBC functionality remains inadequately understood. This research employs holotomography to explore the effects of two distinct WBC separation techniques, namely conventional centrifugation and microfluidic separation, on the functionality of the isolated cells. We utilize three-dimensional refractive index distribution and time-lapse dynamics to conduct an in-depth analysis of individual WBCs, focusing on their morphology, motility, and phagocytic capabilities. Our observations highlight that centrifugal processes negatively impacts WBC motility and phagocytic capacity, whereas microfluidic separation yields a more favorable outcome in preserving WBC functionality. These findings emphasize the potential of microfluidic separation techniques as a viable alternative to traditional centrifugation for WBC isolation, potentially enabling more precise analyses in immunology research and improving the accuracy of hematologic disorder diagnoses.

biophysics↗

bioRxiv2023

Sulfasalazine promotes myogenic differentiation via increasing of fast myosin heavy chain isoforms

Sarcopenia is a debilitating condition characterized by the progressive and generalized degeneration of skeletal muscle mass and function. As of now, there is no approved pharmacological treatment for sarcopenia. Previously, our research revealed that Yin Yang 1 (YY1) plays a crucial role in PHD finger protein 20 (PHF20)-mediated myogenic differentiation. A significant enhancement in YY1 transcription, mediated by PHF20, was observed in C2C12 myoblasts. Within skeletal muscle, YY1 is traditionally considered to inhibit myogenesis by directly repressing the synthesis of late-stage differentiation genes, such as skeletal muscle actin, muscle creatine kinase, and myosin heavy chain IIb. Through screening of a drug library using a PHF20/YY1 promoter reporter assay, sulfasalazine emerged as a promising candidate. Sulfasalazine is known for its anti-inflammatory and immunomodulatory properties and is commonly prescribed for autoimmune diseases. In this study, the treatment of C2C12 myoblasts with sulfasalazine accelerated the myogenic differentiation and bolstered the gene and protein expression of fast myosin heavy chain via a metabolic shift towards glycolysis. Additionally, oral administration of sulfasalazine demonstrated improvement in physical performance in aged mice, as well as in mice models with hindlimb disuse or damage. Moreover, sulfasalazine exhibited a remarkable ability to facilitate the recovery of muscle fibers damaged by Velcro immobilization. Collectively, our findings suggest that sulfasalazine could represent a novel therapeutic avenue for the amelioration of muscle weakness, including sarcopenia.

biochemistry↗

bioRxiv2023

Data-driven signal analysis of sensory cortical processing using high-resolution fMRI across different studies

The analysis of large data sets within and across preclinical studies has always posed a particular challenge in terms of data volume and method heterogeneity between studies. Recent developments in machine learning (ML) and artificial intelligence (AI) allow to address these challenges in complex macro- and microscopic data sets. Because of their complex data structure, functional magnetic resonance imaging (fMRI) measurements are perfectly suited to develop such ML/AI frameworks for data-driven analyses. These approaches have the potential to reveal patterns, including temporal kinetics, in blood-oxygen-level-dependent (BOLD) time series with a reduced workload. However, the typically poor signal-to-noise ratio (SNR) and low temporal resolution of fMRI time series have so far hampered such advances. Therefore, we used line scanning fMRI measurements with high SNR and high spatio-temporal resolution obtained from three independent studies and two imaging centers with heterogeneous study protocols. Unbiased time series clustering techniques were applied for the analysis of somatosensory information processing during electrical paw and optogenetic stimulation. Depending on the similarity formulation, our workflow revealed multiple patterns in BOLD time series. It produced consistent outcomes across different studies and study protocols, demonstrating the generalizability of the data-driven method for cross-study analyzes. Further, we introduce a statistical analysis that is entirely based on cluster distribution. Using this method, we can reproduce previous findings including differences in temporal BOLD characteristics between two stimulation modalities. Our data-driven approach proves high sensitivity, robustness, reproducibility, and generalizability and further quickly provides highly detailed insight into characteristics of BOLD time series. Therefore, it holds great potential for further applications in fMRI data including whole-brain task and resting-state fMRI, which can support fMRI routines. Furthermore, the analytic framework can be used for datasets that have a time-dependent data structure to integrate study results and create robust and generalizable datasets, despite different study protocols.

neuroscience↗

bioRxiv2023

Highly effective gene inactivation in tetraploid Xenopus laevis with low-temperature-active engineered Cas12a

Gene knockout using the CRISPR/Cas (clustered regulatory interspaced short palindromic repeats/CRISPR-associated protein) system revolutionized reverse genetic studies in model and non-model organisms, as almost all genetic elements can be targeted with few limitations. Although the CRISPR/Cas system with SpCas9 (Cas9 derived from Streptococcus pyogenes) remains the most popular for genome editing, another CRISPR/Cas system with Cas12a (Cpf1) has expanded its application. However, Cas12a is challenging to use in some aquatic model organisms, such as Xenopus laevis, because of its low activity at the temperature at which X. laevis embryos are usually raised (lower than 25{degrees}C). Recently, an engineered Cas12a called Cas12a-Ultra was developed, which has improved in vivo endonuclease activity with reduced temperature dependency. Here, we evaluated the performance of these engineered Cas12a enzymes in X. laevis embryos. We first confirmed that they were more active than SpCas9 at the low temperature at which X. laevis embryos are mostly raised (20-22{degrees}C), based on in vitro digestion experiments. Then, we evaluated in vivo activities of Cas12a-Ultra by disrupting several genes in X. laevis whose phenotypic consequences are previously reported. LbCpf1 (Cas12a derived from Lachnospiraceae bacterium)-Ultra outperformed the other enzymes, producing more than 80% of embryos with severely defective phenotypes even in low-temperature conditions. In addition, duplicated copies of two paralogous lysine demethylases (kdm5b and kdm5c) were successfully disrupted, which recapitulated the previously reported phenotypes observed upon morpholino-mediated knockdown. This study demonstrated that this engineered Cas12a is valuable for gene function studies in Xenopus and other model organisms with low growth temperatures.

bioengineering↗

bioRxiv2023

No Replication of Direct Neuronal Activity-related (DIANA) fMRI in Anesthetized Mice

Direct imaging of neuronal activity (DIANA) by fMRI could be a revolutionary approach for advancing systems neuroscience research. To independently replicate this observation, we performed fMRI experiments in anesthetized mice. The BOLD response to whisker stimulation was reliably detected in the primary barrel cortex before and after DIANA experiments; however, no direct neuronal activity-like fMRI peak was observed in data of individual animals with the 50-300 trials. Extensively averaged data involving 1,050 trials in 6 mice showed a flat baseline and no detectable neuronal activity-like fMRI peak. However, spurious, non-replicable peaks were found when using a small number of trials, and artifactual peaks were detected when some outlier-like trials were excluded. Further, no detectable DIANA peak was observed in the BOLD-responding thalamus from the selected trials with the neuronal activity-like reference function in the barrel cortex. Thus, we were unable to replicate the previously reported results without data pre-selection.

neuroscience↗

bioRxiv2023

A Hypothalamic Circuit Underlying the Dynamic Control of Social Homeostasis

Social grouping increases survival in many species, including humans1,2. By contrast, social isolation generates an aversive state (loneliness) that motivates social seeking and heightens social interaction upon reunion3-5. The observed rebound in social interaction triggered by isolation suggests a homeostatic process underlying the control of social drive, similar to that observed for physiological needs such as hunger, thirst or sleep3,6. In this study, we assessed social responses in multiple mouse strains and identified the FVB/NJ line as exquisitely sensitive to social isolation. Using FVB/NJ mice, we uncovered two previously uncharacterized neuronal populations in the hypothalamic preoptic nucleus that are activated during social isolation and social rebound and that orchestrate the behavior display of social need and social satiety, respectively. We identified direct connectivity between these two populations of opposite function and with brain areas associated with social behavior, emotional state, reward, and physiological needs, and showed that animals require touch to assess the presence of others and fulfill their social need, thus revealing a brain-wide neural system underlying social homeostasis. These findings offer mechanistic insight into the nature and function of circuits controlling instinctive social need and for the understanding of healthy and diseased brain states associated with social context.

neuroscience↗

bioRxiv2023

Alpha-180 spin-echo based line-scanning method for high resolution laminar-specific fMRI

Laminar-specific functional magnetic resonance imaging (fMRI) has been widely used to study circuit-specific neuronal activity by mapping spatiotemporal fMRI response patterns across cortical layers. Hemodynamic responses reflect indirect neuronal activity given limit of spatial and temporal resolution. Previous gradient-echo based line-scanning fMRI (GELINE) method was proposed with high temporal (50 ms) and spatial (50 {micro}m) resolution to better characterize the fMRI onset time across cortical layers by employing 2 saturation RF pulses. However, the imperfect RF saturation performance led to poor boundary definition of the reduced region of interest (ROI) and aliasing problems outside of the ROI. Here, we propose (alpha)-180 spin-echo-based line-scanning fMRI (SELINE) method to resolve this issue by employing a refocusing 180{degrees} RF pulse perpendicular to the excitation slice. In contrast to GELINE signals peaked at the superficial layer, we detected varied peaks of laminar-specific BOLD signals across deeper cortical layers with the SELINE method, indicating the well-defined exclusion of the large drain-vein effect with the spin-echo sequence. Furthermore, we applied the SELINE method with 200 ms TR to sample the fast hemodynamic changes across cortical layers with a less draining vein effect. In summary, this SELINE method provides a novel acquisition scheme to identify microvascular-sensitive laminar-specific BOLD responses across cortical depth.

neuroscience↗

bioRxiv2023

Bcl-xL is translocated to the nucleus via CtBP2 to epigenetically promote metastasis

Besides its mitochondria-based anti-apoptotic role, Bcl-xL also travels to the nucleus to promote cancer metastasis by upregulating global histone H3 trimethyl Lys4 (H3K4me3) and TGF{beta} transcription. How Bcl-xL is translocated into the nucleus and how nuclear Bcl-xL regulates H3K4me3 modification are not understood. Here, we report that C-terminal Binding Protein 2 (CtBP2) binds Bcl-xL via its N-terminus and translocates Bcl-xL into the nucleus. Knockdown of CtBP2 by shRNA decreases the nuclear portion of Bcl-xL and reverses Bcl-xL-induced cell migration and metastasis in mouse models. Furthermore, knockout of CtBP2 suppresses Bcl-xL transcription. The binding between Bcl-xL and CtBP2 is required for their interaction with MLL1, a histone H3K4 methyltransferase. Pharmacologic inhibition of MLL1 enzymatic activity reverses Bcl-xL-induced H3K4me3 and TGF{beta} mRNA upregulation as well as cell invasion. Moreover, cleavage under targets and release using nuclease (CUT&RUN) coupled with next generation sequencing reveals that H3K4me3 modifications are particularly enriched in the promotor region of genes encoding TGF{beta} and its signaling pathway in the cancer cells overexpressing Bcl-xL. Altogether, the metastatic function of Bcl-xL is mediated by its interaction with CtBP2 and MLL1.

cancer biology↗

bioRxiv2023

Xylazine effects on opioid-induced brain hypoxia

Xylazine has emerged in recent years as an adulterant in an increasing number of opioid-positive overdose deaths in the United States. Although its exact role in opioid-induced overdose deaths is largely unknown, xylazine is known to depress vital functions and cause hypotension, bradycardia, hypothermia, and respiratory depression. In this study, we examined the brain-specific hypothermic and hypoxic effects of xylazine and its mixtures with fentanyl and heroin in freely moving rats. In the temperature experiment, we found that intravenous xylazine at low, human-relevant doses (0.33, 1.0, 3.0 mg/kg) dose-dependently decreases locomotor activity and induces modest but prolonged brain and body hypothermia. In the electrochemical experiment, we found that xylazine at the same doses dose-dependently decreases nucleus accumbens oxygenation. In contrast to relatively weak and prolonged decreases induced by xylazine, intravenous fentanyl (20 g/kg) and heroin (600 g/kg) induce stronger biphasic brain oxygen responses, with the initial rapid and strong decrease, resulting from respiratory depression, followed by a slower, more prolonged increase reflecting a post-hypoxic compensatory phase, with fentanyl acting much quicker than heroin. The xylazine-fentanyl mixture eliminated the hyperoxic phase of oxygen response and prolonged brain hypoxia, suggesting xylazine-induced attenuation of the brains compensatory mechanisms to counteract brain hypoxia. The xylazine-heroin mixture strongly potentiated the initial oxygen decrease, and the pattern lacked the hyperoxic portion of the biphasic oxygen response, suggesting more robust and prolonged brain hypoxia. These findings suggest that xylazine exacerbates the life-threatening effects of opioids, proposing worsened brain hypoxia as the mechanism contributing to xylazine-positive opioid-overdose deaths.

pharmacology and toxicology↗