Biology subjects

Balasubramanian, N.

Publications and source records attributed to Balasubramanian, N..

At least 19 recordsLinked to original sources

bioRxiv2026

Adolescent Social Isolation Facilitates Tau Spread in Raphe Nuclei Linking Depression and Hyperalgesia in Alzheimers Disease

Tau pathology in brainstem serotonergic circuits drives early neuropsychiatric dysfunction in Alzheimers disease (AD), yet mechanisms linking the exposome, particularly social stress exposures to depression and altered pain perception, remain unclear. Here, we demonstrate that adolescent social isolation, a critical psychosocial exposome factor and major trigger of depression, facilitates tau propagation in the dorsal raphe nucleus (DRN) and downstream raphe nuclei, producing both neuropsychiatric and pain-related sequelae. Tau[P301L] was transduced into the DRN of 30-day socially isolated or group housed C57BL/6J mice using AAV, with control mice receiving AAV-GFP. Four weeks post-transduction, anxiety, social behavior, and pain sensitivity were assessed, and phosphorylated tau (ptau) within the DRN and spread to the median raphe (MRN) and raphe magnus (RMg) serotonergic neurons were evaluated. Socially isolated tau[P301L] mice exhibited hyperlocomotion, anxiety-like behavior, social deficits and hyperalgesia. Histological analysis revealed elevated ptau within TPH2 neurons in the DRN and trans-synaptic tau spread to MRN and RMg, accompanied by reduced TPH2 and increased ptau at the downstream raphe nuclei. Fluorescence in situ hybridization confirmed altered expression of Slc6a4 and Tgm2, a stress-responsive gene implicated in AD. These results indicate that DRN tau under social stress drives neuropsychiatric phenotypes, while tau spread to MRN and RMg disrupts serotonergic modulation of pain. This study provides the first evidence that adolescent stress promotes tau propagation within the raphe nuclei, linking early neuropsychiatric and pain-processing deficits to prodromal Alzheimers disease and identifying a critical pathway through which psychosocial exposome risk converges with tau pathology to enable early intervention.

neuroscience↗

bioRxiv2025

Selective reduction of KCNA4 in vulnerable glutamatergic-serotonin neurons of the dorsal raphe nucleus in Alzheimers Disease

INTRODUCTIONWe previously demonstrated that htau mice recapitulate many neuropsychiatric features of early Alzheimers disease (AD), and that the dorsal raphe nucleus (DRN) contains distinct subregions. Herein, we investigate vulnerability of the centromedial DRN to pathologically-phosphorylated tau (pTau), a region composed predominantly of dually serotonergic/glutamatergic (5HT/glut) neurons. METHODSWe use computational, molecular, biophysical, and behavioral techniques to assess the centromedial DRN across preclinical and post-mortem settings. RESULTSThe centromedial DRN contains 5HT/glut neurons that differentially express ion-channel genes in the htau mouse. 5HT/glut neurons exhibit increased excitability, which we demonstrate may dually promote pTau accumulation and the severity of depressive-like behaviors in htau mice. At Braak 2, KCNA4 is reduced in 5HT/glut neurons in AD, which are especially vulnerable to pTau compared to 5HT-nonglut neurons. DISCUSSIONTau-mediated dysfunction of the DRN may be driven by changes in ion channel activity that concomitantly promote the spread of pTau in Braak progression.

neuroscience↗

bioRxiv2025

Caveolin-1 dependent regulation of cell-matrix interphase in 3D collagen gels.

Cell and extracellular matrix (ECM) interactions are essential for maintaining tissue function and homeostasis. Changes in the biochemical or mechanical properties of the ECM can lead to diseases such as fibrosis or cancer. In a 3D microenvironment, cell-matrix interaction is vital to how cells sense and respond to biochemical and biophysical cues. This study examines the reciprocal interactions between fibroblasts and collagen in 3D hydrogels. We quantitatively measured changes in collagen branch number and junctions in 3D hydrogels using confocal reflectance microscopy and existing analysis protocols. This reveals the impact small changes in collagen concertation (1.0 vs 1.5 mg/ml) over time (15 minutes to 4 hours) have on 3D gels. Embedded in 3D hydrogels, wild-type mouse fibroblasts differentially affect collagen organisation in their immediate proximity with changing concentration and time. This regulation is interestingly lost in Caveolin-1 null fibroblasts with altered stiffness, mechanosensing and cytoskeletal regulation. Inhibition of the Rho-ROCK pathway (known to be changed in Caveolin-1 null fibroblasts) drives cellular protrusions and concentration-dependent 3D collagen organisation in wildtype fibroblasts, but surprisingly not in Caveolin-1 null fibroblasts. This depends on dynamin-dependent endocytosis, which, when inhibited, disrupts ROCK-dependent protrusions and alters collagen organisation in 3D collagen. Together, these observations quantitatively demonstrate how cells respond at the cell-matrix interphase to subtle changes in collagen concentration and organisation in 3D hydrogels, regulated by the presence of Caveolin-1. Statement of SignificanceThis study highlights the critical role of Caveolin-1 in cell-mediated regulation of the extracellular matrix (ECM) in a 3D microenvironment. Using confocal reflectance microscopy, we demonstrate that subtle changes in collagen concentration significantly influence collagen organisation over time. While wild-type fibroblasts exhibit dynamic, concentration-dependent regulation of the cell-matrix interphase, Caveolin-1 null fibroblasts lose this regulation. Furthermore, Rho-ROCK pathway inhibition promotes protrusions and collagen reorganisation in wild-type cells but not Caveolin-1 null fibroblasts. Dynamin-dependent endocytosis also emerges as a key modulator of this process. These findings provide quantitative insights into how mechanosensing and cytoskeletal regulation, dependent on endocytosis can control the cell-matrix interphase, with possible implications for understanding disease-associated matrix changes.

cell biology↗

bioRxiv2025

KIF5B and Dynein regulate adhesion-dependent Golgi organization and microtubule acetylation

Cell-matrix adhesion regulates Golgi organization through Arf1-mediated dynein recruitment, maintaining its juxtanuclear localization. On loss of adhesion, Arf1 activation drops, causing loss of dynein, promoting differential disorganization of cis- vs trans-Golgi along microtubules. Golgi regulates microtubule nucleation and stability. In fibroblasts, acetylated tubulin levels drop on loss of adhesion, recovering on re-adhesion with time. Active Arf1 overexpression in preventing Golgi disorganization sustains microtubule acetylation, also seen in T24 bladder cancer cells. Active Arf1 binds KIF5B, recruiting it to the Golgi. KIF5B and dynein knockdown disorganize the Golgi as ministacks, with cis- and trans-Golgi. Dynein knockdown disrupts MTOC positioning, causing ministacks to disperse, preventing Golgi reorganization upon re-adhesion. Dispersed ministacks interestingly maintain microtubule acetylation in adherent and non-adherent cells. The joint KIF5B-dynein knockdown causes the Golgi to lose its ribbon morphology, becoming compact while keeping cis- and trans-Golgi together. This also causes a change in spreading, aspect ratio and migration of knockdown cells, which could be regulated by their Golgi phenotype. In evaluating adhesion-dependent Golgi organization, we reveal the Arf1-KIF5B-dynein crosstalk to regulate Golgi-dependent tubulin acetylation and cell function. SummaryKIF5B and dynein are vital microtubule-associated motors that drive organelle positioning and organization. Adhesion-dependent Arf1 activation mediates KIF5B and dyneins recruitment to the Golgi, regulating its organization and position. This, in turn, regulates microtubule acetylation levels, localization, and cellular functions.

cell biology↗

bioRxiv2025

Receptor tyrosine kinase AXL regulates Golgi organization and function through an adhesion-Arf1 signaling axis in breast and lung cancers

Cell-matrix adhesion regulates membrane trafficking, Golgi organisation and function. Differential Golgi organisation in cancer cells could drive changes in trafficking and processing of cargoes. A simple screen evaluating Golgi organisation identifies breast (MDAMB231 vs MCF7) and lung cancer (A549 vs CaLu1) cell line pairs with differently organised Golgi, regulated differentially by loss of adhesion. In silico analysis of differentially expressed genes in the CCLE database, evaluated for their association with the Golgi in interaction networks and literature, identified AXL as a putative regulator of Golgi in these cancers. AXL prominently localized at the Golgi, undergoes displacement from the Golgi when inhibited by R428 and knocked down using siRNA, causing the Golgi to disorganize. AXL-dependent regulation of Golgi organisation is also dependent on cell-matrix adhesion. AXL binds active Arf1, whose recruitment to the Golgi is vital for its organisation. On loss of adhesion, loss of AXL and active Arf1 from the Golgi, drives its disorganization to affect Golgi-dependent microtubule acetylation and cell surface glycosylation in MDAMB231 and A549 cells respectively. Together, this validates our screen to identify novel regulators of the Golgi, and identifies AXL-Arf1 crosstalk as a vital mediator of its organisation and function in cancer cells.

cell biology↗

bioRxiv2025

Differential AXL expression and regulation of Arf1 controls matrix stiffness-dependent Golgi organization and function in breast cancer cells

Integrin-mediated cell-matrix adhesion regulates cell growth and survival and is often deregulated in transformed cancer cells, promoting anchorage independence. Integrins are essential regulators of cellular mechanotransduction, known to be altered in cancer cells. In breast cancers, tumour stiffening is a well-characterized feature of the disease progression. The Golgi apparatus, regulated by integrin-mediated adhesion in responding to mechanosensory cues, could support cancer progression. MDAMB231 and MCF7 cells with distinct Golgi organization and altered mechanosensing were evaluated. In MDAMB231 cells the organized Golgi in stable adherent cells becomes disorganised on loss of adhesion. This contrasts with MCF7 cells, where the Golgi remains disorganized regardless of the adhesion status. In MDAMB231 cells, increasing matrix stiffness promotes Golgi organization and regulates Golgi-dependent microtubule acetylation. In MCF7 cells, the Golgi stays disorganised despite increasing stiffness. Both cell types show stiffness-dependent cell spreading, with MCF7 cells spreading more efficiently than MDAMB231 cells - a difference that may be partially mediated by their differential Golgi organization. AXL, a receptor tyrosine kinase, is known to be involved in rigidity sensing and is differentially expressed in MDAMB231 (high) vs MCF7 (no expression) cells. AXL inhibition (by R428) and siRNA-mediated AXL knockdown disrupt stiffness-dependent Golgi organization in MDAMB231 cells, promoting cell spreading. Transient and stable AXL expression in MCF7 cells causes the Golgi to become predominantly organised and respond to higher matrix stiffness, affecting cell spreading. Stiffness-dependent AXL expression supports stiffness-dependent Arf1 expression and activation to drive Golgi organization. Thus, matrix mechanosensing through the AXL-Arf1-Golgi pathway could regulate vital cellular processes in breast cancer cells.

cell biology↗

bioRxiv2024

CRISPR-Cas9 RALA knockout and reconstitution. Detection and role of RALA S194 phosphorylation in RAS-dependent and RAS-independent cancers.

Downstream of oncogenic RAS, RALA is critical for cancer tumorigenesis, possibly regulated by phosphorylation of its Serine194 residue. We made CRISPR-Cas9 RALA knockout (RALA KO) in three RAS-dependent and two RAS-independent cancer cells. Detection of RALA S194 phosphorylation using the commercial anti-phospho-RALA antibody lacks specificity in all three RAS-dependent cancers. siRNA knockdown of RALA and AURKA inhibition by MLN8237 (VMLN) also did not affect pS194RALA detection in these cancers. RALA KO MiaPaCa2 (RAS-dependent) and MCF7 (RAS-independent) cells, stably reconstituted with WT-RALA and S194A-RALA mutants, showed no effect on RALA activation. Tumour growth was, however, restored partly by WT-RALA, but not S194A-RALA mutant. Thus, RALA S194 phosphorylation is needed for tumor formation, not affecting its activation but possibly through its localization.

cancer biology↗

bioRxiv2024

Cell-surface glycans are quantitative reporters of Golgi dysfunction in single cells

Complex sugar polymers known as glycans contribute to the high molecular diversity of the eukaryotic cell surface. The types and levels of glycans on one cell can be sensed by other cells using carbohydrate-specific binding proteins such as lectins, enabling glycans to regulate cell-cell interactions. Glycans are covalently assembled onto proteins and lipids as they traverse the secretory pathway, a tightly regulated process known as glycosylation and carried out by Golgi-resident enzymes. Errors in glycosylation due to the dysfunctional trafficking of enzymes and substrates in the Golgi are implicated in human diseases. Here we ask how much information about Golgi dysfunction is encoded by surface glycans in single cells. This task is challenging due to high cell-to-cell variability in glycan levels. We exploited the loss-of-adhesion driven disorganization of the Golgi in mouse fibroblasts to generate a highly reproducible gradient of Golgi morphology phenotypes, by titrating the Arf1 inhibitor Brefeldin A (BFA). We measured the resulting distribution of cell-surface glycans in single cells using two fluorescently tagged lectin probes (ConA and WGA). A mathematical model of intracellular traffic, parameterized against measurements of Golgi fragmentation and endocytosis, quantitatively explains cell-surface lectin levels across time and BFA concentrations. We used this model to construct an optimal Bayesian decoder and showed that singlecell lectin measurements predict Golgi phenotypes with accuracy far greater than chance. By combining signals from two lectins we further improved prediction accuracy and speed. Such multi-lectin information may be exploited during natural cell-cell communication, and in the development of single-cell diagnostics.

cell biology↗

bioRxiv2024

A new insight into the role of CART peptide in serotonergic function and anxiety

Cocaine and amphetamine-regulated transcript (CART) peptide has been established as a contributor to anxiogenic behavior. Genetic mutations in the CART gene are associated with anxiety and depression, and increased CART expression has been reported in suicide victims. Extensive research has focused on the role of CART peptide in mesolimbic neurocircuitry, but its involvement in the dorsal raphe nucleus (DRN) and serotonin (5HT) system remains unexplored. Here we demonstrate that CART processes are proximal to 5HTDRN neurons and that microinjection of CART (55-102) peptide into the DRN has an anxiogenic effect in mice. Furthermore, central CART administration reduced cfos activation in 5HT neurons of the ventral DRN, which is a putative reward/anti-stress circuit. The inhibitory effect of CART on 5HTDRN neuronal function and local 5HT release is further demonstrated with in vivo fiber photometry coupled with calcium and 5HT biosensors and by mass spectrometry. Moreover, using Cre-dependent retrograde tracing, we observed DRN-projecting CART neurons in the Edinger Westphal nucleus (EW), nucleus accumbens (NAc), and various hypothalamic nuclei including the ventromedial hypothalamus (VMH). Interestingly, based on ex vivo electrophysiological recordings, acute stress increased excitability in DRN-projecting CART neurons located in the EW, but not in the VMH or NAc. This suggests that the stress may promote anxiety-like behavior by activating the EWCART[->]5HTDRN circuit that ultimately inhibits 5HT transmission. In sum, understanding the intricate dynamics of the CARTergic and 5HTergic systems proves crucial in addressing 5HT-related dysfunctions, providing invaluable insights into both health and disease.

neuroscience↗

bioRxiv2023

Lateral Septal Circuits Govern Schizophrenic-Like Effects of Ketamine on Social Behavior

Schizophrenia is marked by poor social functioning that can have a severe impact on quality of life and independence, but the underlying neural circuity is not well understood. Here we used a translational model of subanesthetic ketamine in mice to delineate neural pathways in the brain linked to social deficits in schizophrenia. Mice treated with chronic ketamine (30 mg/kg/day for 10 days) exhibit profound social and sensorimotor deficits as previously reported. Using three- dimensional c-Fos immunolabeling and volume imaging (iDISCO), we show that ketamine treatment resulted in hypoactivation of the lateral septum (LS) in response to social stimuli. Chemogenetic activation of the LS rescued social deficits after ketamine treatment, while chemogenetic inhibition of previously active populations in the LS (i.e. social engram neurons) recapitulated social deficits in ketamine-naive mice. We then examined the translatome of LS social engram neurons and found that ketamine treatment dysregulated genes implicated in neuronal excitability and apoptosis, which may contribute to LS hypoactivation. We also identified 38 differentially expressed genes (DEGs) in common with human schizophrenia, including those involved in mitochondrial function, apoptosis, and neuroinflammatory pathways. Chemogenetic activation of LS social engram neurons induced downstream activity in the ventral part of the basolateral amygdala, subparafascicular nucleus of the thalamus, intercalated amygdalar nucleus, olfactory areas, and dentate gyrus, and it also reduces connectivity of the LS with the piriform cortex and caudate-putamen. In sum, schizophrenia-like social deficits may emerge via changes in the intrinsic excitability of a discrete subpopulation of LS neurons that serve as a central hub to coordinate social behavior via downstream projections to reward, fear extinction, motor and sensory processing regions of the brain.

neuroscience↗

bioRxiv2023

Involvement of a serotonin/GLP-1 circuit in adolescent isolation-induced diabetes

In 2020, stay-at-home orders were implemented to stem the spread of SARS-CoV-2 worldwide. Social isolation can be particularly harmful to children and adolescents--during the pandemic, the prevalence of obesity increased by [~]37% in persons aged 2-19. Obesity is often comorbid with type 2 diabetes, which was not assessed in this human pandemic cohort. Here, we investigated whether male mice isolated throughout adolescence develop type 2 diabetes in a manner consistent with human obesity-induced diabetes, and explored neural changes that may underlie such an interaction. We find that isolating C57BL/6J mice throughout adolescence is sufficient to induce type 2 diabetes. We observed fasted hyperglycemia, diminished glucose clearance in response to an insulin tolerance test, decreased insulin signaling in skeletal muscle, decreased insulin staining of pancreatic islets, increased nociception, and diminished plasma cortisol levels compared to group-housed control mice. Using Promethion metabolic phenotyping chambers, we observed dysregulation of sleep and eating behaviors, as well as a time-dependent shift in respiratory exchange ratio of the adolescent-isolation mice. We profiled changes in neural gene transcription from several brain areas and found that a neural circuit between serotonin-producing and GLP-1-producing neurons is affected by this isolation paradigm. Overall, spatial transcription data suggest decreased serotonin neuron activity (via decreased GLP-1-mediated excitation) and increased GLP-1 neuron activity (via decreased serotonin-mediated inhibition). This circuit may represent an intersectional target to further investigate the relationship between social isolation and type 2 diabetes, as well as a pharmacologically-relevant circuit to explore the effects of serotonin and GLP-1 receptor agonists. Article HighlightsO_LIIsolating C57BL/6J mice throughout adolescence is sufficient to induce type 2 diabetes, presenting with fasted hyperglycemia. C_LIO_LIAdolescent-isolation mice have deficits in insulin responsiveness, impaired peripheral insulin signaling, and decreased pancreatic insulin production. C_LIO_LITranscriptional changes across the brain include the endocannabinoid, serotonin, and GLP-1 neurotransmitters and associated receptors. C_LIO_LIThe neural serotonin/GLP-1 circuit may represent an intersectional target to further investigate the relationship between social isolation and type 2 diabetes. Serotonin-producing neurons of adolescent-isolation mice produce fewer transcripts for the GLP-1 receptor, and GLP-1 neurons produce fewer transcripts for the 5-HT1A serotonin receptor. C_LI

neuroscience↗

bioRxiv2023

Alcohol inhibits sociability via serotonin inputs to the nucleus accumbens

Social interaction is a core component of motivational behavior that is perturbed across multiple neuropsychiatric disorders, including alcohol use disorder (AUD). Positive social bonds are neuroprotective and enhance recovery from stress, so reduced social interaction in AUD may delay recovery and lead to alcohol relapse. We report that chronic intermittent ethanol (CIE) induces social avoidance in a sex-dependent manner and is associated with hyperactivity of serotonin (5-HT) neurons in the dorsal raphe nucleus (DRN). While 5-HTDRN neurons are generally thought to enhance social behavior, recent evidence suggests that specific 5-HT pathways can be aversive. Using chemogenetic iDISCO, the nucleus accumbens (NAcc) was identified as one of 5 regions that were activated by 5-HTDRN stimulation. We then employed an array of molecular genetic tools in transgenic mice to show that 5-HTDRN inputs to NAcc dynorphin neurons drive social avoidance in male mice after CIE by activating 5-HT2C receptors. NAcc dynorphin neurons also inhibit dopamine release during social interaction, reducing the motivational drive to engage with social partners. This study reveals that excessive serotonergic drive after chronic alcohol can promote social aversion by inhibiting accumbal dopamine release. Drugs that boost brain serotonin levels may be contraindicated for individuals with AUD.

neuroscience↗

bioRxiv2022

Tau pathology in the dorsal raphe may be a prodromal indicator of Alzheimer's disease

Protein aggregation in brainstem nuclei is thought to occur in the early stages of Alzheimers disease (AD), but its specific role in driving prodromal symptoms and disease progression is largely unknown. The dorsal raphe nucleus (DRN) contains a large population of serotonin (5-hydroxytryptamine; 5-HT) neurons that regulate mood, reward-related behavior, and sleep, which are all disrupted in AD. We report here that tau pathology is present in the DRN of individuals 54-80 years old without a known history of dementia and was found at higher frequency than -synuclein and TDP-43. Most AD cases had tau pathology in the DRN (90%), whereas only a subset contained TDP-43 or -synuclein, but not both (30%). To evaluate how early tau pathology impacts behavior, we overexpressed human P301L-tau in the DRN of mice and observed depressive-like behaviors and hyperactivity without any deficits in spatial memory. Tau pathology was predominantly found in neurons relative to glia and colocalized with a significant proportion of Tph2-expressing neurons in the DRN. 5-HT neurons were also hyperexcitable in P301L-tauDRN mice, and there was an increase in the amplitude of excitatory post-synaptic currents (EPSCs), suggestive of increased glutamatergic transmission. Moreover, astrocytic density was elevated in the DRN and accompanied by an increase in IL-1 and Frk expression, which is indicative of inflammation. Additionally, tau pathology was detected in axonal processes in the thalamus, hypothalamus, amygdala, and caudate putamen and a significant proportion of this tau pathology colocalized with the serotonin reuptake transporter (SERT), suggesting that tau may spread in an anterograde manner to regions outside the DRN. Together these results indicate that tau pathology accumulates in the DRN in a subset of individuals over 50 years and may lead to behavioral dysregulation, 5-HT neuronal dysfunction, and activation of local astrocytes which may be prodromal indicators of AD.

neuroscience↗

bioRxiv2022

Golgi localized Arl15 regulates cargo transport, cell adhesion and motility

Arf-like GTPases (Arls) regulate membrane trafficking and cytoskeletal organization. Genetic studies predicted a role for Arl15 in type-2 diabetes, insulin resistance, adiposity, and rheumatoid arthritis. Recent studies indicate a possible role for Arl15 in multiple physiological processes, including magnesium homeostasis. However, the molecular function of Arl15 is poorly defined. We evaluated the role of Arl15 in vesicular transport using techniques to quantify cargo trafficking, to mechanobiology. Fluorescence microscopy of stably expressing Arl15-GFP HeLa cells showed its localization to the Golgi and cell surface, including filopodia, and a cohort to recycling endosomes. The dissociation of Golgi, using small molecular inhibitors or the expression of Arf1 dominant-negative mutant, completely mislocalized Arl15 to the cytosol. Interestingly, site-directed mutagenesis analysis identified a novel V80A mutation in the GTP-binding domain that turns Arl15 into a dominant-negative form with reduced number of filopodia. Depletion of Arl15 in HeLa cells caused mislocalization of cargo, such as caveolin-2 and STX6, from the Golgi. Arl15 knockdown cells displayed reduced filopodial number, altered focal adhesion kinase organization, and enhanced soluble and receptor-mediated cargo uptake without affecting the TfR recycling. Arl15 knockdown decreased cell migration and enhanced cell spreading and adhesion strength. Traction force microscopy experiments revealed that Arl15 depleted cells exert higher tractions and generate multiple focal adhesion points during the initial phase of cell adhesion as compared to control cells. Collectively, these studies demonstrated a functional role for Arl15 in the Golgi, which includes regulating cargo transport to organize membrane domains at the cell surface. Key pointsO_LIArl15 primarily localizes to Golgi and plasma membrane, including filopodia C_LIO_LIMembrane localization of Arl15 is dependent on Golgi integrity or Arf1 activation C_LIO_LIArl15 knockdown mislocalizes STX6-dependent Golgi localized cargo required for cell surface organization and reduces the filopodial number C_LIO_LIArl15 is involved in cell spreading, adhesion, and migration C_LI

cell biology↗

bioRxiv2022

Behavioral dysregulation and monoaminergic deficits precede memory impairments in human tau-overexpressing (htau) mice

Alzheimers disease (AD) poses an ever-increasing public health concern as the population ages, affecting more than 6 million Americans. AD patients present with mood and sleep changes in the prodromal stages that may be partly driven by loss of monoaminergic neurons in brainstem, but a causal relationship has not been firmly established. The goal of the present study was to evaluate depressive and anxiety-like behaviors in a mouse model of human tauopathy (htau mice) at 4 and 6 months of age prior to the onset of cognitive impairments and correlate these behavior changes with tau pathology, neuroinflammation, and monoaminergic dysregulation in the DRN and LC. We observed depressive-like behaviors at 4 months of age in male and female htau mice and hyperlocomotion in male htau mice. At 6 months, male htau mice developed anxiety-like behavior in the EZM, whereas hyperlocomotion had resolved by this time point. Depressive-like behaviors in the social interaction test persisted at 6 months but were resolved in the sucrose preference test. There was also a significant reduction in number and density of 5-HT-immunoreactive neurons in the rostral DRN in htau mice at 4 months and 5-HT neuronal density was negatively correlated with the intensity of phosphorylated tau staining in this subregion. Additionally, we found evidence of microglial activation in the mid and caudal DRN and astrocytic activation in the rostral DRN. 5-HT neuronal activity was reduced in the DRN and accompanied by downregulation of Tph2 and Sert, whereas genes that promote neuroinflammation and tau phosphorylation were upregulated. Finally, there was enhanced ptau202/205 staining and microglial activity in the LC of htau mice and reduced TH optical density, although the number and density of TH+ neurons were not altered. In total, these results suggest that tau pathology in the DRN and the resulting loss of serotonergic neurotransmission may drive depressive-like behaviors in the early stages of AD, whereas anxiety-like behaviors develop later and may result from neurodegeneration in other regions.

animal behavior and cognition↗

bioRxiv2022

Repeated ethanol exposure and withdrawal alters ACE2 expression in discrete brain regions: Implications for SARS-CoV-2 infection

Emerging evidence suggests that people with alcohol use disorders are at higher risk for SARS-CoV-2. SARS-CoV-2 engages angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2) receptors for cellular entry. While ACE2 and TMPRSS2 genes are upregulated in the cortex of alcohol-dependent individuals, information on expression in specific brain regions and neural populations implicated in SARS-CoV-2 neuroinvasion, particularly monoaminergic neurons, is limited. We sought to clarify how chronic alcohol exposure affects ACE2 and TMPRSS2 expression in monoaminergic brainstem circuits and other putative SARS-CoV-2 entry points. C57BL/6J mice were exposed to chronic intermittent ethanol (CIE) vapor for 4 weeks and brains were examined using immunofluorescence. We observed increased ACE2 levels in the olfactory bulb and hypothalamus following CIE, which are known to mediate SARS-CoV-2 neuroinvasion. Total ACE2 immunoreactivity was also elevated in the raphe magnus (RMG), raphe obscurus (ROB), and locus coeruleus (LC), while in the dorsal raphe nucleus (DRN), ROB, and LC we observed increased colocalization of ACE2 with monoaminergic neurons. ACE2 also increased in the periaqueductal gray (PAG) and decreased in the amygdala. Whereas ACE2 was detected in most brain regions, TMPRSS2 was only detected in the olfactory bulb and DRN but was not significantly altered after CIE. Our results suggest that previous alcohol exposure may increase the risk of SARS-CoV-2 neuroinvasion and render brain circuits involved in cardiovascular and respiratory function as well as emotional processing more vulnerable to infection, making adverse outcomes more likely. Additional studies are needed to define a direct link between alcohol use and COVID-19 infection.

neuroscience↗

bioRxiv2021

Adhesion-growth factor crosstalk regulates AURKB activation and ERK signaling in re-adherent fibroblasts.

Aurora kinases despite their similarity have distinct roles in the cell cycle, which is regulated by cell-matrix adhesion and growth factors. This study reveals loss of adhesion and re-adhesion to differentially regulate Aurora kinases. AURKB activation that drops on the loss of adhesion recovers on re-adhesion in serum-deprived conditions but not in the presence of serum growth factors. A rapid 30min serum treatment of serum-deprived cells blocks the adhesion-dependent recovery of AURKB, which negatively corelates with Erk activation. AZD mediated inhibition of AURKB in serum-deprived re-adherent cells promotes Erk activation and membrane ruffling, comparable to presence of serum. These studies thus define a novel adhesion-growth factor-dependent regulation of AURKB that controls adhesion-dependent Erk activation in re-adherent fibroblasts.

cell biology↗

bioRxiv2021

A pan-cancer analysis of matrisome proteins reveals CTHRC1and LOXL2 as major ECM regulators across cancers

The extracellular matrix as part of the tumor microenvironment can regulate cancer cell growth and progression. Using TCGA data from 30 cancer types, the top 5% of matrisome genes with amplifications or deletions that affect survival in cancers were identified. Eight of these genes show altered expression in ~50% or more cancers affecting survival in ~20% or more. Among them SNED1 is the most downregulated and CTHRC1 and LOXL2 most upregulated. Differential gene expression analysis of SNED-1 did not identify any genes it regulates across cancers, while CTHRC1 and LOXL2 affected 19 and 5 genes respectively in 3 or more cancers. STRING analysis of these genes classified them as extracellular, involved prominently in ECM organization. Their correlation and co-occurrence in context of their effect on survival and staging of the disease identified MMP13, POSTN and SFRP4 along with COL11A1, COL10A1, COL1A1, ADAMTS12 and PPAPDC1A as possible interactors of CTHRC1 and LOXL2 in cancers. These are implicated in collagen organization, making it vital to matrisome regulation of cancers. Clinical Proteomic Tumor Analysis Consortium data confirms the changes in expression of these genes along with CTHRC1 and LOXL2 in breast and lung cancer, further supporting their implication as vital pan-cancer matrisome mediators. HighlightsO_LICTHRC1 and LOXL2 are prominently upregulated pan-cancer matrisome genes. C_LIO_LIHigh CTHRC1 and LOXL2 expression is associated with disease progression and poor survival in cancers. C_LIO_LICTHRC1 with POSTN, MMP13 and SFRP4 and LOXL2 with COL11A1, COL10A1, COL1A1, ADAMTS12 and PPAPDC1A drive matrisome regulation of cancers. C_LIO_LICTHRC1 and LOXL2 could prominently drive collagen organization and function across cancers. C_LI

bioinformatics↗