Biology subjects

Lee, A.

Publications and source records attributed to Lee, A..

At least 91 records · Page 5Linked to original sources

bioRxiv2023

Unsupervised pattern discovery in spatial gene expression atlas reveals mouse brain regions beyond established ontology

The rapid growth of large-scale spatial gene expression data demands efficient and reliable computational tools to extract major trends of gene expression in their native spatial context. Here, we used stability-driven unsupervised learning (i.e. staNMF) to identify principal patterns (PPs) of 3D gene expression profiles and understand spatial gene distribution and anatomical localization at the whole mouse brain level. Our subsequent spatial correlation analysis systematically compared the PPs to known anatomical regions and ontology from the Allen Mouse Brain Atlas using spatial neighborhoods. We demonstrate that our stable and spatially coherent PPs, whose linear combinations accurately approximate the spatial gene data, are highly correlated with combinations of expert-annotated brain regions. These PPs yield a new brain ontology based purely on spatial gene expression. Our PP identification approach outperforms principal component analysis (PCA) and typical clustering algorithms on the same task. Moreover, we show that the stable PPs reveal marked regional imbalance of brainwide genetic architecture, leading to region-specific marker genes and gene co-expression networks. Our findings highlight the advantages of stability-driven machine learning for plausible biological discovery from dense spatial gene expression data that are infeasible by conventional manual approaches.

neuroscience↗

bioRxiv2023

IL-15 promotes inflammatory Th17 cells in the intestine

Ulcerative Colitis (UC) is a chronic gastrointestinal condition with high morbidity. While modern medical therapies have revolutionized the care of UC, 10-25% of patients fail medications and still progress to surgery. Thus, developing new treatments is a core problem in UC. T-cells, especially Th17 cells, are strongly linked with UC and are major targets of medications in UC. Tissue-resident memory T-cells (TRM) are a distinct class of T-cells that are highly enriched in the intestine, closely aligned with the microbiota, and are implicated in the pathogenesis of UC. Unlike circulating T-cells, TRM are difficult to target because they do not recirculate. Thus, we focused on cytokines like IL-15 which act as a tissue danger signal and regulate T-cells in situ. We found that the IL15 axis is upregulated in UC and predicts treatment response. IL-15 was redundant for Th17 differentiation but could activate terminally differentiated Th17 cells to promote intestinal inflammation. Finally, in CD4+ TRM from patients with UC, IL-15 upregulated RORC, the master transcription factor for Th17 cells, via a Janus Kinase (JAK)1 pathway. Thus, IL-15 promotes terminally differentiated inflammatory Th17 cells in the intestine raising the possibility that IL-15 may be a target for UC treatments.

immunology↗

bioRxiv2023

Identifying the core genome of the nucleus-forming bacteriophage family and characterization of Erwinia phage RAY

We recently discovered that some bacteriophages establish a nucleus-like replication compartment (phage nucleus), but the core genes that define nucleus-based phage replication and their phylogenetic distribution were unknown. By studying phages that encode the major phage nucleus protein chimallin, including previously sequenced yet uncharacterized phages, we discovered that chimallin-encoding phages share a set of 72 highly conserved genes encoded within seven distinct gene blocks. Of these, 21 core genes are unique to this group, and all but one of these unique genes encode proteins of unknown function. We propose that phages with this core genome comprise a novel viral family we term Chimalliviridae. Fluorescence microscopy and cryo-electron tomography studies of Erwinia phage vB_EamM_RAY confirm that many of the key steps of nucleus-based replication encoded in the core genome are conserved among diverse chimalliviruses, and reveal that non-core components can confer intriguing variations on this replication mechanism. For instance, unlike previously studied nucleus-forming phages, RAY doesnt degrade the host genome, and its PhuZ homolog appears to form a five-stranded filament with a lumen. This work expands our understanding of phage nucleus and PhuZ spindle diversity and function, providing a roadmap for identifying key mechanisms underlying nucleus-based phage replication.

microbiology↗

bioRxiv2023

Texture-Based Image Analysis For the Assessment of Soybeans

At 4.44 billion bushels worth an estimated $57.7 billion dollars, soybeans are one of the most produced crops in the United States and are appraised using a standard grading system set by the USDA(NASS, 2022). The grading and inspection process is based on twenty factors, including six that are visual based (USDA, 2020). The aim of this research is to apply texture-based image analysis to assess visual indicators of damage in soybeans and demonstrate potential use in increasing efficiency and consistency in soybean grading. Surface texture is one of the characteristics that is examined by inspectors as part of assessing soybean damage, while "image texture" is a calculated set of parameters that are used in image processing and analysis to quantify the apparent actual texture captured in an image. In this study, texture analysis using Haralick textural features is performed on sets of soybean images to assess damage types (as defined by the USDA inspection handbook and visual reference images) and improve soybean classification.

bioengineering↗

bioRxiv2023

Primed to resolve: A single cell atlas of the shoulder capsule reveals a cellular basis for resolving inflammatory fibrosis

Fibrotic conditions are a significant global disease burden. While some therapies delay disease progression, none reverse fibrosis. To gain insights into how fibrosis might resolve, we developed a comparative single cell atlas of frozen shoulder capsule tissue; a chronic inflammatory fibrotic human disease that resolves spontaneously. We identified both a population of pro-inflammatory MERTKlowCD48+ macrophages (M{varphi}) and a population of MERTK+LYVE1+MRC1+M{varphi} enriched for negative regulators of inflammation. Micro-cultures of patient-derived cells identified cell-matrix interactions between MERTK+M{varphi} and DKK3+ and POSTN+ fibroblasts, suggesting that matrix remodelling plays a role in the resolution of frozen shoulder. Cross-tissue analysis revealed a shared gene expression cassette between MERTK+M{varphi} in the shoulder capsule and a similar cell population enriched in synovial tissues from rheumatoid arthritis patients in disease remi ssion, supporting the concept that MERTK+M{varphi} provide a cellular basis for the resolution of inflammation and fibrosis. Single-cell transcriptomic profiling and spatial analysis of human foetal shoulder tissues identified MERTK+LYVE1+MRC1+M{varphi} and DKK3+ and POSTN+ fibroblast populations analogous to those identified in adult shoulder capsule, suggesting that the template to resolve fibrosis is established during development. Therapeutic enhancement of crosstalk between MerTK+M{varphi} and pro-resolving DKK3+ and POSTN+ fibroblasts could accelerate resolution of frozen shoulder and resolve persistent inflammatory fibrotic disease in other tissues.

cell biology↗

bioRxiv2023

Early life drought predicts components of adult body size in wild female baboons

ObjectivesIn many taxa, adverse early-life environments are associated with reduced growth and smaller body size in adulthood. However, in wild primates, we know very little about whether, where, and to what degree trajectories are influenced by early adversity, or which types of early adversity matter most. Here, we use parallel-laser photogrammetry to assess inter-individual predictors of three measures of body size (leg length, forearm length, and shoulder-rump length) in a population of wild female baboons studied since birth. Materials and MethodsUsing >2,000 photogrammetric measurements of 127 females, we present a cross-sectional growth curve of wild female baboons (Papio cynocephalus) from juvenescence through adulthood. We then test whether females exposed to three important sources of early-life adversity - drought, maternal loss, or a cumulative measure of adversity - were smaller for their age than females who experienced less adversity. Using the animal model, we also test whether body size is heritable in this study population. ResultsProlonged early-life drought predicted shorter limbs but not shorter torsos (i.e., shoulder-rump lengths). Our other two measures of early-life adversity did not predict any variation in body size. Heritability estimates for body size measures were 36%-58%. Maternal effects accounted for 13%-22% of the variance in leg and forearm length, but no variance in torso length. DiscussionOur results suggest that baboon limbs, but not torsos, grow plastically in response to maternal effects and energetic early-life stress. Our results also reveal considerable heritability for all three body size measures in this study population.

ecology↗

bioRxiv2022

Cell-Sized Lipid Vesicles as Artificial Antigen-Presenting Cells for Antigen-Specific T Cell Activation

In this study, efficient T cell activation is demonstrated using cell-sized artificial antigen-presenting cells (aAPCs) with protein-conjugated bilayer lipid membranes that mimic biological cell membranes. The highly uniform aAPCs are generated by a facile method based on standard droplet microfluidic devices. These aAPCs are able to activate the T cells in peripheral blood mononuclear cells (PBMCs), showing a 28-fold increase in IFN{gamma} secretion, a 233-fold increase in antigen-specific CD8 T cells expansion, and a 16-fold increase of CD4 T cell expansion. The aAPCs do not require repetitive boosting or additional stimulants and can function at a relatively low aAPC-to-T cell ratio (1-to-17). The research presents strong evidence that the surface fluidity and size of the aAPCs are critical to the effective formation of immune synapses essential for T cell activation. The findings demonstrate that the microfluidic-generated aAPCs can be instrumental in investigating the physiological conditions and mechanisms for T cell activation. Finally, this method demonstrates the feasibility of customizable aAPCs for a cost-effective off-the-shelf approach to immunotherapy.

bioengineering↗

bioRxiv2022

Endothelial FABP4 constitutes the majority of basal circulating hormone levels and regulates lipolysis-driven insulin secretion

Fatty acid binding protein 4 (FABP4) is a lipid chaperone secreted from adipocytes upon stimulation of lipolysis. Circulating FABP4 levels strongly correlate with body mass index and obesity-related pathologies in experimental models and humans. While adipocytes have been presumed to be the major source of hormonal FABP4, this question has not been addressed definitively in vivo. We generated mice with FABP4 deletion in cells known to express the gene; adipocytes (Adipo-KO), endothelial cells (Endo-KO), myeloid cells (Myeloid-KO), and the whole body (Total-KO) to examine the contribution of these cell types to basal and stimulated plasma FABP4 levels. Unexpectedly, baseline plasma FABP4 was only reduced by [~]25% in Adipo-KO mice, whereas Endo-KO mice showed [~]75% decreases compared to wildtype controls. In contrast, Adipo-KO mice exhibited [~]62% reduction in FABP4 responses to lipolysis, while there was minimal reduction in Endo-KO mice, indicating that adipocytes are the main FABP4 source in lipolysis. We did not detect any myeloid cell contribution to circulating FABP4. Surprisingly, despite the nearly intact FABP4 responses, Endo-KO mice showed blunted lipolysis-induced insulin secretion, identical to Total-KO mice. We conclude that the endothelium is the major source of baseline hormonal FABP4 and is required for the insulin response to lipolysis. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=114 SRC="FIGDIR/small/511807v1_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@1b2d566org.highwire.dtl.DTLVardef@1d82083org.highwire.dtl.DTLVardef@3e9726org.highwire.dtl.DTLVardef@1357648_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

bioRxiv2022

ATGL is differentially required for adipocyte FABP4 secretion in vivo and ex vivo

Fatty acid binding protein 4 (FABP4) is linked with the pathogenesis of metabolic diseases, including diabetes and cardiovascular disease in both mice and humans. It has also been demonstrated that the levels of hormonal FABP4 are strongly associated with obesity, and secretion is stimulated under conditions of fasting and lipolysis both in vivo and in vitro. Here, we utilized adipocyte-specific deficiency of adipose triglyceride lipase (ATGL) in a mouse model (ATGLAdpKO) to evaluate the regulation of FABP4 secretion by lipolytic signals in the absence of actual lipolysis in vivo. Previously, lipolysis-induced FABP4 secretion was found to be significantly reduced upon pharmacological inhibition of ATGL, and from adipose tissue explants from ATGLAdpKO mice. Unexpectedly, upon activation beta-adrenergic receptors, ATGLAdpKO mice exhibited significantly higher levels of circulating FABP4 as compared to ATGLfl/fl controls in vivo, with no corresponding increase in non-esterified free fatty acids or glycerol, confirming the lack of lipolysis. We also generated an additional model with adipocyte-specific deletion of FABP4 in the background of ATGLAdpKO mice (ATGL/FABP4AdpKO or DKO) to evaluate the cellular source of circulating FABP4. In these animals, there was no evidence of lipolysis-induced FABP4 secretion, indicating that the elevated FABP4 hormone levels in the ATGLAdpKO mice were indeed from the adipocytes. ATGLAdpKO mice did not exhibit an increase in insulin secretion upon stimulation of lipolysis, but had a normal insulin response to glucose injection along with increased FABP4 secretion, suggesting the elevated FABP4 secretion is not due to lack of insulin. Inhibition of sympathetic signaling during lipolysis using hexamethonium significantly reduced FABP4 secretion in ATGLAdpKO mice compared to controls. Therefore, activity of a key enzymatic step of lipolysis mediated by ATGL, per se, is not required for stimulated in vivo FABP4 secretion from adipocytes, which can be induced through sympathetic signaling.

physiology↗

bioRxiv2022

PTH regulates osteogenesis and suppresses adipogenesis through Zfp 467 in a feed-forward, cyclic AMP-dependent manner

Conditional deletion of the PTH1R in mesenchymal progenitors reduces osteoblast differentiation, enhances marrow adipogenesis and increases zinc finger protein 467 (Zfp467) expression. In contrast, genetic loss of Zfp467 increased Pth1r expression and shifts mesenchymal progenitor cell fate towards osteogenesis and higher bone mass. In this study we hypothesized that PTH1R and ZFP467 could constitute a feedback loop that facilitates PTH-induced osteogenesis and that conditional deletion of Zfp467 in osteogenic precursors would lead to high bone mass. We report that PrrxCre Zfp467 but not AdipoCre Zfp467 mice exhibit an identical phenotype to the Zfp467-/-mice with high bone mass and greater osteogenic differentiation We also found that PTH suppressed Zfp467 expression primarily via the cyclic AMP/PKA pathway. Not surprisingly, PKA activation inhibited the expression of Zfp467 and gene silencing of Pth1r caused an increase in Zfp467 mRNA transcription. Dual fluorescence reporter assays and confocal immunofluorescence demonstrated that genetic deletion of Zfp467 resulted in higher nuclear translocation of p50 that binds to the P2 promoter of the Pth1r and increased its transcription. As expected, Zfp467-/- cells had enhanced production of cyclic AMP and increased glycolysis in response to exogenous PTH. Additionally, the osteogenic response to PTH was also enhanced in Zfp467 -/-calvarial osteoblasts, and the pro-osteogenic effect of Zfp467 deletion was blocked by gene silencing of Pth1r or a PKA inhibitor. In conclusion, our findings suggest that loss or PTH1R-mediated repression of Zfp467 results in a pathway that increases Pth1r transcription via p50 and thus cellular responsiveness to PTH, ultimately leading to enhanced bone formation.

cell biology↗

bioRxiv2022

Modelling the gastrointestinal carriage of Klebsiella pneumoniae infections.

Klebsiella pneumoniae is a leading cause of nosocomial and community acquired infections, making K. pneumoniae the second pathogen associated with the most deaths attributed to any antibiotic resistant infection. K. pneumoniae colonises the nasopharynx and the gastrointestinal tract in an asymptomatic manner without dissemination to other tissues; importantly gastrointestinal colonisation is a requisite for infection. Our understanding of K. pneumoniae colonisation is still based on interrogating mouse models in which animals are pre-treated with antibiotics to disturb the colonisation resistance imposed by the gut microbiome. In these models, infection disseminates to other tissues. Here, we report a murine model to allow for the study of the gastrointestinal colonisation of K. pneumoniae without tissue dissemination. Hypervirulent and antibiotic resistant strains stably colonise the gastrointestinal tract of in an inbred mouse population without antibiotic treatment. The small intestine is the primary site of colonisation followed by a transition to the colon over time without dissemination to other tissues. Our model also mimics the disease dynamics of metastatic K. pneumoniae strains able to disseminate from the gastrointestinal tract to other sterile sites. Colonisation is associated with mild to moderate histopathology, no significant inflammation, and no effect on the richness of the microbiome. Our model recapitulates the clinical scenario in which antibiotic treatment disturbs the colonisation of K. pneumoniae resulting in dissemination to other tissues. Finally, we establish that the capsule polysaccharide is necessary for the colonisation of the large intestine whereas the type VI secretion system contributes to colonisation across the gastrointestinal tract. IMPORTANCEKlebsiella pneumoniae is one of the pathogens sweeping the World in the antibiotic resistance pandemic. Klebsiella colonises the nasopharynx and the gut of healthy subjects in an asymptomatic manner, being gut colonisation a requisite for infection. This makes essential to understand the gastrointestinal carriage to prevent Klebsiella infections. Current research models rely on the perturbation of the gut microbiome by antibiotics, resulting in an invasive infection. Here, we report a new model of K. pneumoniae gut colonisation that recapitulates key features of the asymptomatic human gastrointestinal tract colonisation. In our model, there is no need to disturb the microbiota to achieve stable colonization without dissemination to other tissues. Our model recapitulates the clinical scenario in which antibiotic treatment triggers invasive infection. We envision our model will be an excellent platform to test therapeutics to eliminate Klebsiella asymptomatic colonisation, and to investigate factors enhancing colonisation and invasive infections.

microbiology↗

bioRxiv2022

The promiscuous development of an unconventional Qa1b-restricted T cell population

MHC-E restricted CD8 T cells show promise in vaccine settings, but their development and specificity remain poorly understood. Here we focus on a CD8 T cell population reactive to a self-peptide (FL9) bound to mouse MHC-E (Qa-1b) that is presented in response to loss of the MHC I processing enzyme ERAAP, termed QFL T cells. We find that mature QFL thymocytes are predominantly CD8{beta}+CD4-, show signs of agonist selection, and give rise to both CD8 and CD8{beta} intraepithelial lymphocytes (IEL), as well as memory phenotype CD8{beta} T cells. QFL T cells require the MHC I subunit {beta}-2 microglobulin ({beta}2m), but do not require Qa1b or classical MHC I for positive selection. However, QFL thymocytes do require Qa1b for agonist selection and full functionality. Our data highlight the relaxed requirements for positive selection of an MHC-E restricted T cell population and suggest a CD8{beta}+CD4-pathway for development of CD8 IELs.

immunology↗

bioRxiv2022

Murine cytomegalovirus downregulates ERAAP and induces an unconventional T cell response to self

The endoplasmic reticulum aminopeptidase associated with antigen presentation (ERAAP) plays a crucial role in shaping the peptide-MHC I repertoire and maintaining immune surveillance. While murine cytomegalovirus (MCMV) has multiple strategies for manipulating the antigen processing pathway to evade immune responses, the host has also developed ways to counter viral immune evasion. In this study, we found that MCMV modulates ERAAP and induces an IFN-{gamma} producing CD8+ T cell effector response that targets uninfected ERAAP deficient cells. We also observed that ERAAP downregulation during infection led to presentation of the self-peptide FL9 on non-classical Qa-1b, thereby eliciting Qa-1b restricted QFL T cells to proliferate in the liver and spleen of infected mice. QFL T cells upregulated effector markers upon MCMV infection and were sufficient to reduce viral load after transfer to immunodeficient mice. Our study highlights the consequences of ERAAP dysfunction during viral infection and provides potential targets for antiviral therapies.

immunology↗

bioRxiv2022

The post-translational modification SUMO affects TDP-43 phase separation, compartmentalization, and aggregation in a zebrafish model

TDP-43 is a nuclear RNA-binding protein that can undergo liquid-liquid phase separation (LLPS) and forms pathological insoluble aggregates in frontotemporal dementia and amyotrophic lateral sclerosis (ALS). Perturbations of TDP-43 function are linked to mislocalization and neurodegeneration. By studying TDP-43 in vivo, we confirmed for the first time that TDP-43 undergoes LLPS and forms biomolecular condensates in spinal motor neurons (MNs). Importantly, we discovered that interfering with the K136 SUMOylation site of TDP-43 altered its phase separation behavior, reducing cytoplasmic mislocalization and aggregation. Introduction of the ALS-linked mutation G294V did not alter these LLPS characteristics, indicating that posttranslational modifications such as lysine-specific alterations can modulate TDP-43 pathogenesis through regulating phase separation. Altogether, our in vivo characterization of TDP-43 confirms the formation of dynamic nuclear TDP-43 condensates in zebrafish spinal neurons and establishes a critical platform to validate the molecular grammar of phase separation that underpins TDP-43 aggregation in ALS and other proteinopathies.

molecular biology↗

bioRxiv2022

SorCS1 inhibits amyloid-β binding to neurexin and rescues amyloid-β-induced synaptic pathology

Amyloid-{beta} oligomers (A{beta}Os), toxic peptide aggregates found in Alzheimers disease (AD), cause synapse pathology. A{beta}Os interact with Neurexins (NRXs), key synaptic organizers, and this interaction dampens normal trafficking and function of NRXs. Axonal trafficking of NRX is in part regulated by its interaction with SorCS1, a protein sorting receptor, but the impact of SorCS1 regulation of NRXs in A{beta} pathology was previously unstudied. Here, we show competitive interaction of SorCS1 and A{beta}Os with {beta}-NRXs and rescue effects of SorCS1 on A{beta}O-induced synaptic pathology. Like A{beta}Os, SorCS1 binds to NRX1{beta} through the histidine-rich-domain (HRD) of NRX1{beta}, and SorCS1 and A{beta}Os compete for NRX1{beta} binding. In cultured hippocampal neurons, SorCS1 colocalizes with NRX1{beta} on the axon surface, and axonal expression of SorCS1 rescues A{beta}O-induced impairment of NRX-mediated presynaptic organization and presynaptic vesicle recycling as well as A{beta}O-induced structural defects in excitatory synapses. Thus, we reveal a role of SorCS1 in the rescue of A{beta}O-induced NRX dysfunction and synaptic pathology, providing the basis for a novel potential therapeutic strategy for AD.

neuroscience↗

bioRxiv2022

Dynamic allostery in substrate binding by human thymidylate synthase

Human thymidylate synthase (hTS) is essential for DNA replication and therefore a therapeutic target for cancer. Effective targeting requires knowledge of the mechanism(s) of regulation of this 72 kDa homodimeric enzyme. Here, we investigate the mechanism of binding cooperativity of the nucleotide substrate. We have employed exquisitely sensitive methyl-based CPMG and CEST NMR experiments enabling us to identify residues undergoing bifurcated linear 3-state exchange, including concerted switching between active and inactive conformations in the apo enzyme. The inactive state is populated to only [~]1.3%, indicating that conformational selection contributes negligibly to the cooperativity. Instead, methyl rotation axis order parameters, determined by 2H transverse relaxation rates, suggest that rigidification of the enzyme upon substrate binding is responsible for the entropically-driven cooperativity. Lack of the rigidification in product binding and substrate binding to an N-terminally truncated enzyme, both non-cooperative, support this idea. In addition, the lack of this rigidification in the N-terminal truncation indicates that interactions between the flexible N-terminus and the rest of the protein, which are perturbed by substrate binding, play a significant role in the cooperativity--a novel mechanism of dynamic allostery. Together, these findings yield a rare depth of insight into the substrate binding cooperativity of an essential enzyme.

biophysics↗

bioRxiv2022

Transcriptional atlas of the human immune response to 13 vaccines reveals a common predictor of vaccine-induced antibody responses

Systems biology approaches have been used to define molecular signatures and mechanisms of immunity to vaccination. However, most such studies have been done with single vaccines, and comparative analysis of the response to different vaccines is lacking. We integrated temporal transcriptional data of over 3,000 samples, obtained from 820 healthy adults across 28 studies of 13 different vaccines and analyzed vaccination-induced signatures associated with the antibody response. Most vaccines induced similar kinetics of shared transcriptional signatures, including signatures of innate immunity occurring 1-3 days post-vaccination, as well as the canonical plasmablast and cell cycle signatures appearing 7 days post-vaccination. However, the yellow fever vaccine YF-17D uniquely induced an early transient signature of T and B cell activation at Day 1, followed by delayed antiviral/interferon and plasmablast signatures that peaked at Days 7 and 14-21, respectively. Thus, despite the shared transcriptional response to most vaccines, at any given time point there was no evidence for a "universal signature" that could be used to predict the antibody response to all vaccines. However, accounting for the asynchronous nature of responses led to the identification of a time-adjusted signature that improved prediction antibody of responses across vaccines. These results provide a transcriptional atlas of the human immune response to vaccination and define a common, time-adjusted signature of antibody responses to vaccination.

immunology↗

bioRxiv2022

Sex differences in contextual pattern separation, activation of new neurons, and functional connectivity within the limbic system

Sex differences in the structure and function of hippocampus exist. Here, we examined sex differences in contextual pattern separation, functional connectivity, and activation of new neurons during fear memory. Two-month-old male and female Sprague-Dawley rats were injected with the DNA synthesis markers, iododeoxyuridine (IdU) and chlorodeoxyuridine (CldU) three weeks and four weeks before perfusion, respectively. One week after CldU injection, the rats underwent a context discrimination task in which rats were placed in context A (shock) and context A (no shock) every day for 12 days. On the test day, rats were placed in the shock context (context A) to measure fear memory and expression of zif268, an immediate early gene across 15 different limbic and reward regions. We found that females, but not males, showed contextual discrimination during the last days of training. On the test day, both sexes displayed similar levels of freezing, indicating equivalent fear memory for context A. Despite similar fear memory, males showed more positive correlations of zif268 activation between the limbic regions and the striatum, whereas females showed more negative correlations among these regions. Females showed greater activation of the frontal cortex, dorsal CA1, and 3-week-old adult-born dentate granular cells compared to males. These results highlight the importance of studying sex differences in fear memory and the contribution of adult neurogenesis to the neuronal network and may contribute to differences in susceptibility to fear related disorders such as posttraumatic stress disorder.

neuroscience↗