scholarly journals A novel bioreactor technology for modelling fibrosis in human and rodent precision-cut liver slices

2018 ◽  
Author(s):  
Hannah L Paish ◽  
Lee H Reed ◽  
Helen Brown ◽  
Mark C Bryan ◽  
Olivier Govaere ◽  
...  
Keyword(s):  
Gene Expression ◽  
Animal Models ◽  
Liver Fibrosis ◽  
Molecular Mechanisms ◽  
List Type ◽  
Bioreactor Culture ◽  
Albumin Secretion ◽  
Liver Slices ◽  
New Findings ◽  
Alk5 Inhibitor

Summary boxWhat is already known about this subject?Currently there are no effective anti-fibrotic drugs to treat liver fibrosis and there is an urgent unmet need to increase our knowledge of the disease process and develop better tools for anti-fibrotic drug discovery.Preclinical in vitro cell cultures and animal models are widely used to study liver fibrosis and test anti-fibrotic drugs, but have shortfalls; cell culture models lack the relevant complex cell-cell interactions of the liver and animal models only reproduce some features of human disease.Precision Cut Liver Slices (PCLS) are structurally representative of the liver and can be used to model liver fibrosis and test anti-fibrotic drugs. However, PCLS are typically cultured in elevated, non-physiological oxygen levels and only have a healthy lifespan of 48h.What are the new findings?We have developed a novel bioreactor culture system that increases the longevity of functional PCLS to up to 6 days under normoxic conditions.Bioreactor cultured PCLS can be used to model fibrogenesis in both normal and fibrotic PCLS using a combination of biochemical and histological outputs.Administration of an Alk5 inhibitor effectively limits fibrogenesis in normal rodent and human PCLS and in rodent PCLS with established fibrosis.How might it impact on clinical practice in the foreseeable future?The extended longevity of bioreactor cultured PCLS represent a novel pre-clinical tool to investigate the cellular and molecular mechanisms of liver fibrosis.Bioreactor cultured human PCLS offer a clinically relevant system to test efficacy of anti-fibrotic drugs.AbstractObjectivePrecision cut liver slices (PCLS) retain the structure and cellular composition of the native liver and represent an improved system to study liver fibrosis compared to two-dimensional mono or co-cultures. The objective of this study was to develop a bioreactor system to increase the healthy lifespan of PCLS and model fibrogenesis.DesignPCLS were generated from normal rat or human liver, or 4-week carbon tetrachloride-fibrotic rat liver and cultured in our patented bioreactor. PCLS function was quantified by albumin ELISA. Fibrosis was induced in PCLS by TGFβ1 and PDGFββ stimulation. Alk5 inhibitor therapy was used. Fibrosis was assessed by fibrogenic gene expression, Picrosirius Red and αSmooth Muscle Actin staining, hydroxyproline assay and collagen 1a1, fibronectin and hyaluronic acid ELISA.ResultsBioreactor cultured PCLS are viable, maintaining tissue structure and stable albumin secretion for up to 6 days under normoxic culture conditions. Conversely, standard static transwell cultured PCLS rapidly deteriorate and albumin secretion is significantly impaired by 48 hours. TGFβ1 and PDGFββ stimulation of rat or human PCLS induced fibrogenic gene expression, release of extracellular matrix proteins, activation of hepatic myofibroblasts and histological fibrosis. Fibrogenesis slowly progresses over 6-days in cultured fibrotic rat PCLS without exogenous challenge. Alk5 inhibitor limited fibrogenesis in both TGFβ1 and PDGFββ stimulated PCLS and fibrotic PCLS.ConclusionWe describe a new bioreactor technology which maintains functional PCLS cultures for 6 days. Bioreactor cultured PCLS can be successfully used to model fibrogenesis and demonstrate efficacy of an anti-fibrotic therapy.

scholarly journals P854 Construction of the immune landscape of durable response to checkpoint blockade therapy by integrating publicly available datasets

2020 ◽  
Vol 8 (Suppl 1) ◽  
pp. A5.2-A6
Author(s):  
Nils-Petter Rudqvist ◽  
Roberta Zappasodi ◽  
Daniel Wells ◽  
Vésteinn Thorsson ◽  
Alexandria Cogdill ◽  
...  
Keyword(s):  
Gene Expression ◽  
Immune Checkpoint ◽  
Molecular Mechanisms ◽  
Cross Validation ◽  
Immune Cell ◽  
Immune Checkpoint Blockade ◽  
Checkpoint Blockade ◽  
Immune Gene ◽  
List Type ◽  
Durable Response

BackgroundImmune checkpoint blockade (ICB) has revolutionized cancer treatment. However, long-term benefits are only achieved in a small fraction of patients. Understanding the mechanisms underlying ICB activity is key to improving the efficacy of immunotherapy. A major limitation to uncovering these mechanisms is the limited number of responders within each ICB trial. Integrating data from multiple studies of ICB would help overcome this issue and more reliably define the immune landscape of durable responses. Towards this goal, we formed the TimIOs consortium, comprising researchers from the Society for Immunotherapy of Cancer Sparkathon TimIOs Initiative, the Parker Institute of Cancer Immunotherapy, the University of North Carolina-Chapel Hill, and the Institute for Systems Biology. Together, we aim to improve the understanding of the molecular mechanisms associated with defined outcomes to ICB, by building on our joint and multifaceted expertise in the field of immuno-oncology. To determine the feasibility and relevance of our approach, we have assembled a compendium of publicly available gene expression datasets from clinical trials of ICB. We plan to analyze this data using a previously reported pipeline that successfully determined main cancer immune-subtypes associated with survival across multiple cancer types in TCGA.1MethodsRNA sequencing data from 1092 patients were uniformly reprocessed harmonized, and annotated with predefined clinical parameters. We defined a comprehensive set of immunogenomics features, including immune gene expression signatures associated with treatment outcome,1,2 estimates of immune cell proportions, metabolic profiles, and T and B cell receptor repertoire, and scored all compendium samples for these features. Elastic net regression models with parameter optimization done via Monte Carlo cross-validation and leave-one-out cross-validation were used to analyze the capacity of an integrated immunogenomics model to predict durable clinical benefit following ICB treatment.ResultsOur preliminary analyses confirmed an association between the expression of an IFN-gamma signature in tumor (1) and better outcomes of ICB, highlighting the feasibility of our approach.ConclusionsIn line with analysis of pan-cancer TCGA datasets using this strategy (1), we expect to identify analogous immune subtypes characterizing baseline tumors from patients responding to ICB. Furthermore, we expect to find that these immune subtypes will have different importance in the model predicting response and survival. Results of this study will be incorporated into the Cancer Research Institute iAtlas Portal, to facilitate interactive exploration and hypothesis testing.ReferencesThorsson V, Gibbs DL, Brown SD, Wolf D, Bortone DS, Yang T-H O, Porta-Pardo E. Gao GF, Plaisier CL, Eddy JA, et al. The Immune Landscape of Cancer. Immunity 2018; 48(4): 812–830.e14. https://doi.org/10.1016/j.immuni.2018.03.023.Auslander N, Zhang G, Lee JS, Frederick DT, Miao B, Moll T, Tian T, Wei Z, Madan S, Sullivan RJ, et al. Robust Prediction of Response to Immune Checkpoint Blockade Therapy in Metastatic Melanoma. Nat. Med 2018; 24(10): 1545. https://doi.org/10.1038/s41591-018-0157-9.

scholarly journals Design of a Gene Panel to Expose the Versatile Role of Hepatic Stellate Cells in Human Liver Fibrosis

Pharmaceutics ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 278 ◽  
Author(s):  
Fransien van Dijk ◽  
Christa M. Hazelhoff ◽  
Eduard Post ◽  
Gerian G. H. Prins ◽  
Krista Rombouts ◽  
...  
Keyword(s):  
Gene Expression ◽  
Growth Factor ◽  
Liver Fibrosis ◽  
Cell Lines ◽  
Human Liver ◽  
Stellate Cells ◽  
Gene Panel ◽  
Liver Slices ◽  
Antifibrotic Drugs

The pivotal cell involved in the pathogenesis of liver fibrosis, i.e., the activated hepatic stellate cell (HSC), has a wide range of activities during the initiation, progression and even regression of the disease. These HSC-related activities encompass cellular activation, matrix synthesis and degradation, proliferation, contraction, chemotaxis and inflammatory signaling. When determining the in vitro and in vivo effectivity of novel antifibrotic therapies, the readout is currently mainly based on gene and protein levels of α-smooth muscle actin (α-SMA) and the fibrillar collagens (type I and III). We advocate for a more comprehensive approach in addition to these markers when screening potential antifibrotic drugs that interfere with HSCs. Therefore, we aimed to develop a gene panel for human in vitro and ex vivo drug screening models, addressing each of the HSC-activities with at least one gene, comprising, in total, 16 genes. We determined the gene expression in various human stellate cells, ranging from primary cells to cell lines with an HSC-origin, and human liver slices and stimulated them with two key profibrotic factors, i.e., transforming growth factor β (TGFβ) or platelet-derived growth factor BB (PDGF-BB). We demonstrated that freshly isolated HSCs showed the strongest and highest variety of responses to these profibrotic stimuli, in particular following PDGF-BB stimulation, while cell lines were limited in their responses. Moreover, we verified these gene expression profiles in human precision-cut liver slices and showed similarities with the TGFβ- and PDGF-BB-related fibrotic responses, as observed in the primary HSCs. With this study, we encourage researchers to get off the beaten track when testing antifibrotic compounds by including more HSC-related markers in their future work. This way, potential compounds will be screened more extensively, which might increase the likelihood of developing effective antifibrotic drugs.

scholarly journals Liver function tests and fibrosis scores in a rural population in Africa: estimation of the burden of disease and associated risk factors

2019 ◽  
Author(s):  
Geraldine A O’Hara ◽  
Jolynne Mokaya ◽  
Jeffrey P Hau ◽  
Louise O Downs ◽  
Anna L McNaughton ◽  
...  
Keyword(s):  
Liver Disease ◽  
Alcohol Consumption ◽  
Liver Fibrosis ◽  
Rural Population ◽  
Liver Function Tests ◽  
List Type ◽  
Reference Ranges ◽  
New Findings ◽  
High Prevalence ◽  
Male Sex

ABSTRACTIntroductionLiver disease is a major cause of morbidity and mortality in sub-Saharan Africa. However, its prevalence, distribution and aetiology have not been well characterised. We examined liver function tests (LFTs) and calculated liver fibrosis scores in a rural population in Uganda.MethodologyA cross-sectional survey of LFTs was undertaken in 2011 in a rural population cohort in South-Western Uganda. We classified abnormal LFTs based on reference ranges set in America and in Africa. We derived fibrosis scores (AST to Platelet Ratio Index, fibrosis-4, GGT to platelet ratio, red cell distribution width to platelet ratio, and S-index) to evaluate the potential prevalence of liver disease. We collected information about alcohol intake, and infection with HIV, HBV and HCV, to determine the contribution made by these factors to liver inflammation or fibrosis.ResultsData were available for 8,099 participants (median age 30 years; 56% female). The prevalence of HBV, HCV and HIV infection were 3%, 0.2% and 8%, respectively. The prevalence of abnormal LFTs was higher based on the American reference range compared to the African reference range (e.g. for AST 13% vs 3%, respectively). The prevalence of AST/ALT ratio >2 was 11%, suggestive of alcoholic hepatitis. The highest prevalence of fibrosis was suggested by the GPR score, with 24% of the population falling above the threshold for fibrosis. By multivariate analysis, elevated LFTs and fibrosis scores were most consistently associated with older age, male sex, being under-weight, infection with HIV or HBV, and alcohol consumption. Based on population attributable risk, the highest proportion of elevated fibrosis scores was associated with alcohol use (e.g. 64% of elevated S-index scores).ConclusionFurther work is required to determine normal reference ranges for LFTs in this setting, to evaluate the specificity and sensitivity of fibrosis scores, and to determine aetiology of liver disease.KEY FINDINGSWhat is already known?Liver disease is not well characterised in many parts of sSA despite the high prevalence of chronic viral infections (HIV, HBV and HCV), and potential exposure to hepatotoxins including alcohol, aflatoxins and traditional herbal medicine.Non-invasive blood tests for markers of fibrosis are relatively simple and offer a safe route to assess for liver fibrosis, however, their diagnostic accuracy is not well established in sSA.Appropriate reference ranges for LFTs are crucial for optimising the sensitivity and specificity of the detection of underlying liver disease.What are the new findings?There is a disparity in the prevalence of abnormal LFTs in our study cohort when comparing two references ranges (American vs. local reference ranges).Based on GPR score, there is a high prevalence of liver fibrosis (almost 1 in 4 of this population) and elevated GPR score is associated with older age, male sex, being under-weight, infection with HIV or HBV, and alcohol consumption.Alcohol consumption accounted for 64% of abnormal S-index scores, 32% of elevated FIB-4 scores, and 19% of GPR abnormalities.What do the new findings imply?Appropriate reference ranges for LFTs are necessary to contribute to an understanding of the burden and aetiology of liver disease.Alcohol, HIV and HBV are risk factors for deranged LFTs and liver fibrosis, with alcohol making the most significant and striking contribution.Further investigation is needed to determine other factors that contribute to liver disease in this setting.

scholarly journals Transcriptomic profiling of long- and short-lived mutant mice implicates mitochondrial metabolism in ageing and shows signatures of normal ageing in progeroid mice

2020 ◽  
Author(s):  
Matias Fuentealba ◽  
Daniel K. Fabian ◽  
Handan Melike Dönertaş ◽  
Janet M. Thornton ◽  
Linda Partridge
Keyword(s):  
Gene Expression ◽  
Mouse Models ◽  
Molecular Mechanisms ◽  
Mitochondrial Metabolism ◽  
Mutant Mice ◽  
Functional Enrichment ◽  
List Type ◽  
Gene Sets ◽  
Normal Ageing ◽  
Transcriptomic Changes

AbstractGenetically modified mouse models of ageing are the living proof that lifespan and healthspan can be lengthened or shortened, yet the molecular mechanisms behind these opposite phenotypes remain largely unknown. In this study, we analysed and compared gene expression data from 10 long-lived and 8 short-lived mouse models of ageing. Transcriptome-wide correlation analysis revealed that mutations with equivalent effects on lifespan induce more similar transcriptomic changes, especially if they target the same pathway. Using functional enrichment analysis, we identified 58 gene sets with consistent changes in long- and short-lived mice, 55 of which were up-regulated in long-lived mice and down-regulated in short-lived mice. Half of these sets represented genes involved in energy and lipid metabolism, among which Ppargc1a, Mif, Aldh5a1 and Idh1 were frequently observed. Based on the gene sets with consistent changes and also the whole transcriptome, we observed that the gene expression changes during normal ageing resembled the transcriptome of short-lived models, suggesting that accelerated ageing models reproduce partially the molecular changes of ageing. Finally, we identified new genetic interventions that may ameliorate ageing, by comparing the transcriptomes of 51 mouse mutants not previously associated with ageing to expression signatures of long- and short-lived mice and ageing-related changes.HighlightsTranscriptomic changes are more similar within mutant mice that show either lengthened or shortened lifespanThe major transcriptomic differences between long- and short-lived mice are in genes controlling mitochondrial metabolismGene expression changes in short-lived, progeroid, mutant mice resemble those seen during normal ageing

scholarly journals Sex Specific Determinants in Osteoarthritis: A Systematic Review of Preclinical Studies

2020 ◽  
Vol 21 (10) ◽  
pp. 3696 ◽  
Author(s):  
Deyanira Contartese ◽  
Matilde Tschon ◽  
Monica De Mattei ◽  
Milena Fini
Keyword(s):  
Gene Expression ◽  
Systematic Review ◽  
Sex Differences ◽  
Animal Models ◽  
Molecular Mechanisms ◽  
Joint Disease ◽  
In Vivo Studies ◽  
Preclinical Studies

Osteoarthritis (OA) is a highly prevalent joint disease that primarily affects about 10% of the world’s population over 60 years old. The purpose of this study is to systematically review the preclinical studies regarding sex differences in OA, with particular attention to the molecular aspect and gene expression, but also to the histopathological aspects. Three databases (PubMed, Scopus, and Web of Knowledge) were screened for eligible studies. In vitro and in vivo papers written in English, published in the last 11 years (2009–2020) were eligible. Participants were preclinical studies, including cell cultures and animal models of OA, evaluating sex differences. Independent extraction of articles and quality assessments were performed by two authors using predefined data fields and specific tools (Animals in Research Reporting In Vivo Experiments (ARRIVE) guideline and Systematic Review Centre for Laboratory animal Experimentation (SYRCLE) tool). Twenty-three studies were included in the review: 4 in vitro studies, 18 in vivo studies, and 1 both in vitro and in vivo study. From in vitro works, sex differences were found in the gene expression of inflammatory molecules, hormonal receptors, and in responsiveness to hormonal stimulation. In vivo research showed a great heterogeneity of animal models mainly focused on the histopathological aspects rather than on the analysis of sex-related molecular mechanisms. This review highlights that many gaps in knowledge still exist; improvementsin the selection and reporting of animal models, the use of advanced in vitro models, and multiomics analyses might contribute to developing a personalized gender-based medicine.

scholarly journals Special Issue on “Cellular and Molecular Mechanisms Underlying the Pathogenesis of Hepatic Fibrosis”

Cells ◽  
2020 ◽  
Vol 9 (5) ◽  
pp. 1105
Author(s):  
Ralf Weiskirchen
Keyword(s):  
Animal Models ◽  
Liver Fibrosis ◽  
Molecular Mechanisms ◽  
Scoring Systems ◽  
Molecular Pathways ◽  
Special Issue ◽  
Liver Fibrogenesis ◽  
Cellular Mediators ◽  
Preclinical Animal Models ◽  
Disease Specific

This Special issue contains 48 contributions highlighting novel findings and current concepts in basic and clinical liver fibrosis research. These articles emphasize issues on pathogenesis, cellular mediators, modulators, molecular pathways, disease-specific therapies, scoring systems, as well as novel preclinical animal models for the study of liver fibrogenesis. This editorial aims to briefly summarize the content of these papers.

scholarly journals Multi-influential interactions alters behaviour and cognition through six main biological cascades in Down syndrome mouse models

2020 ◽  
Author(s):  
Arnaud Duchon ◽  
Maria del Mar Muñiz Moreno ◽  
Sandra Martin Lorenzo ◽  
Márcia Priscilla Silva de Souza ◽  
Claire Chevalier ◽  
...  
Keyword(s):  
Gene Expression ◽  
Down Syndrome ◽  
Mouse Models ◽  
Brain Function ◽  
Molecular Mechanisms ◽  
Chromosome 21 ◽  
List Type ◽  
Depth Analysis ◽  
Altered Gene

AbstractDown syndrome (DS) is the most common genetic form of intellectual disability caused by the presence of an additional copy of human chromosome 21. To provide novel insights into genotype–phenotype correlations, we screened the in vivo DS mouse library with standardized behavioural tests, magnetic resonance imaging (MRI) and hippocampal gene expression. Altogether this approach brings novel insights into the field. First, we unravelled several genetic interactions between different regions of the chromosome 21 and how they importantly contribute in altering the outcome of the phenotypes in brain function and structure. Then, in depth analysis of misregulated expressed genes involved in synaptic dysfunction highlitghed 6 biological cascades centered around DYRK1A, GSK3β, NPY, SNARE, RHOA and NPAS4. Finally, we provide a novel vision of the existing altered gene-gene crosstalk and molecular mechanisms targeting specific hubs in DS models that should become central to advance in our understanding of DS and therapies development.HighlightsBrain function and morphology changes in DS mouse models result from multiple genetic lociEach combination of loci induces specific alteration of gene expression profile in mouse modelsAltered gene expression converges to a few functional pathwys in DS mouse hippocampiThe synaptic pathway analysis leads to six connected biological cascades and defines a specific DS disease network

scholarly journals Relevance of cancer cachexia models – muscle whole genome gene expression in human and animal cachexia

2020 ◽  
Author(s):  
Rogier L.C. Plas ◽  
Guido Hooiveld ◽  
Renger F. Witkamp ◽  
Klaske van Norren
Keyword(s):  
Gene Expression ◽  
Animal Models ◽  
Molecular Mechanisms ◽  
Gene Set Enrichment Analysis ◽  
The Other ◽  
Control Group ◽  
Whole Genome ◽  
Transport Pathway ◽  
Different Levels ◽  
Human Dataset

Abstract BackgroundCancer cachexia is a complex and multi-factorial syndrome. As currently available therapeutic options are limited, more in-depth knowledge on cachexia pathophysiology and the underlying molecular mechanisms remains warranted. Studies with animal models provide useful insights but they only mimic the human situation to a certain degree. Furthermore, there is heterogeneity in the design of published animal studies and outcomes. To further address this issue, we performed a comparative study analysing muscle whole genome gene expression of different cachexia studies in mice and human.MethodsWe selected data sets from the NCBI Gene Expression Omnibus database containing muscle gene expression data measured by micro-array or RNA-sequencing, at least comprising a cachectic/tumour bearing group (n>3) and a non-cachectic/control group (n>3). This provided 12 datasets; 9 from mouse models and 3 human datasets. All datasets were quality checked, normalised and annotated. Datasets were merged and compared at different levels. General similarity and differences in gene expression were determined using ordered list analysis and principal component analysis (PCA). Moreover, similarities and differences at pathway level were studied by applying gene set enrichment analysis (GSEA) of KEGG pathways.ResultsAnimal models displayed similarities to each other and to human datasets at different levels and with different processes. At the gene level, a similarity analysis indicated little similarity between the animal models and the human datasets, while animal models showed high similarity. Only one of the C26 mice models (GSE121972) showed significant similarity to more than one human dataset. Moreover, one human dataset comparing cachectic and non-cachectic cancer patients showed no similarity to any of the other datasets. PCA results indicated that a xenograft model showed most different expression from the other datasets and the Lewis lung carcinoma model to be least different from the human datasets. GSEA results showed four pathways clearly standing out across experiments with downregulation of oxidative phosphorylation and thermogenesis pathway, and upregulation of the proteasome and RNA transport pathway. However, these pathways were not consistently changed in the human datasets.ConclusionsOur comparative analysis showed that there is currently no basis to define a preferred animal model for human cachexia. More human datasets containing proper controls are needed. Repetition of the current analysis upon publication of additional human datasets is warranted.

scholarly journals Animal models for the study of liver fibrosis: new insights from knockout mouse models

2011 ◽  
Vol 300 (5) ◽  
pp. G729-G738 ◽  
Author(s):  
Hiromitsu Hayashi ◽  
Takao Sakai
Keyword(s):  
Animal Models ◽  
Liver Fibrosis ◽  
Molecular Mechanisms ◽  
Clinical Importance ◽  
Genetically Engineered ◽  
Loss Of Function ◽  
Genetically Engineered Mice ◽  
Gene Knockouts ◽  
Would Healing ◽  
Excessive Accumulation

Fibrosis arises as part of a would-healing response that maintains organ structure and integrity following tissue damage but also contributes to a variety of human pathologies such as liver fibrosis. Liver fibrosis is an abnormal response of the liver to persistent injury with the excessive accumulation of collagenous extracellular matrices. Currently there is no effective treatment, and many patients end up with a progressive form of the disease, eventually requiring a liver transplant. The clarification of mechanisms underlying pathogenesis of liver fibrosis and the development of effective therapy are of clinical importance. Experimental animal models, in particular targeted gene knockouts (loss of function) in mice, have become a powerful resource to address the molecular mechanisms or significance of the targeted gene in hepatic functions and diseases. This review will focus on the recent advances in knowledge obtained from genetically engineered mice that provide novel insights into the pathophysiology of liver fibrosis.

scholarly journals ELAV proteins bind and stabilize C/EBP mRNA in the induction of long-term memory in Aplysia

2020 ◽  
Author(s):  
Anastasios A. Mirisis ◽  
Ashley M. Kopec ◽  
Thomas J. Carew
Keyword(s):  
Gene Expression ◽  
Molecular Mechanisms ◽  
Rna Binding ◽  
De Novo ◽  
Rna Binding Proteins ◽  
Early Gene ◽  
Long Term Memory ◽  
Term Memory ◽  
New Findings

AbstractLong-term memory (LTM) formation is a critical survival process by which an animal retains information about prior experiences in order to guide future behavior. In the experimentally advantageous marine mollusk Aplysia, LTM for sensitization can be induced by the presentation of two aversive shocks to the animal’s tail. Each of these training trials recruits distinct growth factor signaling systems that promote LTM formation. Specifically, whereas intact TrkB signaling during Trial 1 promotes an initial and transient increase of the immediate early gene apc/ebp mRNA, a prolonged increase in apc/ebp gene expression required for LTM formation requires the addition of TGFβ signaling during Trial 2. Here we explored the molecular mechanisms by which Trial 2 achieves the essential prolonged gene expression of apc/ebp. We find that this prolonged gene expression is not dependent on de novo transcription, but that apc/ebp mRNA synthesized by Trial 1 is post-transcriptionally stabilized by interacting with the RNA-binding protein ApELAV. This interaction is promoted by p38 MAPK activation initiated by TGFβ. We further demonstrate that blocking the interaction of ApELAV with its target mRNA during Trial 2 blocks both the prolonged increase in apc/ebp gene expression and the behavioral induction of LTM. Collectively, our findings elucidate both when and how ELAV proteins are recruited for the stabilization of mRNA in LTM formation.Significance StatementIn the present paper we significantly extend the general field of molecular processing in LTM by describing a novel form of pre-translational processing required for LTM which relies on the stabilization of a newly synthesized mRNA by a unique class of RNA binding proteins (ELAVs). In the broad field of molecular mechanisms of transcription-dependent LTM, there are now compelling data showing that important processing can occur after transcription of a gene, but before translation of the message into protein. Although the potential importance of ELAV proteins in LTM formation has previously been reported, to date there has been no mechanistic insight into the specific actions of ELAV proteins in stabilization of mRNAs known to be critical for LTM. Our new findings thus complement and extend this literature by demonstrating when and how this post-transcriptional gene regulation is mediated in the induction of LTM.

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