Quantitative proteomics reveals GIMAP family proteins 1 and 4 to be differentially regulated during human T helper cell differentiation

Identification and validation of GIMAP family genes as immune-related prognostic biomarkers in lung adenocarcinoma

Background

The GIMAP family genes play a key role in immune function. Increasing evidence suggests that GIMAP genes were implicated in the tumorigenesis of lung adenocarcinoma (LUAD). This study aimed to investigate the clinical significance of GIMAP family genes in LUAD.

Methods

In this study, we explored the expression, mutation, prognostic value of GIMAP family genes and the correlation with immune microenvironment in LUAD. We further investigated the relationship between GIMAP family genes expression and immunotherapy response in GEO LUAD and melanoma cohorts.

Results

Among the GIMAP family genes, the expression levels of GIMAP1, GIMAP2, GIMAP4, GIMAP5, GIMAP6, GIMAP7, and GIMAP8 were significantly lower in LUAD tumor tissues than normal tissues. Most GIMAP genes were closely related to age, tumor grade and T stage, but not significantly related to sex, N stage and M stage. In the overall population, patients with high expression of GIMAP family genes had a significant longer overall survival (OS). GO and KEGG enrichment analysis showed that GIMAP family genes were highly enriched in immune-related biological process. The expression of GIMAP family genes was positively correlated with immune cell infiltration and immune checkpoint molecules. Furthermore, high expression of GIMAP family genes were correlated with therapeutic response to immunotherapy in LUAD and melanoma patients.

Conclusion

In this study, we identified that GIMAP family genes were significantly associated with immune cell infiltration and immune checkpoint molecules. They potentially play a critical role in anti-tumor immunity and serve as immunotherapy biomarkers.

Identifying Hub Genes and Immune Cell Infiltration for the Progression of Carotid Atherosclerotic Plaques in the Context of Predictive and Preventive Using Integrative Bioinformatics Approaches and Machine-Learning Strategies

Emerging evidence shows that carotid atherosclerosis is related to the activation of immune-related pathways and inflammatory cell infiltration. However, the immune-linked pathways that helped in the advancement of the carotid atherosclerotic plaque and the association of such plaques with the infiltration status of the body's immune cells still unclear. Here, the expression profiles of the genes expressed during the progression of the carotid atherosclerotic plaques were retrieved from the Gene Expression Omnibus database and 178 differentially expressed genes were examined. The Weighted Gene Coexpression Network Analysis technique identified one of the brown modules showed the greatest correlation with carotid atherosclerotic plaques. In total, 66 intersecting genes could be detected after combining the DEGs. LASSO regression analysis was subsequently performed to obtain five hub genes as potential biomarkers for carotid atherosclerotic plaques. The functional analysis emphasized the vital roles played by the inflammation- and immune system-related pathways in this disease. The immune cell infiltration results highlighted the significant correlation among the CD4+ T cells, B cells, macrophages, and CD8+ T cells. Thereafter, the gene expression levels and the diagnostic values related to every hub gene were further validated. The above results indicated that macrophages, B cells, CD4+ T cells, and CD8 + T cells were closely related to the formation of the advanced-stage carotid atherosclerotic plaques. Based on the results, it could be hypothesized that the expression of hub genes (C3AR1, SLAMF8, TMEM176A, FERMT3, and GIMAP4) assisted in the advancement of the early-stage to advanced-stage carotid atherosclerotic plaque through immune-related signaling pathways. This may help to provide novel strategies for the treatment of carotid plaque in the context of predictive, preventive, and personalized medicine.

Prognostic Value of GIMAP4 and Its Role in Promoting Immune Cell Infiltration into Tumor Microenvironment of Lung Adenocarcinoma

GIMAPs are recognized as an important regulator in the carcinogenesis and development of lung cancer, but the function of GIMAP4 in the tumor microenvironment (TME) of lung cancers is unclear. In this study, we investigated the expression and variation of GIMAP4 in lung adenocarcinoma (LUAD), to explore its association with infiltration of immune cells. The Cancer Genome Atlas (TCGA) data and Gene Expression Omnibus (GEO) data were analyzed. Infiltration of immune cells was identified with TIMER (Tumor Immune Estimation Resource) and TISIDB (an integrated repository portal for tumor-immune system interactions). GIMAP4 expression declined in non-small-cell lung cancer (NSCLC), correlated with a poor overall survival (OS) in LUAD, indicating that GIMAP4 was a promising prognostic biomarker in LUAD. GIMAP4 mutation frequency was 1.76% in TCGA cohort and was relevant to the expression of immune components. TIMER and CIBERSORT analysis further confirmed that high GIMAP4 expression possibly promoted immune cell infiltration into the TME, with low GIMAP4 impairing the efficacy of immunotherapies targeting common immune check point inhibitors (ICI). GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) analyses were performed to provide insights into biological processes involved in LUAD. GIMAP4 was expected to be a prognostic biomarker in LUAD and provides potential adjuvant or neoadjuvant therapeutic strategies for targeting ICIs.

ILC1s control leukemia stem cell fate and limit development of AML

Type I innate lymphoid cells (ILC1s) are critical regulators of inflammation and immunity in mammalian tissues. However, their function in cancer is mostly undefined. Here, we show that a high density of ILC1s induces leukemia stem cell (LSC) apoptosis in mice. At a lower density, ILC1s prevent LSCs from differentiating into leukemia progenitors and promote their differentiation into non-leukemic cells, thus blocking the production of terminal myeloid blasts. All of these effects, which require ILC1s to produce interferon-γ after cell-cell contact with LSCs, converge to suppress leukemogenesis in vivo. Conversely, the antileukemia potential of ILC1s wanes when JAK-STAT or PI3K-AKT signaling is inhibited. The relevant antileukemic properties of ILC1s are also functional in healthy individuals and impaired in individuals with acute myeloid leukemia (AML). Collectively, these findings identify ILC1s as anticancer immune cells that might be suitable for AML immunotherapy and provide a potential strategy to treat AML and prevent relapse of the disease.

Single cell transcriptomic landscape of diabetic foot ulcers

Diabetic foot ulceration (DFU) is a devastating complication of diabetes whose pathogenesis remains incompletely understood. Here, we profile 174,962 single cells from the foot, forearm, and peripheral blood mononuclear cells using single-cell RNA sequencing. Our analysis shows enrichment of a unique population of fibroblasts overexpressing MMP1, MMP3, MMP11, HIF1A, CHI3L1, and TNFAIP6 and increased M1 macrophage polarization in the DFU patients with healing wounds. Further, analysis of spatially separated samples from the same patient and spatial transcriptomics reveal preferential localization of these healing associated fibroblasts toward the wound bed as compared to the wound edge or unwounded skin. Spatial transcriptomics also validates our findings of higher abundance of M1 macrophages in healers and M2 macrophages in non-healers. Our analysis provides deep insights into the wound healing microenvironment, identifying cell types that could be critical in promoting DFU healing, and may inform novel therapeutic approaches for DFU treatment.

The GIMAP Family Proteins: An Incomplete Puzzle

Overview: Long-term survival of T lymphocytes in quiescent state is essential to maintain their cell numbers in secondary lymphoid organs and in peripheral circulation. In the BioBreeding diabetes-prone strain of rats (BB-DP), loss of functional GIMAP5 (GTPase of the immune associated nucleotide binding protein 5) results in profound peripheral T lymphopenia. This discovery heralded the identification of a new family of proteins initially called Immune-associated nucleotide binding protein (IAN) family. In this review we will use ‘GIMAP’ to refer to this family of proteins. Recent studies suggest that GIMAP proteins may interact with each other and also be involved in the movement of the cellular cargo along the cytoskeletal network. Here we will summarize the current knowledge on the characteristics and functions of GIMAP family of proteins.

Comparative Analysis of Global Proteome and Lysine Acetylome Between Naive CD4+ T Cells and CD4+ T Follicular Helper Cells

As a subgroup of CD4⁺ T helper cells, follicular helper T (Tfh) cells provide help to germinal center B cells and mediate the development of long-lived humoral immunity. Dysregulation of Tfh cells is associated with several major autoimmune diseases. Although recent studies showed that Tfh cell differentiation is controlled by the transcription factor Bcl6, cytokines, and cell-cell signals, limited information is available on the proteome and post-translational modifications (PTMs) of proteins in human Tfh cells. In the present study, we investigated quantitative proteome and acetylome in human naive CD4⁺ T cells and in vitro induced Tfh (iTfh) cells using the tandem mass tag (TMT) labeling technique, antibody-based affinity enrichment, and high-resolution liquid chromatography-mass spectrometry (LC-MS)/mass spectrometry (MS) analysis. In total, we identified 802 upregulated proteins and 598 downregulated proteins at the threshold of 1.5-fold in iTfh cells compared to naive CD4⁺ T cells. With the aid of intensive bioinformatics, the biological process, the cellular compartment, the molecular function, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, and protein–protein interaction of these differentially expressed proteins were revealed. Moreover, the acetylome data showed that 22 lysine (K) acetylated proteins are upregulated and 26 K acetylated proteins are downregulated in iTfh cells compared to the naive CD4⁺ T cells, among which 11 differentially acetylated K residues in core histones were identified, indicating that protein acetylation and epigenetic mechanism are involved in regulating Tfh cell differentiation. The study provides some important clues for investigating T cell activation and Tfh cell differentiation.

Gene Expression Changes and Associated Pathways Involved in the Progression of Prostate Cancer Advanced Stages

Prostate cancer (PC) is one of the most common cancers among men worldwide, and advanced PCs, such as locally advanced PC (LAPC) and castration-resistant PC (CRPC), present the greatest challenges in clinical management. Current indicators have limited capacity to predict the disease course; therefore, better prognostic markers are greatly needed. In this study, we performed a bioinformatic analysis of The Cancer Genome Atlas (TCGA) datasets, including RNA-Seq data from the prostate adenocarcinoma (PRAD; n = 55) and West Coast Dream Team – metastatic CRPC (WCDT-MCRPC; n = 84) projects, to evaluate the transcriptome changes associated with progression-free survival (PFS) for LAPC and CRPC, respectively. We identified the genes whose expression was positively/negatively correlated with PFS. In LAPC, the genes with the most significant negative correlations were ZC2HC1A, SQLE, and KIF11, and the genes with the most significant positive correlations were SOD3, LRRC26, MIR22HG, MEG3, and MIR29B2CHG. In CRPC, the most significant positive correlations were found for BET1, CTAGE5, IFNGR1, and GIMAP6, and the most significant negative correlations were found for CLPB, PRPF19, ZNF610, MPST, and LINC02001. In addition, we performed a gene network interaction analysis using STRINGdb, which revealed a significant relationship between genes predominantly involved in the cell cycle and characterized by upregulated expression in early recurrence. Based on the results, we propose several genes that can be used as potential prognostic markers.

Integrated Bioinformatical Analysis Identifies GIMAP4 as an Immune-Related Prognostic Biomarker Associated With Remodeling in Cervical Cancer Tumor Microenvironment

Tumor microenvironment (TME) is emerging as an essential part of cervical cancer (CC) tumorigenesis and development, becoming a hotspot of research these years. However, comprehending the specific composition of TME is still facing enormous challenges, especially the immune and stromal components. In this study, we downloaded the RNA-seq profiles and somatic mutation data of 309 CC cases from The Cancer Genome Atlas (TCGA) database, which were analyzed by integrative bioinformatical methods. Initially, ESTIMATE computational method was employed to calculate the amount of immune and stromal components. Then, based on the high- and low-immunity cohorts, we recognized the differentially expressed genes (DEGs) as well as the differentially mutated genes (DMGs). Additionally, we conducted an intersection analysis of DEGs and DMGs, ultimately determining an immune-related prognostic signature, GTPase, IMAP Family Member 4 (GIMAP4). Moreover, sequential analyses demonstrated that GIMAP4 was a protective factor in CC, positively correlated with the overall survival (OS) and negatively with distant metastasis. Besides, we utilized the Gene Set Enrichment Analysis (GSEA) to explore the enrichment-pathways in high and low-expression cohorts of GIMAP4. The results indicated that the genes of the high-expression cohort had a high enrichment in immune-related biological processes and metabolic activities in the low one. Furthermore, CIBERSORT analysis was applied to evaluate the proportion of tumor-infiltrating immune cells (TICs), illustrating that several activated TICs were strongly associated with GIMAP4 expression, which suggested that GIMAP4 had the potential to be an indicator for the immune state in TME of CC. Hence, GIMAP4 contributed to predicting the CC patients’ clinical outcomes, such as survival rate, distant metastasis and immunotherapy response. Moreover, GIMAP4 could serve as a promising biomarker for TME remodeling, suggesting the possible underlying mechanisms of tumorigenesis and CC progression, which may provide different therapeutic perceptions of CC, and therefore improve treatment.

Transcriptomic study in women with trisomy 21 identifies a possible role of the GTPases of the immunity-associated proteins (GIMAP) in the protection of breast cancer

BACKGROUND

People with trisomy 21 (T21) are predisposed to developing hematological tumors, but have significantly lower-than-expected age-adjusted incidence rates of having a solid tumor.

MATERIAL AND METHODS

To identify novel genetic factors implicated in the lower breast cancer (BC) frequency observed in women with T21 than in the general population, we compared the transcriptome pattern of women with a homogeneous T21, aged more than 30 years, with or without BC, and tumoral BC tissue of control women with a normal karyotype from the study of Varley et al. (2014).

RESULTS

Differential analysis of gene expression between the 15 women in the T21 without BC group and BC patients in the other groups (two women with T21 and fifteen control women, respectively) revealed 154 differentially expressed genes, of which 63 were found to have similar expression profile (up- or downregulated). Of those 63 genes, four were in the same family, namely GIMAP4, GIMAP6, GIMAP7 and GIMAP8, and were strongly upregulated in the T21 without BC group compared to the other groups. A significant decrease in mRNA levels of these genes in BC tissues compared to non-tumor breast tissues was also noted.

CONCLUSION

We found that the expression of some GIMAPs is significantly higher in women with T21 without BC than in patients with sporadic BC. Our findings support the hypothesis that GIMAPs may play a tumor-suppressive role against BC, and open the possibility that they may also have the same role for other solid tumors in T21 patients. The search for new prognostic factors and hopefully new therapeutic or preventive strategies against BC are discussed.

Development of a Bioinformatics Framework for Identification and Validation of Genomic Biomarkers and Key Immunopathology Processes and Controllers in Infectious and Non-infectious Severe Inflammatory Response Syndrome

Sepsis is defined as dysregulated host response caused by systemic infection, leading to organ failure. It is a life-threatening condition, often requiring admission to an intensive care unit (ICU). The causative agents and processes involved are multifactorial but are characterized by an overarching inflammatory response, sharing elements in common with severe inflammatory response syndrome (SIRS) of non-infectious origin. Sepsis presents with a range of pathophysiological and genetic features which make clinical differentiation from SIRS very challenging. This may reflect a poor understanding of the key gene inter-activities and/or pathway associations underlying these disease processes. Improved understanding is critical for early differential recognition of sepsis and SIRS and to improve patient management and clinical outcomes. Judicious selection of gene biomarkers suitable for development of diagnostic tests/testing could make differentiation of sepsis and SIRS feasible. Here we describe a methodologic framework for the identification and validation of biomarkers in SIRS, sepsis and septic shock patients, using a 2-tier gene screening, artificial neural network (ANN) data mining technique, using previously published gene expression datasets. Eight key hub markers have been identified which may delineate distinct, core disease processes and which show potential for informing underlying immunological and pathological processes and thus patient stratification and treatment. These do not show sufficient fold change differences between the different disease states to be useful as primary diagnostic biomarkers, but are instrumental in identifying candidate pathways and other associated biomarkers for further exploration.

Comprehensive RNA-Seq Data Analysis Identifies Key mRNAs and lncRNAs in Atrial Fibrillation

Long non-coding RNAs (lncRNAs) are an emerging class of RNA species that may play a critical regulatory role in gene expression. However, the association between lncRNAs and atrial fibrillation (AF) is still not fully understood. In this study, we used RNA sequencing data to identify and quantify the both protein coding genes (PCGs) and lncRNAs. The high enrichment of these up-regulated genes in biological functions concerning response to virus and inflammatory response suggested that chronic viral infection may lead to activated inflammatory pathways, thereby alter the electrophysiology, structure, and autonomic remodeling of the atria. In contrast, the downregulated GO terms were related to the response to saccharides. To identify key lncRNAs involved in AF, we predicted lncRNAs regulating expression of the adjacent PCGs, and characterized biological function of the dysregulated lncRNAs. We found that two lncRNAs, ETF1P2, and AP001053.11, could interact with protein-coding genes (PCGs), which were implicated in AF. In conclusion, we identified key PCGs and lncRNAs, which may be implicated in AF, which not only improves our understanding of the roles of lncRNAs in AF, but also provides potentially functional lncRNAs for AF researchers.

The relevance between the immune response-related gene module and clinical traits in head and neck squamous cell carcinoma

PURPOSE

Head and neck squamous cell carcinoma (HNSCC) is the sixth most prevalent cancer in the world, accounting for more than 90% of head and neck malignant tumors. However, its molecular mechanism is largely unknown. To help elucidate the potential mechanism of HNSCC tumorigenesis, we investigated the gene interaction patterns associated with tumorigenesis.

METHODS

Weighted gene co-expression network analysis (WGCNA) can help us to predict the intrinsic relationship or correlation between gene expression. Additionally, we further explored the combination of clinical information and module construction.

RESULTS

Sixteen modules were constructed, among which the key module most closely associated with clinical information was identified. By analyzing the genes in this module, we found that the latter may be related to the immune response, inflammatory response and formation of the tumor microenvironment. Sixteen hub genes were identified-ARHGAP9, SASH3, CORO1A, ITGAL, PPP1R16B, TBC1D10C, IL10RA, ITK, AKNA, PRKCB, TRAF3IP3, GIMAP4, CCR7, P2RY8, GIMAP7, and SP140. We further validated these genes at the transcriptional and translation levels.

CONCLUSION

The innovative use of a weighted network to analyze HNSCC samples provides new insights into the molecular mechanism and prognosis of HNSCC. Additionally, the hub genes we identified can be used as biomarkers and therapeutic targets of HNSCC, laying the foundation for the accurate diagnosis and treatment of HNSCC in clinical and research in the future.

Quantitative Proteomics Reveals the Dynamic Protein Landscape during Initiation of Human Th17 Cell Polarization

Th17 cells contribute to the pathogenesis of inflammatory and autoimmune diseases and cancer. To reveal the Th17 cell-specific proteomic signature regulating Th17 cell differentiation and function in humans, we used a label-free mass spectrometry-based approach. Furthermore, a comprehensive analysis of the proteome and transcriptome of cells during human Th17 differentiation revealed a high degree of overlap between the datasets. However, when compared with corresponding published mouse data, we found very limited overlap between the proteins differentially regulated in response to Th17 differentiation. Validations were made for a panel of selected proteins with known and unknown functions. Finally, using RNA interference, we showed that SATB1 negatively regulates human Th17 cell differentiation. Overall, the current study illustrates a comprehensive picture of the global protein landscape during early human Th17 cell differentiation. Poor overlap with mouse data underlines the importance of human studies for translational research.

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Quantitative proteomics analysis of early human Th17 cell polarization

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The proteome and transcriptome highly correlate during early Th17 polarization

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Poor overlap of proteome profiles of human and mouse during early Th17 polarization

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The results underline the importance of human studies for translational research

Immune Regulatory Genes Are Major Genetic Factors to Behcet Disease: Systematic Review

Behcet's disease (BD) is a chronic refractory multi-system autoimmune disorder that occurs in a genetically susceptible host. Multiple genetic factors have been identified that may contribute to the pathogenesis of BD. The major genes with polymorphisms associated with BD include HLA-B and -A, CIITA, ERAP1, MICA, IL10, IL12A, IL12RB2, IL23R, MEFV, IRF8, TNFAIP3, REL, TLR4, NOD1,2, CCR1,CCR3, GIMAP1,2,4, KLRC4, STAT4, NCOA5, FOXP3, PSORS1C1, FUT2, UBAC2, SUMO4, ADO-EGR2, CEBPB-PTPN1, and JPKL-CNTN5. These genes encode proteins involved mainly in immune regulation and inflammation, and some in transcription and post-translational modification. A complete view of these BD-associated genes may provide a clue to this complex disease in terms of its pathogenesis and exploring potentially targeted therapies for BD.

Perspectives on Systems Modeling of Human Peripheral Blood Mononuclear Cells

Human peripheral blood mononuclear cells (PBMCs) are the key drivers of the immune responses. These cells undergo activation, proliferation and differentiation into various subsets. During these processes they initiate metabolic reprogramming, which is coordinated by specific gene and protein activities. PBMCs as a model system have been widely used to study metabolic and autoimmune diseases. Herein we review various omics and systems-based approaches such as transcriptomics, epigenomics, proteomics, and metabolomics as applied to PBMCs, particularly T helper subsets, that unveiled disease markers and the underlying mechanisms. We also discuss and emphasize several aspects of T cell metabolic modeling in healthy and disease states using genome-scale metabolic models.

T Cell Transcriptomes from Paroxysmal Nocturnal Hemoglobinuria Patients Reveal Novel Signaling Pathways

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare acquired disorder originating from hematopoietic stem cells and is a life-threating disease characterized by intravascular hemolysis, bone marrow (BM) failure, and venous thrombosis. The etiology of PNH is a somatic mutation in the phosphatidylinositol glycan class A gene (PIG-A) on the X chromosome, which blocks synthesis of the glycolipid moiety and causes deficiency in GPI-anchored proteins. PNH is closely related to aplastic anemia, in which T cells mediate destruction of BM. To identify aberrant molecular mechanisms involved in immune targeting of hematopoietic stem cells in BM, we applied RNA-seq to examine the transcriptome of T cell subsets (CD4⁺ naive, CD4⁺ memory, CD8⁺ naive, and CD8⁺ memory) from PNH patients and healthy control subjects. Differentially expressed gene analysis in four different T cell subsets from PNH and healthy control subjects showed distinct transcriptional profiles, depending on the T cell subsets. By pathway analysis, we identified novel signaling pathways in T cell subsets from PNH, including increased gene expression involved in TNFR, IGF1, NOTCH, AP-1, and ATF2 pathways. Dysregulation of several candidate genes (JUN, TNFAIP3, TOB1, GIMAP4, GIMAP6, TRMT112, NR4A2, CD69, and TNFSF8) was validated by quantitative real-time RT-PCR and flow cytometry. We have demonstrated molecular signatures associated with positive and negative regulators in T cells, suggesting novel pathophysiologic mechanisms in PNH. These pathways may be targets for new strategies to modulate T cell immune responses in BM failure.

Mass spectrometry-based proteomic exploration of the human immune system: focus on the inflammasome, global protein secretion, and T cells

INTRODUCTION

The immune system is our defense system against microbial infections and tissue injury, and understanding how it works in detail is essential for developing drugs for different diseases. Mass spectrometry-based proteomics can provide in-depth information on the molecular mechanisms involved in immune responses. Areas covered: Summarized are the key immunology findings obtained with MS-based proteomics in the past five years, with a focus on inflammasome activation, global protein secretion, mucosal immunology, immunopeptidome and T cells. Special focus is on extracellular vesicle-mediated protein secretion and its role in immune responses. Expert commentary: Proteomics is an essential part of modern omics-scale immunology research. To date, MS-based proteomics has been used in immunology to study protein expression levels, their subcellular localization, secretion, post-translational modifications, and interactions in immune cells upon activation by different stimuli. These studies have made major contributions to understanding the molecular mechanisms involved in innate and adaptive immune responses. New developments in proteomics offer constantly novel possibilities for exploring the immune system. Examples of these techniques include mass cytometry and different MS-based imaging approaches which can be widely used in immunology.

Functional and biochemical characterization of a T cell-associated anti-apoptotic protein, GIMAP6

GTPases of immunity-associated proteins (GIMAPs) are expressed in lymphocytes and regulate survival/death signaling and cell development within the immune system. We found that human GIMAP6 is expressed primarily in T cell lines. By sorting human peripheral blood mononuclear cells and performing quantitative RT-PCR, GIMAP6 was found to be expressed in CD3+ cells. In Jurkat cells that had been knocked down for GIMAP6, treatment with hydrogen peroxide, FasL, or okadaic acid significantly increased cell death/apoptosis. Exogenous expression of GMAP6 protected Huh-7 cells from apoptosis, suggesting that GIMAP6 is an anti-apoptotic protein. Furthermore, knockdown of GIMAP6 not only rendered Jurkat cells sensitive to apoptosis but also accelerated T cell activation under phorbol 12-myristate 13-acetate/ionomycin treatment conditions. Using this experimental system, we also observed a down-regulation of p65 phosphorylation (Ser-536) in GIMAP6 knockdown cells, indicating that GIMAP6 might display anti-apoptotic function through NF-κB activation. The conclusion from the study on cultured T cells was corroborated by the analysis of primary CD3+ T cells, showing that specific knockdown of GIMAP6 led to enhancement of phorbol 12-myristate 13-acetate/ionomycin-mediated activation signals. To characterize the biochemical properties of GIMAP6, we purified the recombinant GIMAP6 to homogeneity and revealed that GIMAP6 had ATPase as well as GTPase activity. We further demonstrated that the hydrolysis activity of GIMAP6 was not essential for its anti-apoptotic function in Huh-7 cells. Combining the expression data, biochemical properties, and cellular features, we conclude that GIMAP6 plays a role in modulating immune function and that it does this by controlling cell death and the activation of T cells.

Survival of mature T cells in the periphery is intrinsically dependent on GIMAP1 in mice

An effective immune system depends upon the survival of mature T cells in the periphery. Members of the GIMAP family of GTPases have been proposed to regulate this homeostasis, supported by the paucity of peripheral T cells in rodents deficient for either GIMAP1 or GIMAP5. It is unclear whether this lack of T cells is a consequence of an ontological defect, causing the thymus to generate and export T cells incapable of surviving in the periphery, or whether (alternatively or additionally) mature T cells intrinsically require GIMAP1 for survival. Using the ER^T2 Cre⁺ transgene, we conditionally deleted Gimap1 in C57BL/6 mice and demonstrate that GIMAP1 is intrinsically required for the survival of mature T cells in the periphery. We show that, in contrast to GIMAP5, this requirement is independent of the T-cells' activation status. We investigated the nature of the survival defect in GIMAP1-deficient CD4⁺ T cells and show that the death occurring after GIMAP1 ablation is accompanied by mitochondrial depolarization and activation of the extrinsic apoptotic pathway. This study shows that GIMAP1 is critical for maintaining the peripheral T-cell pool in mice and offers a potent target for the treatment of T-cell-mediated diseases.

Quantitative Proteomics of Gut-Derived Th1 and Th1/Th17 Clones Reveal the Presence of CD28+ NKG2D- Th1 Cytotoxic CD4+ T cells

T-helper cells are differentiated from CD4+ T cells and are traditionally characterized by inflammatory or immunosuppressive responses in contrast to cytotoxic CD8+ T cells. Mass-spectrometry studies on T-helper cells are rare. In this study, we aimed to identify the proteomes of human Th1 and Th1/Th17 clones derived from intestinal biopsies of Crohn's disease patients and to identify differentially expressed proteins between the two phenotypes. Crohn's disease is an inflammatory bowel disease, with predominantly Th1- and Th17-mediated response where cells of the "mixed" phenotype Th1/Th17 have also been commonly found. High-resolution mass spectrometry was used for protein identification and quantitation. In total, we identified 7401 proteins from Th1 and Th1/Th17 clones, where 334 proteins were differentially expressed. Major differences were observed in cytotoxic proteins that were overrepresented in the Th1 clones. The findings were validated by flow cytometry analyses using staining with anti-granzyme B and anti-perforin and by a degranulation assay, confirming higher cytotoxic features of Th1 compared with Th1/Th17 clones. By testing a larger panel of T-helper cell clones from seven different Crohn's disease patients, we concluded that only a subgroup of the Th1 cell clones had cytotoxic features, and these expressed the surface markers T-cell-specific surface glycoprotein CD28 and were negative for expression of natural killer group 2 member D.

S100A9: A Potential Biomarker for the Progression of Non-Alcoholic Fatty Liver Disease and the Diagnosis of Non-Alcoholic Steatohepatitis

Non-alcoholic fatty liver (NAFL) has the potential to progress to non-alcoholic steatohepatitis (NASH) or to promote type 2 diabetes mellitus (T2DM). However, NASH and T2DM do not always develop coordinately. Additionally, there are no definite noninvasive methods for NASH diagnosis currently. We established rat models of NAFL, NASH, and NAFL + T2DM to recapitulate different phenotypes associated with non-alcoholic fatty liver disease (NAFLD) and its progression. Histologic features of rat livers were scored according to criteria established by the Nonalcoholic Steatohepatitis Clinical Research Network. Microarray was performed to assess gene expression changes in rat livers. We find that gene expression of s100a9 was higher in NAFL group compared with control, and was increased in NASH groups and decreased in NAFL + T2DM group compared with NAFL. In contrast, srebf1, tbx21, and gimap4 only showed limited discriminating abilities in different groups. There is a significant positive correlation between serum levels of S100A9 and NAFLD Activity Score (NAS), the severity of hepatic steatosis, and lobular inflammation (r = 0.80, 0.64 and 0.86, P < 0.001). These findings suggest that S100A9 may be extremely useful in the diagnosis of NASH (AUROC: 0.947, CI: 0.845-1.049). Additionally, serum S100A9 levels displayed a strong correlation with ALT, AST and TBil (r = 0.81, 0.89 and 0.91, P < 0.001) but a weak correlation with FBG, HOMA-IR, TG, and TC (r = -0.41, -0.40, 0.47 and 0.49, P < 0.05). Conclusions: The results we provide here suggest that S100A9 may be useful as a biomarker for the hepatic and metabolic progression of NAFLD and the non-invasive diagnosis of NASH.

GIMAP GTPase family genes: potential modifiers in autoimmune diabetes, asthma, and allergy

GTPase of the immunity-associated protein (GIMAP) family members are differentially regulated during human Th cell differentiation and have been previously connected to immune-mediated disorders in animal studies. GIMAP4 is believed to contribute to the Th cell subtype-driven immunological balance via its role in T cell survival. GIMAP5 has a key role in BB-DR rat and NOD mouse lymphopenia. To elucidate GIMAP4 and GIMAP5 function and role in human immunity, we conducted a study combining genetic association in different immunological diseases and complementing functional analyses. Single nucleotide polymorphisms tagging the GIMAP haplotype variation were genotyped in Finnish type 1 diabetes (T1D) families and in a prospective Swedish asthma and allergic sensitization birth cohort. Initially, GIMAP5 rs6965571 was associated with risk for asthma and allergic sensitization (odds ratio [OR] 3.74, p = 0.00072, and OR 2.70, p = 0.0063, respectively) and protection from T1D (OR 0.64, p = 0.0058); GIMAP4 rs13222905 was associated with asthma (OR 1.28, p = 0.035) and allergic sensitization (OR 1.27, p = 0.0068). However, after false discovery rate correction for multiple testing, only the associations of GIMAP4 with allergic sensitization and GIMAP5 with asthma remained significant. In addition, transcription factor binding sites surrounding the associated loci were predicted. A gene-gene interaction in the T1D data were observed between the IL2RA rs2104286 and GIMAP4 rs9640279 (OR 1.52, p = 0.0064) and indicated between INS rs689 and GIMAP5 rs2286899. The follow-up functional analyses revealed lower IL-2RA expression upon GIMAP4 knockdown and an effect of GIMAP5 rs2286899 genotype on protein expression. Thus, the potential role of GIMAP4 and GIMAP5 as modifiers of immune-mediated diseases cannot be discarded.

Tubulin- and actin-associating GIMAP4 is required for IFN-γ secretion during Th cell differentiation

Although GTPase of the immunity-associated protein (GIMAP) family are known to be most highly expressed in the cells of the immune system, their function and role remain still poorly characterized. Small GTPases in general are known to be involved in many cellular processes in a cell type-specific manner and to contribute to specific differentiation processes. Among GIMAP family, GIMAP4 is the only member reported to have true GTPase activity, and its transcription is found to be differentially regulated during early human CD4(+) T helper (Th) lymphocyte differentiation. GIMAP4 has been previously connected mainly with T- and B-cell development and survival and T-cell apoptosis. Here we show GIMAP4 to be localized into cytoskeletal elements and with the component of the trans golgi network, which suggests it to have a function in cellular transport processes. We demonstrate that depletion of GIMAP4 with RNAi results in downregulation of endoplasmic reticulum localizing chaperone VMA21. Most importantly, we discovered that GIMAP4 regulates secretion of cytokines in early differentiating human CD4(+) Th lymphocytes and in particular the secretion of interferon-γ also affecting its downstream targets.

Expression profiling of genes modulated by minocycline in a rat model of neuropathic pain

Background

The molecular mechanisms underlying neuropathic pain are constantly being studied to create new opportunities to prevent or alleviate neuropathic pain. The aim of our study was to determine the gene expression changes induced by sciatic nerve chronic constriction injury (CCI) that are modulated by minocycline, which can effectively diminish neuropathic pain in animal studies. The genes associated with minocycline efficacy in neuropathic pain should provide insight into the etiology of neuropathic pain and identify novel therapeutic targets.

Results

We screened the ipsilateral dorsal part of the lumbar spinal cord of the rat CCI model for differentially expressed genes. Out of 22,500 studied transcripts, the abundance levels of 93 transcripts were altered following sciatic nerve ligation. Percentage analysis revealed that 54 transcripts were not affected by the repeated administration of minocycline (30 mg/kg, i.p.), but the levels of 39 transcripts were modulated following minocycline treatment. We then selected two gene expression patterns, B1 and B2. The first transcription pattern, B1, consisted of 10 mRNA transcripts that increased in abundance after injury, and minocycline treatment reversed or inhibited the effect of the injury; the B2 transcription pattern consisted of 7 mRNA transcripts whose abundance decreased following sciatic nerve ligation, and minocycline treatment reversed the effect of the injury. Based on the literature, we selected seven genes for further analysis: Cd40, Clec7a, Apobec3b, Slc7a7, and Fam22f from pattern B1 and Rwdd3 and Gimap5 from pattern B2. Additionally, these genes were analyzed using quantitative PCR to determine the transcriptional changes strongly related to the development of neuropathic pain; the ipsilateral DRGs (L4-L6) were also collected and analyzed in these rats using qPCR.

Conclusion

In this work, we confirmed gene expression alterations previously identified by microarray analysis in the spinal cord and analyzed the expression of selected genes in the DRG. Moreover, we reviewed the literature to illustrate the relevance of these findings for neuropathic pain development and therapy. Further studies are needed to elucidate the roles of the individual genes in neuropathic pain and to determine the therapeutic role of minocycline in the rat neuropathic pain model.

From a gene-centric to whole-proteome view of differentiation of T helper cell subsets

Proper differentiation of naïve T helper cells into functionally distinct subsets is of critical importance to human health. Consequently, the process is tightly controlled by a complex intracellular signalling network. To dissect the regulatory principles of this network, immunologists have early on embraced system-wide transcriptomics tools, leading to identification of large panels of potential regulatory factors. In contrast, the use of proteomics approaches in T helper cell research has been notably rare, and to this date relatively few high-throughput datasets have been reported. Here, we discuss the importance of such research and envision the possibilities afforded by mass spectrometry-based proteomics in the near future.

Regulatory T Cells Control Immune Responses through Their Non-Redundant Tissue Specific Features

Regulatory T cells (Treg) are needed in the control of immune responses and to maintain immune homeostasis. Of this subtype of regulatory lymphocytes, the most potent are Foxp3 expressing CD4+ T cells, which can be roughly divided into two main groups; natural Treg cells (nTreg), developing in the thymus, and induced or adaptive Treg cells (iTreg), developing in the periphery from naïve, conventional T cells. Both nTreg cells and iTreg cells have their own, non-redundant roles in the immune system, with nTreg cells mainly maintaining tolerance toward self-structures, and iTreg developing in response to externally delivered antigens or commensal microbes. In addition, Treg cells acquire tissue specific features and are adapted to function in the tissue they reside. This review will focus on some specific features of Treg cells in different compartments of the body.

Holistic systems biology approaches to molecular mechanisms of human helper T cell differentiation to functionally distinct subsets

Current knowledge of helper T cell differentiation largely relies on data generated from mouse studies. To develop therapeutical strategies combating human diseases, understanding the molecular mechanisms how human naïve T cells differentiate to functionally distinct T helper (Th) subsets as well as studies on human differentiated Th cell subsets is particularly valuable. Systems biology approaches provide a holistic view of the processes of T helper differentiation, enable discovery of new factors and pathways involved and generation of new hypotheses to be tested to improve our understanding of human Th cell differentiation and immune-mediated diseases. Here, we summarize studies where high-throughput systems biology approaches have been exploited to human primary T cells. These studies reveal new factors and signalling pathways influencing T cell differentiation towards distinct subsets, important for immune regulation. Such information provides new insights into T cell biology and into targeting immune system for therapeutic interventions.

Genome-wide association study identifies GIMAP as a novel susceptibility locus for Behcet's disease

OBJECTIVES

To identify non-major histocompatibility complex susceptible genes that might contribute to Behçet's disease (BD).

METHODS

We performed a genome-wide association study using DNA samples from a Korean population consisting of 379 BD patients and 800 controls. A replication study was performed in a Japanese population (363 BD patients and 272 controls). To evaluate the functional implication of the target single nucleotide polymorphisms (SNP), gene expression levels in peripheral T cells, allele-specific modulation of promoter activity and biological effect of mRNA knockdown were investigated.

RESULTS

We found a novel association of BD to the GIMAP locus, mapped to chromosome 7q36.1 (rs1608157, p=6.01×10(-8) in a minor allele dominant model; rs11769828, allele based p=1.60×10(-6)). A fine mapping study identified an association with four additional SNP: rs1522596 (OR=1.45, p=7.70×10(-6)) in GIMAP4; rs10266069 (OR=1.32, p=2.67×10(-4)) and rs10256482 (OR=1.27, p=5.27×10(-4)) in GIMAP2; and rs2286900 (OR=1.61, p=3.53×10(-5)) in GIMAP1 areas. Replication study using DNA samples from the Japanese population validated the significant association between BD and the GIMAP locus. The GIMAP4 promoter construct plasmid with the minor allele of rs1608157 displayed significantly lower activity than one with the major allele. Moreover, CD4 T cells from BD patients showed a lower level of GIMAP4 mRNA, and GIMAP4 knockdown was protective against Fas-mediated apoptosis.

CONCLUSIONS

These results suggest that a GIMAP cluster is a novel susceptibility locus for BD, which is involved in T-cell survival, and T-cell aberration can contribute to the development of BD.

Galectin-9 functionally impairs natural killer cells in humans and mice

Galectin-9 is a pleiotropic immune modulator affecting numerous cell types of innate and adaptive immunity. Patients with chronic infection with either hepatitis C virus (HCV) or HIV have elevated circulating levels. Limited data exist on the regulation of natural killer (NK) cell function through interaction with galectin-9. We found that galectin-9 ligation downregulates multiple immune-activating genes, including eight involved in the NK cell-mediated cytotoxicity pathway, impairs lymphokine-activated killing, and decreases the proportion of gamma interferon (IFN-γ)-producing NK cells that had been stimulated with interleukin-12 (IL-12)/IL-15. We demonstrate that the transcriptional and functional changes induced by galectin-9 are independent of Tim-3. Consistent with these results for humans, we find that the genetic absence of galectin-9 in mice is associated with greater IFN-γ production by NK cells and enhanced degranulation. We also show that in the setting of a short-term (4-day) murine cytomegalovirus infection, terminally differentiated NKs accumulate in the livers of galectin-9 knockout mice, and that hepatic NKs spontaneously produce significantly more IFN-γ in this setting. Taken together, our results indicate that galectin-9 engagement impairs the function of NK cells, including cytotoxicity and cytokine production.

Early response of gene expression in the distal intestine of Atlantic salmon (Salmo salar L.) during the development of soybean meal induced enteritis

Plant products in general and soybeans in particular can challenge the function and health of the intestinal tract. Salmonids develop an intestinal inflammation when fed diets containing soybean meal (SBM) and certain other legume ingredients. In the present study a 44K oligonucleotide salmonid microarray, qPCR and histology were used to investigate early response mechanisms in the distal intestine of Atlantic salmon (Salmo salar L.) during the first week of oral exposure to a diet containing 20% extracted SBM. The distal intestine transcriptome was profiled on days 1, 2, 3, 5 and 7 and compared to a control group fed fishmeal as the sole protein source. Histological evaluation of the distal intestine revealed the first signs of inflammation on day 5. The most prominent gene expression changes were seen on days 3 and 5. Up-regulation in immune-related genes was observed during the first 5 days, including GTPase IMAP family members, NF-kB-related genes and regulators of T cell and B cell function. Many functional genes involved in lipid metabolism, proteolysis, transport, metabolism and detoxification were initially up-regulated on days 1-3, possibly as an attempt by the tissue to compensate for the initiating immune response. Cell repair and extracellular matrix remodeling genes were up-regulated (heparanase, collagenase) on days 3 and 5. Down regulation of genes related to endocytosis, exocytosis, detoxification, transporters and metabolic processes from day 5 indicated initiation of dysfunction of digestive and metabolic functions that may occur as a result of inflammation or as a response to the introduction of soybean meal in the diet. This is the first study conducting transcriptomic profiling to characterize early responses during the development of SBMIE. Switching Atlantic salmon from a fishmeal to a 20% SBM diet resulted in rapid changes to the intestinal transcriptome, indicating an immune reaction with subsequent impaired epithelial barrier function and other vital intestinal functions.

Gene-expression signatures differ between different clinical forms of familial hemophagocytic lymphohistiocytosis

We performed gene-expression profiling of PBMCs obtained from patients with familial hemophagocytic lymphohistiocytosis (FHL) to screen for biologic correlates with the genetic and/or clinical forms of this disease. Unsupervised hierarchical clustering of 167 differentially expressed probe sets, representing 143 genes, identified 3 groups of patients corresponding to the genetic forms and clinical presentations of the disease. Two clusters of up- and down-regulated genes separated patients with perforin-deficient FHL from those with unidentified genetic cause(s) of the disease. The clusterscomprised genes involved in defense/immune responses, apoptosis, zinc homeostasis, and systemic inflammation. Unsupervised hierarchical clustering partitioned patients with unknown genetic cause(s) of FHL into 2 well-distinguished subgroups. Patterns of up- and down-regulated genes separated patients with “late-onset” and “relapsing” forms of FHL from patients with an “early onset and rapidly evolving” form of the disease. A cluster was identified in patients with “late onset and relapsing” form of FHL related to B- and T-cell differentiation/survival, T-cell activation, and vesicular transport. The resulting data suggest that unique gene-expression signatures can distinguish between genetic and clinical subtypes of FHL. These differentially expressed genes may represent biomarkers that can be used as predictors of disease progression.

Increased immune gene expression and immune cell infiltration in high-grade astrocytoma distinguish long-term from short-term survivors

Survival in the majority of high-grade astrocytoma (HGA) patients is very poor, with only a rare population of long-term survivors. A better understanding of the biological factors associated with long-term survival in HGA would aid development of more effective therapy and survival prediction. Factors associated with long-term survival have not been extensively studied using unbiased genome-wide expression analyses. In the current study, gene expression microarray profiles of HGA from long-term survivors were interrogated for discovery of survival-associated biological factors. Ontology analyses revealed that increased expression of immune function-related genes was the predominant biological factor that positively correlated with longer survival. A notable T cell signature was present within this prognostic immune gene set. Using immune cell-specific gene classifiers, both T cell-associated and myeloid linage-associated genes were shown to be enriched in HGA from long-term versus short-term survivors. Association of immune function and cell-specific genes with survival was confirmed independently in a larger publicly available glioblastoma gene expression microarray data set. Histology was used to validate the results of microarray analyses in a larger cohort of long-term survivors of HGA. Multivariate analyses demonstrated that increased immune cell infiltration was a significant independent variable contributing to longer survival, as was Karnofsky/Lansky performance score. These data provide evidence of a prognostic anti-tumor adaptive immune response and rationale for future development of immunotherapy in HGA.

BB rat Gimap gene expression in sorted lymphoid T and B cells

AIMS

The Gimap gene family has been shown to be integral to T cell survival and development. A frameshift mutation in Gimap5, one of seven members of the Gimap family, results in lymphopenia and is a prerequisite for spontaneous type 1 diabetes (T1D) in the BioBreeding (BB) rat. While not contributing to lymphopenia, the Gimap family members proximal to Gimap5, encompassed within the Iddm39 quantitative trait locus (QTL), have been implicated in T1D. We hypothesized that expression of the Gimap family members within the Iddm39 QTL, during thymocyte development as well as in peripheral T and B cells contribute to T1D.

MAIN METHODS

Cell sorted subpopulations were analyzed by quantitative real time (qRT) PCR.

KEY FINDINGS

Gimap4 expression was reduced in DR.(lyp/lyp) rat double negative, double positive and CD8 single positive (SP) thymocytes while expression of Gimap8, Gimap6, and Gimap7 was reduced only in CD8 SP thymocytes. Interestingly, expression of the entire Gimap gene family was reduced in DR.(lyp/lyp) rat peripheral T cells compared to non-lymphopenic, non-diabetic DR.(+/+) rats. With the exception of Gimap6, the Gimap family genes were not expressed in B cells from spleen and mesenteric lymph node (MLN). Expression of Gimap9 was only detected in hematopoietic cells of non B cell lineage such as macrophage, dendritic or NK cells.

SIGNIFICANCE

These results suggest that lack of the Gimap5 protein in the DR.(lyp/lyp) congenic rat was associated with impaired expression of the entire family of Gimap genes and may regulate T cell homeostasis in the peripheral lymphoid organs.

GIMAP Proteins in T-Lymphocytes

(GIMAPs) GTPase of the immunity associated protein family are a novel protein family of putative small GTPases. GIMAPs are mainly expressed in the cells of the immune system and have been associated with immunological functions, such as thymocyte development, apoptosis of peripheral lymphocytes and T helper cell differentiation. GIMAPs have also been linked to immunological diseases, such as T cell lymphopenia, leukemia and autoimmune diseases. In this review we examine the role of GIMAP proteins in T-lymphocyte biology.

Genome-wide profiling of interleukin-4 and STAT6 transcription factor regulation of human Th2 cell programming

Dissecting the molecular mechanisms by which T helper (Th) cells differentiate to effector Th2 cells is important for understanding the pathogenesis of immune-mediated diseases, such as asthma and allergy. Because the STAT6 transcription factor is an upstream mediator required for interleukin-4 (IL-4)-induced Th2 cell differentiation, its targets include genes important for this process. Using primary human CD4(+) T cells, and by blocking STAT6 with RNAi, we identified a number of direct and indirect targets of STAT6 with ChIP sequencing. The integration of these data sets with detailed kinetics of IL-4-driven transcriptional changes showed that STAT6 was predominantly needed for the activation of transcription leading to the Th2 cell phenotype. This integrated genome-wide data on IL-4- and STAT6-mediated transcription provide a unique resource for studies on Th cell differentiation and, in particular, for designing interventions of human Th2 cell responses.

Quantitative proteomics analysis of the nuclear fraction of human CD4+ cells in the early phases of IL-4-induced Th2 differentiation

We used stable isotope labeling with 4-plex iTRAQ (isobaric tags for relative and absolute quantification) reagents and LC-MS/MS to investigate proteomic changes in the nucleus of activated human CD4⁺ cells during the early stages of Th2 cell differentiation. The effects of IL-4 stimulation upon activated naïve CD4⁺ cells were measured in the nuclear fractions from 6 and 24 h in three biological replicates, each using pooled cord blood samples derived from seven or more individuals. In these analyses, in the order of 800 proteins were detected with two or more peptides and quantified in three biological replicates. In addition to consistent differences observed with the nuclear localization/expression of established human Th2 and Th1 markers, there were changes that suggested the involvement of several proteins either only recently reported or otherwise not known in this context. These included SATB1 and among the novel changes detected and validated an IL-4-induced increase in the level of YB1. This unique data set from human cord blood CD4⁺ T cells details an extensive list of protein determinations that compares with and complements previous data determined from the Jurkat cell nucleus.

A role for the atopy-associated gene PHF11 in T-cell activation and viability

Polymorphisms within plant homeodomain finger protein 11 (PHF11) are associated with total IgE, allergic asthma and eczema. PHF11 is a transcriptional co-activator of the Th1 effector cytokine genes, interleukin-2 (IL2) and interferon-γ (IFNG), co-operating with nuclear factor kappa B (NF-κB). The involvement with NF-κB led us to test whether PHF11 might have a broader function in T-cell activation and viability. We show that PHF11 is abundant in the cytoplasm of T-cells and imported into the nucleus of activated T-cells. Consistent with its presence in the nucleus, PHF11 was recruited to the IFNG promoter and over-expression of PHF11 increased the binding of NF-κB to the IFNG promoter and IFNG gene transcription. Over-expression of PHF11 did not increase IL2 gene transcription, suggesting some specificity in promoter recognition. In contrast, small-interfering RNA knock-down of PHF11 decreased transcription of both IFNG and IL2 and led to decreased CD28 cell-surface expression and reduced NF-κB nuclear import and DNA binding. Knock-down of PHF11 also decreased cell viability and was accompanied by reduced expression of GIMAP4 and 5 genes required for T-cell differentiation, viability and homeostasis. Therefore, in addition to its earlier identified function in regulating Th1 cytokine gene expression, we now show that PHF11 has a broader function in contributing to T-cell activation and viability.

Putative GTPase GIMAP1 is critical for the development of mature B and T lymphocytes

The guanosine triphosphatases (GTPases) of the immunity-associated protein (GIMAP) family of putative GTPases has been implicated in the regulation of T-lymphocyte development and survival. A mouse conditional knockout allele was generated for the immune GTPase gene GIMAP1. Homozygous loss of this allele under the influence of the lymphoid-expressed hCD2-iCre recombinase transgene led to severe (> 85%) deficiency of mature T lymphocytes and, unexpectedly, of mature B lymphocytes. By contrast there was little effect of GIMAP1 deletion on immature lymphocytes in either B or T lineages, although in vitro studies showed a shortening of the survival time of both immature and mature CD4+ single-positive thymocytes. These findings show a vital requirement for GIMAP1 in mature lymphocyte development/survival and draw attention to the nonredundant roles of members of the GIMAP GTPase family in these processes.

Activating transcription factor 3 is a positive regulator of human IFNG gene expression

IL-12 and IL-18 are essential for Th1 differentiation, whereas the role of IFN-alpha in Th1 development is less understood. In this microarray-based study, we searched for genes that are regulated by IFN-alpha, IL-12, or the combination of IL-12 plus IL-18 during the early differentiation of human umbilical cord blood CD4(+) Th cells. Twenty-six genes were similarly regulated in response to treatment with IL-12, IFN-alpha, or the combination of IL-12 plus IL-18. These genes could therefore play a role in Th1 lineage decision. Transcription factor activating transcription factor (ATF) 3 was upregulated by these cytokines and selected for further study. Ectopic expression of ATF3 in CD4(+) T cells enhanced the production of IFN-gamma, the hallmark cytokine of Th1 cells, whereas small interfering RNA knockdown of ATF3 reduced IFN-gamma production. Furthermore, ATF3 formed an endogenous complex with JUN in CD4(+) T cells induced to Th1. Chromatin immunoprecipitation and luciferase reporter assays showed that both ATF3 and JUN are recruited to and transactivate the IFNG promoter during early Th1 differentiation. Collectively, these data indicate that ATF3 promotes human Th1 differentiation.

Differential proteomic analysis of STAT6 knockout mice reveals new regulatory function in liver lipid homeostasis

Increased inflammatory signaling is a key feature of metabolic disorders. In this context, the role of increased pro-inflammatory signals has been extensively studied. By contrast, no efforts have been dedicated to study the contrasting scenario: the attenuation of anti-inflammatory signals and their role in metabolic homeostasis. IL-4 and IL-13 are anti-inflammatory cytokines signaling through the Signal Transducer and Activator of Transcription 6 (STAT6). Our study was aimed at evaluating the lack of STAT6 signaling on liver homeostasis. To this end we analyzed the liver proteome of wild type and STAT6 knock-out mice using 2D nanoscale LC-MS/MS with iTRAQ labeling technique. The coordinated changes in proteins identified by this quantitative proteome analysis indicated disturbed lipid homeostasis and a state of hepatocellular stress. Most significantly, the expression of the liver fatty acid binding protein (FABP1) was increased in the knock-out mice. In line with the elevated FABP1 expression we found latent liver lipid accumulation in the STAT6-deficient mice which was further aggravated when mice were challenged by a high fat diet. In conclusion, our study revealed a so far uncharacterized role for STAT6 in regulating liver lipid homeostasis and demonstrates the importance of anti-inflammatory signaling in the defense against the development of liver steatosis.

Sequence variation and expression of the Gimap gene family in the BB rat

Positional cloning of lymphopenia (lyp) in the BB rat revealed a frameshift mutation in Gimap5, a member of at least seven related GTPase Immune Associated Protein genes located on rat chromosome 4q24. Our aim was to clone and sequence the cDNA of the BB diabetes prone (DP) and diabetes resistant (DR) alleles of all seven Gimap genes in the congenic DR.lyp rat line with 2 Mb of BB DP DNA introgressed onto the DR genetic background. All (100%) DR.^lyp/lyp rats are lymphopenic and develop type 1 diabetes (T1D) by 84 days of age while DR.^+/+ rats remain T1D and lyp resistant. Among the seven Gimap genes, the Gimap5 frameshift mutation, a mutant allele that produces no protein, had the greatest impact on lymphopenia in the DR.^lyp/lyp rat. Gimap4 and Gimap1 each had one amino acid substitution of unlikely significance for lymphopenia. Quantitative RT-PCR analysis showed a reduction in expression of all seven Gimap genes in DR.^lyp/lyp spleen and mesenteric lymph nodes when compared to DR.^+/+. Only four; Gimap1, Gimap4, Gimap5, and Gimap9 were reduced in thymus. Our data substantiates the Gimap5 frameshift mutation as the primary defect with only limited contributions to lymphopenia from the remaining Gimap genes.