DNA polymerase-α regulates the activation of type I interferons through cytosolic RNA:DNA synthesis.

Aberrant nucleic acids generated during viral replication are the main trigger for antiviral immunity, and mutations that disrupt nucleic acid metabolism can lead to autoinflammatory disorders. Here we investigated the etiology of X-linked reticulate pigmentary disorder (XLPDR), a primary immunodeficiency with autoinflammatory features. We discovered that XLPDR is caused by an intronic mutation that disrupts the expression of POLA1, which encodes the catalytic subunit of DNA polymerase-α. Unexpectedly, POLA1 deficiency resulted in increased production of type I interferons. This enzyme is necessary for the synthesis of RNA:DNA primers during DNA replication and, strikingly, we found that POLA1 is also required for the synthesis of cytosolic RNA:DNA, which directly modulates interferon activation. Together this work identifies POLA1 as a critical regulator of the type I interferon response.

Trex1 regulates lysosomal biogenesis and interferon-independent activation of antiviral genes.

The sensing of viral nucleic acids by the innate immune system triggers the production of type I interferons, which activates interferon-stimulated genes (ISGs) and directs a multifaceted antiviral response. ISGs can also be activated through interferon-independent pathways, although the precise mechanisms remain elusive. Here we found that the cytosolic exonuclease Trex1 regulated the activation of a subset of ISGs independently of interferon. Both Trex1(-/-) mouse cells and Trex1-mutant human cells had high expression of genes encoding antiviral molecules ('antiviral genes') and were refractory to viral infection. The interferon-independent activation of antiviral genes in Trex1(-/-) cells required the adaptor STING, the kinase TBK1 and the transcription factors IRF3 and IRF7. We also found that Trex1-deficient cells had an expanded lysosomal compartment, altered subcellular localization of the transcription factor TFEB and diminished activity of the regulator mTORC1. Together our data identify Trex1 as a regulator of lysosomal biogenesis and interferon-independent activation of antiviral genes and show that dysregulation of lysosomes can elicit innate immune responses.

Serum IgG Profiling of Toddlers Reveals a Subgroup with Elevated Seropositive Antibodies to Viruses Correlating with Increased Vaccine and Autoantigen Responses.

PURPOSE: The human antibody repertoire forms in response to infections, the microbiome, vaccinations, and environmental exposures. The specificity of such antibody responses was compared among a cohort of toddlers to identify differences between seropositive versus seronegative responses. METHODS: An assessment of the serum IgM and IgG antibody reactivities in 197 toddlers of 1- and 2-years of age was performed with a microfluidic array containing 110 distinct antigens. Longitudinal profiling was done from years 1 to 2. Seropositivity to RNA and DNA viruses; bacteria; live attenuated, inactive, and subunit vaccines; and autoantigens was compared. A stratification was developed based on quantitative variations in the IgG responses. Clinical presentations and previously known genetic risk alleles for various immune system conditions were investigated in relation to IgG responses. RESULTS: IgG reactivities stratified toddlers into low, moderate, and high responder groups. The high group (17%) had elevated IgG responses to multiple RNA and DNA viruses (e.g., respiratory syncytial virus, Epstein-Barr virus, adenovirus, Coxsackievirus) and this correlated with increased responses to live attenuated viral vaccines and certain autoantigens. This high group was more likely to be associated with gestational diabetes and an older age. Genetic analyses identified polymorphisms in the IL2RB, TNFSF4, and INS genes in two high responder individuals that were associated with their elevated cytokine levels and clinical history of eczema and asthma. CONCLUSION: Serum IgG profiling of toddlers reveals correlations between the magnitude of the antibody responses towards viruses, live attenuated vaccines, and certain autoantigens. A low responder group had much weaker responses overall, including against vaccines. The serum antibody screen also identifies individuals with IgG responses to less common infections (West Nile virus, parvovirus, tuberculosis). The characterization of the antibody responses in combination with the identification of genetic risk alleles provides an opportunity to identify children with increased risk of clinical disease.

RAD51 interconnects between DNA replication, DNA repair and immunity.

RAD51, a multifunctional protein, plays a central role in DNA replication and homologous recombination repair, and is known to be involved in cancer development. We identified a novel role for RAD51 in innate immune response signaling. Defects in RAD51 lead to the accumulation of self-DNA in the cytoplasm, triggering a STING-mediated innate immune response after replication stress and DNA damage. In the absence of RAD51, the unprotected newly replicated genome is degraded by the exonuclease activity of MRE11, and the fragmented nascent DNA accumulates in the cytosol, initiating an innate immune response. Our data suggest that in addition to playing roles in homologous recombination-mediated DNA double-strand break repair and replication fork processing, RAD51 is also implicated in the suppression of innate immunity. Thus, our study reveals a previously uncharacterized role of RAD51 in initiating immune signaling, placing it at the hub of new interconnections between DNA replication, DNA repair, and immunity.

Differential outcome of TRIF-mediated signaling in TLR4 and TLR3 induced DC maturation.

Recognition of pathogen-associated molecular patterns by Toll-like receptors (TLRs) on dendritic cells (DCs) leads to DC maturation, a process involving up-regulation of MHC and costimulatory molecules and secretion of proinflammatory cytokines. All TLRs except TLR3 achieve these outcomes by using the signaling adaptor myeloid differentiation factor 88. TLR4 and TLR3 can both use the Toll-IL-1 receptor domain-containing adaptor inducing IFN-ß (TRIF)-dependent signaling pathway leading to IFN regulatory factor 3 (IRF3) activation and induction of IFN-ß and -α4. The TRIF signaling pathway, downstream of both of these TLRs, also leads to DC maturation, and it has been proposed that the type I IFNs act in cis to induce DC maturation and subsequent effects on adaptive immunity. The present study was designed to understand the molecular mechanisms of TRIF-mediated DC maturation. We have discovered that TLR4-TRIF-induced DC maturation was independent of both IRF3 and type I IFNs. In contrast, TLR3-mediated DC maturation was completely dependent on type I IFN feedback. We found that differential activation of mitogen-activated protein kinases by the TLR4- and TLR3-TRIF axes determined the type I IFN dependency for DC maturation. In addition, we found that the adjuvanticity of LPS to induce T-cell activation is completely independent of type I IFNs. The important distinction between the TRIF-mediated signaling pathways of TLR4 and TLR3 discovered here could have a major impact in the design of future adjuvants that target this pathway.

MicroRNA-205 Maintains T Cell Development following Stress by Regulating Forkhead Box N1 and Selected Chemokines.

The thymus, an organ responsible for T cell development, is one of the more stress-sensitive tissues in the body. Stress, in the form of infections, radiation exposure, and steroids, impairs thymic epithelial cell (TEC) functions and induces the programmed cell death of immature thymocytes. MicroRNAs are small noncoding RNAs involved in tissue repair and homeostasis, with several supporting T cell development. We report that miR-205, an epithelial-specific miR, maintains thymopoiesis following inflammatory perturbations. Thus, the activation of diverse pattern recognition receptors in mice causes a more severe thymic hypoplasia and delayed T cell recovery when miR-205 is conditionally ablated in TECs. Gene expression comparisons in the TECs with/without miR-205 revealed a significant differential regulation of chemokine/chemokine receptor pathways, antigen processing components, and changes in the Wnt signaling system. This was partly a consequence of reduced expression of the transcriptional regulator of epithelial cell function, Forkhead Box N1 (Foxn1), and its two regulated targets, stem cell factor and ccl25, following stress. miR-205 mimics supplemented into miR-205-deficient fetal thymic organ cultures restored Foxn1 expression along with ccl25 and stem cell factor A number of putative targets of miR-205 were up-regulated in TECs lacking miR-205, consistent with an important role for this miR in supporting T cell development in response to stress.

T/B-cell interactions are more transient in response to weak stimuli in SLE-prone mice.

Changes in immune function during the course of systemic lupus erythematosus (SLE) are well characterized. Class-switched antinuclear antibodies are the hallmark of SLE, and T/B-cell interactions are thus critical. However, changes in immune function contributing to disease susceptibility are unknown. Here, we have analyzed primary T and B cells from a mouse model of SLE prior to the onset of disease. To allow cognate T-cell activation with low affinity, we have developed a lower potency peptide ligand for the OTII TCR. T- and B-cell couples formed less frequently and retained their polarity less efficiently preferentially in response to low-affinity stimulation in SLE-prone mice. This matched decreased recruitment of actin and Vav1 and an enhanced PKCΘ recruitment to the cellular interface in T cells. The induction of the GC B-cell marker GL7 was increased in T/B cell couples from SLE-prone mice when the T-cell numbers were limited. However, the overall gene expression changes were marginal. Taken together, the enhanced cell-couple transience may allow a more efficient sampling of a large number of T/B cell couples, preferentially in response to limiting stimuli, therefore enhancing the immune reactivity in the development of SLE.

Murine lupus susceptibility locus Sle1c2 mediates CD4+ T cell activation and maps to estrogen-related receptor γ.

Sle1c is a sublocus of the NZM2410-derived Sle1 major lupus susceptibility locus. We have shown previously that Sle1c contributes to lupus pathogenesis by conferring increased CD4(+) T cell activation and increased susceptibility to chronic graft-versus-host disease (cGVHD), which mapped to the centromeric portion of the locus. In this study, we have refined the centromeric sublocus to a 675-kb interval, termed Sle1c2. Mice from recombinant congenic strains expressing Sle1c2 exhibited increased CD4(+) T cell intrinsic activation and cGVHD susceptibility, similar to mice with the parental Sle1c. In addition, B6.Sle1c2 mice displayed a robust expansion of IFN-γ-expressing T cells. NZB complementation studies showed that Sle1c2 expression exacerbated B cell activation, autoantibody production, and renal pathology, verifying that Sle1c2 contributes to lupus pathogenesis. The Sle1c2 interval contains two genes, only one of which, Esrrg, is expressed in T cells. B6.Sle1c2 CD4(+) T cells expressed less Esrrg than B6 CD4(+) T cells, and Esrrg expression was correlated negatively with CD4(+) T cell activation. Esrrg encodes an orphan nuclear receptor that regulates oxidative metabolism and mitochondrial functions. In accordance with reduced Esrrg expression, B6.Sle1c2 CD4(+) T cells present reduced mitochondrial mass and altered mitochondrial functions as well as altered metabolic pathway utilization when compared with B6 CD4(+) T cells. Taken together, we propose Esrrg as a novel lupus susceptibility gene regulating CD4(+) T cell function through their mitochondrial metabolism.

Pre-B cell leukemia homeobox 1 is associated with lupus susceptibility in mice and humans.

Sle1a.1 is part of the Sle1 susceptibility locus, which has the strongest association with lupus nephritis in the NZM2410 mouse model. In this study, we show that Sle1a.1 results in the production of activated and autoreactive CD4(+) T cells. Additionally, Sle1a.1 expression reduces the peripheral regulatory T cell pool, as well as induces a defective response of CD4(+) T cells to the retinoic acid expansion of TGF-ß-induced regulatory T cells. At the molecular level, Sle1a.1 corresponds to an increased expression of a novel splice isoform of Pbx1, Pbx1-d. Pbx1-d overexpression is sufficient to induce an activated/inflammatory phenotype in Jurkat T cells and to decrease their apoptotic response to retinoic acid. PBX1-d is expressed more frequently in the CD4(+) T cells from lupus patients than from healthy controls, and its presence correlates with an increased central memory T cell population. These findings indicate that Pbx1 is a novel lupus susceptibility gene that regulates T cell activation and tolerance.

Signature MicroRNA expression patterns identified in humans with 22q11.2 deletion/DiGeorge syndrome.

Patients with 22q11.2 deletion syndrome have heterogeneous clinical presentations including immunodeficiency, cardiac anomalies, and hypocalcemia. The syndrome arises from hemizygous deletions of up to 3Mb on chromosome 22q11.2, a region that contains 60 genes and 4 microRNAs. MicroRNAs are important post-transcriptional regulators of gene expression, with mutations in several microRNAs causal to specific human diseases. We characterized the microRNA expression patterns in the peripheral blood of patients with 22q11.2 deletion syndrome (n=31) compared to normal controls (n=22). Eighteen microRNAs had a statistically significant differential expression (p<0.05), with miR-185 expressed at 0.4× normal levels. The 22q11.2 deletion syndrome cohort exhibited microRNA expression hyper-variability and group dysregulation. Selected microRNAs distinguished patients with cardiac anomalies, hypocalcemia, and/or low circulating T cell counts. In summary, microRNA profiling of chromosome 22q11.2 deletion syndrome/DiGeorge patients revealed a signature microRNA expression pattern distinct from normal controls with clinical relevance.

Identification of outcome-correlated cytokine clusters in chronic lymphocytic leukemia.

Individual cytokines and groups of cytokines that might represent networks in chronic lymphocytic leukemia (CLL) were analyzed and their prognostic values determined. Serum levels of 23 cytokines were measured in 84 patients and 49 age-matched controls; 17 levels were significantly elevated in patients. Unsupervised hierarchical bicluster analysis identified 3 clusters (CLs) of highly correlated but differentially expressed cytokines: CL1 (CXCL9, CXCL10, CXCL11, CCL3, CCL4, CCL19, IL-5, IL-12, and IFNγ), CL2 (TNFα, IL-6, IL-8, and GM-CSF), and CL3 (IL-1ß, IL-2, IL-4, IL-15, IL-17, and IFNα). Combination scores integrating expression of CL1/CL2 or CL1/CL3 strongly correlated (P < .005) with time-to-first-treatment and overall survival (OS), respectively. Patients with the worst course had high CL1 and low CL2 or CL3 levels. Multivariate analysis revealed that CL1/CL2 combination score and immunoglobulin heavy chain variable region mutation status were independent prognostic indicators for time-to-first-treatment, whereas CL1/CL3 combination score and immunoglobulin heavy chain variable region mutation status were independent markers for OS. Thus, we identified groups of cytokines differentially expressed in CLL that are independent prognostic indicators of aggressive disease and OS. These findings indicate the value of multicytokine analyses for prognosis and suggest therapeutic strategies in CLL aimed at reducing CL1 and increasing CL2/CL3 cytokines.

Cyclin-dependent kinase inhibitor Cdkn2c regulates B cell homeostasis and function in the NZM2410-derived murine lupus susceptibility locus Sle2c1.

Sle2c1 is an NZM2410- and NZB-derived lupus susceptibility locus that induces an expansion of the B1a cell compartment. B1a cells have a repertoire enriched for autoreactivity, and an expansion of this B cell subset occurs in several mouse models of lupus. A combination of genetic mapping and candidate gene analysis presents Cdkn2c, a gene encoding for cyclin-dependent kinase inhibitor p18(INK4c) (p18), as the top candidate gene for inducing the Slec2c1-associated expansion of B1a cells. A novel single nucleotide polymorphism in the NZB allele of the Cdkn2c promoter is associated with a significantly reduced Cdkn2c expression in the splenic B cells and peritoneal cavity B1a cells from Sle2c1-carrying mice, which leads to a defective G1 cell cycle arrest in splenic B cells and increased proliferation of peritoneal cavity B1a cells. As the cell cycle is differentially regulated in B1a and B2 cells, these results suggest that Cdkn2c plays a critical role in B1a cell self-renewal and that its impaired expression leads to an accumulation of these cells with high autoreactive potential.

Internal standard-based analysis of microarray data2--analysis of functional associations between HVE-genes.

In this work we apply the Internal Standard-based analytical approach that we described in an earlier communication and here we demonstrate experimental results on functional associations among the hypervariably-expressed genes (HVE-genes). Our working assumption was that those genetic components, which initiate the disease, involve HVE-genes for which the level of expression is undistinguishable among healthy individuals and individuals with pathology. We show that analysis of the functional associations of the HVE-genes is indeed suitable to revealing disease-specific differences. We show also that another possible exploit of HVE-genes for characterization of pathological alterations is by using multivariate classification methods. This in turn offers important clues on naturally occurring dynamic processes in the organism and is further used for dynamic discrimination of groups of compared samples. We conclude that our approach can uncover principally new collective differences that cannot be discerned by individual gene analysis.

External Qi of Yan Xin Qigong induces cell death and gene expression alterations promoting apoptosis and inhibiting proliferation, migration and glucose metabolism in small-cell lung cancer cells.

Small-cell lung cancer (SCLC) is a highly malignant carcinoma with poor long-term survival. Effective treatment remains highly demanded. In the present study, we demonstrated that External Qi of Yan Xin Qigong (YXQ-EQ) exerted potent cytotoxic effect towards SCLC cell line NCI-H82 via induction of apoptosis. Global gene expression profiling identified 39 genes whose expression was altered by YXQ-EQ in NCI-82 cells. Among them, semi-quantitative RT-PCR and real-time qPCR analyses confirmed that the gene expression levels of apoptotic proteins death-associated protein kinase 2 and cell death-inducing DFFA-like effector b were upregulated, whereas that of oncoproteins DEK and MYCL1, cell migration-promoting proteins CD24 and integrin-alpha 9, and glycolytic enzyme aldolase A were downregulated. These findings suggest that YXQ-EQ may exert anticancer effect through modulating gene expression in a way that facilitates cancer cell apoptosis while represses proliferation, metastasis, and glucose metabolism.

Defective Human SRP Induces Protein Quality Control and Triggers Stress Response.

Regulation of Aberrant Protein Production (RAPP) is a protein quality control in mammalian cells. RAPP degrades mRNAs of nascent proteins not able to associate with their natural interacting partners during synthesis at the ribosome. However, little is known about the molecular mechanism of the pathway, its substrates, or its specificity. The Signal Recognition Particle (SRP) is the first interacting partner for secretory proteins. It recognizes signal sequences of the nascent polypeptides when they are exposed from the ribosomal exit tunnel. Here, we reveal the generality of the RAPP pathway on the whole transcriptome level through depletion of human SRP54, an SRP subunit. This depletion triggers RAPP and leads to decreased expression of the mRNAs encoding a number of secretory and membrane proteins. The loss of SRP54 also leads to the dramatic upregulation of a specific network of HSP70/40/90 chaperones (HSPA1A, DNAJB1, HSP90AA1, and others), increased ribosome associated ubiquitination, and change in expression of RPS27 and RPS27L suggesting ribosome rearrangement. These results demonstrate the complex nature of defects in protein trafficking, mRNA and protein quality control, and provide better understanding of their mechanisms at the ribosome.

Mesenchymal cell replacement corrects thymic hypoplasia in murine models of 22q11.2 deletion syndrome.

22q11.2 deletion syndrome (22q11.2DS) is the most common human chromosomal microdeletion, causing developmentally linked congenital malformations, thymic hypoplasia, hypoparathyroidism, and/or cardiac defects. Thymic hypoplasia leads to T cell lymphopenia, which most often results in mild SCID. Despite decades of research, the molecular underpinnings leading to thymic hypoplasia in 22q11.2DS remain unknown. Comparison of embryonic thymuses from mouse models of 22q11.2DS (Tbx1neo2/neo2) revealed proportions of mesenchymal, epithelial, and hematopoietic cell types similar to those of control thymuses. Yet, the small thymuses were growth restricted in fetal organ cultures. Replacement of Tbx1neo2/neo2 thymic mesenchymal cells with normal ones restored tissue growth. Comparative single-cell RNA-Seq of embryonic thymuses uncovered 17 distinct cell subsets, with transcriptome differences predominant in the 5 mesenchymal subsets from the Tbx1neo2/neo2 cell line. The transcripts affected included those for extracellular matrix proteins, consistent with the increased collagen deposition we observed in the small thymuses. Attenuating collagen cross-links with minoxidil restored thymic tissue expansion for hypoplastic lobes. In colony-forming assays, the Tbx1neo2/neo2-derived mesenchymal cells had reduced expansion potential, in contrast to the normal growth of thymic epithelial cells. These findings suggest that mesenchymal cells were causal to the small embryonic thymuses in the 22q11.2DS mouse models, which was correctable by substitution with normal mesenchyme.

Metabolites enhance innate resistance to human Mycobacterium tuberculosis infection.

To determine the mechanisms that mediate resistance to Mycobacterium tuberculosis (M. tuberculosis) infection in household contacts (HHCs) of patients with tuberculosis (TB), we followed 452 latent TB infection-negative (LTBI-) HHCs for 2 years. Those who remained LTBI- throughout the study were identified as nonconverters. At baseline, nonconverters had a higher percentage of CD14+ and CD3-CD56+CD27+CCR7+ memory-like natural killer (NK) cells. Using a whole-transcriptome and metabolomic approach, we identified deoxycorticosterone acetate as a metabolite with elevated concentrations in the plasma of nonconverters, and further studies showed that this metabolite enhanced glycolytic ATP flux in macrophages and restricted M. tuberculosis growth by enhancing antimicrobial peptide production through the expression of the surface receptor sialic acid binding Ig-like lectin-14. Another metabolite, 4-hydroxypyridine, from the plasma of nonconverters significantly enhanced the expansion of memory-like NK cells. Our findings demonstrate that increased levels of specific metabolites can regulate innate resistance against M. tuberculosis infection in HHCs of patients with TB who never develop LTBI or active TB.

Intraclonal complexity in chronic lymphocytic leukemia: fractions enriched in recently born/divided and older/quiescent cells.

The failure of chemotherapeutic regimens to eradicate cancers often results from the outgrowth of minor subclones with more dangerous genomic abnormalities or with self-renewing capacity. To explore such intratumor complexities in B-cell chronic lymphocytic leukemia (CLL), we measured B-cell kinetics in vivo by quantifying deuterium ((2)H)-labeled cells as an indicator of a cell that had divided. Separating CLL clones on the basis of reciprocal densities of chemokine (C-X-C motif) receptor 4 (CXCR4) and cluster designation 5 (CD5) revealed that the CXCR4(dim)CD5(bright) (proliferative) fraction contained more (2)H-labeled DNA and hence divided cells than the CXCR4(bright)CD5(dim) (resting) fraction. This enrichment was confirmed by the relative expression of two cell cycle-associated molecules in the same fractions, Ki-67 and minichromosome maintenance protein 6 (MCM6). Comparisons of global gene expression between the CXCR4(dim)CD5(bright) and CXCR4(bright)CD5(dim) fractions indicated higher levels of pro-proliferation and antiapoptotic genes and genes involved in oxidative injury in the proliferative fraction. An extended immunophenotype was also defined, providing a wider range of surface molecules characteristic of each fraction. These intraclonal analyses suggest a model of CLL cell biology in which the leukemic clone contains a spectrum of cells from the proliferative fraction, enriched in recently divided robust cells that are lymphoid tissue emigrants, to the resting fraction enriched in older, less vital cells that need to immigrate to lymphoid tissue or die. The model also suggests several targets preferentially expressed in the two populations amenable for therapeutic attack. Finally, the study lays the groundwork for future analyses that might provide a more robust understanding of the development and clonal evolution of this currently incurable disease.

FOXP3 inhibits activation-induced NFAT2 expression in T cells thereby limiting effector cytokine expression.

The forkhead DNA-binding protein FOXP3 is critical for the development and suppressive function of CD4(+)CD25(+) regulatory T cells (T(REG)), which play a key role in maintaining self-tolerance. Functionally, FOXP3 is capable of repressing transcription of cytokine genes regulated by NFAT. Various mechanisms have been proposed by which FOXP3 mediates these effects. Using novel cell lines that inducibly express either wild-type or mutant FOXP3, we have identified NFAT2 as an early target of FOXP3-mediated transcriptional repression. NFAT2 is typically expressed at low levels in resting T cells, but is up-regulated by NFAT1 upon cellular activation. We demonstrate that transcription from the NFAT2 promoter is significantly suppressed by FOXP3, and NFAT2 protein expression is markedly diminished in activated CD4(+)CD25(+)FOXP3(+) T(REG) compared with CD4(+)CD25(-)FOXP3(-) T cells. Chromatin immunoprecipitation experiments indicate that FOXP3 competes with NFAT1 for binding to the endogenous NFAT2 promoter. This antagonism of NFAT2 activity by FOXP3 is important for the anergic phenotype of T(REG), as ectopic expression of NFAT2 from a retroviral LTR partially restores expression of IL-2 in FOXP3(+) T(REG). These data suggest that FOXP3 functions not only to suppress the first wave of NFAT-mediated transcriptional responses, but may also affect sustained NFAT-mediated inflammatory gene expression through suppression of inducible NFAT2 transcription.