To explore the mechanisms controlling erythroid differentiation and development, we analyzed the genome-wide transcription dynamics occurring during the differentiation of human embryonic stem cells (HESCs) into the erythroid lineage and development of embryonic to adult erythropoiesis using high throughput sequencing technology. HESCs and erythroid cells at three developmental stages: ESER (embryonic), FLER (fetal), and PBER (adult) were analyzed. Our findings revealed that the number of expressed genes decreased during differentiation, whereas the total expression intensity increased. At each of the three transitions (HESCs–ESERs, ESERs–FLERs, and FLERs–PBERs), many differentially expressed genes were observed, which were involved in maintaining pluripotency, early erythroid specification, rapid cell growth, and cell–cell adhesion and interaction. We also discovered dynamic networks and their central nodes in each transition. Our study provides a fundamental basis for further investigation of erythroid differentiation and development, and has implications in using ESERs for transfusion product in clinical settings.
High-throughput RNA sequencing; Erythropoiesis; Cell differentiation; Development; Gene regulatory networks
The promyelocytic zinc finger transcription factor (PLZF) is required for the development of activated phenotypes in NKT and other innate T lymphocytes. Although strong TCR stimulation has been implicated in the induction of PLZF, the factors regulating PLZF expression are incompletely understood. We show here that costimulation of pre-selection double positive thymocytes through the Signaling lymphocyte activation molecule (SLAM) family receptor Ly108 markedly enhanced PLZF expression compared to that induced by T cell receptor (TCR) stimulation alone. Costimulation with Ly108 increased expression of Egr-2 and binding of Egr-2 to the promoter of Zbtb16, which encodes PLZF, and resulted in PLZF levels similar to those seen in NKT cells. In contrast, costimulation with αCD28 failed to enhance Egr-2 binding and Zbtb16 expression. Moreover, mice lacking Ly108 showed decreased numbers of PLZF expressing CD4+ T cells. Together, these results support a potential role for Ly108 in the induction of PLZF.
The increased risk of thrombosis in systemic lupus erythematosus (SLE) may be partially explained by interrelated genetic pathways for thrombosis and SLE. In a case-control analysis, we investigated whether 33 established and novel single nucleotide polymorphisms (SNP) in 20 genes involved in hemostasis pathways that have been associated with deep venous thrombosis in the general population were risk factors for SLE development among Asians.
Patients in the discovery cohort were enrolled in one of two North American SLE cohorts. Patients in the replication cohort were enrolled in one of four Asian or two North American cohorts. SLE cases met American College of Rheumatology classification criteria. We first genotyped 263 Asian SLE and 357 healthy Asian control individuals for 33 SNPs using Luminex multiplex technology in the discovery phase, and then used Taqman and Immunochip assays to examine 5 SNPs in up to an additional 1496 cases and 993 controls in the Replication phase. SLE patients were compared to healthy controls for association with minor alleles in allelic models. Principal components analysis was used to control for intra-Asian ancestry in an analysis of the replication cohort.
Two genetic variants in the gene VKORC1, rs9934438 and rs9923231, were highly significant in both the discovery and replication cohorts: OR(disc) = 2.45 (p=2×10−9), OR(rep) = 1.53 (p=5×10−6) and OR(disc) = 2.40 (p=6×10−9), OR(rep) = 1.53 (p=5×10−6), respectively. These associations were significant in the replication cohort after adjustment for intra-Asian ancestry: rs9934438 OR(adj) = 1.34 (p=0.0029) and rs9923231 OR(adj) = 1.34 (p=0.0032).
Genetic variants in VKORC1, involved in vitamin K reduction and associated with DVT, are associated with SLE development in Asians. These results suggest intersecting genetic pathways for the development of SLE and thrombosis.
systemic lupus erythematosus; single nucleotide polymorphisms; genetic risk factors
Systemic Lupus Erythematosus (SLE) is a chronic systemic autoimmune disease characterized by the production of anti-nuclear autoantibodies (ANA). ANA development is recognized as one of the initial stages of disease which often results in systemic inflammation, kidney disease and death. The etiology is complex, but it is clear that innate pathways may play an important role in disease progression. Recent data has highlighted an important role for the TLR family, particularly TLR7 in both human disease and murine models. In the studies presented here, we have presented a low copy conditional TLR7 transgenic (Tg7) mouse strain which does not develop spontaneous autoimmunity. When we combine Tg7 with the Sle1 lupus susceptibility locus, the mice develop severe disease. Using the CD19Cre-recombinase system, we normalized expression of TLR7 solely within the B cells. Using this method we demonstrated that overexpression of TLR7 within the B cell compartment reduces the marginal zone B cell compartment and increases B and T cell activation but not T follicular helper cell development. Moreover, this enhanced B-cell TLR7 expression permits the specific development of antibodies to RNA/protein complexes and exacerbates SLE disease.
Analysis of the ImmunoChip single nucleotide polymorphism (SNP) array in 2816 individuals, comprising the most common subtypes (oligoarticular and RF negative polyarticular) of juvenile idiopathic arthritis (JIA) and 13056 controls strengthens the evidence for association to three known JIA-risk loci (HLA, PTPN22 and PTPN2) and has identified fourteen risk loci reaching genome-wide significance (p < 5 × 10-8) for the first time. Eleven additional novel regions showed suggestive evidence for association with JIA (p < 1 × 10-6). Dense-mapping of loci along with bioinformatic analysis has refined the association to one gene for eight regions, highlighting crucial pathways, including the IL-2 pathway, in JIA disease pathogenesis. The entire ImmunoChip loci, HLA region and the top 27 loci (p < 1 × 10-6) explain an estimated 18%, 13% and 6% risk of JIA, respectively. Analysis of the ImmunoChip dataset, the largest cohort of JIA cases investigated to date, provides new insight in understanding the genetic basis for this childhood autoimmune disease.
Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by autoantibody production and altered type I interferon expression. Genetic surveys and genome-wide association studies have identified more than 30 SLE susceptibility genes. One of these genes, TNIP1, encodes the ABIN1 protein. ABIN1 functions in the immune system by restricting the NF-κB signaling. In order to better understand the genetic factors that influence association with SLE in genes that regulate the NF-κB pathway, we analyzed a dense set of genetic markers spanning TNIP1 and TAX1BP1, as well as the TNIP1 homolog, TNIP2, in case-control sets of diverse ethnic origins.
We fine-mapped TNIP1, TNIP2, and TAX1BP1 in a total of 8372 SLE cases and 7492 healthy controls from European-ancestry, African-American, Hispanic, East Asian, and African-American Gullah populations. Levels of TNIP1 mRNA and ABIN1 protein were analyzed using quantitative RT-PCR and Western blotting, respectively, in EBV-transformed human B cell lines.
We found significant associations between genetic variants within TNIP1 and SLE but not in TNIP2 or TAX1BP1. After resequencing and imputation, we identified two independent risk haplotypes within TNIP1 in individuals of European-ancestry that were also present in African-American and Hispanic populations. These risk haplotypes produced lower levels of TNIP1 mRNA and ABIN1 protein suggesting they harbor hypomorphic functional variants that influence susceptibility to SLE by restricting ABIN1 expression.
Our results confirmed the association signals between SLE and TNIP1 variants in multiple populations and provide new insight into the mechanism by which TNIP1 variants may contribute to SLE pathogenesis.
Among various surface molecules screened, CXCR4 was significantly up-regulated on monocytes, neutrophils, B-cell subsets, and plasma cells in multiple murine models of lupus with active nephritis, including B6.Sle1Yaa, BXSB, and MRL.lpr. TLR-mediated signaling and inflammatory cytokines accounted in part for this increase. Increased CXCR4 expression was associated with functional consequences, including increased migration and enhanced B-cell survival. Simultaneously, the ligand for CXCR4, CXCL12, was significantly upregulated in the nephritic kidneys. Treatment with a peptide antagonist of CXCR4 prolonged survival and reduced serum autoantibodies, splenomegaly, intra-renal leukocyte trafficking and end organ disease in a murine model of lupus. These findings underscore the pathogenic role of CXCR4/CXCL12 in lymphoproliferative lupus and lupus nephritis and highlight this axis as a promising therapeutic target in this disease.
Systemic lupus erythematosus (SLE) is a common systemic autoimmune disease with complex etiology but strong clustering in families (λS = ~30). We performed a genome-wide association scan using 317,501 SNPs in 720 women of European ancestry with SLE and in 2,337 controls, and we genotyped consistently associated SNPs in two additional independent sample sets totaling 1,846 affected women and 1,825 controls. Aside from the expected strong association between SLE and the HLA region on chromosome 6p21 and the previously confirmed non-HLA locus IRF5 on chromosome 7q32, we found evidence of association with replication (1.1 × 10−7 < Poverall < 1.6 × 10−23; odds ratio 0.82–1.62)in four regions: 16p11.2 (ITGAM), 11p15.5 (KIAA1542), 3p14.3 (PXK) and 1q25.1 (rs10798269). We also found evidence for association (P < 1 × 10−5) at FCGR2A, PTPN22 and STAT4, regions previously associated with SLE and other autoimmune diseases, as well as at ≥9 other loci (P < 2 × 10−7). Our results show that numerous genes, some with known immune-related functions, predispose to SLE.
Innate immune sensing of viral nucleic acids triggers type I interferon (IFN) production, which activates interferon-stimulated genes (ISGs) and directs a multifaceted antiviral response. ISGs can also be activated through IFN-independent pathways, although the precise mechanisms remain elusive. Here we found that the cytosolic exonuclease Trex1 regulates the activation of a subset of ISGs independently of IFN. Both Trex1−/− mouse and TREX1-mutant human cells express high levels of antiviral genes and are refractory to viral infections. The IFN-independent activation of antiviral genes in Trex1−/− cells requires STING, TBK1 and IRF3 and IRF7. We also found that Trex1-deficient cells display expanded lysosomal compartment, altered subcellular localization of the transcription factor EB (TFEB), and reduced mTORC1 activity. Together, our data identify Trex1 as a regulator of lysosomal biogenesis and IFN-independent activation of antiviral genes, and shows dysregulation of lysosomes can elicit innate immune responses.
Systemic lupus erythematosus (SLE) is a chronic autoimmune disease that is characterized by defective immune tolerance combined with immune cell hyperactivity resulting in the production of pathogenic autoantibodies. Previous gene expression studies employing whole blood or peripheral blood mononuclear cells (PBMC) have demonstrated that a majority of patients with active disease have increased expression of type I interferon (IFN) inducible transcripts known as the IFN signature. The goal of the current study was to assess the gene expression profiles of isolated leukocyte subsets obtained from SLE patients. Subsets including CD19+ B lymphocytes, CD3+CD4+ T lymphocytes and CD33+ myeloid cells were simultaneously sorted from PBMC. The SLE transcriptomes were assessed for differentially expressed genes as compared to healthy controls. SLE CD33+ myeloid cells exhibited the greatest number of differentially expressed genes at 208 transcripts, SLE B cells expressed 174 transcripts and SLE CD3+CD4+ T cells expressed 92 transcripts. Only 4.4% (21) of the 474 total transcripts, many associated with the IFN signature, were shared by all three subsets. Transcriptional profiles translated into increased protein expression for CD38, CD63, CD107a and CD169. Moreover, these studies demonstrated that both SLE lymphoid and myeloid subsets expressed elevated transcripts for cytosolic RNA and DNA sensors and downstream effectors mediating IFN and cytokine production. Prolonged upregulation of nucleic acid sensing pathways could modulate immune effector functions and initiate or contribute to the systemic inflammation observed in SLE.
The emergence and rapid spreading of multidrug-resistant Acinetobacter baumannii strains has become a major health threat worldwide. To better understand the genetic recombination related with the acquisition of drug-resistant elements during bacterial infection, we performed complete genome analysis on three newly isolated multidrug-resistant A. baumannii strains from Beijing using next-generation sequencing technology.
Whole genome comparison revealed that all 3 strains share some common drug resistant elements including carbapenem-resistant blaOXA-23 and tetracycline (tet) resistance islands, but the genome structures are diversified among strains. Various genomic islands intersperse on the genome with transposons and insertions, reflecting the recombination flexibility during the acquisition of the resistant elements. The blood-isolated BJAB07104 and ascites-isolated BJAB0868 exhibit high similarity on their genome structure with most of the global clone II strains, suggesting these two strains belong to the dominant outbreak strains prevalent worldwide. A large resistance island (RI) of about 121-kb, carrying a cluster of resistance-related genes, was inserted into the ATPase gene on BJAB07104 and BJAB0868 genomes. A 78-kb insertion element carrying tra-locus and blaOXA-23 island, can be either inserted into one of the tniB gene in the 121-kb RI on the chromosome, or transformed to conjugative plasmid in the two BJAB strains. The third strains of this study, BJAB0715, which was isolated from spinal fluid, exhibit much more divergence compared with above two strains. It harbors multiple drug-resistance elements including a truncated AbaR-22-like RI on its genome. One of the unique features of this strain is that it carries both blaOXA-23 and blaOXA-58 genes on its genome. Besides, an Acinetobacter lwoffii adeABC efflux element was found inserted into the ATPase position in BJAB0715.
Our comparative analysis on currently completed Acinetobacter baumannii genomes revealed extensive and dynamic genome organizations, which may facilitate the bacteria to acquire drug-resistance elements into their genomes.
The effect of the cellular reprogramming process per se on mutation load remains unclear. To address this issue, we performed whole exome sequencing analysis of induced pluripotent stem cells (iPSCs) reprogrammed from human cord blood (CB) CD34+ cells. Cells from a single donor and improved lentiviral vectors for high-efficiency (2–14%) reprogramming were used to examine the effects of three different combinations of reprogramming factors: OCT4 and SOX2 (OS), OS and ZSCAN4 (OSZ), OS and MYC and KLF4 (OSMK). Five clones from each group were subject to whole exome sequencing analysis. We identified 14, 11, and 9 single nucleotide variations (SNVs), in exomes, including untranslated regions (UTR), in the five clones of OSMK, OS, and OSZ iPSC lines. Only 8, 7, and 4 of these, respectively, were protein-coding mutations. An average of 1.3 coding mutations per CB iPSC line is remarkably lower than previous studies using fibroblasts and low-efficiency reprogramming approaches. These data demonstrate that point nucleotide mutations during cord blood reprogramming are negligible and that the inclusion of genome stabilizers like ZSCAN4 during reprogramming may further decrease reprogramming-associated mutations. Our findings provide evidence that CB is a superior source of cells for iPSC banking.
Systemic lupus erythematosus (SLE) is an autoimmune disease with diverse clinical manifestations characterized by the development of pathogenic autoantibodies manifesting in inflammation of target organs such as the kidneys, skin and joints. Genome-wide association studies have identified genetic variants in the UBE2L3 region that are associated with SLE in subjects of European and Asian ancestry. UBE2L3 encodes an ubiquitin-conjugating enzyme, UBCH7, involved in cell proliferation and immune function. In this study, we sought to further characterize the genetic association in the region of UBE2L3 and use molecular methods to determine the functional effect of the risk haplotype. We identified significant associations between variants in the region of UBE2L3 and SLE in individuals of European and Asian ancestry that exceeded a Bonferroni corrected threshold (P < 1 × 10−4). A single risk haplotype was observed in all associated populations. Individuals harboring the risk haplotype display a significant increase in both UBE2L3 mRNA expression (P = 0.0004) and UBCH7 protein expression (P = 0.0068). The results suggest that variants carried on the SLE associated UBE2L3 risk haplotype influence autoimmunity by modulating UBCH7 expression.
Systemic Lupus Erythematosus; UBE2L3; Multi Ethnic Association Study; UBCH7 Expression
Homozygous C1q deficiency is an extremely rare condition and strongly associated with systemic lupus erythematosus. To assess and characterize C1q deficiency in an African-American lupus pedigree, C1q genomic region was evaluated in the lupus cases and family members.
Genomic DNA from patient was obtained and C1q A, B and C gene cluster was sequenced using next generation sequencing method. The identified mutation was further confirmed by direct Sanger sequencing method in the patient and all blood relatives. C1q levels in serum were measured using sandwich ELISA method.
In an African-American patient with lupus and C1q deficiency, we identified and confirmed a novel homozygote start codon mutation in C1qA gene that changes amino acid Methionine to Arginine at position 1. The Met1Arg mutation prevents protein translation (Met1Arg). Mutation analyses of the patient’s family members also revealed the Met1Arg homozygote mutation in her deceased brother who also had lupus with absence of total complement activity consistent with a recessive pattern of inheritance.
The identification of new mutation in C1qA gene that disrupts the start codon (ATG to AGG (Met1Arg)), has not been reported previously and it expands the knowledge and importance of the C1q gene in the pathogenesis of lupus especially in high risk African-American population.
Sle1 and Sle3 are 2 loci that confer susceptibility to lupus nephritis in the NZM2410 strain of mice. Our previous work has shown that B6.NZMc1 mice, congenic for Sle1, exhibit loss of tolerance to chromatin but do not develop any pathogenic autoantibodies or disease. B6.NZMc7 mice, congenic for Sle3, exhibit low-grade polyclonal B- and T-cell activation, elevated CD4/CD8 ratios, and mildly penetrant glomerulonephritis. In contrast to these monocongenics, the present study reveals that B6.NZMc1|c7 mice, bicongenic for Sle1 and Sle3, exhibit splenomegaly, significantly expanded populations of activated B and CD4+ T cells, and a robust, variegated IgG autoantibody response targeting multiple components of chromatin (including double-stranded DNA), intact glomeruli, and basement membrane matrix antigens. As one might predict, these mice, particularly the females, exhibit highly penetrant glomerulonephritis.
These findings lend strong support to a two-step epistatic model for the formation of pathogenic, nephrophilic autoantibodies in lupus. Whereas loci such as Sle1 may serve to breach tolerance to chromatin, full-blown pathogenic maturation of the autoantibody response appears to require additional input from other loci (such as Sle3) and gender-based factors.
J. Clin. Invest. 103:1685–1695 (1999).
The mammalian intestine is home to ~100 trillion bacteria that perform important metabolic functions for their hosts. The proximity of vast numbers of bacteria to host intestinal tissues raises the question of how symbiotic host-bacterial relationships are maintained without eliciting potentially harmful immune responses. Here we show that RegIIIγ, a secreted antibacterial lectin, was essential for maintaining a ~50 μm zone that physically separates the microbiota from the small intestinal epithelial surface. Loss of host-bacterial segregation in RegIIIγ−/− mice was coupled to increased bacterial colonization of the intestinal epithelial surface and enhanced activation of intestinal adaptive immune responses by the microbiota. Together, our findings reveal that RegIIIγ is a fundamental immune mechanism that promotes host-bacterial mutualism by regulating the spatial relationships between microbiota and host.
Carbon monoxide (CO) is a vasoactive molecule that is generated by vascular cells as a byproduct of heme catabolism and it plays an important physiological role in circulation system. In order to investigate whether exogenous CO can mediate the growth and proliferation of vascular cells, in this study, we used 250 parts per million (ppm) of CO to treat human umbilical artery smooth muscle cell (hUASMC) and human umbilical vein endothelial cell (HuVEC) and further evaluated the growth and apoptosis status of SMC and HuVEC. After SMC and HuVEC were exposed to CO for 7-day, the growth of SMC and HuVEC was significantly inhibited by CO in vitro on day 5 of CO exposure. And CO blocked cell cycle progress of SMC and HuVEC, more SMC and HuVEC stagnated at G0/G1 phase by flow cytometric analysis. Moreover, CO treatment inhibited SMC and HuVEC apoptosis caused by hydrogen peroxide through decreasing caspase 3 and 9 activities. To confirm the molecular mechanism of CO effect on SMC and HuVEC growth, we compared the gene expression profile in SMC and CO-treated SMC, HuVEC and CO-treated HuVEC. By microarray analysis, we found the expression level of some genes which are related to cell cycle regulation, cell growth and proliferation, and apoptosis were changed during CO exposure. We further identified that the down-regulated CDK2 contributed to arresting cell growth and the down-regulated Caspase 3 (CASP3) and Caspase 9 (CASP9) were associated with the inhibition of cell apoptosis. Therefore, CO exerts a certain growth arrest on SMC and HuVEC by inhibiting cell cycle transition from G0/G1 phase to S phase and has regulatory effect on cell apoptosis by regulating the expression of apoptosis-associated genes.
CO; smooth muscle cell; human umbilical vein endothelial cell; cell proliferation; apoptosis.
CD1d-restricted NKT cells comprise an innate-like T cell subset that hasbeen demonstrated to play a role in amplifying the response of innate immune leukocytesto TLR ligands. The Slam locus contains genes that have been implicated in both innate and adaptive immune responses. Here, we demonstrate that divergent Slam locus haplotypesmodulate the response of macrophages to TLR ligands such as LPS through their control of NKT cell number and function. In response to LPS challenge in vivo, macrophage TNF production in Slam haplotype-2-associated 129S1/SvImJ and 129X1/SvJ mice was significantly impaired in comparison to macrophage TNF production in Slam haplotype -1-positive C57BL/6J mice. Although no cell-intrinsic differences in macrophage responses to LPS were observed between strains, 129 mice were found to be deficient in liver NKT cell number, in NKT cell cytokine production in response to the CD1d ligand α-galactosylceramide, and in NKT cell IFN-γ production after LPS challenge in vivo. Using B6.129 c1congenic mice and adoptive transfer, we found that divergent Slam haplotypes controlled both the response to LPS in vivo as well as the diminished NKT cell number and function, and that these phenotypes were associated with differential expression of SLAM family receptors on NKT cells. These data suggest that the polymorphisms that distinguish two Slam haplotypes significantly modulate the innate immune response in vivothrough their effect on NKT cell s.
The finding of antinuclear antibody (ANA) positivity in a healthy individual is usually of unknown significance and in most cases is benign. However, a subset of such individuals is at risk for development of autoimmune disease. We examined demographic and immunological features that are associated with ANA positivity in clinically healthy persons to develop insights into when this marker carries risk of progression to lupus.
Biological samples from healthy individuals and patients with systemic lupus erythematosus (SLE) were obtained from the Dallas Regional Autoimmune Disease Registry (DRADR). Measurements carried out on serum samples included ANA, extractable nuclear antibodies (ENA) and autoantibody profiling using an array with more than 100 specificities. Whole blood RNA samples from a subset of individuals were used to analyze gene expression on the Illumina platform. Data were analyzed for associations of high ANA levels with demographic features, the presence of other autoantibodies and with gene expression profiles.
Overall, ANA levels are significantly higher in females than in males and this association holds in patients with the autoimmune diseases lupus and rheumatoid arthritis (RA) as well as in healthy controls (HC). Age was not significantly associated with ANA levels and the elevated ANA values could not be explained by higher IgG levels. Another autoantibody, anti- cyclic citrullinated peptide (CCP), did not show gender dimorphism in rheumatoid arthritis (RA) or healthy individuals. The autoantigen array showed significant elevations of other autoantibodies in high ANA HCs. Some of these autoantibodies were directed to antigens in skin and others were related to autoimmune conditions of kidney, thyroid or joints. Gene expression analyses showed a greater prevalence of significantly upregulated genes in HCs with negative ANA values than in those with significant ANA positivity. Genes upregulated in high ANA HCs included a celiac disease autoantigen and some components of the Type I interferon (IFN) gene signature.
Risks for ANA positivity include female gender and organ-specific autoimmunity. Upregulation of skin-specific autoantibodies may indicate that early events in the break of tolerance take place in cutaneous structures. Some of these changes may be mediated by Type I IFN. Blood profiling for expressed autoantibodies and genes has the potential to identify individuals at risk for development of autoimmune diseases including lupus.
CD4+ T cells deficient in signaling lymphocyte activation molecule (SLAM)-associated protein (SAP) exhibit a selective impairment in adhesion to antigen presenting B cells but not dendritic cells (DC), resulting in defective germinal center formation. However, the nature of this selective adhesion defect remained unclear. We found that whereas T:DC interactions were primarily integrin-dependent, T:B cell interactions had both an early integrin-dependent phase and a sustained phase that also required SAP. We further found that the SLAM family member, CD84, was required for prolonged T:B cell contact, optimal T follicular helper function, and germinal center formation in vivo. Moreover, both CD84 and another SLAM member, Ly108, mediated T cell adhesion and participated in stable T:B cell interactions in vitro. Our results reveal insight into the dynamic regulation of T:B cell interactions and identify SLAM family members as critical components of sustained T:B cell adhesion required for productive humoral immunity.
The y-linked autoimmune accelerating (Yaa) locus drives the transition to fatal lupus nephritis when combined with B6.Sle1 in our B6-congenic model of systemic autoimmunity. We and others recently demonstrated that the translocation of a cluster of X-linked genes onto the Y chromosome is the genetic lesion underlying Yaa (Subramanian, S. et al., Proc Natl Acad Sci USA 2006. 103: 9970–9975; Pisitkun, P. et al., Science 2006. 312: 1669–1672). In male mice carrying Yaa, the transcription of several genes within the translocated segment is increased roughly 2-fold. Although the translocated X chromosome segment in Yaa may contain as many as 16 genes, the major candidate gene for causation of the Yaa-associated autoimmune phenotypes has been TLR7. To confirm the role of TLR7 in Yaa-mediated autoimmune phenotypes, we introgressed a targeted disruption of TLR7 (TLR7−) onto B6.Sle1Yaa to produce B6.Sle1YaaTLR7− and examined evidence of disease at 6 and 9 months of age. Our results demonstrate that the upregulation of TLR7 in the B6.Sle1Yaa strain is responsible for splenomegaly, glomerular nephritis and the majority of the cellular abnormalities of B, T and myeloid cells. The upregulation of TLR7 was also responsible for driving the infiltration and activation of leukocytes into the kidney, in which activated T cellswere a primary component. However, the resolution of TLR7 upregulation did not eliminate the enhanced humoral autoimmunity observed in B6.SleYaa, suggesting that additional elements in the translocation may contribute to the disease phenotype.
Autoimmunity; TLR7; genetics; SLE; congenic
B6.Sle1b mice, which contain the Sle1b gene interval derived from lupus prone NZM2410 mice on a C57BL/6 background, present with gender-biased, highly penetrant anti-nuclear antibody (ANA) production. To obtain some insight into the possible induction mechanism of autoantibodies in these mice we compared antigen specific T dependent (TD) and T independent (TI-II) responses between B6.Sle1b and B6 mice before the development of high ANA titers. Our results show that B6.Sle1b mice mount enhanced responses to a TI-II antigen. Additionally, the memory T cell response generated by a TD antigen was also increased. This enhancement correlates with the greater ability of B cells from B6.Sle1b mice to present antigen to T cells. The SLAM Associated Protein (SAP) is critical for signaling of many of the molecules encoded by the SLAM/CD2 gene cluster, candidates for mediating the Sle1b phenotype; therefore, we also investigated the effect of sap deletion in these strains on the TD and TI-II responses as well as on ANA production. The results of these studies of responses to non-self antigens provide further insight for the mechanism by which responses to self-antigens might be initiated in the context of specific genetic alterations.
ANA; antigen-specific responses; SAP; SLE
Increased Type I IFNs or IFN-I have been associated with human systemic lupus erythematosus. Interestingly augmenting or negating IFN-I activity in murine lupus not only modulates systemic autoimmunity, but also impacts lupus nephritis, suggesting that IFN-I may be acting at the level of the end-organ. We find resident renal cells to be a dominant source of IFN-I in an experimental model of autoantibody-induced nephritis. In this model, augmenting IFN-I amplified antibody-triggered nephritis, whereas ablating IFN-I activity ameliorated disease. One mechanism through which increased IFN-I drives immune-mediated nephritis might be operative through increased recruitment of inflammatory monocytes and neutrophils, though this hypothesis needs further validation. Collectively, these studies indicate that an important contribution of IFN-I toward the disease pathology seen in systemic autoimmunity may be exercised at the level of the end-organ.
Complement cascade plasma proteins have a complex role in the etiopathogenesis of SLE. Hereditary C1q deficiency has been strongly related to SLE; however, there are very few published SLE studies that evaluate the polymorphisms of the genes encoding for C1q (A, B, and C). In this study, we evaluated 17 single nucleotide polymorphisms (SNPs) across 37 kb of C1QA, B and C in a lupus cohort of peoples of African-American and Hispanic origin. In a case only analysis, significant association at multiple SNPs in the C1QA gene was detected in African-Americans with kidney nephritis (best p=4.91 × 10−6). In addition, C1QA was associated with SLE in African-Americans with a lack of nephritis and accompanying photosensitivity when compared to normal controls (p=6.80 × 10−6). A similar trend was observed in the Hispanic subjects (p=0.003). Quantitative analysis demonstrates that some SNPs in the C1q genes might be correlated with C3 complement levels in an additive model among African-Americans (best p=0.0001). The CIQA gene is associated with subphenotypes of lupus in African-American and Hispanic subjects. Further studies with higher SNP densities in this region and other complement components are necessary to elucidate the complex genetics and phenotypic interactions between complement components and SLE.