Association of an activity-enhancing variant of IRAK1 and an MECP2-IRAK1 haplotype with increased susceptibility to rheumatoid arthritis

Sex bias in celiac disease: XWAS and monocyte eQTLs in women identify TMEM187 as a functional candidate gene

BACKGROUND

Celiac disease (CeD) is an immune-mediated disorder that develops in genetically predisposed individuals upon gluten consumption. HLA risk alleles explain 40% of the genetic component of CeD, so there have been continuing efforts to uncover non-HLA loci that can explain the remaining heritability. As in most autoimmune disorders, the prevalence of CeD is significantly higher in women. Here, we investigated the possible involvement of the X chromosome on the sex bias of CeD.

METHODS

We performed a X chromosome-wide association study (XWAS) and a gene-based association study in women from the CeD Immunochip (7062 cases, 5446 controls). We also constructed a database of X chromosome cis-expression quantitative trait loci (eQTLs) in monocytes from unstimulated (n = 226) and lipopolysaccharide (LPS)-stimulated (n = 130) female donors and performed a Summary-data-based MR (SMR) analysis to integrate XWAS and eQTL information. We interrogated the expression of the potentially causal gene (TMEM187) in peripheral blood mononuclear cells (PBMCs) from celiac patients at onset, on a gluten-free diet, potential celiac patients and non-celiac controls.

RESULTS

The XWAS and gene-based analyses identified 13 SNPs and 25 genes, respectively, 22 of which had not been previously associated with CeD. The X chromosome cis-eQTL analysis found 18 genes with at least one cis-eQTL in naïve female monocytes and 8 genes in LPS-stimulated female monocytes, 2 of which were common to both situations and 6 were unique to LPS stimulation. SMR identified a potentially causal association of TMEM187 expression in naïve monocytes with CeD in women, regulated by CeD-associated, eQTL-SNPs rs7350355 and rs5945386. The CeD-risk alleles were correlated with lower TMEM187 expression. These results were replicated using eQTLs from LPS-stimulated monocytes. We observed higher levels of TMEM187 expression in PBMCs from female CeD patients at onset compared to female non-celiac controls, but not in male CeD individuals.

CONCLUSION

Using X chromosome genotypes and gene expression data from female monocytes, SMR has identified TMEM187 as a potentially causal candidate in CeD. Further studies are needed to understand the implication of the X chromosome in the higher prevalence of CeD in women.

IRAK4 inhibition dampens pathogenic processes driving inflammatory skin diseases

Innate immunity not only shapes the way epithelial barriers interpret environmental cues but also drives adaptive responses. Therefore, modulators of innate immune responses are expected to have high therapeutic potential across immune-mediated inflammatory diseases. IRAK4 is a kinase that integrates signaling downstream of receptors acting at the interface between innate and adaptive immune responses, such as Toll-like receptors (TLRs), interleukin-1R (IL-1R), and IL-18R. Because effects of IRAK4 inhibition are stimulus, cell type, and species dependent, the evaluation of the therapeutic potential of IRAK4 inhibitors requires a highly translational approach. Here, we profiled a selective IRAK4 inhibitor, GLPG2534, in an extensive panel of models of inflammatory skin diseases, translationally expanding evidence from in vitro to in vivo and from mouse to human. In vitro, IRAK4 inhibition resulted in substantial inhibition of TLR and IL-1 responses in dendritic cells, keratinocytes, granulocytes, and T cells but only weakly affected dermal fibroblast responses. Furthermore, disease activity in murine models of skin inflammation (IL-23-, IL-33-, imiquimod-, and MC903-induced) was markedly dampened by IRAK4 inhibition. Last, inhibiting IRAK4 reversed pathogenic molecular signatures in human lesional psoriasis and atopic dermatitis biopsies. Over the variety of models used, IRAK4 inhibition consistently affected central mediators of psoriasis (IL-17A) and atopic dermatitis (IL-4 and IL-13). Overall, our data highlight IRAK4 as a central player in skin inflammatory processes and demonstrate the potential of IRAK4 inhibition as a therapeutic strategy in chronic inflammatory skin diseases.

Identification of circular RNAs hsa_circ_0140271 in peripheral blood mononuclear cells as a novel diagnostic biomarker for female rheumatoid arthritis

Background

Rheumatoid arthritis (RA) is a chronic autoimmune disease, which commonly affects women. Accumulating evidence shows that differentially expressed circular RNAs (circRNAs) play crucial roles in the progress of RA. However, the roles of circRNAs in female RA remains unclear. This study explores potential role and diagnostic value of hsa_circ_0140271 from peripheral blood mononuclear cells (PBMC) in female RA.

Methods

Differential expression of circRNAs was determined by RNA-sequencing in PBMC from 4 healthy controls (HC) and 4 RA patients, and we further measured the level of hsa_circ_0140271 in a validation cohort consisting of 47 RA and 47 HC via RT-qPCR. Besides, correlation studies with clinical variables were also examined. What’s more, we performed bioinformatics analysis to predict the potential role of hsa_circ_0140271.

Results

PBMC expression of hsa_circ_0140271 of female RA was significantly higher than that of female HC, and it was positively correlated with antistreptolysin (ASO). Furthermore, the receiver operating characteristic (ROC) curve indicated that hsa_circ_0140271 could distinguish female RA from female HC and female patients with ankylosing spondylitis (AS) or osteoarthritis (OA). Besides, the combined diagnosis anti-cyclic citrullinated peptide (Anti-CCP) + hsa_circ_0140271 could improve diagnostic accuracy with an area under the curve (AUC) of 0.818 to compared with Anti-CCP. Furthermore, KEGG pathway enrichment analysis indicated hsa_circ_0140271 may act as microRNA sponge and participate in fatty acid metabolism pathways.

Conclusion

Hsa_circ_0140271 was likely to be used as a promising diagnostic biomarker for female RA; it may act as microRNA sponge to regulate fatty acid metabolism pathways in RA.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-021-02794-8.

Interleukin-1 receptor-associated kinase gene polymorphisms contribute to rheumatoid arthritis risk: A meta-analysis

AIM

Rheumatoid arthritis (RA) is a systemic autoimmune disease affecting about 1% of world population. Three polymorphisms of Interleukin-1 receptor-associated kinase (IRAK1) gene, rs3027898, rs1059702 and rs1059703, are studied to associate with RA risk. However, the findings are inconclusive. Therefore, we performed a meta-analysis to derive a more precise estimation of the impact of the 3 polymorphisms on RA risk.

METHOD

The strength of association between 3 polymorphisms and RA risk was assessed by calculating odds ratios (ORs) with the corresponding 95% confidence intervals (CIs).

RESULTS

Overall, for rs3027898 polymorphism, no association was observed in pooled analysis, but the stratified analysis suggested that rs3027898 CA genotype was associated with a reduced risk of RA in an Asian population (heterozygous model: OR = 0.79, 95% CI = 0.66-0.96, P = .018). Rs1059702 polymorphism was related with an increased RA risk (homozygous model: OR = 1.59, 95% CI = 1.19-2.13, P = .002, heterozygous model: OR = 1.49, 95% CI = 1.17-1.88, P = .001, and allele comparison model: OR = 1.35, 95% CI = 1.20-1.53, P < .001). Moreover, rs1059703 was also associated with an increased RA risk (dominant model: OR = 1.26, 95% CI = 1.07-1.49, P = .006), especially in Caucasian populations.

CONCLUSION

These results indicated that all 3 Interleukin-1 receptor-associated kinase (IRAK1) gene polymorphisms, rs3027898, rs1059702 and rs1059703 were related to RA risk.

IRAK1 Gene Polymorphism in Rheumatoid Arthritis

Background: Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease. The present study intends to specify rs1059703, rs4810485, and rs1883832 gene polymorphisms of interleukin-1 receptor-associated kinase (IRAK1) and cluster of differentiation 40 (CD40) in RA. IRAK1 is a serine/threonine kinase and CD40 is a tumor necrosis factor receptor, both of which are involved in RA. There are conflicting results on functional effects of these polymorphisms, so we performed this research for a more accurate estimation on rheumatoid arthritis risk. Methods: Two-hundred RA patients diagnosed according to ACR criteria and 200 normal controls participated in this case-control study. DNA Purification kit (Gene Transfer Pioneers, GTP) was used for genomic DNA extraction and three SNPs, including IRAK1 rs1059703 (C/T), CD40 rs1883832 (C/T) and rs4810485 (G/T), were genotyped by PCR-RFLP. The genotypes and allele frequencies of SNPs were analyzed by chi-square test to detect their contribution to RA. Results: A significant correlation was found between rs1059703 T allele (OR = 2.36, 95% CI = 1.7-3.1, p = .0001) and TT and CT genotypes (TT genotype, OR = 2.54, 95%CI = 1.2-3.3, P = .0078, CT genotype; OR = 2.18 95%CI = 1.4-3.2P = .0002) of rs1059703 C/T polymorphism in terms of susceptibility to RA in recessive and over-dominant models. Alleles and genotypes of CD40 SNPs were not significantly different between RA cases and controls. The findings showed significant differences in rs1059703 IRAK1 genotypes with medical and laboratory features of patients. Conclusion: Our results showed that the rs1059703 T allele (risk allele) of IRAK1 gene increases the risk of RA and the severity of disease, affecting the onset age of RA in Iranian patients.

Interleukin-1 Receptor-Associated Kinase (IRAK) Signaling in Kaposi Sarcoma-Associated Herpesvirus-Induced Primary Effusion Lymphoma

Kaposi sarcoma-associated herpesvirus (KSHV) is necessary but not sufficient for primary effusion lymphoma (PEL) development. Alterations in cellular signaling pathways are also a characteristic of PEL. Other B cell lymphomas have acquired an oncogenic mutation in the myeloid differentiation primary response 88 (MYD88) gene. The MYD88 L265P mutant results in the activation of interleukin-1 receptor associated kinase (IRAK). To probe IRAK/MYD88 signaling in PEL, we employed CRISPR/Cas9 technology to generate stable deletion clones in BCBL-1Cas9 and BC-1Cas9 cells. To look for off-target effects, we determined the complete exome of the BCBL-1Cas9 and BC-1Cas9 cells. Deletion of either MYD88, IRAK4, or IRAK1 abolished interleukin-1 beta (IL-1β) signaling; however, we were able to grow stable subclones from each population. Transcriptome sequencing (RNA-seq) analysis of IRAK4 knockout cell lines (IRAK4 KOs) showed that the IRAK pathway induced cellular signals constitutively, independent of IL-1β stimulation, which was abrogated by deletion of IRAK4. Transient complementation with IRAK1 increased NF-κB activity in MYD88 KO, IRAK1 KO, and IRAK4 KO cells even in the absence of IL-1β. IL-10, a hallmark of PEL, was dependent on the IRAK pathway, as IRAK4 KOs showed reduced IL-10 levels. We surmise that, unlike B cell receptor (BCR) signaling, MYD88/IRAK signaling is constitutively active in PEL, but that under cell culture conditions, PEL rapidly became independent of this pathway.IMPORTANCE One hundred percent of primary effusion lymphoma (PEL) cases are associated with Kaposi sarcoma-associated herpesvirus (KSHV). PEL cell lines, such as BCBL-1, are the workhorse for understanding this human oncovirus and the host pathways that KSHV dysregulates. Understanding their function is important for developing new therapies as well as identifying high-risk patient groups. The myeloid differentiation primary response 88 (MYD88)/interleukin-1 receptor associated kinase (IRAK) pathway, which has progrowth functions in other B cell lymphomas, has not been fully explored in PEL. By performing CRISPR/Cas9 knockout (KO) studies targeting the IRAK pathway in PEL, we were able to determine that established PEL cell lines can circumvent the loss of IRAK1, IRAK4, and MYD88; however, the deletion clones are deficient in interleukin-10 (IL-10) production. Since IL-10 suppresses T cell function, this suggests that the IRAK pathway may serve a function in vivo and during early-stage development of PEL.

Synergistic activation of NF-κB by TNFAIP3 (A20) reduction and UBE2L3 (UBCH7) augment that synergistically elevate lupus risk

Background

Systemic lupus erythematosus (SLE) is an autoimmune inflammatory rheumatic disease. SLE susceptibility is affected by multiple genetic elements, environmental factors, and their interactions. We aimed in this study to statistically and functionally characterize a gene-gene interaction (epistasis) recently documented to affect SLE risk.

Methods

Two single-nucleotide polymorphisms, rs2230926 in TNFAIP3 (A20) gene and rs131654 in UBE2L3 (UBCH7) gene, were genotyped in all 3525 Korean participants, and their SLE risk association and epistasis were statistically analyzed by calculating odds ratio (OR), 95% confidence interval (CI), and P values in genotype comparisons between 1318 SLE patients and 2207 healthy controls. Furthermore, their effects on gene functions were assessed by comparatively examining separate and combined effects of TNFAIP3 and UBE2L3 knockdowns on NF-κB transcription factor activity in human cells.

Results

SLE susceptibility is associated with TNFAIP3 rs2230926 (OR = 1.9, 95% CI 1.6–2.4, P = 8.6 × 10⁻¹¹) and UBE2L3 rs131654 (OR = 1.2, 95% CI 1.1–1.4, P = 1.1 × 10⁻⁴) in a Korean population of this study. Their risk-associated alleles synergistically elevate SLE susceptibility in both multivariate logistic regression analysis (OR_interaction = 1.6, P = 0.0028) and genotype-stratified analysis (OR_interaction = 2.4), confirming the synergistic TNFAIP3-UBE2L3 interaction in SLE risk. Additionally, the SLE-susceptible alleles confer decreased TNFAIP3 expression (P = 1.1 × 10⁻⁶, n = 610) and increased UBE2L3 expression (P = 9.5 × 10⁻¹¹, n = 475), respectively, in B cell analysis of the International HapMap Project individuals with adjustment for ethnicity. Furthermore, when compared with TNFAIP3 non-knockdown and UBE2L3 knockdown in human HeLa cells, TNFAIP3 knockdown and UBE2L3 non-knockdown synergistically increase three cytokines, CCL2, CXCL8 (IL8), and IL6, all regulated by NF-κB in the human TNFR signaling pathway.

Conclusions

A synergistic interaction between TNFAIP3 and UBE2L3 genes is observed in SLE risk, as being evident in comparison of genotype distributions between SLE patients and controls. Additionally, the synergistic gene-gene interaction is functionally validated, as TNFAIP3 reduction and UBE2L3 augment exert synergism in activation of NF-κB and subsequent induction of inflammatory cytokines. Accordingly, SLE inflammation and risk could be synergistically alleviated by TNFAIP3 upregulation and UBE2L3 downregulation.

The evolution in our understanding of the genetics of rheumatoid arthritis and the impact on novel drug discovery

Introduction: Rheumatoid arthritis (RA) is an autoimmune disease that is characterized by chronic inflammation of the joints and affects 1% of the population. Polymorphisms of genes that encode proteins that primarily participate in inflammation may influence RA occurrence or become useful biomarkers for certain types of anti-rheumatic treatment.Areas covered: The authors summarize the recent progress in our understanding of the genetics of RA. In the last few years, multiple variants of genes that are associated with RA risk have been identified. The development of new technologies and the detection of new potential therapeutic targets that contribute to novel drug discovery are also described.Expert opinion: There is still the need to search for new genes which may be a potential target for RA therapy. The challenge is to develop appropriate strategies for achieving insight into the molecular pathways involved in RA pathogenesis. Understanding the genetics, immunogenetics, epigenetics and immunology of RA could help to identify new targets for RA therapy. The development of new technologies has enabled the detection of a number of new genes, particularly genes associated with proinflammatory cytokines and chemokines, B- and T-cell activation pathways, signal transducers and transcriptional activators, which might be potential therapeutic targets in RA.

Association between IRAK1 rs3027898 and miRNA-499 rs3746444 polymorphisms and rheumatoid arthritis : A case control study and meta-analysis

BACKGROUND

The IRAK1 and miR-499 polymorphisms play an important role in the etiology of rheumatoid arthritis (RA). Several studies have been carried out to estimate the association between IRAK1 rs3027898 and miR-499 rs3746444 and RA risk; however, the results were inconsistent.

AIM

A case control study was carried out to explore the association between IRAK1 rs3027898 and miR-499 rs3746444 and the RA risk in a Chinese population. Meta-analyses combining present with previous studies were conducted to further explore the association.

MATERIAL AND METHODS

A total of 386 RA patients were enrolled along with 576 matched healthy controls. Genotyping was performed by using TaqMan genotyping assays on Fluidigm 192.24 system. For the meta-analysis, a systematic literature search was conducted to identify all relevant studies.

RESULTS

This case control study showed that the IRAK1 rs3027898 C allele was associated with increased risk of RA with an odds ratio (OR) = 1.4 and 95 % confidence intervals (CI) = 1.093-1.793, P = 0.008 but miR-499 rs3746444 polymorphisms were not significantly associated with the risk for RA. The meta-analyses included a total of 4 case control studies on IRAK1 rs3027898 and 4 studies on miR-499 rs3746444. The IRAK1 rs3027898 C allele had an overall OR of 1.268 (95 % CI = 1.130-1.424, P < 0.001). After stratification by ethnicity the C allele had an OR of 1.238 (95 % CI = 1.096-1.398, P = 0.001) in Asians. No association between miR-499 rs3746444 polymorphism and RA was found in the overall and Asian populations.

CONCLUSION

The results from our case control study and the meta-analyses indicate that the IRAK1 rs3027898 C allele is significantly associated with an increased risk of RA, especially in Asians.

Inhibition of interleukin-1 receptor-associated kinase 1 (IRAK1) as a therapeutic strategy

Interleukin-1 receptor-associated kinases (IRAK1, IRAK2, IRAK3 [IRAK-M], and IRAK4) are serine-threonine kinases involved in toll-like receptor and interleukin-1 signaling pathways, through which they regulate innate immunity and inflammation. Evidence exists that IRAKs play key roles in the pathophysiologies of cancers, and metabolic and inflammatory diseases, and that IRAK inhibition has potential therapeutic benefits. Molecules capable of selectively interfering with IRAK function and expression have been reported, paving the way for the clinical evaluation of IRAK inhibition. Herein, we focus on IRAK1, review its structure and physiological roles, and summarize emerging data for IRAK1 inhibitors in preclinical and clinical studies.

Type I interferon in rheumatic diseases

The type I interferon pathway has been implicated in the pathogenesis of a number of rheumatic diseases, including systemic lupus erythematosus, Sjögren syndrome, myositis, systemic sclerosis, and rheumatoid arthritis. In normal immune responses, type I interferons have a critical role in the defence against viruses, yet in many rheumatic diseases, large subgroups of patients demonstrate persistent activation of the type I interferon pathway. Genetic variations in type I interferon-related genes are risk factors for some rheumatic diseases, and can explain some of the heterogeneity in type I interferon responses seen between patients within a given disease. Inappropriate activation of the immune response via Toll-like receptors and other nucleic acid sensors also contributes to the dysregulation of the type I interferon pathway in a number of rheumatic diseases. Theoretically, differences in type I interferon activity between patients might predict response to immune-based therapies, as has been demonstrated for rheumatoid arthritis. A number of type I interferon and type I interferon pathway blocking therapies are currently in clinical trials, the results of which are promising thus far. This Review provides an overview of the many ways in which the type I interferon system affects rheumatic diseases.

Transcriptional profile of human macrophages stimulated by ultra-high molecular weight polyethylene particulate debris of orthopedic implants uncovers a common gene expression signature of rheumatoid arthritis

Osteolysis is a serious postoperative complication of total joint arthroplasty that leads to aseptic loosening and surgical revision. Osteolysis is a chronic destructive process that occurs when host macrophages recognize implant particles and release inflammatory mediators that increase bone-resorbing osteoclastic activity and attenuate bone-formation osteoblastic activity. Although much progress has been made in understanding the molecular responses of macrophages to implant particles, the pathways/signals that initiate osteolysis remain poorly characterized. Transcriptomics and gene-expression profiling of these macrophages may unravel key mechanisms in the pathogenesis of osteolysis and aid the identification of molecular candidates for therapeutic intervention. To this end, we analyzed the transcriptional profiling of macrophages exposed to ultra-high molecular weight polyethylene (UHMWPE) particles, the most common components used in bearing materials of orthopedic implants. Regulated genes in stimulated macrophages were involved in cytokine, chemokine, growth factor and receptor activities. Gene enrichment analysis suggested that stimulated macrophages elicited common gene expression signatures for inflammation and rheumatoid arthritis. Among the regulated genes, tumor necrosis factor superfamily member 15 (TNFSF15) and chemokine ligand 20 (CCL20) were further characterized as molecular targets involved in the pathogenesis of osteolysis. Treatment of monocyte cultures with TNFSF15 and CCL20 resulted in an increase in osteoclastogenesis and bone-resorbing osteoclastic activity, suggesting their potential contribution to loosening between implants and bone tissues.

STATEMENT OF SIGNIFICANCE

Implant loosening due to osteolysis is the most common mode of arthroplasty failure and represents a great challenge to orthopedic surgeons and a significant economic burden for patients and healthcare services worldwide. Bone loss secondary to a local inflammatory response initiated by particulate debris from implants is considered the principal feature of the pathogenesis of osteolysis. In the present study, we analyzed the transcriptional profiling of human macrophages exposed to UHMWPE particles and identified a large number of inflammatory genes that were not identified previously in macrophage responses to wear particles. Our data provide a new insight into the molecular pathogenesis of osteolysis and highlights a number of molecular targets with prognostic and therapeutic implications.

Micro RNA-146a But Not IRAK1 is Associated with Rheumatoid Arthritis in the Tunisian Population

BACKGROUND

Rheumatoid arthritis (RA) is characterized by the production of an array of proinflammatory cytokines through the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling pathway. Interleukin-1 receptor (IL-1R) and Toll-like receptors contain a common cytoplasmic motif the Toll/IL-1R (TIR) homology domain. This motif is required for NF-κB activation. IL-1R-associated kinase 1 (IRAK1) is a key adapter molecule recruited during the signaling cascade of the TIR. Its gene expression is regulated by the micro-RNA (miR)-146a.

OBJECTIVE

We investigated the role of IRAK1 single-nucleotide polymorphism (SNP) rs3027898 (IRAK1 rs3027898) and miR-146a SNP rs2910164 (miR-146a rs2910164) in Tunisian patients with RA and their association with C reactive protein (CRP), rheumatoid factor (RF), anticyclic citrullinated peptide (anti-CCP) antibodies, and erosion.

PATIENTS AND METHODS

In a cohort of 172 adult RA patients and 224 matched controls, IRAK1 rs3027898 genotyping was determined by mutagenically separated polymerase chain reaction (MS-PCR) with newly designed primers, and miR-146a rs2910164 genotyping was determined by fragment length polymorphism PCR-restriction (RFLP-PCR).

RESULTS

The IRAK1 rs3027898 A allele was detected in 67% of RA patients and 70% of controls indicating that it is not associated with RA in codominant, dominant, or recessive models even after stratification by age and gender. The miR-146a rs2910164 G allele was detected in 76% of RA patients and 68% of controls, thus the C allele confers some protection based on a dominant model [CC+GC (odds ratio (95% confidence interval) = 0.6 (0.3-0.9), p = 0.03)]. No association with CRP, RF, anti-CCP, or erosion was found for either SNPs.

CONCLUSION

The IRAK1 rs3027898 was not associated with RA, whereas C allele of miR-146a rs2910164 was found to be protective. Functional studies are required to investigate the exact role of miR-146a rs2910164 during RA.

TMEM187-IRAK1 Polymorphisms Associated with Rheumatoid Arthritis Susceptibility in Tunisian and French Female Populations: Influence of Geographic Origin

Polymorphisms have been identified in the Xq28 locus as risk loci for rheumatoid arthritis (RA). Here, we investigated the association between three polymorphisms in the Xq28 region containing TMEM187 and IRAK1 (rs13397, rs1059703, and rs1059702) in two unstudied populations: Tunisian and French. The rs13397 G and rs1059703 T major alleles were significantly increased in RA patients (n = 408) compared with age-matched controls (n = 471) in both Tunisian and French women. These results were confirmed by a meta-analysis replication study including two independent Greek and Korean cohorts. The rs1059702 C major allele was significantly associated with RA, only with French women. In the French population, the GTC haplotype displayed a protective effect against RA, while the ATC, GCC, and GTT haplotypes conferred significant risk for RA. No association for these haplotypes was found in the Tunisian population. Our results replicated for the first time the association of the three Xq28 polymorphisms with RA risk in Tunisian and French populations and suggested that RA susceptibility is associated with TMEM187-IRAK1 polymorphisms in women. Our data further support the involvement of X chromosome in RA susceptibility and evidence ethnicities differences that might be explained by differences in the frequencies of SE HLA-DRB1 alleles between both populations.

Update on the genetic architecture of rheumatoid arthritis

Human genetic studies into rheumatoid arthritis (RA) have uncovered more than 100 genetic loci associated with susceptibility to RA and have refined the RA-association model for HLA variants. The majority of RA-risk variants are highly shared across multiple ancestral populations and are located in noncoding elements that might have allele-specific regulatory effects in relevant tissues. Emerging multi-omics data, high-density genotype data and bioinformatic approaches are enabling researchers to use RA-risk variants to identify functionally relevant cell types and biological pathways that are involved in impaired immune processes and disease phenotypes. This Review summarizes reported RA-risk loci and the latest insights from human genetic studies into RA pathogenesis, including how genetic data has helped to identify currently available drugs that could be repurposed for patients with RA and the role of genetics in guiding the development of new drugs.

Rheumatoid arthritis onset in postmenopausal women: Does the ACPA seropositive subset result from genetic effects, estrogen deficiency, skewed profile of CD4(+) T-cells, and their interactions?

Rheumatoid arthritis (RA) incidence displays a differentiated age-dependent female-to-male ratio in which women outnumber men. Evidence that the peak incidence of RA in women coincides with menopause age, suggests a potential estrogenic role to disease etiology. Estrogens exert physiologically both stimulatory and inhibitory effects on the immune system. Epidemiologic and animal model studies with estrogen deprivation or supplementation suggested estrogens as to play, mainly, a protective role in RA immunopathology. In this review, we propose that some yet unidentified disturbances associated with estrogen circulating levels, differentiated by the menopausal status, play a major role in women's RA susceptibility. We focus on the interaction between estrogen deprivation and genetic risk alleles for anti-citrullinated protein antibodies (ACPA) seropositive RA, as a major driving force for increased immune reactivity and RA susceptibility, in postmenopausal women. This opens up new fields for research concerning the association among different irregular estrogenic conditions, the cytokine milieu, and age/menopausal status bias in RA.

Variants in IRAK1-MECP2 region confer susceptibility to autoimmune thyroid diseases

Our objective was to investigate whether interleukin-1 receptor-associated kinase (IRAK1) and methyl-CpG-binding protein 2 (MECP2) are associated with autoimmune thyroid diseases (AITDs). We selected four single nucleotide polymorphisms (SNPs), rs3027898, rs1059703 in IRAK1 and rs2075596, rs2239464 in MECP2, for genotyping using PCR-based ligase detection reaction (LDR) method in 1042 AITDs patients and 897 controls. Minor alleles in the four SNPs were strongly associated with AITDs, and similar associations were found in Graves' disease (GD). In Hashimoto's thyroiditis (HT) patients, a significantly increased risk of T allele in rs1059703 was found. There were obvious differences in allele and genotype distributions in female AITDs, GD and HT patients. Moreover, the haplotypes CCAA and ATGG were the associated variants for AITDs and GD. Besides, these two haplotypes showed similar associations with AITDs and GD in female patients. Our results firstly indicated that IRAK1 and MECP2 genes are crucial risk factors for AITDs.

Immune dysfunction in Rett syndrome patients revealed by high levels of serum anti-N(Glc) IgM antibody fraction

Rett syndrome (RTT), a neurodevelopmental disorder affecting exclusively (99%) female infants, is associated with loss-of-function mutations in the gene encoding methyl-CpG binding protein 2 (MECP2) and, more rarely, cyclin-dependent kinase-like 5 (CDKL5) and forkhead box protein G1 (FOXG1). In this study, we aimed to evaluate the function of the immune system by measuring serum immunoglobulins (IgG and IgM) in RTT patients (n = 53) and, by comparison, in age-matched children affected by non-RTT pervasive developmental disorders (non-RTT PDD) (n = 82) and healthy age-matched controls (n = 29). To determine immunoglobulins we used both a conventional agglutination assay and a novel ELISA based on antibody recognition by a surrogate antigen probe, CSF114(Glc), a synthetic N-glucosylated peptide. Both assays provided evidence for an increase in IgM titer, but not in IgG, in RTT patients relative to both healthy controls and non-RTT PDD patients. The significant difference in IgM titers between RTT patients and healthy subjects in the CSF114(Glc) assay (P = 0.001) suggests that this procedure specifically detects a fraction of IgM antibodies likely to be relevant for the RTT disease. These findings offer a new insight into the mechanism underlying the Rett disease as they unveil the possible involvement of the immune system in this pathology.

Epigenetic-based immune intervention for rheumatic diseases

Rheumatic disease is a large spectrum of heterogeneous conditions affecting the loco-motor system including joints, muscles, connective tissues, and soft tissues around the joints and bones. Many rheumatic diseases have an element of autoimmunity including systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). Aberrant epigenetic regulation of gene expression is emerging as a major factor within rheumatic disease, and indicates potential new therapeutic avenues of approach to these debilitating conditions. Understanding the precise role of epigenetics in the development and treatment of rheumatic diseases particularly those which have an associated autoimmune element may be important for the long-term management of such conditions.