Trans-Ethnic Mapping of BANK1 Identifies Two Independent SLE-Risk Linkage Groups Enriched for Co-Transcriptional Splicing Marks

Genetic interrogation for sequence and copy number variants in systemic lupus erythematosus

Early-onset systemic lupus erythematosus presents with a more severe disease and is associated with a greater genetic burden, especially in patients from Black, Asian or Hispanic ancestries. Next-generation sequencing techniques, notably whole exome sequencing, have been extensively used in genomic interrogation studies to identify causal disease variants that are increasingly implicated in the development of autoimmunity. This Review discusses the known casual variants of polygenic and monogenic systemic lupus erythematosus and its implications under certain genetic disparities while suggesting an age-based sequencing strategy to aid in clinical diagnostics and patient management for improved patient care.

Emerging role of EZH2 in rheumatic diseases: A comprehensive review

Enhancer of zeste homolog 2 (EZH2) is a histone methylated enzyme. It trimethylates histone 3 lysine 27 (H3K27) to regulate epigenetic processes. Recently, studies showed excessive expression of EZH2 in rheumatic diseases, such as systemic lupus erythematosus, rheumatoid arthritis, osteoarthritis, and systemic sclerosis. Moreover, epigenetic modification of EZH2 regulates differentiation and proliferation of different immune cells. Therefore, in this review, we comprehensively discuss the role of EZH2 in rheumatic diseases. Collection of the evidence may provide a basis for further understanding the role of EZH2 and give potential for targeting these diseases.

Variants in BANK1 are associated with lupus nephritis of European ancestry

The genetic background of lupus nephritis (LN) has not been completely elucidated. We performed a case-only study of 2886 SLE patients, including 947 (33%) with LN. Renal biopsies were available from 396 patients. The discovery cohort (Sweden, n = 1091) and replication cohort 1 (US, n = 962) were genotyped on the Immunochip and replication cohort 2 (Denmark/Norway, n = 833) on a custom array. Patients with LN, proliferative nephritis, or LN with end-stage renal disease were compared with SLE without nephritis. Six loci were associated with LN (p < 1 × 10⁻⁴, NFKBIA, CACNA1S, ITGA1, BANK1, OR2Y, and ACER3) in the discovery cohort. Variants in BANK1 showed the strongest association with LN in replication cohort 1 (p = 9.5 × 10⁻⁴) and proliferative nephritis in a meta-analysis of discovery and replication cohort 1. There was a weak association between BANK1 and LN in replication cohort 2 (p = 0.052), and in the meta-analysis of all three cohorts the association was strengthened (p = 2.2 × 10⁻⁷). DNA methylation data in 180 LN patients demonstrated methylation quantitative trait loci (meQTL) effects between a CpG site and BANK1 variants. To conclude, we describe genetic variations in BANK1 associated with LN and evidence for genetic regulation of DNA methylation within the BANK1 locus. This indicates a role for BANK1 in LN pathogenesis.

The Role of BANK1 in B Cell Signaling and Disease

The B cell scaffold protein with ankyrin repeats (BANK1) is expressed primarily in B cells and with multiple but discrete roles in B cell signaling, including B cell receptor signaling, CD40-related signaling, and Toll-like receptor (TLR) signaling. The gene for BANK1, located in chromosome 4, has been found to contain genetic variants that are associated with several autoimmune diseases and also other complex phenotypes, in particular, with systemic lupus erythematosus. Common genetic variants are associated with changes in BANK1 expression in B cells, while rare variants modify their capacity to bind efferent effectors during signaling. A BANK1-deficient model has shown the importance of BANK1 during TLR7 and TLR9 signaling and has confirmed its role in the disease. Still, much needs to be done to fully understand the function of BANK1, but the main conclusion is that it may be the link between different signaling functions within the B cells and they may act to synergize the various pathways within a cell. With this review, we hope to enhance the interest in this molecule.

From hepatitis C virus immunoproteomics to rheumatology via cross-reactivity in one table

PURPOSE OF REVIEW

To give an overview of molecular and immunologic data that link hepatitis C virus (HCV) infection to rheumatic diseases in the human host.

RECENT FINDINGS

A high level of peptide sharing exists between immunopositive HCV epitopes and human proteins that, when altered, associate with rheumatic manifestations.

SUMMARY

The findings suggest the involvement of HCV infection in the induction of most rheumatic diseases via a mechanism of autoimmune cross-reactivity.

Negative Regulation of TLR Signaling by BCAP Requires Dimerization of Its DBB Domain

Dimerization of the BCAP Toll/IL1 domain is required for function.

BCAP TIR modulates the oligomerization state of TLR signaling adaptor MAL.

TIG domains are a promiscuous dimerization module in gene expression and signaling.

The B cell adaptor protein (BCAP) is a multimodular regulator of inflammatory signaling in diverse immune system cells. BCAP couples TLR signaling to phosphoinositide metabolism and inhibits MyD88-directed signal transduction. BCAP is recruited to the TLR signalosome forming multitypic interactions with the MAL and MyD88 signaling adaptors. In this study, we show that indirect dimerization of BCAP TIR is required for negative regulation of TLR signaling. This regulation is mediated by a transcription factor Ig (TIG/IPT) domain, a fold found in the NF-κB family of transcription factors. We have solved the crystal structure of the BCAP TIG and find that it is most similar to that of early B cell factor 1 (EBF1). In both cases, the dimer is stabilized by a helix-loop-helix motif at the C terminus and interactions between the β-sheets of the Ig domains. BCAP is exclusively localized in the cytosol and is unable to bind DNA. Thus, the TIG domain is a promiscuous dimerization module that has been appropriated for a range of regulatory functions in gene expression and signal transduction.

Association of BLK and BANK1 Polymorphisms and Interactions With Rheumatoid Arthritis in a Latin-American Population

Introduction

BLK has been identified as a risk factor to rheumatoid arthritis (RA) primarily in Asian or European-derived populations. However, this finding has not been evaluated in other populations such as Latin-Americans, except for Colombians. On the other hand, BANK1 single nucleotide variants (SNVs) have been scarcely studied in RA patients.

Objective

The aim of this study was to determine whether the BLK rs2736340T/C, rs13277113A/G, and BANK1 rs10516487G/A (R61H) and rs3733197G/A (A383T) polymorphisms are risk factors to RA in a sample of patients from Central Mexico.

Materials and Methods

We studied 957 women; 487 controls and 470 patients with RA by means of a TaqMan® SNP genotyping assay with fluorescent probes for the BLK rs13277113A/G, rs2736340T/C and BANK1 10516487G/A (R61H) and rs3733197G/A (A383T) variants.

Result

The BLK rs2736340T/C and rs13277113A/G variants were associated with risk for RA: C vs T; OR 1.39, p = 0.001, and G vs A; OR 1.37, p = 0.004, respectively. In addition, there was also an association between BANK1 R61H and RA: A vs G; OR 1.49, p = 0.003, but no with BANK1 A383T. We also identified an interaction significant between genotypes of BLK rs2736340T/C-BANK1 rs10516487G/A and RA: OR 1.65, p = 0.0001.

Conclusions

Our data suggest that both BLK and BANK1 confer susceptibility to RA in Mexican patients. The individual association of BANK1 rs1054857G/A with RA had not been previously reported in a particular population (except for pooled patients from several countries), therefore, our study presents the first evidence of association between this BANK1 variant and RA.

BANK1 interacts with TRAF6 and MyD88 in innate immune signaling in B cells

Evidence supports a possible role of BANK1 in innate immune signaling in B cells. In the present study, we investigated the interaction of BANK1 with two key mediators in interferon and inflammatory cytokine production, TRAF6 and MyD88. We revealed by coimmunoprecipitation (CoIP) analyses the binding of BANK1 with TRAF6 and MyD88, which were mediated by the BANK1 Toll/interleukin-1 receptor (TIR) domain. In addition, the natural BANK1–40C variant showed increased binding to MyD88. Next, we demonstrated in mouse splenic B cells that BANK1 colocalized with Toll-like receptor (TLR) 7 and TLR9 and that after stimulation with TLR7 and TLR9 agonists, the number of double-positive BANK1–TLR7, –TLR9, –TRAF6, and –MyD88 cells increased. Furthermore, we identified five TRAF6-binding motifs (BMs) in BANK1 and confirmed by point mutations and decoy peptide experiments that the C-terminal domain of BANK1-full-length (-FL) and the N-terminal domain of BANK1–Delta2 (-D2) are necessary for this binding. Functionally, we determined that the absence of the TIR domain in BANK1–D2 is important for its lysine (K)63-linked polyubiquitination and its ability to produce interleukin (IL)-8. Overall, our study describes a specific function of BANK1 in MyD88–TRAF6 innate immune signaling in B cells, clarifies functional differences between the two BANK1 isoforms and explains for the first time a functional link between autoimmune phenotypes including SLE and the naturally occurring BANK1–40C variant.

Insights into rheumatic diseases from next-generation sequencing

Rheumatic diseases have complex aetiologies that are not fully understood, which makes the study of pathogenic mechanisms in these diseases a challenge for researchers. Next-generation sequencing (NGS) and related omics technologies, such as transcriptomics, epigenomics and genomics, provide an unprecedented genome-wide view of gene expression, environmentally responsive epigenetic changes and genetic variation. The integrated application of NGS technologies to samples from carefully phenotyped clinical cohorts of patients has the potential to solve remaining mysteries in the pathogenesis of several rheumatic diseases, to identify new therapeutic targets and to underpin a precision medicine approach to the diagnosis and treatment of rheumatic diseases. This Review provides an overview of the NGS technologies available, showcases important advances in rheumatic disease research already powered by these technologies and highlights NGS approaches that hold particular promise for generating new insights and advancing the field.