Hematopoietic not systemic impairment of Roquin expression accounts for intestinal inflammation in Roquin-deficient mice

Uncovering the Role of RNA-Binding Proteins in Gene Expression in the Immune System

Fighting external pathogens requires an ever-changing immune system that relies on tight regulation of gene expression. Transcriptional control is the first step to build efficient responses while preventing immunodeficiencies and autoimmunity. Post-transcriptional regulation of RNA editing, location, stability, and translation are the other key steps for final gene expression, and they are all controlled by RNA-binding proteins (RBPs). Nowadays we have a deep understanding of how transcription factors control the immune system but recent evidences suggest that post-transcriptional regulation by RBPs is equally important for both development and activation of immune responses. Here, we review current knowledge about how post-transcriptional control by RBPs shapes our immune system and discuss the perspective of RBPs being the key players of a hidden immune cell epitranscriptome.

Involvement of Ly6C, 4-1BB, and KLRG1 in the activation of lamina propria lymphocytes in the small intestine of sanroque mice

Roquin is an E3 ligase that regulates mRNA stability. Mice with a mutation in the Rc3h1 gene and Roquin protein, referred to as Roquin^san/san or sanroque mice, develop broad-spectrum chronic inflammatory conditions and autoimmune pathologies. Our laboratory recently reported that sanroque mice also develop extensive inflammation that is localized in the small intestine but is rare in the colon. Here, we demonstrate that small intestinal intraepithelial lymphocytes (IELs) are present in the epithelium of sanroque mice but that cell recoverability is low using standard extraction techniques even though lamina propria lymphocytes (LPLs) can be recovered in normal numbers. In studies aimed at characterizing T cell costimulatory markers and activation molecules on LPLs in sanroque mice, we identified Ly6C and 4-1BB (CD137) as being expressed at elevated levels on sanroque small intestinal LPLs, and we show that both of those subsets, in conjunction with cells expressing the KLRG1 T cell activation molecule, are sources of IL-17A, IFN-γ, and TNFα. TNFα was primarily produced by 4-1BB+, KLRG1-cells, but was also made by some 4-1BB-, KLRG1-cells, and 4-1BB-, KLRG1+ cells. These findings collectively suggest that the small intestinal inflammatory response in sanroque mice is driven, at least in part, by LPL activation through Ly6C and 4-1BB signaling, and they provide further evidence in support of using the sanroque mouse as an animal model of chronic small intestinal inflammation.

ROQUIN signalling pathways in innate and adaptive immunity

ROQUIN is an RNA-binding protein that plays important roles in both the innate and adaptive immune systems. ROQUIN binds to several key immune-relevant messenger RNA (mRNA) targets through its ROQ domain modulating their stability and influencing macrophage function and the peripheral homeostasis of T cells and B cells. More recently, the E3 ubiquitin ligase activity of the ROQUIN RING domain has been shown to be crucial for T-cell-dependent B-cell responses against infection. Defective ROQUIN activity can culminate in a range of diseases, such as systemic autoimmunity, immunodeficiency, and inflammatory bowel disorder. Here, we provide a current overview of the immunomodulatory role of ROQUIN defined by its ribonucleoprotein-like structure, its repertoire of mRNA targets shared by related RNA-binding enzymes, and its involvement in a range of intracellular signalling pathways central to shaping immune responses.

Roquin--a multifunctional regulator of immune homeostasis

Roquin-1 (Rc3h1) is an E3 ubiquitin ligase originally discovered in a mutational screen for genetic factors contributory to systemic lupus erythematosus-like symptoms in mice. A single base-pair mutation in the Rc3h1 gene resulted in the manifestation of autoantibody production and sustained immunological inflammation characterized by excessive T follicular helper cell activation and formation of germinal centers. Subsequent studies have uncovered a multifactorial process by which Roquin-1 contributes to the maintenance of immune homeostasis. Through its interactions with partner proteins, Roquin-1 targets mRNAs for decay with inducible costimulator being a primary target. In this review, we discuss newly discovered functions of Roquin-1 in the immune system and inflammation, and in disease manifestation, and discuss avenues of further research. A model is presented for the role of Roquin in health and disease.

MicroRNA signatures differentiate Crohn's disease from ulcerative colitis

Background

Excessive and inappropriate immune responses are the hallmark of several autoimmune disorders, including the inflammatory bowel diseases (IBD): Crohn’s disease (CD) and ulcerative colitis (UC). A complex etiology involving both environmental and genetic factors influences IBD pathogenesis. The role of microRNAs (miRNAs), noncoding RNAs involved in regulating numerous biological processes, to IBD pathology, in terms of initiation and progression, remains ill-defined. In the present study, we evaluated the relationship between colon, peripheral blood, and saliva whole miRNome expression in IBD patients and non-inflammatory bowel disease (non-IBD) controls to identify miRNAs that could discriminate CD from UC. Quantitative real-time PCR (qRT-PCR) was used to validate and assess miRNA expression.

Results

Microarray analysis demonstrated that upwards of twenty six miRNAs were changed in CD and UC colon biopsies relative to the non-IBD controls. CD was associated with the differential expression of 10 miRNAs while UC was associated with 6 miRNAs in matched colon tissues. CD was associated with altered expression of 6 miRNAs while UC was associated with 9 miRNAs in whole blood. Expression of miR-101 in CD patients and miR-21, miR-31, miR-142-3p, and miR-142-5p in UC patients were altered in saliva.

Conclusions

Our results suggest that there is specific miRNA expression patterns associated with UC versus CD in three separate tissue/body fluids (colon, blood, and saliva). Further, the aberrant miRNA expression profiles indicate that miRNAs may be contributory to IBD pathogenesis, or at least reflect the underlying inflammation. Scrutinizing miRNA expression in saliva and blood samples may be beneficial in monitoring or diagnosing disease in IBD patients. A panel of miRNAs (miR-19a, miR-21, miR-31, miR-101, miR-146a, and miR-375) may be used as markers to identify and discriminate between CD and UC.

Electronic supplementary material

The online version of this article (doi:10.1186/s12865-015-0069-0) contains supplementary material, which is available to authorized users.