Role of FOXP3 gene polymorphism in the susceptibility to Tunisian endemic Pemphigus Foliaceus

Pemphigus: trigger and predisposing factors

Pemphigus is a life-threatening autoimmune blistering disease affecting skin and mucous membranes. Despite its etiopathogenesis remains largely unknown, several trigger and predisposing factors have been reported. Pemphigus is caused by autoantibodies that target desmoglein 1 and desmoglein 3, impacting desmosome function. However, circulating autoantibodies are often the consequence of a precipitating factor that occurs in predisposed individuals. This review aims to describe and discuss almost all trigger and predisposing factors reported as possible or probable cause of the disease. Among the reported trigger factors that may induce or exacerbate pemphigus, we have found of particular interest: drug intake (especially thiol- and phenol-containing compounds), vaccines, infections, as well as some reports about pregnancy, radiations, emotional stress, pesticides and physical trauma. Moreover, we discuss the possible role of food intake in pemphigus onset and particular attention is given to dietary factors containing thiol, phenol and tannin compounds. A trigger factor is "the straw that breaks the camel's back," and often acts together with predisposing factors. Here we discuss how pemphigus onset may be influenced by genetic susceptibility and comorbidities like thyroid diseases, malignancies and other autoimmune disorders. To identify other hitherto unknown trigger and predisposing factors, well designed prospective studies are needed. In this context, future research should explore their connection with the aim to advance our understanding of pemphigus pathogenesis.

Association of genetic variations in FoxP3 gene with Graves' disease in a Southwest Chinese Han population

BACKGROUND

Graves' disease (GD) is a T cell-mediated organ-specific autoimmune disease. Forkhead box P3 (FoxP3) is an excellent marker for the induction and development of regulatory T cells (Tregs). Recent studies showed that single-nucleotide polymorphisms (SNPs) in the FoxP3 gene were associated with the increased susceptibility to several autoimmune diseases. In the present study, we investigated the association of FoxP3 gene polymorphisms with GD in a Southwest Chinese Han population.

METHODS

A two-stage case-control study was performed in 890 healthy controls (male, 282; female, 608) and 503 patients with GD (male, 138; female, 365). Four SNPs (rs3761548, rs3761549, rs3761547, and rs2280883) were genotyped by the polymerase chain reaction-restriction fragment length polymorphism assay. The χ2 test was used to compare the genotype distributions and allele frequencies between GD patients and healthy controls.

RESULTS

In the first stage, the significantly increased frequencies of the A allele (p = .031, odds ratio [OR] = 1.635) and AA genotype (p = .023, OR = 3.257), together with a significantly decreased frequency of the C allele (p = .031, OR = 0.611) of FoxP3/rs3761548 were found in female patients with GD. None of the other FoxP3 SNPs was associated with GD susceptibility. Subsequent validation and combination of data confirmed the association between FoxP3/rs3761548 and the female patients with GD (A allele: p < .001, OR = 1.672; AA genotype: p = .005, OR = 2.488; CC genotype: p = .001, OR = 0.622; C allele: p < .001, OR = 0.615, respectively).

CONCLUSION

Our findings suggest that FoxP3/rs3761548 is significantly associated with female GD patients in a Southwest Chinese Han population.

Evaluation of X chromosome inactivation in endemic Tunisian pemphigus foliaceus

BACKGROUND

Almost 5% of the world's population develops an autoimmune disease (AID), it is considered the fourth leading cause of disability for women, who represent 78% of cases. The sex ratio when it comes to the most prevalent AID varies from 9:1 in systemic lupus erythematosus (SLE) to 13:1 in endemic Tunisian pemphigus foliaceus (PF).

METHODS

To test the potential involvement of skewed x-inactivation in the pathogenesis of Tunisian PF, we analyzed the methylation status of a highly polymorphic CAG repeat in the androgen receptor gene and evaluated the x chromosome inactivation (XCI) patterns in peripheral blood-leukocyte-derived DNA samples of female patients with PF (n = 98) compared to healthy control (HC) subjects (n = 150), as well as female patients with SLE (n = 98) were enrolled as a reference group.

RESULTS

XCI status was informative for 50 of the 98 PF patients (51%) and 70 of the 150 HC women (47%). Extremely skewed XCI patterns were more frequent in PF and SLEwomen than HC, but the difference was statistically significant only in women with SLE. No statistical difference was observed in XCI patterns between PF and SLE patients. PF phenotype-XCI correlation analysis revealed that (i) skewed XCI patterns may be involved in the disease's subtype and (ii) it was more pronounced in the endemic group than the sporadic one. Furthermore, preferential XCI showed an increase in heterozygote genotypes of PF's susceptibility polymorphisms in immunity-related X genes (FOXP3, AR, and TLR7) in PF patients compared to HC.

CONCLUSION

Our results suggest that skewed XCI could lead to hemizygosity of X-linked alleles that might unmask X-linked deleterious alleles.

Autoantibody-Specific Signalling in Pemphigus

Pemphigus is a severe autoimmune disease impairing barrier functions of epidermis and mucosa. Autoantibodies primarily target the desmosomal adhesion molecules desmoglein (Dsg) 1 and Dsg 3 and induce loss of desmosomal adhesion. Strikingly, autoantibody profiles in pemphigus correlate with clinical phenotypes. Mucosal-dominant pemphigus vulgaris (PV) is characterised by autoantibodies (PV-IgG) against Dsg3 whereas epidermal blistering in PV and pemphigus foliaceus (PF) is associated with autoantibodies against Dsg1. Therapy in pemphigus is evolving towards specific suppression of autoantibody formation and autoantibody depletion. Nevertheless, during the acute phase and relapses of the disease additional treatment options to stabilise desmosomes and thereby rescue keratinocyte adhesion would be beneficial. Therefore, the mechanisms by which autoantibodies interfere with adhesion of desmosomes need to be characterised in detail. Besides direct inhibition of Dsg adhesion, autoantibodies engage signalling pathways interfering with different steps of desmosome turn-over. With this respect, recent data indicate that autoantibodies induce separate signalling responses in keratinocytes via specific signalling complexes organised by Dsg1 and Dsg3 which transfer the signal of autoantibody binding into the cell. This hypothesis may also explain the different clinical pemphigus phenotypes.

Critical appraisal of different triggering pathways for the pathobiology of pemphigus vulgaris-A review

Pemphigus vulgaris is an autoimmune blistering disease with an increased potential for mortality. The epithelium is key in understanding the pathobiology as it is specialized to perform functions like mechanical protection, immunological defense, and proprioception. In order to perform these array of functions, epithelial integrity is important. This integrity is maintained by a host of molecules which orchestrate the ability of the keratinocytes to function as a single unit. Desmoglein 3 antibodies formed in genetically susceptible individuals are known to cause the disruption of the intact oral mucosa leading to the formation of blisters in pemphigus vulgaris patients. However, there are underlying complex triggering pathways leading to the clinical disease. The aim of the review is to congregate and critically appraise the various triggering pathways which contribute toward the pathobiology of pemphigus vulgaris. Articles relevant to the pathobiology of pemphigus vulgaris were identified from various search databases till the year 2020. The pathogenesis of pemphigus vulgaris is complex, and it involves an in-depth understanding of the various predisposing factors, provoking factors, and progression mechanisms. Congregation of the various triggering pathways will open our minds to understand pemphigus vulgaris better and in turn develop a reliable treatment in the near future.

The role of FOXP3 rs3761548 and rs2294021 polymorphisms in pediatrics acute lymphoblastic leukemia: association with risk and response to therapy

FOXP3 X-linked gene has crucial roles in the development and function of regulatory T cells. We investigated the association of FOXP3 rs3761548, rs3761549 and rs2294021 single nucleotide polymorphisms (SNPs) with acute lymphoblastic leukemia (ALL) susceptibility and response to therapy. Genotyping was performed in 247 patients and 210 healthy subjects. We observed a higher frequency of rs3761548 A carriers and rs2294021 C carriers (p < 0.04) in male patients, and lower frequencies of rs3761548 AC genotype (p = 0.04) and rs2294021 CT genotype (p = 0.01) in female patients compared to controls. ACC (p = 0.04) and ATC haplotypes (p = 0.002) were associated with susceptibility to ALL. There was a significant correlation between the genotypes of rs3761548 and rs2294021 SNPs with event-free survival (EFS) and overall survival (OS). The rs3761548 A genotype in male patients was associated with increased risk of relapse (p < 0.0001), shorter EFS, increased death rate (p = 0.002) and shorter OS compared to C genotype (p = 0.001). Similar significant results were observed for the relation of rs2294021 C genotype with response to therapy in male patients. In females, patients with rs3761548 AC genotype had longer EFS (p = 0.02) and those with rs2294021 CT had longer EFS and OS (p < 0.005). According to haplotype analysis, patients carrying ACC or ATC haplotypes had the highest number of WBCs and shorter EFS or OS, and patients with CCT haplotype had the lowest number of WBCs and longer EFS or OS. These results provided evidence for the impact of these polymorphisms on susceptibility and response to therapy in children with ALL.

Toll-like-Receptor Gene Polymorphisms in Tunisian Endemic Pemphigus Foliaceus

Pemphigus foliaceus (PF) is considered to be caused by the combined effects of susceptibility genes and environmental triggers. The polymorphisms of Toll-like receptors (TLRs) genes have been associated with the risk of various autoimmune diseases. The aim of this study was to evaluate the potential association of TLR2-3-4 and 7 gene polymorphisms with Tunisian PF. Fourteen polymorphisms were analyzed in 93 Tunisian PF patients compared to 193 matched healthy controls: rs5743703-rs5743709 and (GT)_n repeat (TLR2); rs5743305, rs3775294, and rs3775291 (TLR3), rs4986790 and rs4986791 (TLR4); and rs3853839 (TLR7). Our results showed that the genetic factors varied depending on the epidemiological feature stratification. In fact, in the whole population, no association with the susceptibility to PF was found. The TLR2 GT repeat seems to be closely associated with PF risk in patients originated from the endemic localities (group 3); the GT₁₈ allele and the heterozygous genotype GT₁₈/GT₁₉ seem to confer risk to endemic PF (P = 0.02; OR = 2.3 [1.1-4.9] and P = 0.0002, OR = 20 [2.5-171], respectively). In contrast, the GT₂₃ repeat could be considered as protector allele (P = 0.02, OR = 0.2 [0.06-0.87]). Furthermore, medium GT alleles which induce high promoter activity were also significantly more frequent in patients versus short or long GT repeats (P = 0.0018 with OR = 3.26 [1.5-7]). On the other hand, the TLR3-rs574305 AA genotype and A allele were significantly more frequent in patients whose age of the onset was above 35 years (group 2) (P = 0.038, OR = 1.78 and P = 0.009, OR = 3.92, respectively). Besides, the TLR4>rs3775294 A allele was found to be protector only in patients with sporadic features (groups 2 and 4) (P = 0.03, OR = 0.57 [0.3-0.9] and P = 0.006, OR = 0.24 [0.08-0.74], respectively). No statistically significant difference was observed in the genotypic and allelic frequencies of TLR-4 and TLR-7 gene polymorphisms. The present data suggest that TLR2and TLR3 polymorphisms are significantly associated with increased susceptibility to PF in the Tunisian population.

Chromosome 2q33genetic polymorphisms in Tunisian endemic pemphigus foliaceus

Background

Several studies have suggested that polymorphisms within genes encoding T‐lymphocyte immune regulating molecules: CD28, CTLA‐4, and ICOS, may alter the signaling process and subsequently could be involved in susceptibility to a broad spectrum of autoimmune diseases.

Methods

This study aimed to replicate associations between common polymorphisms in the 2q33.2 cluster and susceptibility to pemphigus foliaceus (PF) in the Tunisian population. We investigated seven polymorphisms: rs3116496 and rs1879877 (CD28), rs231775, rs3087243, and (AT)_n repeat (CTLA4); rs11889031 and rs10932029 (ICOS) in a case–control study which enrolled 106 Tunisian PF patients and 205 matched healthy controls.

Results

We confirmed the associations with CTLA4((AT)₁₃, p = 0.00137, OR = 3.96 and (AT)₂₀, p = 0.008, OR = 5.22; respectively) and ICOS genes (rs10932029>CT, p = 0.034, OR = 2.12 and rs10932029>TT, p = 0.04 and OR = 0.41).

Conclusion

Our results indicate that susceptibility to PF is located in the proximal and the distal 3′ flanking region of the CTLA4/ICOS promoter. These findings may open avenues to the treatment of patients with biological drugs targeting CTLA4/ICOS molecules, in a personalized manner to achieve more effective treatment.

Beyond the HLA polymorphism: A complex pattern of genetic susceptibility to pemphigus

Pemphigus is a group of autoimmune bullous skin diseases that result in significant morbidity. As for other multifactorial autoimmune disorders, environmental factors may trigger the disease in genetically susceptible individuals. The goals of this review are to summarize the state of knowledge about the genetic variation that may affect the susceptibility and pathogenesis of pemphigus vulgaris and pemphigus foliaceus – both the endemic and the sporadic forms –, to compare and discuss the possible meaning of the associations reported, and to propose recommendations for new research initiatives. Understanding how genetic variants translate into pathogenic mechanisms and phenotypes remains a mystery for most of the polymorphisms that contribute to disease susceptibility. However, genetic studies provide a strong foundation for further developments in this field by generating testable hypotheses. Currently, results still have limited influence on disease prevention and prognosis, drug development, and clinical practice, although the perspectives for future applications for the benefit of patients are encouraging. Recommendations for the continued advancement of our understanding as to the impact of genetic variation on pemphigus include these partially overlapping goals: (1) Querying the functional effect of genetic variants on the regulation of gene expression through their impact on the nucleotide sequence of cis regulatory DNA elements such as promoters and enhancers, the splicing of RNA, the structure of regulatory RNAs and proteins, binding of these regulatory molecules to regulatory DNA elements, and alteration of epigenetic marks; (2) identifying key cell types and cell states that are implicated in pemphigus pathogenesis and explore their functional genomes; (3) integrating structural and functional genomics data; (4) performing disease-progression longitudinal studies to disclose the causal relationships between genetic and epigenetic variation and intermediate disease phenotypes; (5) understanding the influence of genetic and epigenetic variation in the response to treatment and the severity of the disease; (6) exploring gene-gene and genotype-environment interactions; (7) developing improved pemphigus-prone and non-prone animal models that are appropriate for research about the mechanisms that link genotypes to pemphigus. Achieving these goals will demand larger samples of patients and controls and multisite collaborations.

The Genetics of Pemphigus Vulgaris

Pemphigus vulgaris (PV) is a severe autoimmune blistering disease caused by auto-antibodies (auto-Abs) directed against epithelial desmosomal components and leading to disruption of cell-cell adhesion. The exact mechanisms underlying the disease pathogenesis remain unknown and treatment is still based on immunosuppressive drugs, such as corticosteroids, which are associated with potentially significant side effects. Ethnic susceptibility, familial occurrence, and autoimmune comorbidity, suggest a genetic component to the pathogenesis of the disease, which, if discovered, could advance our understanding of PV pathogenesis and thereby point to novel therapeutic targets for this life-threatening disorder. In this article, we review the evidence for a genetic basis of PV, summarize the different approaches used to investigate susceptibility traits for the disease and describe past and recent discoveries regarding genes associated with PV, most of which belong to the human leukocyte antigen (HLA) locus with limited data regarding association of non-HLA genes with the disease.

Fc receptor-like 3 (-169T>C) polymorphism increases the risk of tendinopathy in volleyball athletes: a case control study

Background

Tendinopathy pathogenesis is associated with inflammation. Regulatory T (Treg) cells contribute to early tissue repair through an anti-inflammatory action, with the forkhead box P3 (FOXP3) transcription factor being essential for Treg function, and the FC-receptor-like 3 (FCRL3) possibly negatively regulating Treg function. FCRL3 –169T>C and FOXP3 –2383C>T polymorphisms are located near elements that regulate respective genes expression, thus it was deemed relevant to evaluate these polymorphisms as risk factors for tendinopathy development in athletes.

Methods

This case-control study included 271 volleyball athletes (146 tendinopathy cases and 125 controls) recruited from the Brazilian Volleyball Federation. Genotyping analyses were performed using TaqMan assays, and the association of the polymorphisms with tendinopathy evaluated by multivariate logistic regression.

Results

Tendinopathy frequency was 63% patellar, 22% rotator cuff and 15% Achilles tendons respectively. Tendinopathy was more common in men (OR = 2.87; 95% CI = 1.67–4.93). Higher age (OR = 8.75; 95% CI = 4.33–17.69) and more years of volleyball practice (OR = 8.38; 95% CI = 3.56–19.73) were risk factors for tendinopathy. The FCRL3 –169T>C frequency was significantly different between cases and controls. After adjustment for potential confounding factors, the FCRL3 –169C polymorphism was associated with increased tendinopathy risk (OR = 1.44; 95% CI = 1.02–2.04), either considering athletes playing with tendon pain (OR = 1.98; 95% CI = 1.30–3.01) or unable to train due to pain (OR = 1.89; 95% CI = 1.01–3.53). The combined variant genotypes, FCRL3 –169TC or –169CC and FOXP3 –2383CT or –2383TT, were associated with an increased risk of tendinopathy among athletes with tendon pain (OR = 2.24; 95% CI: 1.14–4.40 and OR = 2.60; 95% CI: 1.11–6.10). The combined analysis of FCRL3 –169T>C and FOXP3 –2383C>T suggests a gene-gene interaction in the susceptibility to tendinopathy.

Conclusions

FCRL3 –169C allele may increase the risk of developing tendinopathy, and together with knowledge of potential risk factors (age, gender and years playing) could be used to personalize elite athletes’ training or treatment in combination with other approaches, with the aim of minimizing pathology development risk.