Transforming growth factor beta receptor II (TGFBR2) polymorphisms and the association with nonsegmental vitiligo in the Korean population

The Immunogenetics of Vitiligo: An Approach Toward Revealing the Secret of Depigmentation

Vitiligo is a hypomelanotic skin disease and considered to be of autoimmune origin due to breaching of immunological self-tolerance, resulting in inappropriate immune responses against melanocytes. The development of vitiligo includes a strong heritable component. Different strategies ranging from linkage studies to genome-wide association studies are used to explore the genetic factors responsible for the disease. Several vitiligo loci containing the respective genes have been identified which contribute to vitiligo and genetic variants for some of the genes are still unknown. These genes include mainly the proteins that play a role in immune regulation and a few other genes important for apoptosis and regulation of melanocyte functions. Despite the available data on genetic variants and risk alleles which influence the biological processes, only few immunological pathways have been found responsible for all ranges of severity and clinical manifestations of vitiligo. However, studies have concluded that vitiligo is of autoimmune origin and manifests due to complex interactions in immune components and their inappropriate response toward melanocytes. The genes involved in the immune regulation and processing the melanocytes antigen and its presentation can serve as effective immune-therapeutics that can target specific immunological pathways involved in vitiligo. This chapter highlights those immune-regulatory genes involved in vitiligo susceptibility and loci identified to date and their implications in vitiligo pathogenesis.

The Role of the NKG2D in Vitiligo

Vitiligo is an acquired multifactorial disease that affects melanocytes and results in skin depigmentation. In this review, we examine the role of cells stress and self-reactive T cells responses. Given the canonical and non-canonical functions of NKG2D, such as authenticating stressed target and enhance TCR signaling, we examine how melanocyte stress leads to the expression of ligands that are recognized by the activating receptor NKG2D, and how its signaling results in the turning of T cells against self (melanocyte suicide by proxy). We also discuss how this initiation phase is followed by T cell perpetuation, as NKG2D signaling results in self-sustained long-lasting T cells, with improved cytolytic properties.

Highlights in pathogenesis of vitiligo

Vitiligo is a common pigmentary disorder. Many studies across decades and all over the world have attempted to illustrate the pathogenesis behind it; however, the pathogenesis of vitiligo remains elusive. This review article, we present the findings behind the most and updated theories behind this psychologically debilitating and disfiguring disease. The discussion begun with the role of genetic predisposition followed by neural theory first proposed in the 1950s. We highlight the autoimmune hypothesis, followed by the reactive oxygen species model, zinc-α2-glycoprotein deficiency hypothesis, viral theory, intrinsic theory and biochemical, molecular and cellular alterations accounting for loss of functioning melanocytes in vitiligo. Many theories were elaborated to clarify vitiligo pathogenesis. It is a multifactorial disease involving the interplay of several factors. Future research is needed to clarify the interaction of these factors for better understanding of vitiligo pathogenesis and subsequent successful treatment.

Regulatory T cells in vitiligo: Implications for pathogenesis and therapeutics

Vitiligo is a hypomelanotic autoimmune skin disease arising from a breakdown in immunological self-tolerance, which leads to aberrant immune responses against melanocytes. Regulatory T cells (Tregs) are crucial to the development of self-tolerance and so are major foci in the study of autoimmune pathogenesis of vitiligo. This review will summarise recent findings concerning the role of Tregs in the pathogenesis of vitiligo. In addition, as antigen-specific Tregs are a potential route for the reinstatement of immune tolerance, new strategies that expand or induce de novo generation of Tregs and which are currently being investigated as therapies for other autoimmune diseases, will be discussed. These approaches will highlight the opportunities for Treg cell-based therapeutics in vitiligo.

Association between a TGFBR2 gene polymorphism (rs2228048, Asn389Asn) and acute rejection in Korean kidney transplantation recipients

Transforming growth factor-β (TGF-β) signaling transduction initiates TGF-β activation, resulting in activation of TGF-β receptor II (TGFBR2). Any quantitative and qualitative changes in TGFBR2 are expected to affect the TGF-β signaling pathway, which occupies a central position with respect to the regulation of cell growth, differentiation, apoptosis, immune reaction, angiogenesis and extracellular matrix formation. Recent studies have shown that TGF-β1 gene polymorphisms may confer susceptibility to early acute and chronic allograft rejection in kidney transplantation recipients. In this study, we assessed whether polymorphisms of the TGFBR2 gene were associated with susceptibility to kidney transplantation rejection. A total of 347 renal allograft recipients transplanted at three centers in Korea were analyzed. Three SNPs (rs764522, rs3087465, rs2228048) of the TGFBR2 gene were genotyped from genomic DNA with direct sequencing. Multiple logistic regression models (codominant, dominant, recessive, and log-additive) were performed to evaluate odds ratios (ORs), 95% confidence intervals (CIs), and p-values. A total of 63 patients (18%) developed acute rejection (AR). There were no significant differences in age, sex, number of HLA mismatches, cause of renal failure, or immunosuppressant regimen between the AR and non-AR group. The synonymous SNP rs2228048 was significantly associated with AR (p = 0.020 in recessive model, and p = 0.036 in log-additive model. The allele frequencies of rs2228048 were different between the AR and non-AR group (p = 0.026). These results suggest that the synonymous TGFBR2 gene SNP rs2228048 may be associated with the development of AR in Korean kidney transplantation recipients. Authors Yeong-Hoon Kim and Tae Hee Kim contributed equally to this work and are considered co-first authors.

The pathogenesis of vitiligo

BACKGROUND

Vitiligo is a commonly encountered pigmentary disorder. Numerous studies and investigations from all over the world have attempted to determine the mechanisms behind this disease; however, the pathogenesis of vitiligo remains elusive.

OBJECTIVE

n this comprehensive review article, we present the findings behind the five overarching theories of what causes this disfiguring and psychologically debilitating disease.

METHOD

We begin our discussion with the role of genetic predisposition and move onward to the neural theory first proposed in the 1950s. Next we discuss the autoimmune hypothesis, followed by the reactive oxygen species model, and conclude by describing the findings of the more recent melanocytorrhagy hypothesis.

CONCLUSION

Although the exact pathogenesis of vitiligo is uncertain, each of these theories likely plays a role. Understanding each theory would pave the way for therapeutic advances for this disease.

TGFBR2 gene polymorphism is associated with ossification of the posterior longitudinal ligament

This preliminary study assessed the association between ossification of the posterior longitudinal ligament (OPLL) and the transforming growth factor β receptor type 2 (TGFBR2) gene, with autoimmune disease examined as a possible underlying factor. Twenty-one patients diagnosed with OPLL and 42 control patients without OPLL (non-OPLL) were enrolled in the study. The TGFBR2 gene, composed of one promoter and seven exons, including the 5' untranslated region and flanking introns of each exon, was sequenced. Laboratory tests, including indirect immunofluorescence, were performed to detect autoimmune antibodies. The most common types of OPLL were the continuous (n=8, 38.1%) and segmental (n=8, 38.1%) types, with the fifth cervical veterbra (C5) the most common level of cervical spine involvement (n=15, 71.4%). In addition, significant associations between 455-4T→A (p=0.007) and 571G→A (p=0.024) gene variation and OPLL were found. The 95-35C→T variation in intron 1, a previously unreported variation, was also found in all patients with OPLL. Four patients revealed positive results for autoimmune antibodies and exhibited a nucleolar pattern by indirect immunofluorescence. Of these four patients, two were diagnosed with Sjogren's syndrome. The previously reported association of 455-4T→A and 571G→A polymorphisms of the TGFBR2 gene with OPLL was confirmed in this study. In addition, the 95-35C→T polymorphism in intron 1, which to our knowledge is a novel, previously unreported, nucleotide variation, was detected in all patients. Additional functional studies are required to verify the association between OPLL and the genetic variations found in this study.

Association between TGFBR2 gene polymorphism (rs2228048, Asn389Asn) and intracerebral hemorrhage in Korean population

Transforming growth factor, beta receptor II (TGFBR2) is mainly expressed by neurons in the central nervous system, and reduced neuronal TGFBR2 signaling results in accelerated age-dependent neurodegeneration. To investigate whether TGFBR2 polymorphisms are associated with ischemic stroke (IS) and intracerebral hemorrhage (ICH), two single nucleotide polymorphisms (SNPs) of TGFBR2 gene (rs764522, -1444C/G; rs2228048, Asn389Asn) were selected and genotyped by direct sequencing in 247 stroke patients (120 IS and 127 ICH) and 655 control subjects (260 for IS and 395 for ICH). SNPStats, SNPAnalyzer, Helixtree, and Haploview version 4.2 were used to analyze genetic data. Multiple logistic regression models (codominant, dominant, recessive, and log-additive) were performed to evaluate odds ratios (ORs), 95% confidence intervals (CIs), and p values. The synonymous SNP rs2228048 was significantly associated with ICH (p = 0.032 in codominant 2 model, p = 0.024 in dominant model, p = 0.020 in recessive model, and p = 0.005 in log-additive model) and Fisher's exact test (p = 0.009). Allele frequencies of rs2228048 were different between ICH and controls (p = 0.006). In Bonferroni correction, these correlations were also significant. These results suggest that the synonymous SNP rs2228048 of TGFBR2 gene may be associated with development of ICH in Korean population.

Comprehensive association analysis of candidate genes for generalized vitiligo supports XBP1, FOXP3, and TSLP

We previously carried out a genome-wide association study of generalized vitiligo (GV) in non-Hispanic whites, identifying 13 confirmed susceptibility loci. In this study, we re-analyzed the genome-wide data set (comprising 1,392 cases and 2,629 controls) to specifically test association of all 33 GV candidate genes that have previously been suggested for GV, followed by meta-analysis incorporating both current and previously published data. We detected association of three of the candidate genes tested: TSLP (rs764916, P=3.0E-04, odds ratio (OR)=1.60; meta-P for rs3806933=3.1E-03), XBP1 (rs6005863, P=3.6E-04, OR=1.17; meta-P for rs2269577=9.5E-09), and FOXP3 (rs11798415, P=5.8E-04, OR=1.19). Association of GV with CTLA4 (rs12992492, P=5.9E-05, OR=1.20; meta-P for rs231775=1.0E-04) seems to be secondary to epidemiological association with other concomitant autoimmune diseases. Within the major histocompatibility complex (MHC), at 6p21.33, association with TAP1-PSMB8 (rs3819721, P=5.2E-06) seems to derive from linkage disequilibrium with major primary signals in the MHC class I and class II regions.