The genetics of shared autoimmunity

Researchers have long suspected that genetic susceptibility is shared among autoimmune diseases. With the increased understanding of genetic risks and disease etiology, we are beginning to comprehend the nature of shared autoimmunity. This article briefly describes the most recent advances in the genetics of autoimmunity and the novel genes discovered.     

Catalog of 238 variations among six human genes encoding solute carriers (hSLCs) in the Japanese population

We screened DNAs of 48 Japanese individuals for single-nucleotide polymorphisms (SNPs) in six genes encoding proteins of the solute carrier (SLC) family by direct sequencing of their entire genomic regions except for repetitive-sequence elements. This approach identified 213 SNPs and 25 insertion/deletion polymorphisms among the six genes. On average, we identified 1 SNP in every 509 nucleotides. Of the 213 SNPs, 14 were identified in the SLC10A1 gene, 51 in SLC15A1, 29 in SLC22A1, 27 in SLC22A2, 54 in SLC22A4, and 38 in SLC22A5. Eight were located in 5′ flanking regions, 172 in introns, 25 in exons, and 8 in 3′ flanking regions. These variants should contribute to investigations of possible correlations between genotypes and phenotypes as regards disease susceptibilities or responsiveness to drug therapy. Received: July 24, 2002 / Accepted: July 25, 2002 Correspondence to:Y. Nakamura     

Direct or indirect association in a complex disease: the role of SLC22A4 and SLC22A5 functional variants in Crohn disease

A common haplotype spanning 250 kb on chromosome 5q31 is strongly associated with Crohn disease (CD). Recently, two functional variants within the SLC22A4 and SLC22A5 genes at this locus (IBD5), L503F (c.1507C > T) and G-207C (c.-207G > C), have been proposed to contribute directly to susceptibility to CD. However, extensive linkage disequilibrium at the IBD5 locus has complicated efforts to distinguish causal variants from association of the general risk haplotype. We genotyped the SLC22A4 and SLC22A5 variants and other polymorphisms across the risk haplotype in four populations of European origin, and applied regression-based haplotype analysis to over 1,200 fully genotyped case-control pairs, modeling case/control status on the presence of one or more SNPs to test for conditional association and to identify risk haplotypes. We found highly significant association of SNPs at the IBD5 locus with Crohn disease in all populations tested. However, the frequencies of L503F and G-207C in individuals who did not carry the general IBD5 risk haplotype were not significantly different in cases and controls, with associated disease odds ratios (ORs) of 0.90 (95% CI, 0.57-1.40) and 0.90 (95% CI, 0.65-1.23), respectively. Haplotype analysis showed that addition of the SLC22A4 and SLC22A5 variants to a null model that included the background risk haplotype did not significantly improve the model fit. In addition to the common risk haplotype, several rare haplotypes had an increased frequency in cases compared to controls. This study suggests that the molecular basis for Crohn disease susceptibility at the IBD5 locus remains to be defined, and highlights the challenge of the identification of causal variants in a complex disease in regions of extensive linkage disequilibrium.     

云南人群中PTPN22和PADI4基因多态性与类风湿关节炎的关联研究

目的 探讨云南人群PTPN22和PADI4基因的7个SNP多态与类风湿关节炎易感性的相关性.方法 选取192例类风湿关节炎患者和288名正常人进行病例对照研究.分别用PCR-RFLP法检测PTPN22基因的rs33996649和1858位点、PADI4基因的rs11203366和rs874881位点,用焦磷酸测序法检测PADI4基因的rs1635579、rs2428736和rs2240340共7个SNP位点的基因型.结果 在7个SNP位点中,PADI4基因的rs2240340位点的等位基因频率和基因型频率在病例组和对照组间差异有统计学意义(P＜0.05).结论 在云南人群中PADI4基因的rs2240340多态性与类风湿关节炎的易感性存在相关性.     

Associations of single nucleotide polymorphisms of PTPN22 and Ctla4 genes with the risk of allergic rhinitis in a Chinese Han population

Background

Allergic rhinitis (AR) is an inflammatory disorder of the upper airway. Protein tyrosine phosphatase non-receptor 22 encoded by PTPN22 gene and cytotoxic T-lymphocyte associated 4 encoded by Ctla4 gene are associated with autoimmune diseases.

ORIGINAL ARTICLE: PTPN22 C1858T Polymorphism in Women with Endometriosis

Citation Gomes FMCS, Bianco B, Teles JS, Christofolini DM, de Souza AMB, Guedes AD, Barbosa CP. PTPN22 C1858T polymorphismin women with endometriosis. Am J Reprod Immunol 2010; 63: 227–232 Problem Endometriosis has been suggested to be an autoimmune disease and recently, an allelic variation of the PTPN22 (C1858T) gene was revealed to be associated with the development of autoimmunity. The aim of the study was to determine the frequency of the PTPN22 (C1858T) polymorphism in Brazilian women with endometriosis as compared with controls. Method of study Case–control study included 140 women with endometriosis and a control group consisting of 180 healthy fertile women without a history of endometriosis and/or autoimmune diseases from the ABC School of Medicine. The PTPN22 (C1858T) polymorphism was studied by restriction fragment length polymorphism polymerase chain reaction (RFLP‐PCR). Results Genotypes CC, CT and TT of PTPN22 polymorphism presented frequencies of 67.9, 30.0 and 2.1% in the women with endometriosis (P = 0.008); 76.2, 19.0 and 4.8% in women with minimal/mild endometriosis (P = 0.173); 61.0, 39.0 and 0.0% in women with moderate/severe endometriosis (P ≤ 0.001) and 82.8, 16.1 and 1.1% in control group. Allele C and T were present in 82.9 and 17.1%; 85.7 and 14.3%; 80.5 and 19.5%; and 90.8 and 9.2% respectively, in women with endometriosis (P = 0.004), women with minimal/mild endometriosis (P = 0.148), women with moderate/severe endometriosis (P = 0.002) and control group. Conclusion The data suggest that in Brazilian women polymorphism PTPN22 (C1858T) may be an important genetic predisposing factor for endometriosis, especially, in advanced disease.     

Identification of susceptibility SNPs in CTLA-4 and PTPN22 for scleritis in Han Chinese

The aim of this study was to determine the association between 13 single nucleotide polymorphisms (SNPs) in the cytotoxic T lymphocyte-associated antigen-4 (CTLA4) and protein tyrosine phosphatase non-receptor type 22 (PTPN22) genes with scleritis in a Chinese Han population. We recruited 432 scleritis patients and 710 healthy controls. Four tag SNPs of CTLA4 and nine tag SNPs of PTPN22 were selected using Haploview. Genotyping was performed with the Sequenom MassArray® iPLEX GOLD Assay. Genotype and allele frequency differences were analyzed by χ² test and Bonferroni correction. Haplotype analysis was performed to further evaluate the association of these two genes with scleritis. In this study, CTLA4/rs3087243 G allele frequency and GG genotype frequency were significantly increased in scleritis patients compared to healthy controls [corrected P-value (Pc) = 0·02, odds ratio (OR) = 1·475, 95% confidence interval (CI) = 1·175–1·851; Pc = 0·04, OR = 1·546, 95% CI = 1·190–2·008, respectively]. None of the tested SNPs in the PTPN22 gene showed an association with scleritis. Haplotype analysis revealed a lower frequency of a CTLA4 TCAA haplotype (order of SNPs: rs733618, rs5742909, rs231775, rs3087243) (Pc = 4·26 × 10^–3, OR = 0·618, 95% CI = 0·540–0·858) and a higher frequency of a PTPN22 TTATACGCG haplotype (order of SNPs: rs3789604, rs150426536, rs1746853, rs1217403, rs1217406, rs3789609, rs1217414, rs3789612, rs2488457) (Pc = 2·83 × 10^–4, OR = 1·457, 95% CI = 1·210-1·754) in scleritis patients when compared to healthy controls. In conclusion, our findings indicate that CTLA4 and PTPN22 might confer genetic susceptibility to scleritis in a Chinese Han population.     

Haplotype variation at the IBD5/SLC22A4 locus (5q31) in coeliac disease in the Irish population

In addition to the well-established association of coeliac disease (CD) with HLA-DQ (6p21) and possibly CTLA4 (2q33), there is considerable evidence for a susceptibility locus on chromosome 5q, which contains many potential candidates for inflammatory disease, including a cluster of cytokine genes in 5q31. CD cases and controls were genotyped for four single-nucleotide polymorphism (SNP) markers that together characterize >90% of the haplotype variation at the IBD5 locus encoding, among others, the SLC22A4 gene. IBD5 and SLC22A4 map to 5q31 and have recently been associated with Crohn's disease and rheumatoid arthritis. Haplotype frequencies do not differ significantly between CD cases and controls in the Irish population, and therefore the chromosome 5 CD susceptibility locus most likely lies elsewhere on 5q.     

Genotype-phenotype correlation in primary carnitine deficiency

Primary carnitine deficiency is caused by defective OCTN2 carnitine transporters encoded by the SLC22A5 gene. Lack of carnitine impairs fatty acid oxidation resulting in hypoketotic hypoglycemia, hepatic encephalopathy, skeletal and cardiac myopathy. Recently, asymptomatic mothers with primary carnitine deficiency were identified by low carnitine levels in their infant by newborn screening. Here, we evaluate mutations in the SLC22A5 gene and carnitine transport in fibroblasts from symptomatic patients and asymptomatic women. Carnitine transport was significantly reduced in fibroblasts obtained from all patients with primary carnitine deficiency, but was significantly higher in the asymptomatic women's than in the symptomatic patients' fibroblasts (P < 0.01). By contrast, ergothioneine transport (a selective substrate of the OCTN1 transporter, tested here as a control) was similar in cells from controls and patients with carnitine deficiency. DNA sequencing indicated an increased frequency of nonsense mutations in symptomatic patients (P < 0.001). Expression of the missense mutations in Chinese hamster ovary (CHO) cells indicated that many mutations retained residual carnitine transport activity, with no difference in the average activity of missense mutations identified in symptomatic versus asymptomatic patients. These results indicate that cells from asymptomatic women have on average higher levels of residual carnitine transport activity as compared to that of symptomatic patients due to the presence of at least one missense mutation.     

Genetically determined neuropathy (CMT 1A) accompanied by immune dysfunction: a case report

Peripheral Myelin Protein 22 (PMP22) is mostly expressed in Schwann cells where it is essential in the compaction of myelin. The duplication of the PMP22 gene results in a hereditary demyelinating neuropathy of the Charcot–Marie–Tooth type 1A (CMT1A). So far there are only a few case reports suggesting that dysimmune mechanisms may take part in the pathophysiology of this disease. We describe three siblings carrying the duplication of the PMP22 gene, with a significant reduction of serum immunoglobulin G levels in all three cases and sural nerve vasculitis in the two women, which supports the proposition, that immune dysfunction may accompany this disease in some cases.     

乳腺癌中印记基因SLC22A18/TSSC5/BWR1A启动子区甲基化及mRNA表达的研究

目的： 研究印记基因SLC22A18启动子区甲基化对乳腺侵润性导管癌组织中的SLC22A18 mRNA表达的影响，探讨其与临床病理特征之间的关系。方法：实时荧光定量逆转录聚合酶链反应（real-time quantitative RT-PCR）方法检测40例乳腺侵润性导管癌及其癌旁组织中SLC22A18 mRNA的表达，甲基化特异性聚合酶链反应(MSP)检测SLC22A18基因启动子区的甲基化状态。检测DNA甲基转移酶抑制剂5-氮杂-2′-脱氧胞苷（5-aza-2′-deoxycytidine，5-aza-dc）和组蛋白去乙酰化酶抑制剂曲古霉素A（TSA）作用于乳腺癌细胞株MDA-MB-231后，对SLC22A18基因启动子区DNA甲基化和mRNA表达的影响。结果：SLC22A18在40例乳腺侵润性导管癌中mRNA表达量低于癌旁组织（0.12±0.10 vs 0.69±1.05，P＜0.01）；40例乳腺侵润性导管癌及对应癌旁组织中，SLC22A18启动子区的甲基化发生率分别为75％和37.5%，差异有统计学意义（P＜0.01）；在40例乳腺侵润性导管癌组织中，甲基化组SLC22A18 mRNA表达量低于非甲基化组（0.11±0.08 vs 0.24±0.18，P＜0.01）。5-aza-dc和5-aza-dc/TSA能不同程度逆转乳腺癌细胞株MDA-MB-231中SLC22A18基因的甲基化状态，并上调SLC22A18基因表达。结论：SLC22A18基因甲基化与乳腺癌发生有一定的关联，SLC22A18基因表达下调与其启动子区CpG岛异常甲基化相关。     

Expression of pendrin and NIS iodide transporters in human breast tumor and peri-tumoral tissue

IntroductionThyroid iodide transporters, Na⁺/I^– symporter (NIS) and pendrin (PDS), are responsible for supplying this vital micronutrient for thyroid hormone synthesis by thyroid peroxidase (TPO). Both proteins were shown to be expressed, apart from the thyroid, also in other human tissues, including lactating mammary gland. NIS expression in human breast cancers has been widely studied. On the other hand, until now PDS mRNA levels in breast tumor tissue have been estimated only in high throughput analyses. Previously, we have observed that TPO is expressed in normal and cancerous human breast tissues and shows enzymatic activity. However, biochemical activity of TPO in human breast cancer cells requires iodide transport by NIS and PDS. Therefore, to extend our previous study on TPO expression and function in human breast tumors we performed analysis of NIS and PDS levels in the same group of patients.Material and methodsThe study involved detection of NIS and PDS protein levels by immunohistochemistry and Western blotting, as well as mRNA levels by real-time quantitative polymerase chain reaction.ResultsHere we provide direct evidence that NIS and PDS are expressed in human breast cancer tissue, with NIS levels being increased and PDS levels decreased in tumor tissue. Interestingly, PDS mRNA levels in breast cancer tissue seem to be influenced by the estrogen receptor status and age of the patients, while NIS mRNA levels were dependent on histological type of the tumor.ConclusionsThis study provides valuable information important for consideration in diagnostic or therapeutic application of radioiodine in breast cancer management.     

IL-22在自身免疫病中作用的研究进展

IL-22为IL-10家族成员之一.作为一种新型细胞因子,其与自身免疫性疾病关系密切.最近大量证据表明IL-22参与了多种自身免疫性疾病,如系统性红斑狼疮、类风湿性关节炎、多发性硬化、干燥综合征、银屑病等.然而在不同的自身免疫性疾病中IL-22所发挥的作用不尽相同,可能起致病性作用,也可能起保护性作用.因此以IL-22作为靶点为多种自身免疫性疾病的治疗提供了新的思路.     

Type 1 diabetes linked PTPN22 gene polymorphism is associated with the frequency of circulating regulatory T cells

Dysfunction of FOXP3-positive regulatory T cells (Tregs) likely plays a major role in the pathogenesis of multiple autoimmune diseases including type 1 diabetes (T1D). Whether genetic polymorphisms associated with the risk of autoimmune diseases affect Treg frequency or function is currently unclear. Here, we analysed the effect of T1D-associated major HLA class II haplotypes and seven single nucleotide polymorphisms in six non-HLA genes [INS (rs689), PTPN22 (rs2476601), IL2RA (rs12722495 and rs2104286), PTPN2 (rs45450798), CTLA4 (rs3087243), and ERBB3 (rs2292239)] on peripheral blood Treg frequencies. These were determined by flow cytometry in 65 subjects who had progressed to T1D, 86 islet autoantibody-positive at-risk subjects, and 215 islet autoantibody-negative healthy controls. The PTPN22 rs2476601 risk allele A was associated with an increase in total (p = 6 × 10⁻⁶) and naïve (p = 4 × 10⁻⁵) CD4+CD25+CD127lowFOXP3+ Treg frequencies. These findings were validated in a separate cohort comprising ten trios of healthy islet autoantibody-negative children carrying each of the three PTPN22 rs2476601 genotypes AA, AG, and GG (p = 0.005 for total and p = 0.03 for naïve Tregs, respectively). In conclusion, our analysis implicates the autoimmune PTPN22 rs2476601 risk allele A in controlling the frequency of Tregs in human peripheral blood.     

Age and origin of the G774A mutation in SLC22A12 causing renal hypouricemia in Japanese

Renal hypouricemia is an inherited disorder characterized by impaired tubular uric acid transport. Impairment of the function of URAT1, the main transporter for the reabsorption of uric acid at the apical membrane of the renal tubules, causes renal hypouricemia. The G774A mutation in the SLC22A12 gene encoding URAT1 predominates in Japanese renal hypouricemia. From data on linkage disequilibrium between the G774 locus and the 13 markers flanking it (12 single nucleotide polymorphisms and 1 dinucleotide insertion/deletion locus), we here estimate the age of this mutation at approximately 6820 years [95% confidence interval (CI) 1860–11,760 years; median = 2460 years]. This indicates that the origin of the G774A mutation dates back from between the time when the Jomon people predominated in Japan and the time when the Yayoi people started to migrate to Japan from the Korean peninsula. These data are consistent with a recent finding that this G774A mutation was also predominant in Koreans with hypouricemia and indicate that the mutation originated on the Asian continent. Thus, this mutation found in Japanese patients was originally brought by immigrant(s) from the continent and thereafter expanded in the Japanese population either by founder effects or by genetic drift (or both).     

Presence of organic anion transporters 3 (OAT3) and 4 (OAT4) in human adrenocortical cells

Since the organic anion transporter-1 (OAT1) has been implicated in cortisol release from bovine and rat adrenal zona fasciculata cells, we addressed the question of whether OATs are present in human adrenal cortical cells. In the human adrenal cell line NCI-H295R, 24-h cortisol secretion increased up to 30-fold on exposure to forskolin. Incubation of forskolin-treated cells for 24 h with the OAT substrates probenecid, p-aminohippurate (PAH), glutarate or cimetidine inhibited cortisol release partly. RT-PCR did not reveal expression of human OAT1 and OAT2, but OAT3 and OAT4 mRNAs were detected in both NCI-H295R cells and human adrenal tissue. When human OAT3 (hOAT3) and hOAT4 were expressed in Xenopus laevis oocytes, only hOAT3 showed [³H]cortisol uptake in excess of that of water-injected control oocytes. Cortisol uptake via OAT3 was saturable with an apparent K_t of 2.4 µM. In NCI-H295R cells, [³H]estrone sulphate uptake was saturable, cis-inhibited by OAT substrates and trans-stimulated by preloading with glutarate or cortisol. Likewise, [³H]PAH uptake was cis-inhibited by estrone sulphate and trans-stimulated by preloading the cells with PAH, glutarate or cortisol, indicating functional expression of OATs in the plasma membrane of NCI-H295R cells.     

Association analysis of <Emphasis Type="Italic">SLC22A4</Emphasis>, <Emphasis Type="Italic">SLC22A5</Emphasis> and <Emphasis Type="Italic">DLG5</Emphasis> in Japanese patients with Crohn disease

Crohn disease (CD) is an inflammatory bowel disease characterized by chronic transmural, segmental, and typically granulomatous inflammation of the gut. Recently, two novel candidate gene loci associated with CD, SLC22A4 and SLC22A5 on chromosome 5 known as IBD5 and DLG5 on chromosome 10, were identified through association analysis of Caucasian CD patients. We validated these candidate genes in Japanese patients with CD and found a weak but possible association with both SLC22A4 (P=0.028) and DLG5 (P=0.023). However, the reported genetic variants that were indicated to be causative in the Caucasian population were completely absent in or were not associated with Japanese CD patients. These findings imply significant differences in genetic background with CD susceptibility among different ethnic groups and further indicate some difficulty of population-based studies.