Mutations analysis in filaggrin gene in northern China patients with atopic dermatitis

Background Recently, we have reported filaggrin mutations (FLG) of atopic dermatitis in southern China. However, there have been few detailed reports of FLG mutations of patients with AD in northern China by now. Objectives The present aim was to establish the mutation spectrum of FLG gene in AD patients in northern China. Methods A total of 339 cases met Hanifin and Rajka diagnostic criteria of AD were recruited. A comprehensive sequencing of the entire FLG coding region in these patients was conducted. All detected FLG null mutations were screened in a cohort of 301 normal controls. Results Seven novel mutations (478insA, Q1070X, 4026delT, Q1712X, Q2397X, 7145del4 and 8001del4) and eleven reported mutations (3222del4, 3321delA, 4271delAA, S1515X, Q1790X, 5757del4, 6834del5, Q2417X, E2422X, 7945delA and K4671X) in AD were identified. Mutations 3321delA and K4671X were two of the most common mutations in AD. FLG null mutations were present in 26.0% of AD patients. FLG null alleles (compound genotypes) were significantly higher in AD (P < 0.001) than in the controls. The compound genotypes for all FLG variants were significantly associated with IV (P < 0.001) and palmar hyperlinearity (P < 0.001). The common mutation, K4671X, was significantly associated with AD‐coexistent allergic rhinitis (P = 0.005). Conclusions Our study increases the total number of FLG mutations. We clearly demonstrated that FLG loss‐of‐function mutations were significantly associated with AD in northern China. The FLG null mutations in the Chinese population differed not only from that in the European population but also from that in sub‐populations of Asians outside of the Chinese mainland.     

特应性皮炎与丝聚蛋白研究进展

丝聚蛋白(FLG)基因的失功能突变可使表皮FLG含量减少或缺失,进而引起表皮屏障功能发生改变,增加特应性皮炎(AD)的患病风险。本文对FLG在表皮屏障形成中的作用、FLG基因结构、FLG基因在AD患者中的突变情况及FLG基因突变与AD临床表型的相关性进行综述。     

Analysis of filaggrin 2 gene polymorphisms in patients with atopic dermatitis

BackgroundPolymorphisms of the filaggrin 2 gene (rs 12568784 and rs 16899374) are associated with persistent atopic dermatitis in African American patients. Filaggrin 2 is a protein with a function similar to filaggrin and also encoded in the epidermal differentiation complex on chromosome 1q21.ObjectiveTo evaluate the polymorphisms in the filaggrin 2 gene (rs 12568784 and rs 16899374) in children and adults with atopic dermatitis and to verify the association of these with the severity of the clinical picture, presence of other allergic diseases, and socio-demographic factors.MethodThe study was carried out with patients and control group. Questionnaires were used to evaluate ethnicity, sex, age, family history, scoring, atopic dermatitis (SCORAD), among other parameters. Genotyping of the filaggrin 2 gene was performed by real-time polymerase chain reaction.ResultsForty-eight patients and 83 controls were evaluated. No correlation was found between the variables studied in patients with atopic dermatitis and polymorphisms, no significant difference between the prevalence of polymorphisms in the patients and in the control group p > 0.05.Study limitsThe exclusive use of self-reported ethnicity information and the sample size.ResultsThe results of this work can be an incentive for the study of the polymorphisms in atopic dermaititis, considering the characteristic of the Brazilian multi ethnic population.ConclusionThis is an unpublished work in Brazil and the first study in the world to have a control group to evaluate alterations in the gene of filaggrin 2.     

中间丝聚合蛋白基因多态性与特应性皮炎发病及临床表型的相关性

目的 探讨中间丝聚合蛋白(FLG)基因多态性与特应性皮炎(AD)发病及临床表型的相关性.方法 采用问卷调查的形式收集261例AD患者伴发过敏性鼻炎、哮喘病史和疾病严重度评分等资料,对部分患者进行混合食物过敏原和混合吸人性过敏原筛选、血清总IgE抗体和嗜酸性粒细胞阳离子蛋白水平检测.采用重叠PCR和DNA测序法对上述AD患者和276例健康对照FLG基因3号外显子17个多态性位点(R444G、T454A、P478S、H519N、D836D、S1482Y、A1805V、R1891Q、1961Q、S2166S、Y2194H、H2330H、D2339N、S2366T、E2398Q、K2444E、E2652D)进行基因分型.结果 二项逻辑回归分析和卡方检验未发现17种FLG多态位点与AD发病相关(均P＞0.05).H519N与AD伴发哮喘相关(x2=8.680,P=0.011),AA基因型可增加AD患者发生哮喘的风险(P=0.004,OR=1.061,95％ CI 1.016 ～ 1.109).S2366T和K2444E与AD患者食物敏感相关(x2值分别为6.520和6.121,P值分别为0.038和0.047),S2366T的GG+ GC基因型(P=0.012,OR=1.396,95％CI 1.054～1.849)和G等位基因(P=0.037,OR=1.350,95％CI 1.008～ 1.807)可提高AD患者食物敏感的风险.K2444E的AA+ AG基因型(P=0.013,OR=1.393,95％ CI 1.049 ～ 1.850)和G等位基因(P=0.028,OR=1.380,95％ CI 1.025 ～ 1.857)可提高AD患者食物敏感的风险.结论 中国汉族人群FLG基因多态性可能是一些AD相关临床表型的危险因素,H519N可能与AD伴发哮喘相关,S2366T和K2444E则可能与AD伴食物敏感相关.     

Absence of filaggrin mutation in a patient affected by pachyonychia congenita and mild atopic dermatitis

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Prevalence of atopic dermatitis in Japanese adults

BACKGROUND: Adult atopic dermatitis (AD) in Japan has become a significant social problem, with as many as one-third of adult patients with severe AD absenting themselves from work or classes due to aggravation of the disease. Reports of such patients have become increasingly common in recent years. Despite the pressing need for epidemiological studies to clarify the prevalence and distribution of AD and to determine its aetiology, no previous research has been carried out on the prevalence of AD within the adult population in Japan. OBJECTIVES: To clarify the prevalence of adult AD in Japan, using the U.K. Working Party's diagnostic criteria. METHODS: The subjects of this study were mostly government officials or their family members visiting the Medical Center of Health Science, Toranomon Hospital in Tokyo for annual health check-ups in the period from September 1997 to August 1998. Questionnaires completed by 10 762 persons (8076 men and 2686 women) aged 30 years or above were analysed. The questionnaire consisted of 14 questions on allergic disease. The U.K. Working Party's diagnostic criteria were used after translation into Japanese. Three types of prevalence were used as indicators of prevalence: point, 1-year and lifetime prevalence. RESULTS: The point prevalence, 1-year prevalence and lifetime prevalence of AD in Japanese adults were 2.9%, 3.0% and 3.3%, respectively. No significant statistical differences were observed between the sexes or among age groups within each sex. The survey indicated that 88.6% of those who had ever had AD were currently affected by active AD, while 93.4% of those who had had at least one episode of AD in the past had experienced an episode over the previous year. CONCLUSIONS: This study gives the first indication of the prevalence of adult AD among the Japanese, based on the U.K. criteria. Both the internal and external validity of this study are believed to be high; it would be safe to conclude that the 1-year prevalence of AD in Japanese adult populations living in urban areas is 3.0%.     

Breaking the (un)sound barrier: filaggrin is a major gene for atopic dermatitis

We have recently shown that loss-of-function mutations in the filaggrin gene, carried by about 10% of people of European ethnicity, cause ichthyosis vulgaris and are strong predisposing factors for atopic dermatitis and asthma secondary to atopic dermatitis. These results demonstrate a prominent role for the epidermal barrier in atopic disease and have important implications for the study of complex traits.     

Single nucleotide polymorphism-based genome-wide linkage analysis in Japanese atopic dermatitis families

Background

Atopic dermatitis (AD) is a common inflammatory skin disorder, affecting up to 15% of children in industrialized countries. Toll-interacting protein (TOLLIP) is an inhibitory adaptor protein within the toll-like receptor (TLR) pathway, a part of the innate immune system that recognizes structurally conserved molecular patterns of microbial pathogens, leading to an inflammatory immune response.

Methods

In order to detect a possible role of TOLLIP variation in the pathogenesis of AD, we screened the entire coding sequence of the TOLLIP gene by SSCP in 50 AD patients. We identified an amino acid exchange in exon 6 (Ala222Ser) and a synonymous variation in exon 4 (Pro139Pro). Subsequently, these two variations and four additional non-coding polymorphisms (-526 C/G, two polymorphisms in intron 1 and one in the 3'UTR) were genotyped in 317 AD patients and 224 healthy controls.

Results

The -526G allele showed borderline association with AD in our cohort (p = 0.012; significance level after correction for multiple testing 0.0102). Haplotype analysis did not yield additional information. Evaluation of mRNA expression by quantitative real-time polymerase chain reaction in six probands with the CC and six with the GG genotype at the -526 C/G locus did not reveal significant differences between genotypes.

Conclusion

Variation in the TOLLIP gene may play a role in the pathogenesis of AD. Yet, replication studies in other cohorts and populations are warranted to confirm these association results.     

Prevalent and rare mutations in the gene encoding filaggrin cause ichthyosis vulgaris and predispose individuals to atopic dermatitis

Mutations in the filament aggregating protein (filaggrin) gene have recently been identified as the cause of the common genetic skin disorder ichthyosis vulgaris (IV), the most prevalent inherited disorder of keratinization. The main characteristics of IV are fine-scale on the arms and legs, palmar hyperlinearity, and keratosis pilaris. Here, we have studied six Irish families with IV for mutations in filaggrin. We have identified a new mutation, 3702delG, in addition to further instances of the reported mutations R501X and 2282del4, which are common in people of European origin. A case of a 2282del4 homozygote was also identified. Mutation 3702delG terminates protein translation in filaggrin repeat domain 3, whereas both recurrent mutations occur in repeat 1. These mutations are semidominant: heterozygotes have an intermediate phenotype most readily identified by palmar hyperlinearity and in some cases fine-scale and/or keratosis pilaris, whereas homozygotes or compound heterozygotes generally have more marked ichthyosis. Interestingly, the phenotypes of individuals homozygous for R501X, 2282del4, or compound heterozygous for R501X and 3702delG, were comparable, suggesting that mutations located centrally in the filaggrin repeats are also pathogenic.     

Association of SPINK5 gene polymorphisms with atopic dermatitis in the Japanese population

BACKGROUND: Netherton's syndrome (NS) is an autosomal recessive disorder characterized by trichorrhexis invaginata ('bamboo hair'), congenital ichthyosiform erythroderma and an atopic diathesis. NS has recently been shown to be due to a defect in the SPINK5 gene, encoding LEKTI, a 15-domain serine protease inhibitor. SPINK5 maps to chromosome 5q31-q32, and has been suggested to be a locus predisposing to atopy in general. Recently, coding polymorphisms in SPINK5 exons 13 and 14 have been reported to be associated with atopy, asthma and atopic dermatitis (AD). OBJECTIVES: To examine whether these polymorphisms are also associated with AD in Japan. METHODS: We characterized eight polymorphisms in SPINK5 exons 13 and 14 in 124 Japanese patients with AD and 110 healthy controls. The polymorphisms we examined were IVS12-26C-->T, IVS12-10A-->G, 1103A-->G (Asn368Ser, in exon 13), 1156G-->A (Asp386Asn, in exon 13), 1188T-->C (His396His, in exon 13), IVS13-50G-->A, 1258G-->A (Glu420Lys, in exon 14) and IVS14+19G-->A. RESULTS: We found significant associations between seven of these polymorphisms and AD in Japanese patients. CONCLUSIONS: This study confirms the previous suggestion of an association between SPINK5 and AD.     

Association between filaggrin null mutations and concomitant atopic dermatitis and contact allergy

Background. The phenotypic traits of people with the filaggrin mutation (FLG) genotype and atopic dermatitis (AD) are still under elucidation, and the association with concomitant AD and contact allergy (CA) has not previously been examined. Aim. To assess FLG status in a subset of patients with AD and a minimum of one positive patch‐test reaction. Methods. In total, 430 people from a hospital population and 3335 people from the general population were tested for FLG mutations by DNA hybridization to paramagnetic polystyrene beads and analysis on a multiplex analysis system. All of the individuals in the hospital population had a minimum of one CA. AD was diagnosed according to the UK Working Party Criteria, (questions‐only version). Individuals from the hospital population who had both AD and CA were considered as cases, and comparison of mutation carrier frequency was estimated (χ² test) against individuals without AD but with CA from the hospital population, individuals from the general population, and individuals with AD from the general population. Results. The mutation frequency in patients with AD and CA in the hospital population was significantly less than that of people with AD from the general population (OR = 0.54; 95% CI 0.30–0.98). No difference in mutation frequency was found between individuals with and without AD in the hospital population (OR = 1.40; 95% CI 0.70–2.79), or between individuals with AD and CA in the hospital population and in the overall general population (OR = 1.29; 95% CI 0.76–2.20). Conclusions. The spectrum of observable traits characteristic for the FLG mutation genotype in patients with AD is at present not defined. Our results indicate that the subset of patients with both AD and CA represent a phenotype of AD that is not associated with FLG mutations.