Filaggrin Gene Null Mutations Research Articles

Revisiting the Roles of Filaggrin in Atopic Dermatitis.

The discovery in 2006 that loss-of-function mutations in the filaggrin gene (FLG) cause ichthyosis vulgaris and can predispose to atopic dermatitis (AD) galvanized the dermatology research community and shed new light on a skin protein that was first identified in 1981. However, although outstanding work has uncovered several key functions of filaggrin in epidermal homeostasis, a comprehensive understanding of how filaggrin deficiency contributes to AD is still incomplete, including details of the upstream factors that lead to the reduced amounts of filaggrin, regardless of genotype. In this review, we re-evaluate data focusing on the roles of filaggrin in the epidermis, as well as in AD. Filaggrin is important for alignment of keratin intermediate filaments, control of keratinocyte shape, and maintenance of epidermal texture via production of water-retaining molecules. Moreover, filaggrin deficiency leads to cellular abnormalities in keratinocytes and induces subtle epidermal barrier impairment that is sufficient enough to facilitate the ingress of certain exogenous molecules into the epidermis. However, although FLG null mutations regulate skin moisture in non-lesional AD skin, filaggrin deficiency per se does not lead to the neutralization of skin surface pH or to excessive transepidermal water loss in atopic skin. Separating facts from chaff regarding the functions of filaggrin in the epidermis is necessary for the design efficacious therapies to treat dry and atopic skin.

Palm reading and water divining: A cross-sectional study of the accuracy of palmar hyperlinearity and transepidermal water loss to identify individuals with a filaggrin gene null mutation

Palm reading and water divining: A cross-sectional study of the accuracy of palmar hyperlinearity and transepidermal water loss to identify individuals with a filaggrin gene null mutation

Prevalence of FLG loss-of-function mutations R501X, 2282del4, and R2447X in Spanish children with atopic dermatitis.

Atopic dermatitis (AD) is the most prevalent inflammatory skin disorder, and is often associated with a personal or family history of atopic disease. The presence of loss-of-function mutations in the filaggrin gene (FLG) is the main predisposing factor for AD FLG mutations show ethnic and geographical variations, even between European populations. We sought to determine the frequency of the 3 most common FLG null mutations in a population of Spanish children consisting of healthy controls and AD patients. We also investigated the association between these 3 FLG mutations and AD. A total of 214 participants (111 AD patients and 103 healthy controls) were enrolled in this study. Genotyping for 3 FLG null mutations (R501X, 2282del4, and R2447X) was performed by conventional Sanger sequencing. The combined mutation frequency was 1.9% in the control group and 12.6% in the AD group. The most common FLG mutation in AD patients was R501X (9.9%), followed by R2447X (2.7%) and 2282del4 (1.8%). These findings further our understanding of the prevalence of FLG null mutations in the Spanish population, and suggest that the frequency of FLG mutations in AD patients in Spain is slightly higher than that of other Mediterranean countries.

Ichthyosis Vulgaris

Ichthyosis Vulgaris

Genetic Risk Factors for Development of Atopic Dermatitis: a Systematic Review

The purpose of this study is to systematically review studies conducted between April 2015 and April 2017 for the genetic risks for the development of atopic dermatitis (AD). We sought to identify (1) specific loci and genes associated with AD, (2) the proportion of studies for each gene, and (3) genetic risks that need further investigation. Studies have found that genetic predisposition and environmental triggers are involved in the pathogenesis of AD. Thirty-four loci and 46 genes have been identified as genetic risk factors, of which filaggrin gene null mutations and genes in the type 2 T-helper lymphocyte (Th2) signaling pathway have been the most extensively studied. Our systematic review found that in the last 2 years, 46 loci and 53 genes have been studied in the development of AD. Genes involved in epidermal barrier, immune regulation, and intracellular functions were identified. We suggest that future research should investigate the intricate interaction of these genes as well as the complex interplay of genetic and environmental factors in the development of AD.

416 No difference in UVB induced changes in antigen presenting cells and cytokines between subjects with and without FLG null-mutation

Epidermal filaggrin deficiency may affect UVB induced immune responses. We examined if common filaggrin gene (FLG) null-mutations were associated with altered responses in antigen presenting cells and cytokines following UVB irradiation of human skin in vivo. Atopic heterozygotic FLG null-mutation carriers and healthy wildtype subjects(WT) were included. Skin on the volar forearm was irradiated with 1.5 minimal erythema dose UVB. Suction blisters were raised on skin irradiated 24 and 72 hours earlier and on non-irradiated control skin(C). Antigen presenting cell numbers and activation markers were examined in epidermal single cell suspensions by flow cytometry. Concentrations of IL-1β, IL-6, IL-10, IL-12p70, TNF-α, TGF-β1, and CCL20 were measured in blister fluid. As expected, UVB irradiation caused a significant decrease in Langerhans cell (LC) numbers, a significant increase in monocyte numbers, and a significant upregulation of activation markers CD86 and OX40 ligand on LCs. These changes did not differ between heterozygotic and WT subjects: deltaLC 24hrs - C; P=0.44, deltaLC 72hrs - C; P=0.20, deltaMonocytes 24hrs - C; P=0.19, deltaMonocytes 72hrs - C; P=0.38, deltaCD86 24hrs - C; P=0.38, deltaCD86 72hrs - C; P=0.10, deltaOX40L 24hrs - C; P=0.28, deltaOX40L 72hrs - C; P=0.51(N=8+8). UVB irradiation upregulated IL-1β, IL-6, and TGF-β1, but these changes were not influenced by FLG mutation status either: deltaIL-1β 24hrs - C; P=0.84(N=5+6), deltaIL-1β 72hrs - C; P>0.99(N=5+6), deltaIL-6 24hrs - C; P=0.91(N=5+6), deltaIL-6 72hrs - C; P=0.91(N=5+6), deltaTGF-β1 24hrs - C; P=0.96(N=5+7), deltaTGF-β1 72hrs - C; P=0.43(N=5+7). Taken together, we found no difference in changes of antigen presenting cells and cytokines in UVB irradiated skin from subjects with and without a FLG null-mutation.

Filaggrin Mutation in Korean Patients with Atopic Dermatitis.

PurposeAtopic dermatitis (AD) is a chronic, relapsing eczematous inflammatory skin disease. Mutations in the filaggrin gene (FLG) are major predisposing factors for AD. Ethnic differences exist between Asian and European populations in the frequency and spectrum of FLG mutations. Moreover, a distinct set of FLG mutations has been reported in Asian populations. The aim of this study was to examine the spectrum of FLG mutations in Koreans with AD. We also investigated the association of FLG mutations and clinical features of AD and compared the Korean FLG landscape with that of other East Asian countries.Materials and MethodsSeventy Korean patients with AD were enrolled in this study. Fourteen FLG mutations previously detected in Korean, Japanese, and Chinese patients were screened by genotyping.ResultsFour FLG null mutations (3321delA, K4022X, S3296X, and S2889X) were identified in eleven patients (15.7%). The most commonly detected mutations in Korean patients with AD were 3321delA (n=6, 9.1%) and K4022X (n=3, 4.5%). FLG mutations were significantly associated with elevated IgE (≥200 KIU/L and/or MAST-CLA >3+, p=0.005), palmar hyperlinearity (p<0.001), and a family history of allergic disease (p=0.021).ConclusionThis study expanded our understanding of the landscape of FLG mutations in Koreans and revealed an association between FLG mutations and AD phenotype.

Quality of life and disease severity in patients with atopic dermatitis.

Atopic dermatitis (AD) affects quality of life (QoL) negatively in patients and their families. We examined the relationship between disease severity and QoL in patients with AD. Consecutive, newly referred outpatients with AD, 4 years of age or older, were assessed from January 2012 onwards by means of the dermatology life quality index (DLQI, range 0-30), the Scoring of AD (SCORAD) disease severity score (range 0-103), filaggrin gene (FLG) mutation status and paraclinical tests related to allergy. A total of 250 patients with a mean age of 26.0 years were identified with complete data on DLQI; 148 (59.2%) females and 102 (40.8%) males. Of these 45.6% had asthma, 46.8% had hay fever, 22.7% had a loss-of-function mutation in FLG, and 61.9% had one or more inhalant allergic sensitizations. The correlation between SCORAD and DLQI was 0.42 (P < 0.001). After multivariate adjustment there was an increasing mean DLQI score with increasing disease severity measured by SCORAD (DLQI in mild = 5.30, moderate = 8.59 and severe = 11.94 AD), P-value for difference between groups <0.001; a higher mean DLQI among females than males (9.73 vs. 8.34), P = 0.028; and among patients reporting facial eczema (9.88 vs. 6.24), P = 0.012. No statistically significant influence on DLQI was found for hand or foot eczema, age, blood eosinophil count, allergic sensitization, asthma, hay fever, FLG mutation status and smoking. FLG null mutation status was not significantly associated with SCORAD. AD impacts negatively on the QoL, proportional to the severity of the disease. Furthermore, female sex and facial eczema are associated with low QoL. Positive FLG null mutation status is not associated with QoL or disease severity.

Association of common filaggrin null mutations with atopy but not chronic rhinosinusitis

Association of common filaggrin null mutations with atopy but not chronic rhinosinusitis

Correlation Between Palmar Hyperlinearity and Early Childhood Atopic Dermatitis with Filaggrin Gene Null Mutations

Correlation Between Palmar Hyperlinearity and Early Childhood Atopic Dermatitis with Filaggrin Gene Null Mutations

The nickel dose–response relationship by filaggrin genotype (FLG)

On skin contact, nickel accumulates in the stratum corneum, where it is probably bound to proteins and amino acids. One probable contributor is filaggrin, which binds nickel avidly. Filaggrin gene (FLG) null mutations lead to a complete lack of filaggrin production from the affected allele, and have been associated with an increased risk of nickel contact sensitization in German and Danish adults. To investigate whether the experimental nickel elicitation threshold level differed between heterozygous FLG mutation and non-mutation carriers. Thirteen nickel-sensitized female patients, seven heterozygous mutation carriers and six non-mutation carriers (genotyped for R501X, 2282del4, or R2447X), were patch tested and performed a repeated open application test (ROAT) with a nickel sulfate dilution series. Logistic threshold dose-response analyses were used to test for differences between the two groups. No difference was found in the dose-response relationship between FLG mutation and non-mutation carriers. On the basis of this small patient study, it appears that the elicitation threshold level for nickel is independent of FLG null mutation single-allele carrier status.

No remarkable differences in rates of sensitization to common type I and IV allergens between FLG loss‐of‐function mutation carriers and wild‐type subjects

Loss-of-function mutations in the filaggrin gene (FLG) have been associated with reduced skin barrier function, possibly allowing increased penetration of irritants and allergens. To study whether FLG loss-of-function mutation carriers show different rates of sensitization to common type I and IV allergens among patients referred for occupational contact dermatitis of the hands. Four hundred and ninety-six Caucasian patients were genotyped for four FLG null mutations and patch tested with the European baseline series. In addition, 431 patients underwent prick testing with common type I allergens. Overall, 67 patients showed a heterozygous mutation in the FLG alleles R501X, R2447X, S3247X, and/or 2282del4. Sensitization rates for type I allergens from a European prick test series did not show significant differences between FLG loss-of-function mutation carriers and wild-type subjects. For type IV allergens, significantly more FLG loss-of-function carriers were found to be sensitized to lanolin and p-tert-butylphenol-formaldehyde resin. Probably a variety of immunological mechanisms other than that resulting from the filaggrin system have an impact on allergic sensitization to a greater degree. Larger cohorts may be necessary to increase the statistical power of the findings presented regarding type I and IV sensitization.

Analyses ofFLGmutation frequency and filaggrin expression in isolated ichthyosis vulgaris (IV) and atopic dermatitis-associated IV

Ichthyosis vulgaris (IV; OMIM 146700) is a very common inherited skin disorder. Loss-of-function mutations in the filaggrin gene (FLG) have been identified as the cause of IV. In a previous study, we found that the percentage of FLG null mutations was lower in IV associated with atopic dermatitis (AD) than in IV not associated with AD (isolated IV). We speculated that some clinical manifestations of IV in patients with AD are not induced by FLG mutations. In order to clarify this issue, we collected 21 IV pedigrees, 33 patients with sporadic isolated IV and 116 patients with AD-associated IV to analyse FLG mutation frequency and filaggrin expression in isolated IV and AD-associated IV. A comprehensive sequencing of the FLG gene in all patients was performed using an overlapping polymerase chain reaction (PCR) strategy. We also studied the immunohistochemistry of profilaggrin/filaggrin protein expression in the skin and measured the mRNA expression using real-time PCR in seven patients, including one patient with IV harbouring the mutation c.3321delA, two patients with AD-associated IV harbouring c.3321delA and c.6834del5, and four patients with AD-associated IV without FLG mutations. The percentage of mutations in the FLG gene was 74% and 43% in patients with isolated IV and patients with AD-associated IV, respectively. Immunohistochemical staining revealed that profilaggrin/filaggrin peptides were remarkably reduced in the epidermis of all the patients. All the patients with either AD or IV showed lower FLG mRNA expression compared with the normal control. These results indicate that factors other than FLG gene mutations can downregulate profilaggrin/filaggrin expression, leading to the ichthyosiform phenotype in the context of AD.

The role of glutathione S-transferase and claudin-1 gene polymorphisms in contact sensitization: a cross-sectional study

Contact sensitization is frequent in the general population and arises from excessive or repeated skin exposure to chemicals and metals. However, little is known about its genetic susceptibility. To determine the role of polymorphisms of glutathione S-transferase (GST) genes and the claudin-1 gene (CLDN1) on the risk of contact sensitization, taking common filaggrin gene (FLG) mutations into account. In total, 3471 adult Danes from the general population were standard patch tested and filled out a questionnaire on their general health. They were genotyped for the following polymorphisms: GSTM1 and GSTT1 deletion, GSTP1 single nucleotide polymorphism (SNP) rs1695, four CLDN1 SNPs (rs893051, rs9290927, rs9290929 and rs17501010) and the FLG null mutations R501X and 2282del4. In individuals without ear piercings, a higher prevalence of nickel sensitization was found in those with the minor allele of CLDN1 SNP rs9290927 (P(trend)=0·013). For CLDN1 rs17501010, contact sensitization to organic compounds was associated with the major allele (P(trend)=0·031). The risk pattern was also identified for self-reported nickel dermatitis (P(trend)=0·011). The fragrance sensitization prevalence differed in a pairwise comparison of the CLDN1 rs893051 SNP genotypes (P=0·022), with the minor allele being associated with a higher prevalence. The associations were confirmed in logistic regression analyses. The CLDN1 polymorphisms rs9290927, rs893051 and rs17501010 were associated, respectively, with nickel contact sensitization in individuals without ear piercings, contact sensitization to fragrances, and with both organic compounds and nickel contact dermatitis. We could not find associations between GST gene polymorphisms and contact sensitization. FLG mutations did not affect the observed associations.

Low frequency of filaggrin null mutations in Croatia and their relation with allergic diseases

Filaggrin gene (FLG) null mutations are considered associated with atopic dermatitis. This study was conducted to determine the prevalence of FLG null mutations R501X, 2282del4, R2447X and S3247X in the Croatian population and their role in the occurrence of allergic diseases including atopic dermatitis, allergic rhinitis, asthma and allergic contact dermatitis (ACD). Study enrolled 440 freshmen with defined allergic diseases by means of both present symptoms in International Study of Asthma and Allergies in Childhood questionnaire (relevant respiratory and/or skin symptoms) and markers of allergic sensitization (positive skin prick and/or patch test). FLG null mutations were successfully genotyped in 423 students of which 11 (2.6%) were carriers of FLG null mutation: 1/423 (0.2%) was heterozygous for R501X and 10/423 (2.4%) were heterozygous for 2282del4. No carriers of R2447X and S3247X mutations were identified. In wild-type FLG carriers (412 subjects), atopic dermatitis was present in 45 (11%), allergic rhinitis in 70 (17%) and allergic asthma in 29 (7%) students. Twenty-five of 393 (7%) patch-tested wild-type FLG carriers had ACD. Among 11 FLG null mutation carriers, four had one or more allergic diseases, and five had reported skin symptoms without defined allergic sensitization (positive skin prick test and/or patch test). FLG null mutations were not confirmed as a predictor of analysed allergic diseases, but were confirmed as an independent predictor of skin symptoms (OR 17.19, 95% CI 3.41-86.6, P < 0.001). Our results in general indicate a low frequency of FLG null mutations in the studied Croatian population supporting a theory of a latitude-dependent distribution of FGL null mutations in Europe, with a decreasing north-south gradient of R501X and 2282del4 mutation frequency. The relation between FLG null mutations and skin disorders was confirmed.

Novel filaggrin mutation but no other loss-of-function variants found in Ethiopian patients with atopic dermatitis

Filaggrin is a key protein involved in maintaining skin barrier function and hydration. Mutations in the filaggrin gene (FLG) cause ichthyosis vulgaris (IV) and are a major predisposing factor for atopic dermatitis (AD) in individuals of European and Asian descent. It has been proposed that FLG mutations are population specific and a difference in the spectra of mutations between different ancestral groups has been described. However, it is unknown whether FLG mutations in the African population are a causative genetic factor for IV and predispose to AD, or whether other mechanisms are more prominent. The present aim was to investigate the role of FLG mutations as predisposing factors for IV or AD among individuals from Ethiopia. A case series of Ethiopian patients with AD (n = 103) and IV (n = 7) together with controls (n = 103; subjects without past or present history of AD, dry skin or atopic manifestations) was collected at the outpatient dermatology clinics at ALERT Dermatology Hospital, Tikur Anbessa Hospital and Gondar University Hospital, Ethiopia. AD was diagnosed by a dermatologist using the U.K. Working Party's diagnostic criteria. The IV diagnosis was based on clinical examination and genetic testing of the steroid sulphatase gene to exclude X-linked recessive ichthyosis. Patients were studied with direct sequencing (n = 40) and/or allelic discrimination (n = 110). Immunohistochemical analysis was performed for filaggrin expression in the skin of patients (n = 7) and controls (n = 2). The Ethiopian patients and controls were genotyped for the four previously described common European FLG null mutations (R501X, 2282del4, S3247X, R2447X) and no carriers were found. In one patient with AD a novel heterozygous 2-bp deletion, 632del2, leading to a premature stop codon was revealed by direct sequencing. No additional carrier of this deletion or other mutations was found. In addition, no difference in filaggrin expression was detected in AD or IV skin compared with healthy control skin. Our results indicate that FLG loss-of-function-variants are less common in patients with IV and AD in the Ethiopian population, suggesting that other factors may be of importance in the pathogenesis in this ethnic group.

Filaggrin Null Mutations Are Not a Protective Factor for Acne Vulgaris

Filaggrin Null Mutations Are Not a Protective Factor for Acne Vulgaris

Filaggrin null mutations increase the risk and persistence of hand eczema in subjects with atopic dermatitis: results from a general population study

Hand eczema is prevalent in the general population. It remains unclear whether or not filaggrin gene (FLG) null mutations increase the overall risk of hand eczema or only increase the risk of hand eczema in subjects with atopic dermatitis. To investigate the association between FLG null mutations and hand eczema. A random sample of 3335 adults from the general population in Denmark was patch tested, FLG genotyped for R501X and 2282del4 null mutations and questioned about hand eczema. Participants with combined presence of atopic dermatitis and FLG null mutation status had a significantly higher prevalence of hand eczema, an earlier onset of hand eczema and a higher persistence of hand eczema compared with subjects with normal FLG status and absence of atopic dermatitis. Logistic regression analyses revealed positive associations between hand eczema within the past 12 months and FLG null mutation status in participants with a history of atopic dermatitis [odds ratio (OR) 2.98; 95% confidence interval (CI) 1.27-7.01], but not in subjects without atopic dermatitis (OR 0.82; 95% CI 0.41-1.67). FLG null mutations were significantly associated with hand eczema (< 12 months) in subjects with atopic dermatitis. Combined atopic dermatitis and filaggrin null mutation status was strongly associated with early onset of hand eczema and hand eczema persistence.

The association between null mutations in the filaggrin gene and contact sensitization to nickel and other chemicals in the general population

It was recently shown that filaggrin gene (FLG) null mutations are positively associated with nickel sensitization. We have hypothesized that histidine-rich filaggrin proteins in the epidermis chelate nickel ions and prevent their skin penetration and exposure to Langerhans cells. Furthermore, we have proposed that the low degree of genetic predisposition to nickel sensitization found by a Danish twin study was explained by a high prevalence of ear piercing among participants resulting in 'bypassing' of the filaggrin proteins. To investigate the association between FLG null mutations and (nickel) contact sensitization. A random sample of 3335 adults from the general population in Denmark was patch tested and genotyped for R501X and 2282del4 in the FLG gene. The combined carrier frequency of FLG null mutations was 8·1%. Nickel, fragrance and contact sensitization to at least one allergen were not associated with FLG null mutations. A crude analysis on women who did not have ear piercings revealed a positive association between FLG null mutations and nickel sensitization [8·3% vs. 2·4%; odds ratio (OR) 3·71, 95% confidence interval (CI) 0·73-18·96] as well as between FLG null mutations and allergic nickel dermatitis (8·3% vs. 1·3%; OR 6·75, 95% CI 1·17-38·91). FLG mutation status and atopic dermatitis were positively associated with neomycin or ethylenediamine sensitization. This study suggests that FLG null mutations may be a risk factor for the development of nickel sensitization. However, ear piercing was a much stronger risk factor in our general population and we could therefore identify a positive association only in women without ear piercings. Contact sensitization to specific chemicals is related to treatment exposure.

Chromosome 11q13.5 variant associated with childhood eczema: An effect supplementary to filaggrin mutations

BackgroundAtopic eczema is a common inflammatory skin disease with multifactorial etiology. The genetic basis is incompletely understood; however, loss of function mutations in the filaggrin gene (FLG) are the most significant and widely replicated genetic risk factor reported to date. The first genome-wide association study in atopic eczema recently identified 2 novel genetic variants in association with eczema susceptibility: a single nucleotide polymorphism on chromosome 11q13.5 (rs7927894) and a single nucleotide polymorphism (rs877776) within the gene encoding hornerin on chromosome 1q21.ObjectiveTo test the association of these 2 novel variants with pediatric eczema and to investigate their interaction with FLG null mutations.MethodsCase-control study to investigate the association of rs7927894, rs877776 and the 4 most prevalent FLG null mutations with moderate-severe eczema in 511 Irish pediatric cases and 1000 Irish controls. Comprehensive testing for interaction between each of the loci was also performed.ResultsThe association between rs7927894 and atopic eczema was replicated in this population (P = .0025, χ2 test; odds ratio, 1.27; 95% CI, 1.09-1.49). The 4 most common FLG null variants were strongly associated with atopic eczema (P = 1.26 × 10−50; combined odds ratio, 5.81; 95% CI, 4.51-7.49). Interestingly, the rs7927894 association was independent of the well-established FLG risk alleles and may be multiplicative in its effect. There was no significant association between rs877776 and pediatric eczema in this study.ConclusionSingle nucleotide polymorphism rs7927894 appears to mark a genuine eczema susceptibility locus that will require further elucidation through fine mapping and functional analysis.