Background Atopic dermatitis (AD) is a common skin disease that is characterized by recurrent episodes of itching. Filaggrin ( FLG ) loss-of-function ( FLG null) mutations have been associated with ...an increased risk of AD. Objective We sought to evaluate the effect of individual FLG null mutations on the persistence of AD over time. Methods We evaluated a multiyear prospective cohort study of children with AD with respect to FLG null mutations (R501X, 2282del4, R2447X, and S3247X). We evaluated the association of these mutations with the persistence of AD symptoms over time with respect to reports of no symptoms of AD and whether topical medication was needed for symptom resolution. Results Eight hundred fifty-seven subjects were followed for 3684 person-years. One or more FLG null mutations were noted in 16.3% of subjects and specifically in 27.5% of white subjects and 5.8% of African American subjects. Subjects with an FLG null mutation were less likely (odds ratio OR, 0.54; 95% CI, 0.41-0.71) to report that their skin was symptom free at any time compared with those without an FLG null mutation. The effect of these mutations was similar in white subjects (OR, 0.42; 95% CI, 0.31-0.57) and African-American subjects (OR, 0.53; 95% CI, 0.25-1.12; P = .62). Children with the R501X mutation (OR, 0.44; 95% CI, 0.22-0.88) were the least responsive to therapy. Conclusions In a US cohort with AD, FLG null mutations were common. Children with FLG null mutations were more likely to have persistent AD. Although these mutations were more common in those of European ancestry, their effect on persistence was similar in those of African ancestry. Response to therapy was not uniform among children with FLG null mutations.
Background Filaggrin (FLG) mutations result in reduced stratum corneum (SC) natural moisturizing factor (NMF) components and consequent increased SC pH. Because higher pH activates SC protease ...activity, we hypothesized an enhanced release of proinflammatory IL-1 cytokines from corneocytes in patients with atopic dermatitis (AD) with FLG mutations (AD FLG ) compared with that seen in patients with AD without these mutations (AD NON-FLG ). Objectives We sought to investigate SC IL-1 cytokine profiles in the uninvolved skin of controls and patients with AD FLG versus patients with AD NON-FLG . We also sought to examine the same profiles in a murine model of filaggrin deficiency ( Flgft /Flgft FlgdelAPfal mice). Methods One hundred thirty-seven patients were studied. NMF levels were ascertained using confocal Raman spectroscopy; transepidermal water loss and skin surface pH were measured. IL-1α, IL-1β, IL-18, IL-1 receptor antagonist (IL-1RA), and IL-8 levels were determined in SC tape strips from 93 patients. All subjects were screened for 9 FLG mutations. Flgft /Flgft (FlgdelAPfal ) mice, separated from maFlgft /maFlgft (flaky tail) mice, were used for the preparation and culture of primary murine keratinocytes and as a source of murine skin. RT-PCR was performed using primers specific for murine IL-1α, IL-1β, and IL-1RA. Results SC IL-1 levels were increased in patients with AD FLG ; these levels were inversely correlated with NMF levels. NMF values were also inversely correlated with skin surface pH. Skin and keratinocytes from Flgft /Flgft mice had upregulated expression of IL-1β and IL-1RA mRNA. Conclusions AD FLG is associated with an increased SC IL-1 cytokine profile; this profile is also seen in a murine homologue of filaggrin deficiency. These findings might have importance in understanding the influence of FLG mutations on the inflammasome in the pathogenesis of AD and help individualize therapeutic approaches.
Background Atopic dermatitis (AD; eczema) is characterized by a widespread abnormality in cutaneous barrier function and propensity to inflammation. Filaggrin is a multifunctional protein and plays a ...key role in skin barrier formation. Loss-of-function mutations in the gene encoding filaggrin (FLG) are a highly significant risk factor for atopic disease, but the molecular mechanisms leading to dermatitis remain unclear. Objective We sought to interrogate tissue-specific variations in the expressed genome in the skin of children with AD and to investigate underlying pathomechanisms in atopic skin. Methods We applied single-molecule direct RNA sequencing to analyze the whole transcriptome using minimal tissue samples. Uninvolved skin biopsy specimens from 26 pediatric patients with AD were compared with site-matched samples from 10 nonatopic teenage control subjects. Cases and control subjects were screened for FLG genotype to stratify the data set. Results Two thousand four hundred thirty differentially expressed genes (false discovery rate, P < .05) were identified, of which 211 were significantly upregulated and 490 downregulated by greater than 2-fold. Gene ontology terms for “extracellular space” and “defense response” were enriched, whereas “lipid metabolic processes” were downregulated. The subset of FLG wild-type cases showed dysregulation of genes involved with lipid metabolism, whereas filaggrin haploinsufficiency affected global gene expression and was characterized by a type 1 interferon–mediated stress response. Conclusion These analyses demonstrate the importance of extracellular space and lipid metabolism in atopic skin pathology independent of FLG genotype, whereas an aberrant defense response is seen in subjects with FLG mutations. Genotype stratification of the large data set has facilitated functional interpretation and might guide future therapy development.
Filaggrin in atopic dermatitis O'Regan, Grainne M., MB; Sandilands, Aileen, PhD; McLean, W.H. Irwin, PhD, DSc ...
Journal of allergy and clinical immunology,
10/2008, Letnik:
122, Številka:
4
Journal Article
Recenzirano
The recent identification of loss-of-function mutations in the structural protein filaggrin as a widely replicated major risk factor for eczema sheds new light on disease mechanisms in eczema, a ...disease that had heretofore largely been considered to have a primarily immunologic etiopathogenesis. The filaggrin gene (FLG) mutation findings are consistent with a recently proposed unifying hypothesis that offers a mechanistic understanding of eczema pathogenesis synthesizing a heritable epithelial barrier defect and resultant diminished epidermal defense mechanisms to allergens and microbes, followed by polarized TH 2 lymphocyte responses with resultant chronic inflammation, including autoimmune mechanisms. Although compelling evidence from genetic studies on FLG implicates perturbed barrier function as a key player in the pathogenesis of eczema in many patients, much is still unknown about the sequence of biologic, physicochemical, and aberrant regulatory events that constitute the transition from an inherited barrier defect to clinical manifestations of inflammatory eczematous lesions and susceptibility to related atopic disorders. The exact contribution of FLG to the wider atopic story, factors modifying FLG expression, and the role of other barrier proteins remain to be delineated. In this review we highlight recent advances in our understanding of the FLG genetics in the cause of eczema and related complex diseases.
Background Atopic dermatitis (AD) is a major inflammatory condition of the skin caused by inherited skin barrier deficiency, with mutations in the filaggrin gene predisposing to development of AD. ...Support for barrier deficiency initiating AD came from flaky tail mice, which have a frameshift mutation in Flg and also carry an unknown gene, matted , causing a matted hair phenotype. Objective We sought to identify the matted mutant gene in mice and further define whether mutations in the human gene were associated with AD. Methods A mouse genetics approach was used to separate the matted and Flg mutations to produce congenic single-mutant strains for genetic and immunologic analysis. Next-generation sequencing was used to identify the matted gene. Five independently recruited AD case collections were analyzed to define associations between single nucleotide polymorphisms (SNPs) in the human gene and AD. Results The matted phenotype in flaky tail mice is due to a mutation in the Tmem79/Matt gene, with no expression of the encoded protein mattrin in the skin of mutant mice. Matt ft mice spontaneously have dermatitis and atopy caused by a defective skin barrier, with mutant mice having systemic sensitization after cutaneous challenge with house dust mite allergens. Meta-analysis of 4,245 AD cases and 10,558 population-matched control subjects showed that a missense SNP, rs6694514, in the human MATT gene has a small but significant association with AD. Conclusion In mice mutations in Matt cause a defective skin barrier and spontaneous dermatitis and atopy. A common SNP in MATT has an association with AD in human subjects.
Background Filaggrin ( FLG ) has a central role in the pathogenesis of atopic dermatitis (AD). FLG is a complex repetitive gene; highly population-specific mutations and multiple rare mutations make ...routine genotyping complex. Furthermore, the mechanistic pathways through which mutations in FLG predispose to AD are unclear. Objectives We sought to determine whether specific Raman microspectroscopic natural moisturizing factor (NMF) signatures of the stratum corneum could be used as markers of FLG genotype in patients with moderate-to-severe AD. Methods The composition and function of the stratum corneum in 132 well-characterized patients with moderate-to-severe AD were assessed by means of confocal Raman microspectroscopy and measurement of transepidermal water loss (TEWL). These parameters were compared with FLG genotype and clinical assessment. Results Three subpopulations closely corresponding with FLG genotype were identified by using Raman spectroscopy. The Raman signature of NMF discriminated between FLG -associated AD and non– FLG -associated AD (area under the curve, 0.94; 95% CI, 0.91-0.99). In addition, within the subset of FLG -associated AD, NMF distinguished between patients with 1 versus 2 mutations. Five novel FLG mutations were found on rescreening outlying patients with Raman signatures suggestive of undetected mutations (R3418X, G1138X, S1040X, 10085delC, and L2933X). TEWL did not associate with FLG genotype subgroups. Conclusions Raman spectroscopy permits rapid and highly accurate stratification of FLG -associated AD. FLG mutations do not influence TEWL within established moderate-to-severe AD.
Filaggrin in atopic dermatitis O'Regan, Grainne M., MB; Sandilands, Aileen, PhD; McLean, W.H. Irwin, PhD, DSc ...
Journal of allergy and clinical immunology,
09/2009, Letnik:
124, Številka:
3
Journal Article
Recenzirano
The recent identification of loss-of-function mutations in the structural protein filaggrin as a widely replicated major risk factor for eczema sheds new light on disease mechanisms in eczema, a ...disease that had heretofore largely been considered to have a primarily immunologic etiopathogenesis. The filaggrin gene (FLG) mutation findings are consistent with a recently proposed unifying hypothesis that offers a mechanistic understanding of eczema pathogenesis synthesizing a heritable epithelial barrier defect and resultant diminished epidermal defense mechanisms to allergens and microbes, followed by polarized TH 2 lymphocyte responses with resultant chronic inflammation, including autoimmune mechanisms. Although compelling evidence from genetic studies on FLG implicates perturbed barrier function as a key player in the pathogenesis of eczema in many patients, much is still unknown about the sequence of biologic, physicochemical, and aberrant regulatory events that constitute the transition from an inherited barrier defect to clinical manifestations of inflammatory eczematous lesions and susceptibility to related atopic disorders. The exact contribution of FLG to the wider atopic story, factors modifying FLG expression, and the role of other barrier proteins remain to be delineated. In this review we highlight recent advances in our understanding of the FLG genetics in the cause of eczema and related complex diseases.
FLG mutations lead to reduced levels of filaggrin degradation products in the SC in a dose-dependent fashion.5 It has been shown that moderate-to-severe AD also has an effect on SC filaggrin ...expression6 as well as on the levels of filaggrin degradation products5 possibly due to the systemic TH2 immune response.6 In the present study, the levels of both PCA and UCA and their sum were significantly decreased in the SC of patients with AD than in control subjects (Fig 1; see Table E1 in this article's Online Repository at www.jacionline.org). ...FLG LOF mutations are not a significant contributor to AD in the amaXhosa population.
Background Filaggrin is a key protein involved in skin barrier function. Recently, mutations in the filaggrin gene, FLG , were identified in European families with ichthyosis vulgaris (IV) and shown ...to be an important predisposing factor for atopic dermatitis (AD). Objective To study the role of FLG mutations in IV/AD in Japan. Methods The known filaggrin mutations were studied by genotyping and new mutations identified by DNA sequencing. Results The European-specific mutations R501X and 2282del4 were absent from 253 Japanese individuals. We therefore sequenced the FLG gene in 4 Japanese families with IV and identified 2 novel mutations, 3321delA and S2554X. Immunohistologic and ultrastructural observations indicated that both truncation mutations lead to a striking reduction of keratohyalin granules in the epidermis. We screened 143 Japanese patients with AD for these FLG null mutations and identified them in 8 patients with AD (5.6%), including S2554X in 6 patients (4.2%) and 3321delA in 2 patients (1.4%). Both null variants were absent from 156 unrelated Japanese nonatopic and nonichthyotic controls, giving a significant statistical association between the FLG mutations and AD (χ2 P value, .0015). This is the first report of FLG mutations in a non-European population. Conclusion Our data indicate that FLG mutations in Japan are unique from those found in European-origin populations. Clinical implications Filaggrin null variants are also significant predisposing factors for AD in Japan and, on the basis of the recent European studies, may predict a more severe and persistent form of atopy.
Background Null mutations within the filaggrin gene (FLG) are associated with moderate-to-severe atopic eczema; their role in mild-to-moderate eczema in the general population is unknown. Objective ...We sought to investigate the significance of 5 common FLG null mutations in childhood atopic eczema in an unselected population cohort. Methods Eight hundred eleven English children aged 7 to 9 years were screened for FLG mutations. Eczema cases were defined by using United Kingdom diagnostic criteria and skin examination. Asthma and seasonal rhinitis cases were defined by parental questionnaire. Association between phenotype and genotype was investigated using Fisher exact test and logistic regression analysis. Results The 12-month period prevalence of atopic eczema was 24.2% (95% CI, 21.2% to 27.2%), with 96% (115/120) of cases having mild-to-moderate disease. The combined null genotype (carriage of ≥1 FLG mutations) was significantly associated with atopic eczema ( P = 1.2 × 10−4 ). The odds ratio (OR) for individuals carrying 2 null mutations was 26.9 (95% CI, 3.3-217.1), but heterozygote carriers showed no significant increase in risk (OR, 1.2; 95% CI, 0.7-1.9). Eight of 190 eczema cases (4.2%) carried 2 FLG null mutations and thus might be attributed to filaggrin deficiency. Asthma in the context of eczema showed significant association with the FLG null mutations ( P = 7.1 × 10−4 ). There was no association of FLG with asthma independent of eczema ( P = .15) and no association with seasonal rhinitis ( P = .66). Conclusion FLG null mutations are significantly associated with mild-to-moderate atopic eczema in childhood, with a recessive pattern of inheritance.
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