[show abstract][hide abstract] ABSTRACT: Background/objectives. Environmental exposure and personal susceptibility both contribute to the development of hand eczema. In this study, we investigated the effect of loss-of-function mutations in the filaggrin gene (FLG), atopic dermatitis and wet work exposure on the development of hand eczema in apprentice nurses. Methods. Dutch apprentice nurses were genotyped for the four most common FLG mutations; atopic dermatitis and hand eczema history were assessed by questionnaire. Exposure and hand eczema during traineeships were assessed with diary cards. Results. The prevalence of hand eczema during traineeships was higher among subjects with a history of hand eczema reported at inclusion. Hand washing during traineeships and at home increased the risk of hand eczema. After adjustment for the effects of exposure and FLG mutations, an odds ratio of 2.5 (90% confidence interval 1.7–3.7) was found for a history of atopic dermatitis. In this study, an increased risk of hand eczema conferred by FLG mutations could not be shown, but subjects with concomitant FLG mutations and atopic dermatitis showed the highest risk of hand eczema during traineeships. Conclusion. A history of atopic dermatitis, a history of hand eczema and wet work exposure were the most important factors increasing the risk of hand eczema during traineeships.
[show abstract][hide abstract] ABSTRACT: The relative contribution of immunological dysregulation and impaired epithelial barrier function to allergic diseases is still a matter of debate. Here we describe a new syndrome featuring severe dermatitis, multiple allergies and metabolic wasting (SAM syndrome) caused by homozygous mutations in DSG1. DSG1 encodes desmoglein 1, a major constituent of desmosomes, which connect the cell surface to the keratin cytoskeleton and have a crucial role in maintaining epidermal integrity and barrier function. Mutations causing SAM syndrome resulted in lack of membrane expression of DSG1, leading to loss of cell-cell adhesion. In addition, DSG1 deficiency was associated with increased expression of a number of genes encoding allergy-related cytokines. Our deciphering of the pathogenesis of SAM syndrome substantiates the notion that allergy may result from a primary structural epidermal defect.
[show abstract][hide abstract] ABSTRACT: Keratin 9 (K9) is a type I intermediate filament protein whose expression is confined to the suprabasal layers of palmoplantar epidermis. Though mutations in the K9 gene are known to cause epidermolytic palmoplantar keratoderma (EPPK), a rare dominant-negative skin disorder, its functional significance is poorly understood. To gain insight into the physical requirement and importance of K9, we generated K9-deficient (Krt9(-/-)) mice. Here, we report that adult Krt9(-/-) mice develop calluses marked by hyperpigmentation that are exclusively localized to the stress-bearing footpads. Histological, immunohistochemical and immunoblot analyses of these regions revealed hyperproliferation, impaired terminal differentiation and abnormal expression of keratins K5, K14 and K2. Furthermore, the absence of K9 induces the stress-activated keratins K6 and K16. Importantly, mice heterozygous for the K9-null allele (Krt9(+/-)) show neither an overt nor histological phenotype, demonstrating that one Krt9 allele is sufficient for developing normal palmoplantar epidermis. Together, our data demonstrates that the complete ablation of K9 is not tolerable in vivo and that K9 is required for terminal differentiation and maintaining the mechanical integrity of palmoplantar epidermis.Journal of Investigative Dermatology accepted article preview online, 20 August 2013. doi:10.1038/jid.2013.356.
Journal of Investigative Dermatology 08/2013; · 6.19 Impact Factor
[show abstract][hide abstract] ABSTRACT: A fifteen-year-old female with pachyonychia congenita (PC) confirmed by genetic testing presented with pain and a localized subcutaneous swelling on her right back. Biopsy confirmed Ewing's sarcoma of the posterior 10(th) rib. Preoperative tumor reduction chemotherapy was commenced as per Euro EWING 99 protocol with vincristine, ifosfamide, doxorubicin and etoposide (VIDE). Ifosfamide was subsequently replaced by cyclophosphamide as per protocol due to potential renal tubule toxicity (VCDE) (Juergens et al, 2006) (Table 1). Surgical resection was performed followed by radiotherapy to the primary site. This article is protected by copyright. All rights reserved.
British Journal of Dermatology 08/2013; · 3.76 Impact Factor
[show abstract][hide abstract] ABSTRACT: Atopic dermatitis (AD) is the most common dermatological disease of childhood. Many children with AD have asthma and AD shares regions of genetic linkage with psoriasis, another chronic inflammatory skin disease. We present here a genome-wide association study (GWAS) of childhood-onset AD in 1563 European cases with known asthma status and 4054 European controls. Using Illumina genotyping followed by imputation, we generated 268 034 consensus genotypes and in excess of 2 million single nucleotide polymorphisms (SNPs) for analysis. Association signals were assessed for replication in a second panel of 2286 European cases and 3160 European controls. Four loci achieved genome-wide significance for AD and replicated consistently across all cohorts. These included the epidermal differentiation complex (EDC) on chromosome 1, the genomic region proximal to LRRC32 on chromosome 11, the RAD50/IL13 locus on chromosome 5 and the major histocompatibility complex (MHC) on chromosome 6; reflecting action of classical HLA alleles. We observed variation in the contribution towards co-morbid asthma for these regions of association. We further explored the genetic relationship between AD, asthma and psoriasis by examining previously identified susceptibility SNPs for these diseases. We found considerable overlap between AD and psoriasis together with variable coincidence between allergic rhinitis (AR) and asthma. Our results indicate that the pathogenesis of AD incorporates immune and epidermal barrier defects with combinations of specific and overlapping effects at individual loci.
Human Molecular Genetics 07/2013; · 7.69 Impact Factor
[show abstract][hide abstract] ABSTRACT: Filaggrin loss-of-function (FLG) skin barrier gene mutations are associated with atopic dermatitis (AD) and transepidermal water loss (TEWL). We investigated whether FLG mutation inheritance, skin barrier impairment and AD also predispose to allergic sensitization to foods. 619 exclusively breastfed infants were recruited at 3 months of age and examined for AD and disease severity (SCORAD) and screened for the common FLG mutations. TEWL was measured on unaffected forearm skin. In addition, skin prick testing to six foods (cow's milk, egg, cod, wheat, sesame, and peanut) was performed. Children with AD were significantly more likely to be sensitized (adjusted OR=6.18 (95% CI 2.94-12.98, P<0.001), but this effect was independent of FLG mutation carriage, TEWL and AD phenotype (flexural vs non-flexural). There was also a strong association between food sensitization and AD severity (adjusted ORSCORAD<20=3.91 (1.70-9.00, P=0.001) vs adjusted ORSCORAD≥20=25.60 (9.03-72.57), P<0.001). Equally, there was a positive association between AD and sensitization to individual foods (adjusted ORegg=9.48 (3.77-23.83), P<0.001; adjusted ORcow's milk=9.11 (2.27-36.59), P=0.002; adjusted ORpeanut=4.09 (1.00-16.76), P=0.05). AD is the main skin-related risk factor for food sensitization in young infants. In exclusively breastfed children this suggests that allergic sensitization to foods can be mediated by cutaneous antigen-presenting cells.Journal of Investigative Dermatology accepted article preview online, 18 July 2013. doi:10.1038/jid.2013.298.
Journal of Investigative Dermatology 07/2013; · 6.19 Impact Factor
[show abstract][hide abstract] ABSTRACT: Autosomal-dominant diffuse nonepidermolytic palmoplantar keratoderma is characterized by the adoption of a white, spongy appearance of affected areas upon exposure to water. After exome sequencing, missense mutations were identified in AQP5, encoding water-channel protein aquaporin-5 (AQP5). Protein-structure analysis indicates that these AQP5 variants have the potential to elicit an effect on normal channel regulation. Immunofluorescence data reveal the presence of AQP5 at the plasma membrane in the stratum granulosum of both normal and affected palmar epidermis, indicating that the altered AQP5 proteins are trafficked in the normal manner. We demonstrate here a role for AQP5 in the palmoplantar epidermis and propose that the altered AQP5 proteins retain the ability to form open channels in the cell membrane and conduct water.
The American Journal of Human Genetics 07/2013; · 11.20 Impact Factor
[show abstract][hide abstract] ABSTRACT: Atopic dermatitis is a common inflammatory skin disease with a strong heritable component. Pathogenetic models consider keratinocyte differentiation defects and immune alterations as scaffolds, and recent data indicate a role for autoreactivity in at least a subgroup of patients. FLG (encoding filaggrin) has been identified as a major locus causing skin barrier deficiency. To better define risk variants and identify additional susceptibility loci, we densely genotyped 2,425 German individuals with atopic dermatitis (cases) and 5,449 controls using the Immunochip array followed by replication in 7,196 cases and 15,480 controls from Germany, Ireland, Japan and China. We identified four new susceptibility loci for atopic dermatitis and replicated previous associations. This brings the number of atopic dermatitis risk loci reported in individuals of European ancestry to 11. We estimate that these susceptibility loci together account for 14.4% of the heritability for atopic dermatitis.
[show abstract][hide abstract] ABSTRACT: The drug molecule PTC124 (Ataluren) has been described as a read-through agent, capable of suppressing premature termination codons (PTCs) and restoring functional protein production from genes disrupted by nonsense mutations. Following the discovery of PTC124 there was some controversy regarding its mechanism of action with two reports attributing its activity to an off-target effect on the Firefly luciferase (FLuc) reporter used in the development of the molecule. Despite questions remaining as to its mechanism of action, development of PTC124 continued into the clinic and it is being actively pursued as a potential nonsense mutation therapy. To thoroughly test the ability of PTC124 to read through nonsense mutations, we conducted a detailed assessment comparing the efficacy of PTC124 with the classical aminoglycoside antibiotic read-through agent geneticin (G418) across a diverse range of in vitro reporter assays. We can confirm the off-target FLuc activity of PTC124 but found that, while G418 exhibits varying activity in every read-through assay, there is no evidence of activity for PTC124.
[show abstract][hide abstract] ABSTRACT: Traditional remedies for common disorders have been known for centuries, but insight into their mechanism of action is often limited. In this issue of the JCI, Joost Schalkwijk's research group at the Radboud University Nijmegen Medical Centre in The Netherlands advances our understanding of why topical coal tar is an effective treatment for atopic dermatitis (AD), both rationalizing the use of this traditional medicine, and providing the scientific basis for new therapeutic approaches.
The Journal of clinical investigation 01/2013; · 15.39 Impact Factor
[show abstract][hide abstract] ABSTRACT: Keratin 7 (K7) is a Type II member of the keratin superfamily and despite its widespread expression in different types of simple and transitional epithelia, its functional role in vivo remains elusive, in part due to the lack of any appropriate mouse models or any human diseases that are associated with KRT7 gene mutations. Using conventional gene targeting in mouse embryonic stem cells, we report here the generation and characterisation of the first K7 knockout mouse. Loss of K7 led to increased proliferation of the bladder urothelium although this was not associated with hyperplasia. K18, a presumptive type I assembly partner for K7, showed reduced expression in the bladder whereas K20, a marker of the terminally differentiated superficial urothelial cells was transcriptionally up-regulated. No other epithelia were seen to be adversely affected by the loss of K7 and western blot and immunofluorescence microscopy analysis revealed that the expression of K8, K18, K19 and K20 were not altered in the absence of K7, with the exception of the kidney where there was reduced K18 expression.
PLoS ONE 01/2013; 8(5):e64404. · 3.73 Impact Factor
[show abstract][hide abstract] ABSTRACT: PURPOSE: TO IDENTIFY AN ALLELE-SPECIFIC SIRNA, AGAINST THE COMMON KRT12 MUTATION ARG135THR IN MEESMANN EPITHELIAL CORNEAL DYSTROPHY (MECD) AS A PERSONALIZED APPROACH TO TREATMENT. METHODS: siRNAs against the K12 Arg135Thr mutation were evaluated using a dual luciferase reporter gene assay and the most potent and specific siRNAs were further screened by western blot. Off-target effects on related keratins were assessed and immunological stimulation of TLR3 was evaluated by RT-PCR. A modified 5' rapid amplification of cDNA ends (RACE) method was used to confirm siRNA-mediated mutant knockdown. Allele discrimination was confirmed by quantitative infrared immunoblotting. RESULTS: The lead siRNA, with an IC50 of thirty picomolar, showed no keratin off-target effects or activation of TLR3 in the concentration ranges tested. We confirmed siRNA-mediated knockdown by the presence of K12 mRNA fragments cleaved at the predicted site. A dual tag infrared immunoblot showed knockdown to be allele-specific with 70-80% silencing of the mutant protein. CONCLUSIONS: A potent allele-specific siRNA against the K12 Arg135Thr mutation was identified. In combination with efficient eye drop formulation delivery, this would represent a personalized medicine approach, aimed at preventing the pathology associated with MECD and other ocular surface pathologies with dominant-negative or gain-of-function pathomechanisms.
[show abstract][hide abstract] ABSTRACT: The Rab GTPase Rab27B and one of its effector proteins, Slac2-b (also known as EXPH5, exophilin-5), have putative roles in intracellular vesicle trafficking but their relevance to human disease is not known. By using whole-exome sequencing, we identified a homozygous frameshift mutation in EXPH5 in three siblings with inherited skin fragility born to consanguineous Iraqi parents. All three individuals harbor the mutation c.5786delC (p.Pro1929Leufs(∗)8) in EXPH5, which truncates the 1,989 amino acid Slac2-b protein by 52 residues. The clinical features comprised generalized scale-crusts and occasional blisters, mostly induced by trauma, as well as mild diffuse pigmentary mottling on the trunk and proximal limbs. There was no increased bleeding tendency, no neurologic abnormalities, and no increased incidence of infection. Analysis of an affected person's skin showed loss of Slac2-b immunostaining (C-terminal antibody), disruption of keratinocyte adhesion within the lower epidermis, and an increased number of perinuclear vesicles. A role for Slac2-b in keratinocyte biology was supported by findings of cytoskeletal disruption (mainly keratin intermediate filaments) and decreased keratinocyte adhesion in both keratinocytes from an affected subject and after shRNA knockdown of Slac2-b in normal keratinocytes. Slac2-b was also shown to colocalize with Rab27B and β4 integrin to early adhesion initiation sites in spreading normal keratinocytes. Collectively, our findings identify an unexpected role for Slac2-b in inherited skin fragility and expand the clinical spectrum of human disorders of GTPase effector proteins.
The American Journal of Human Genetics 11/2012; · 11.20 Impact Factor
[show abstract][hide abstract] ABSTRACT: To gain further insight into the genetic architecture of psoriasis, we conducted a meta-analysis of 3 genome-wide association studies (GWAS) and 2 independent data sets genotyped on the Immunochip, including 10,588 cases and 22,806 controls. We identified 15 new susceptibility loci, increasing to 36 the number associated with psoriasis in European individuals. We also identified, using conditional analyses, five independent signals within previously known loci. The newly identified loci shared with other autoimmune diseases include candidate genes with roles in regulating T-cell function (such as RUNX3, TAGAP and STAT3). Notably, they included candidate genes whose products are involved in innate host defense, including interferon-mediated antiviral responses (DDX58), macrophage activation (ZC3H12C) and nuclear factor (NF)-κB signaling (CARD14 and CARM1). These results portend a better understanding of shared and distinctive genetic determinants of immune-mediated inflammatory disorders and emphasize the importance of the skin in innate and acquired host defense.