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 play a crucial role in maintaining epidermal integrity and barrier function. SAM syndrome-causing mutations 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. The deciphering of the pathogenesis of SAM syndrome substantiates the notion that allergy may result from a primary structural epidermal defect.

P-cadherin is a key component of epithelial adherens junctions, and it is prominently expressed in the hair follicle (HF) matrix. Loss-of-function mutations in CDH3, which encodes P-cadherin, result in hypotrichosis with juvenile macular dystrophy (HJMD), an autosomal recessive disorder featuring sparse and short hair. Here, we attempted to recapitulate some aspects of HJMD in vitro by transfecting normal, organ-cultured human scalp HFs with lipofectamine and CDH3-specific or scrambled control siRNAs. As in HJMD patients, P-cadherin silencing inhibited hair shaft growth, prematurely induced HF regression (catagen), and inhibited hair matrix keratinocyte proliferation. In situ, membrane β-catenin expression and transcription of the β-catenin target gene, axin2, were significantly reduced, whereas glycogen synthase kinase 3 β (GSK3β) and phospho-β-catenin immunoreactivity were increased. These effects were partially reversed by inhibiting GSK3β. P-cadherin silencing reduced the expression of the anagen-promoting growth factor, IGF-1, whereas that of transforming growth factor β 2 (TGFβ2; catagen promoter) was enhanced. Neutralizing TGFβ antagonized the catagen-promoting effects of P-cadherin silencing. In summary, we introduce human HFs as an attractive preclinical model for studying the functions of P-cadherin in human epithelial biology and pathology. This model demonstrates that cadherins can be successfully knocked down in an intact human organ in vitro, and shows that P-cadherin is needed for anagen maintenance by regulating canonical Wnt signaling and suppressing TGFβ2.

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Despite recent advances in our understanding of the pathogenesis of ectodermal dysplasias (EDs), the molecular basis of many of these disorders remains unknown. In the present study, we aimed at elucidating the genetic basis of a new form of ED featuring facial dysmorphism, scalp hypotrichosis and hypodontia. Using whole exome sequencing, we identified 2 frameshift and 2 missense mutations in TSPEAR segregating with the disease phenotype in 3 families. TSPEAR encodes the thrombospondin-type laminin G domain and EAR repeats (TSPEAR) protein, whose function is poorly understood. TSPEAR knock-down resulted in altered expression of genes known to be regulated by NOTCH and to be involved in murine hair and tooth development. Pathway analysis confirmed that down-regulation of TSPEAR in keratinocytes is likely to affect Notch signaling. Accordingly, using a luciferase-based reporter assay, we showed that TSPEAR knock-down is associated with decreased Notch signaling. In addition, NOTCH1 protein expression was reduced in patient scalp skin. Moreover, TSPEAR silencing in mouse hair follicle organ cultures was found to induce apoptosis in follicular epithelial cells, resulting in decreased hair bulb diameter. Collectively, these observations indicate that TSPEAR plays a critical, previously unrecognized role in human tooth and hair follicle morphogenesis through regulation of the Notch signaling pathway.

In the GWAS group, age at onset was 36 years and in the non-GWAS group 28 years. The difference is mainly owing to the inclusion of a subset of individuals from a paediatric cohort (disease onset before 15 years of age) into the non-GWAS samples whereas the GWAS samples included only individuals with adult onset of disease.Strong association to HLA genes is a hallmark of common immune-mediated diseases. HLA genes are extremely polymorphic with minor sequence variation between genotypes. In view of increasing demand for dissection of genetic and clinical heterogeneity of many common immunologically based diseases, precise determination of HLA genotypes will become critical. In this respect, we propose that the method presented herein represents a real contribution in the psoriasis field. AcknowledgementsThe authors thank Anna-Lena Kastman, Anna Ehrensvärd, Kerstin Bergh, Leonid Padyukov and Maria Seddighzadeh for the excellent assistance, technical support and advice. This work was supported by grants from the Swedish Medical Research Council, the Swedish Psoriasis Association, the Welander and Finsen Foundations, Stockholm County and Karolinska Institutet. Conflict of interestsThe authors have declared no conflicting interests. Supporting InformationAdditional Supporting Information may be found in the online version of this article: Table S1. HLA-Cw*06:02 readings from four SNPs genotypes.Please note: Wiley-Blackwell is not responsible for the content or functionality of any supporting materials supplied by the authors. Any queries (other than missing material) should be directed to the corresponding author for the article. Abstract: Interferon-c (IFNc)-induced collapse of hair follicle (HF) immune privilege (IP) is a key element in the pathogenesis of alopecia areata. In this pilot study, we investigated whether the immunosuppressive neuropeptide, calcitonin gene-related peptide (CGRP), can protect from and ⁄ or restore IFNc-induced HF-IP collapse. After showing that human scalp HFs express CGRP receptor-like receptor (CRLR) immunoreactivity, anagen HFs were cultured in the presence of IFNc, with CGRP added before or after. Adding CGRP after IFNc administration ('restoration assay') failed to downregulate IFNc-induced ectopic MHC class I expression, while MHC class II expression was reduced. However, administering CGRP before IFNc application ('protection assay') significantly reduced the IFNc-induced overexpression and ectopic expression of MHC class I and II and reduced the increased degranulation of perifollicular mast cells induced by IFNc. This suggests that CGRP may not restore HF-IP once it has collapsed, but may protect it from collapsing. Therefore, CRLR stimulation might help to retard AA progression.

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Background: Atopic dermatitis (AD) is a highly prevalent chronic inflammatory skin disease that is known to be, at least in part, genetically determined. Mutations in caspase recruitment domain-containing protein 14 (CARD14) have been shown to result in various forms of psoriasis and related disorders. Objective: We aimed to identify rare DNA variants conferring a significant risk for AD through genetic and functional studies in a cohort of patients affected with severe AD. Methods: Whole-exome and direct gene sequencing, immunohistochemistry, real-time PCR, ELISA, and functional assays in human keratinocytes were used. Results: In a cohort of patients referred with severe AD, DNA sequencing revealed in 4 patients 2 rare heterozygous missense mutations in the gene encoding CARD14, a major regulator of nuclear factor kB (NF-kB). A dual luciferase reporter assay demonstrated that both mutations exert a dominant loss-offunction effect and result in decreased NF-kB signaling.