Epidermal nevi are common congenital skin lesions with an incidence of 1 in 1,000 people; however, their genetic basis remains elusive. Germline mutations of the FGF receptor 3 (FGFR3) cause autosomal dominant skeletal disorders such as achondroplasia and thanatophoric dysplasia, which can be associated with acanthosis nigricans of the skin. Acanthosis nigricans and common epidermal nevi of the nonorganoid, nonepidermolytic type share some clinical and histological features. We used a SNaPshot multiplex assay to screen 39 epidermal nevi of this type of 33 patients for 11 activating FGFR3 point mutations. In addition, exon 19 of FGFR3 was directly sequenced. We identified activating FGFR3 mutations, almost exclusively at codon 248 (R248C), in 11 of 33 (33%) patients with nonorganoid, nonepidermolytic epidermal nevi. In 4 of these cases, samples from adjacent histologically normal skin could be analyzed, and FGFR3 mutations were found to be absent. Our results suggest that a large proportion of epidermal nevi are caused by a mosaicism of activating FGFR3 mutations in the human epidermis, secondary to a postzygotic mutation in early embryonic development. The R248C mutation appears to be a hot spot for FGFR3 mutations in epidermal nevi.
Christian Hafner, Johanna M.M. van Oers, Thomas Vogt, Michael Landthaler, Robert Stoehr, Hagen Blaszyk, Ferdinand Hofstaedter, Ellen C. Zwarthoff, Arndt Hartmann
We found that sterile wounding of human skin induced epidermal expression of the antimicrobial (poly)peptides human β-defensin–3, neutrophil gelatinase–associated lipocalin, and secretory leukocyte protease inhibitor through activation of the epidermal growth factor receptor. After skin wounding, the receptor was activated by heparin-binding epidermal growth factor that was released by a metalloprotease-dependent mechanism. Activation of the epidermal growth factor receptor generated antimicrobial concentrations of human β-defensin–3 and increased the activity of organotypic epidermal cultures against Staphylococcus aureus. These data demonstrate that sterile wounding initiates an innate immune response that increases resistance to overt infection and microbial colonization.
Ole E. Sørensen, Dharma R. Thapa, K. Markus Roupé, Erika V. Valore, Ulf Sjöbring, Alice A. Roberts, Artur Schmidtchen, Tomas Ganz
Inflammatory skin disorders result in significant epidermal changes, including keratinocyte hyperproliferation, incomplete differentiation, and impaired barrier. Here we test whether, conversely, an impaired epidermal barrier can promote an inflammatory response. Mice lacking the transcription factor Kruppel-like factor 4 (Klf4) have a severe defect in epidermal barrier acquisition. Transcription profiling of Klf4–/– newborn skin revealed similar changes in gene expression to involved psoriatic plaques, including a significant upregulation of the gap junction protein connexin 26 (Cx26). Ectopic expression of Cx26 from the epidermis-specific involucrin (INV) promoter (INV-Cx26) demonstrated that downregulation of Cx26 is required for barrier acquisition during development. In juvenile and adult mice, persistent Cx26 expression kept wounded epidermis in a hyperproliferative state, blocked the transition to remodeling, and led to an infiltration of immune cells. Mechanistically, ectopic expression of Cx26 in keratinocytes resulted in increased ATP release, which delayed epidermal barrier recovery and promoted an inflammatory response in resident immune cells. These results provide a molecular link between barrier acquisition in utero and epidermal remodeling after wounding. More generally, these studies suggest that the most effective treatments for inflammatory skin disorders might concomitantly suppress the immune response and enhance epidermal differentiation to restore the barrier.
Ali R. Djalilian, David McGaughey, Satyakam Patel, Eun Young Seo, Chenghua Yang, Jun Cheng, Melanija Tomic, Satrajit Sinha, Akemi Ishida-Yamamoto, Julia A. Segre
The human hair follicle bulge is an important niche for keratinocyte stem cells (KSCs). Elucidation of human bulge cell biology could be facilitated by analysis of global gene expression profiles and identification of unique cell-surface markers. The lack of distinctive bulge morphology in human hair follicles has hampered studies of bulge cells and KSCs. In this study, we determined the distribution of label-retaining cells to define the human anagen bulge. Using navigated laser capture microdissection, bulge cells and outer root sheath cells from other follicle regions were obtained and analyzed with cDNA microarrays. Gene transcripts encoding inhibitors of WNT and activin/bone morphogenic protein signaling were overrepresented in the bulge, while genes responsible for cell proliferation were underrepresented, consistent with the existence of quiescent noncycling KSCs in anagen follicles. Positive markers for bulge cells included CD200, PHLDA1, follistatin, and frizzled homolog 1, while CD24, CD34, CD71, and CD146 were preferentially expressed by non-bulge keratinocytes. Importantly, CD200+ cells (CD200hiCD24loCD34loCD71loCD146lo) obtained from hair follicle suspensions demonstrated high colony-forming efficiency in clonogenic assays, indicating successful enrichment of living human bulge stem cells. The stem cell behavior of enriched bulge cells and their utility for gene therapy and hair regeneration will need to be assessed in in vivo assays.
Manabu Ohyama, Atsushi Terunuma, Christine L. Tock, Michael F. Radonovich, Cynthia A. Pise-Masison, Steven B. Hopping, John N. Brady, Mark C. Udey, Jonathan C. Vogel
Nicotinic acid (niacin) has long been used as an antidyslipidemic drug. Its special profile of actions, especially the rise in HDL-cholesterol levels induced by nicotinic acid, is unique among the currently available pharmacological tools to treat lipid disorders. Recently, a G-protein–coupled receptor, termed GPR109A (HM74A in humans, PUMA-G in mice), was described and shown to mediate the nicotinic acid–induced antilipolytic effects in adipocytes. One of the major problems of the pharmacotherapeutical use of nicotinic acid is a strong flushing response. This side effect, although harmless, strongly affects patient compliance. In the present study, we show that mice lacking PUMA-G did not show nicotinic acid–induced flushing. In addition, flushing in response to nicotinic acid was also abrogated in the absence of cyclooxygenase type 1, and mice lacking prostaglandin D2 (PGD2) and prostaglandin E2 (PGE2) receptors had reduced flushing responses. The mouse orthologue of GPR109A, PUMA-G, is highly expressed in macrophages and other immune cells, and transplantation of wild-type bone marrow into irradiated PUMA-G–deficient mice restored the nicotinic acid–induced flushing response. Our data clearly indicate that GPR109A mediates nicotinic acid–induced flushing and that this effect involves release of PGE2 and PGD2, most likely from immune cells of the skin.
Zoltán Benyó, Andreas Gille, Jukka Kero, Marion Csiky, Marie Catherine Suchánková, Rolf M. Nüsing, Alexandra Moers, Klaus Pfeffer, Stefan Offermanns
Autoantibodies against the epidermal desmosomal cadherins desmoglein 1 (Dsg1) and Dsg3 have been shown to cause severe to lethal skin blistering clinically defined as pemphigus foliaceus (PF) and pemphigus vulgaris (PV). It is unknown whether antibody-induced dissociation of keratinocytes is caused by direct inhibition of Dsg1 transinteraction or by secondary cellular responses. Here we show in an in vitro system that IgGs purified from PF patient sera caused cellular dissociation of cultured human keratinocytes as well as significant release of Dsg1-coated microbeads attached to Dsg-containing sites on the keratinocyte cellular surface. However, cell dissociation and bead release induced by PF-IgGs was not caused by direct steric hindrance of Dsg1 transinteraction, as demonstrated by single molecule atomic force measurements and by laser trapping of surface-bound Dsg1-coated microbeads. Rather, our experiments strongly indicate that PF-IgG–mediated dissociation events must involve autoantibody-triggered cellular signaling pathways, resulting in destabilization of Dsg1-based adhesive sites and desmosomes.
Jens Waschke, Paola Bruggeman, Werner Baumgartner, Detlef Zillikens, Detlev Drenckhahn
Harlequin ichthyosis (HI) is a devastating skin disorder with an unknown underlying cause. Abnormal keratinocyte lamellar granules (LGs) are a hallmark of HI skin. ABCA12 is a member of the ATP-binding cassette transporter family, and members of the ABCA subfamily are known to have closely related functions as lipid transporters. ABCA3 is involved in lipid secretion via LGs from alveolar type II cells, and missense mutations in ABCA12 have been reported to cause lamellar ichthyosis type 2, a milder form of ichthyosis. Therefore, we hypothesized that HI might be caused by mutations that lead to serious ABCA12 defects. We identify 5 distinct ABCA12 mutations, either in a compound heterozygous or homozygous state, in patients from 4 HI families. All the mutations resulted in truncation or deletion of highly conserved regions of ABCA12. Immunoelectron microscopy revealed that ABCA12 localized to LGs in normal epidermal keratinocytes. We confirmed that ABCA12 defects cause congested lipid secretion in cultured HI keratinocytes and succeeded in obtaining the recovery of LG lipid secretion after corrective gene transfer of ABCA12. We concluded that ABCA12 works as an epidermal keratinocyte lipid transporter and that defective ABCA12 results in a loss of the skin lipid barrier, leading to HI. Our findings not only allow DNA-based early prenatal diagnosis but also suggest the possibility of gene therapy for HI.
Masashi Akiyama, Yoriko Sugiyama-Nakagiri, Kaori Sakai, James R. McMillan, Maki Goto, Ken Arita, Yukiko Tsuji-Abe, Nobuko Tabata, Kentaro Matsuoka, Rikako Sasaki, Daisuke Sawamura, Hiroshi Shimizu
Pemphigus is a life-threatening blistering disorder of the skin and mucous membranes caused by pathogenic autoantibodies to desmosomal adhesion proteins desmoglein 3 (Dsg3) and Dsg1. Mechanisms of antibody pathogenicity are difficult to characterize using polyclonal patient sera. Using antibody phage display, we have isolated repertoires of human anti-Dsg mAbs as single-chain variable-region fragments (scFvs) from a patient with active mucocutaneous pemphigus vulgaris. ScFv mAbs demonstrated binding to Dsg3 or Dsg1 alone, or both Dsg3 and Dsg1. Inhibition ELISA showed that the epitopes defined by these scFvs are blocked by autoantibodies from multiple pemphigus patients. Injection of scFvs into neonatal mice identified 2 pathogenic scFvs that caused blisters histologically similar to those observed in pemphigus patients. Similarly, these 2 scFvs, but not others, induced cell sheet dissociation of cultured human keratinocytes, indicating that both pathogenic and nonpathogenic antibodies were isolated. Genetic analysis of these mAbs showed restricted patterns of heavy and light chain gene usage, which were distinct for scFvs with different desmoglein-binding specificities. Detailed characterization of these pemphigus mAbs should lead to a better understanding of the immunopathogenesis of disease and to more specifically targeted therapeutic approaches.
Aimee S. Payne, Ken Ishii, Stephen Kacir, Chenyan Lin, Hong Li, Yasushi Hanakawa, Kazuyuki Tsunoda, Masayuki Amagai, John R. Stanley, Don L. Siegel
Desmogleins (Dsgs), cadherin-type cell adhesion molecules, are targeted in skin-blistering diseases such as pemphigus and staphylococcal scalded skin syndrome (SSSS). The role of Dsg4, a new isoform, was investigated in these diseases. Dsg4 was recognized by 30 (77%) of 39 pemphigus sera containing anti-Dsg1 IgG but not by 16 pemphigus sera containing no anti-Dsg1 IgG or by 34 normal control sera. The Dsg4 immunoreactivity of these sera was abolished by removal of anti-Dsg1 IgG. Conversely, the removal of anti-Dsg4 IgG from pemphigus sera reduced the immunoreactivity against Dsg1 only 13.8% ± 8.8% (n = 23) and did not affect its ability to induce blisters in neonatal mice. IgG that was affinity-purified on Dsg4 recognized Dsg1 but failed to induce blisters, while IgG purified on Dsg1 from the same pemphigus foliaceus sera induced blisters. Thus, pemphigus sera show Dsg4 reactivity due to cross-reactivity of a subset of anti-Dsg1 IgG, and the Dsg4/Dsg1–cross-reacting IgG has no demonstrable pathogenic effect. In addition, Dsg4 was not cleaved by exfoliative toxins that induce blisters in SSSS. These findings suggest that Dsg4 may play a role other than adhesion and that the cross-reactivity of desmoglein autoantibodies should be factored into the framework of future studies of autoimmune mechanisms in pemphigus.
Takeshi Nagasaka, Koji Nishifuji, Takayuki Ota, Neil V. Whittock, Masayuki Amagai
Dermatitis herpetiformis (DH) is an autoimmune blistering skin disorder that is associated with gluten sensitivity. It presents as a papulovesicular rash and is often associated with enteropathy. The rash resolves when the patient is placed on a gluten-free diet and/or dapsone. DH, as well as celiac disease, is tightly associated with DQ2 and DQ8. A novel mouse model for DH is described that utilizes the NOD background and the HLA-DQ8 transgene. The addition of DQ8 contributes sensitivity to gliadin, and the addition of the NOD background contributes to autoimmunity and pathogenesis. Fifteen NOD DQ8+ mice of 90 that were sensitized to gluten developed blistering pathology similar to that seen in DH. Neutrophil infiltration of the dermis, deposition of IgA at the dermal-epidermal junction, and a complete reversal of the blistering phenomenon with the administration of a gluten-free diet with or without dapsone were observed. None of the 3 blistering mice examined had small-bowel pathology. This animal model of DH will be useful to determine the specificity of the IgA deposits, as well as the pathogenic mechanisms that occur in the skin as a result of gluten ingestion.
Eric Marietta, Kay Black, Michael Camilleri, Patricia Krause, Roy S. Rogers III, Chella David, Mark R. Pittelkow, Joseph A. Murray