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Biomedical subjects

Irene M Leigh

Publications and source records attributed to Irene M Leigh.

At least 19 recordsLinked to original sources
PubMed2007

Role for WNT16B in human epidermal keratinocyte proliferation and differentiation.

WNT signalling regulates a variety of cell functions including cell fate, polarity, and differentiation via the canonical or beta-catenin stabilisation pathway and/or the planar cell polarity or non-canonical pathway. We have previously demonstrated that two isoforms (A and B) from the WNT16 locus have differential expression in various adult human tissues. In this study we show that WNT16B but not WNT16A isoform was upregulated in basal cell carcinomas compared with normal skin. We further investigated the cellular and molecular functions of WNT16B in primary human epidermal keratinocytes and a keratinocyte cell line. Cellular expression of WNT16B neither stabilised beta-catenin nor activated the lymphoid enhancer factor or T-cell factor transcriptional reporter in primary keratinocytes. WNT16B activated the Jun-N-terminal kinase cascade suggesting the activation of a non-canonical WNT signalling pathway. Constitutive expression of WNT16B significantly enhanced the rate of cell proliferation and prolonged clonogenicity in primary keratinocytes. Silencing WNT16B by RNA interference reduced keratinocyte proliferation. Furthermore, overexpression of WNT16B induced a hyperproliferation phenotype in an organotypical culture system. This work presents the first evidence that WNT16B activates human keratinocyte proliferation possibly via a beta-catenin-independent non-canonical WNT transduction pathway.

Adenosine Triphosphate↗
PubMed2006

Clinicopathologic features of skin cancer in organ transplant recipients: a retrospective case-control series.

BACKGROUND: Non-melanoma skin cancers (NMSCs) are increased in organ transplant recipients, but transplant and immunocompetent squamous and basal cell carcinomas (SCCs, BCCs) have not been compared previously in a single-center study. OBJECTIVE: To compare clinicopathologic features of transplant and immunocompetent NMSCs. METHODS: Consecutive transplant NMSCs (60 SCCs, 100 BCCs) and immunocompetent NMSCs (40 SCCs, 125 BCCs) presenting between 1995-1997. RESULTS: Transplant patients were 15 years younger at time of NMSC diagnosis compared with immunocompetent individuals, and transplant tumors were often more multiple and extracephalic. Spindle cell morphology was more common in transplant SCCs, a superficial component was more common in transplant BCCs, and histologic features of HPV infection were overrepresented in transplant tumors. Outcome was worse for transplant SCCs but not transplant BCCs. LIMITATIONS: Histologic features required to identify HPV infection have not been validated. CONCLUSIONS: These findings have direct implications for clinical care. The increased frequency and distribution of transplant NMSCs underscore the importance of whole-body surveillance. Transplant SCCs, particularly those with diffuse spindle cell change, may require more aggressive management, whereas transplant BCCs do not. Finally, our data support differences in the pathogenesis of transplant NMSC, which may influence future preventive and therapeutic strategies.

Aged↗
PubMed2005

Mutations in ABCA12 underlie the severe congenital skin disease harlequin ichthyosis.

Harlequin ichthyosis (HI) is the most severe and frequently lethal form of recessive congenital ichthyosis. Although defects in lipid transport, protein phosphatase activity, and differentiation have been described, the genetic basis underlying the clinical and cellular phenotypes of HI has yet to be determined. By use of single-nucleotide-polymorphism chip technology and homozygosity mapping, a common region of homozygosity was observed in five patients with HI in the chromosomal region 2q35. Sequencing of the ABCA12 gene, which maps within the minimal region defined by homozygosity mapping, revealed disease-associated mutations, including large intragenic deletions and frameshift deletions in 11 of the 12 screened individuals with HI. Since HI epidermis displays abnormal lamellar granule formation, ABCA12 may play a critical role in the formation of lamellar granules and the discharge of lipids into the intercellular spaces, which would explain the epidermal barrier defect seen in this disorder. This finding paves the way for early prenatal diagnosis. In addition, functional studies of ABCA12 will lead to a better understanding of epidermal differentiation and barrier formation.

ATP-Binding Cassette Transporters↗
PubMed2005

Low-dose retinoids in the prevention of cutaneous squamous cell carcinomas in organ transplant recipients: a 16-year retrospective study.

OBJECTIVE: To evaluate the long-term efficacy of systemic retinoids in reducing the incidence of cutaneous squamous cell carcinomas (SCCs) in organ transplant recipients (OTRs), who are at greatly increased risk of SCCs. DESIGN: A retrospective before-after study of OTRs who had received low-dose systemic retinoids during 1 to 16 years for prevention of SCCs. SETTING: A specialist dermatology clinic for organ transplant recipients at St Bartholomew's and the Royal London Hospital, University of London, London, England. PATIENTS: Thirty-two OTRs with at least 1 histologically proved SCC. INTERVENTIONS: Continuous systemic retinoids at dosages of 0.2 to 0.4 mg/kg per day for a minimum of 12 months. MAIN OUTCOME MEASURES: The mean difference between the number of SCCs developing annually during retinoid treatment and the number during the 12-month pretreatment interval. RESULTS: In 28 continuously treated individuals, the mean number of SCCs in the 12-month pretreatment interval was 2.9. The number of SCCs was significantly reduced, with a mean difference of 1.46 in the first year of treatment (P = .006), 2.20 in the second (P<.001), and 2.14 in the third (P = .02). The numbers of SCCs were also reduced in subsequent years, but this effect was no longer significant because of smaller patient numbers. Six patients in whom retinoid treatment was interrupted subsequently had a significant increase in SCCs. CONCLUSIONS: Low-dose systemic retinoids significantly reduce SCC development in OTRs for the first 3 years of treatment, and this effect may be sustained for at least 8 years, with a generally well-tolerated side-effect profile. Studies are now required to further optimize their use as a chemopreventive strategy in high-risk OTRs.

Adult↗
PubMed2005

Missense mutations in fumarate hydratase in multiple cutaneous and uterine leiomyomatosis and renal cell cancer.

Heterozygous germline mutations in fumarate hydratase (FH) predispose to the multiple cutaneous and uterine leiomyomatosis syndrome (MCUL), which, when co-existing with renal cancer, is also known as hereditary leiomyomatosis and renal cell cancer. Twenty-seven distinct missense mutations represent 68% of FH mutations reported in MCUL. Here we show that FH missense mutations significantly occurred in fully conserved residues and in residues functioning in the FH A-site, B-site, or subunit-interacting region. Of 24 distinct missense mutations, 13 (54%) occurred in the substrate-binding A-site, 4 (17%) in the substrate-binding B-site, and 7 (29%) in the subunit-interacting region. Clustering of missense mutations suggested the presence of possible mutational hotspots. FH functional assay of lymphoblastoid cell lines from 23 individuals with heterozygous FH missense mutations showed that A-site mutants had significantly less residual activity than B-site mutants, supporting data from Escherichia coli that the A-site is the main catalytic site. Missense FH mutations predisposing to renal cancer had no unusual features, and identical mutations were found in families without renal cancer, suggesting a role for genetic or environmental factors in renal cancer development in MCUL. That all missense FH mutations associating with MCUL/hereditary leiomyomatosis and renal cell cancer showed diminished FH enzymatic activity suggests that the tumor suppressor role of fumarate hydratase may relate to its enzymatic function.

Amino Acid Sequence↗
PubMed2005

Clinical and genetic heterogeneity of erythrokeratoderma variabilis.

The skin disease erythrokeratoderma variabilis (EKV) has been shown to be associated with mutations in GJB3 and GJB4 encoding connexin (Cx)31 and Cx30.3, respectively. Gap junctions composed of Cx proteins are intracellular channels providing a mechanism of synchronized cellular response facilitating metabolic and electronic functions of the cell. In the skin, Cx31 and Cx30.3 are expressed in the stratum granulosum of the epidermis with a suggested role in late keratinocyte differentiation. Molecular investigations of GJB3 and GJB4 were performed in five pedigrees and three sporadic cases of EKV. Mutational analyzes revealed disease-associated Cx31 or Cx30.3 mutations in only three probands of which two were novel mutations and one was a recurrent mutation. These genetic studies further demonstrate the heterogeneous nature of the erythrokeratodermas as not all individuals that were clinically diagnosed with EKV harbor Cx31 or Cx30.3 mutations.

Connexins↗
PubMed2005

Treatment of pachyonychia congenita.

There are currently no specific treatments for pachyonychia congenita (PC). Available treatments generally are directed at specific manifestations of the disorder, and an effective treatment plan must recognize that different patients are more or less troubled by different manifestations of the disease. Treatment for all aspects of PC has been less than completely satisfactory. Very few studies have compared different approaches to treatment, and fewer still have given longitudinal follow-up of efficacy and patient acceptance. This review is essentially a compilation of anecdotes. It was collected from physicians' reports in the literature, from direct communication with physicians currently following patients with PC and from patients who answered a questionnaire on the Pachyonychia Congenita Project web page (http://www.pachyonychia.org/Registry.html).

Darier Disease↗
PubMed2005

The role of hyaluronic acid in wound healing: assessment of clinical evidence.

Hyaluronic acid (hyaluronan), a naturally occurring polymer within the skin, has been extensively studied since its discovery in 1934. It has been used in a wide range of medical fields as diverse as orthopedics and cosmetic surgery, but it is in tissue engineering that it has been primarily advanced for treatment. The breakdown products of this large macromolecule have a range of properties that lend it specifically to this setting and also to the field of wound healing. It is non-antigenic and may be manufactured in a number of forms, ranging from gels to sheets of solid material through to lightly woven meshes. Epidermal engraftment is superior to most of the available biotechnologies and, as such, the material shows great promise in both animal and clinical studies of tissue engineering. Ongoing work centers around the ability of the molecule to enhance angiogenesis and the conversion of chronic wounds into acute wounds.

Adjuvants, Immunologic↗
PubMed2004

The keratins and their disorders.

Diseases caused by mutations in gene encoding keratin intermediate filaments (IF) are characterized by a loss of structural integrity in the cells expressing those keratins in vivo. This is manifested as cell fragility, compensatory epidermal hyperkeratosis, and keratin filament aggregation in some affected tissues. Keratin disorders are a novel molecular category including quite different phenotypes such as epidermolysis bullosa simplex (EBS), bullous congenital ichthyosiform erthroderma (BCIE), pachyonychia congenital (PC), steatocystoma multiplex, ichthyosis bullosa of Siemens (IBS), and white sponge nevus (WSN) of the orogenital mucosa.

Epidermis↗
PubMed2004

Novel microsatellite markers and single nucleotide polymorphisms refine the tylosis with oesophageal cancer (TOC) minimal region on 17q25 to 42.5 kb: sequencing does not identify the causative gene.

Tylosis (focal non-epidermolytic palmoplantar keratoderma) is associated with the early onset of squamous cell oesophageal cancer in three families. Linkage and haplotype analyses have previously mapped the tylosis with oesophageal cancer ( TOC) locus to a 500-kb region on chromosome 17q25 that has also been implicated in sporadically occurring squamous cell oesophageal cancer. In the current study, 17 additional putative microsatellite markers were identified within this 500-kb region by using sequence data and seven of these were shown to be polymorphic in the UK and US families. In addition, our complete sequence analysis of the non-repetitive parts of the TOC minimal region identified 53 novel and six known single nucleotide polymorphisms (SNPs) in one or both of these families. Further fine mapping of the TOC disease locus by haplotype analysis of the seven polymorphic markers and 21 of the 59 SNPs allowed the reduction of the minimal region to 42.5 kb. One known and two putative genes are located within this region but none of these genes shows tylosis-specific mutations within their protein-coding regions. Alternative mechanisms of disease gene action must therefore be considered.

Base Sequence↗
PubMed2004

Conformational changes in the rod domain of human keratin 8 following heterotypic association with keratin 18 and its implication for filament stability.

Keratin intermediate filaments are heteropolymers of type I and type II polypeptides that constitute the bulk of the epithelial cytoskeleton. We microinjected seven keratin monoclonal antibodies into human epithelial cells, and two of them, only A45-B/B3 and LP3K, caused the formation of keratin aggregates. The keratin filaments in human epithelial cells were also disrupted by a monovalent A45-B/B3 Fab fragment, suggesting that the binding of the antibody, rather than cross-linking, collapses the filaments. Immunoblotting and ELISA experiments suggested that the antibody reacted weakly with recombinant K8 but did not react with recombinant K18 at all. However, the antibody reactivity increased substantially when a mixture of the two keratin polypeptides, either recombinant or derived from MCF-7, was used. The epitopes of 15 monoclonal antibodies recognizing human K8 were characterized by their reactivity with recombinant fragments of K8. Reactivity of antibody A45-B/B3 with fragments of K8 in the presence of K18 revealed that the antibody recognizes an epitope in the rod domain of K8, between residues 313 and 332, on the amino-terminal side of the stutter in helix 2B, which is involved in heterotypic association. The data suggest that this region of K8 undergoes a conformational change following interaction with the complementary K18 either to expose the epitope or to increase its affinity for the antibody. Taken together, the data highlight the role of this epitope in heterotypic association and in filament stabilization.

Amino Acid Sequence↗
PubMed2004

Recurrent mutations in kindlin-1, a novel keratinocyte focal contact protein, in the autosomal recessive skin fragility and photosensitivity disorder, Kindler syndrome.

Kindler syndrome (OMIM 173650) is a rare autosomal recessive disorder characterized by trauma-induced blister formation (especially in childhood) and photosensitivity. Other features include mucocutaneous scarring and progressive poikiloderma. There is also an increased risk of skin and mucous membrane malignancy. The disorder was recently mapped to 20p12.3 and pathogenic mutations were identified in a new gene, KIND1. This gene encodes a 677 amino acid protein, kindlin-1, a component of focal contacts in keratinocytes. In this study, we identified four new recurrent mutations in KIND1 in 16 individuals with Kindler syndrome from 13 families of Pakistani (676insC), UK Caucasian (E304X), Omani (W616X), or Italian (958-1G > A) origins. Haplotype analysis demonstrated common ancestral mutant alleles for each mutation, apart from one of the six Pakistani families in which the mutation 676insC (which occurs in a repeat of seven cytosines) was present on a different genetic background. All mutations were homozygous, apart from the three UK Caucasian cases that were all compound heterozygotes (second allele mutations: L302X, 1161delA, 1909delA). All mutations were associated with markedly reduced or absent skin immunostaining with an antikindlin-1 antibody. These loss-of-function KIND1 mutations demonstrate the importance of kindlin-1 in maintaining epithelial integrity, although the mechanism linking this mutant protein to photosensitivity and poikiloderma remains to be determined. Delineation of these recurrent mutations is also relevant to optimizing mutation detection strategies in Kindler syndrome patients from particular ethnic backgrounds.

Adult↗
PubMed2004

Epidermal and hair follicle progenitor cells express melanoma-associated chondroitin sulfate proteoglycan core protein.

Basal keratinocytes in the epidermis and hair follicle are biologically heterogeneous but must include a stable subpopulation of epidermal stem cells. In animal models these can be identified by their retention of radioactive label due to their slow cycle (label-retaining cells) but human studies largely depend on in vitro characterization of colony forming efficiency and clonogenicity. Differential integrin expression has been used to detect cells of increased proliferative potential but further stem cell markers are urgently required for in vivo and in vitro characterization. Using LHM2, a monoclonal antibody reacting with a high molecular weight melanoma-associated proteoglycan core protein, a subset of basal keratinocytes in both the interfollicular epidermis and the hair follicle has been identified. Coexpression of melanoma-associated chondroitin sulfate proteoglycan with keratins 15 and 19 as well as beta 1 and alpha 6 integrins has been examined in adult and fetal human skin from hair bearing, nonhair bearing, and palmoplantar regions. Although melanoma-associated chondroitin sulfate proteoglycan coexpression with a subset of beta 1 integrin bright basal keratinocytes within the epidermis suggests that melanoma-associated chondroitin sulfate proteoglycan colocalizes with epidermal stem cells, melanoma-associated chondroitin sulfate proteoglycan expression within the hair follicle was more complex and multiple subpopulations of basal outer root sheath keratinocytes are described. These data suggest that epithelial compartmentalization of the outer root sheath is more complex than interfollicular epidermis and further supports the hypothesis that more than one hair follicle stem cell compartment may exist.

Animals↗
PubMed2004

The role of allogenic fibroblasts in an acute wound healing model.

Skin is the first tissue-engineered organ to have been successfully developed in the laboratory, and it has been clinically available for use as epidermal sheets for some time. As refinements in this field of tissue engineering continue, several key issues give cause for concern. One issue is the need to form a more complete dermal analogue before grafting. To this end, fibroblasts may be used in vitro to deposit extracellular matrix components within a basic scaffold, laying down those molecules not endogenous to the material and thereby improving the quality of the skin replacement. Many studies have shown the benefits of in vitro seeding with fibroblasts, but there has been some debate regarding the longevity of such cells after allotransplantation into an immunocompetent host. In this study, the authors set out to determine the longevity of transplanted cells in an immunocompetent porcine model. A total of 24 wounds were made on four female animals, 12 of which were covered with acellular hyaluronic acid dermal matrices, and the remainder of which were covered with matrices seeded with allogenic (male) fibroblasts. After a week in vivo, the wounds were grafted with either split-thickness skin grafts or cultured epithelial autograft. Biopsy specimens were obtained from wounds at varying time intervals and assessed using genetic analysis to determine the survival of allotransplanted cells. No cells were detectable by polymerase chain reaction analysis (sensitivity, 1:100,000) after 7 days in vivo. Subsequent histologic examination demonstrated little difference in wound morphology. The authors conclude that allogenic fibroblasts do not survive transplantation in a porcine wound model.

Animals↗
PubMed2003

Lack of plakophilin 1 increases keratinocyte migration and reduces desmosome stability.

Ablation of the desmosomal plaque component plakophilin 1 underlies the autosomal recessive genodermatosis, skin fragility-ectodermal dysplasia syndrome (OMIM 604536). Skin from affected patients is thickened with increased scale, and there is loss of adhesion between adjacent keratinocytes, which exhibit few small, poorly formed desmosomes. To investigate further the influence of plakophilin 1 on keratinocyte adhesion and desmosome morphology, we compared plakophilin 1-deficient keratinocytes (vector controls) with those expressing recombinant plakophilin 1 introduced by retroviral transduction. We found that plakophilin 1 increases desmosomal protein content within the cell rather than enhancing transcriptional levels of desmosomal genes. Re-expression of plakophilin 1 in null cells retards cell migration but does not alter keratinocyte cell growth. Confluent sheets of plakophilin 1-deficient keratinocytes display fewer calcium-independent desmosomes than do plakophilin 1-deficient keratinocytes expressing recombinant plakophilin 1 or keratinocytes expressing endogenous plakophilin 1. In addition electron microscopy studies show that re-expression of plakophilin 1 affects desmosome size and number. Collectively, these results demonstrate that restoration of plakophilin 1 function in our culture system influences the transition of desmosomes from a calcium-dependent to a calcium-independent state and this correlates with altered keratinocyte migration in response to wounding. Thus, plakophilin 1 has a key role in increasing desmosomal protein content, in desmosome assembly, and in regulating cell migration.

3T3 Cells↗
PubMed2003

Adducin expression in cutaneous and oral lesions: alpha- and beta-adducin transcripts down-regulate with keratinocyte differentiation in stratified epithelia.

Adducin is a heterodimer of alpha- with beta- or gamma-subunits that regulates the assembly of the spectrin-based membrane skeleton in erythrocytes. Although adducin has been identified in various non-erythroid cells and tissues, it has been localized at intercellular junctions only in keratinocytes and epidermis. However, no data are available yet on the regulation of individual adducin genes in differentiating versus hyperproliferating keratinocytes. Due to the unavailability of mono-specific antibodies for individual adducins, this study has used RT-PCR and in situ hybridization to investigate the expression of alpha- and beta-adducins in cultured cells and in stratified epithelia including cutaneous and oral lesions. Using RT-PCR, the alpha-transcripts were consistently expressed in all cell lines tested, as well as in normal interfollicular epidermis, whereas the beta-transcripts were more variable and were strongly expressed in K562, A431, and primary keratinocytes. However, in normal skin, oral mucosa, and attached gingivae, the levels of alpha-transcripts closely paralleled those for the beta-subunit. In most normal tissues, adducin expression was observed primarily in the proliferating compartments including the basal layer and lower suprabasal layers. Expression of both genes was also up-regulated in skin diseases characterized by increased cell proliferation and keratinocyte activation, such as basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and psoriasis. It was observed that, in most cases, the expression of both alpha- and beta-adducin was accompanied by increased expression of the proliferation marker Ki-67 and keratins K6 and K16. Differentiating keratinocytes in normal epithelia as well as in tumours appear to suppress the expression of adducin transcripts. The data suggest that the expression of adducin genes may be linked to cell proliferation and starts to down-regulate at the onset of differentiation.

Calmodulin-Binding Proteins↗