Genetics of Cutaneous Melanoma

A portion of melanoma is familial and has been associated with atypical mole syndrome. This review outlines the current understanding of the genetics of melanoma and the relationship to cutaneous nevus phenotypes. A review of genetic studies of melanoma is presented, including linkage studies. Data from a linkage study of 12 Utah kindreds and one Texas kindred are detailed.There is strong evidence both for a genetic component to melanoma and, to a lesser extent, for a genetic component to the atypical mole phenotype. Reports of linkage of melanoma/dysplastic nevus syndrome to chromosome 1p markers are now strongly in doubt. The Utah group has shown strong evidence of linkage of melanoma to chromosome 9p21 without evidence for heterogeneity. This is in the same region where chromosomal deletions are common in tumors of numerous tissues.We conclude that there is a specific melanoma susceptibility locus located on chromosome 9p. The combination of the results of linkage in families with multiple cases of melanoma and the deletion of this chromosomal region in sporadic cases of melanoma strongly suggests that this melanoma susceptibility locus acts as a tumor suppressor. J Invest Dermatol 103:112S-116S, 199

IgA Autoimmune Disorders: Development of a Passive Transfer Mouse Model

IgA is present in the skin in several dermatoses, including dermatitis herpetiformis, linear IgA bullous dermatosis, and Henoch-Schoenlein purpura. The neutrophilic infiltration in the area of the IgA deposition suggests that IgA is responsible for the associated inflammatory events. The mechanism for this process is unproven, but is likely to involve IgA-mediated neutrophil chemotaxis with inhibition of chemotaxis by dapsone. Elucidation of the mechanism of IgA-mediated inflammation will require an animal model. We have established a model for linear IgA bullous dermatosis as a prototype disease to be studied. IgA mouse monoclonal antibodies against a linear IgA bullous dermatosis antigen have been passively transferred to SCID mice with human skin grafts. This has produced neutrophil infiltration and basement membrane vesiculation in 4 of 12 mice tested. We conclude that an animal model for the pathogenesis of IgA dermatoses with IgA deposition and inflammation can be produced by passive transfer of mouse IgA antibodies against a linear IgA antigen

Granular C3 Dermatosis

There has been no previous systematic study of bullous skin diseases with granular basement membrane zone deposition exclusively of C3. In this study we collected 20 such patients, none of whom showed cutaneous vasculitis histopathologically. Oral dapsone and topical steroids were effective. Various serological tests detected no autoantibodies or autoantigens. Direct immunofluorescence for various complement components revealed deposition only of C3 and C5?C9, indicating that no known complement pathways were involved. Studies of in situ hybridization and micro-dissection with quantitative RT-PCR revealed a slight reduction in expression of C3 in patient epidermis. These patients may represent a new disease entity, for which we propose the term “granular C3 dermatosis”. The mechanism for granular C3 deposition in these patients is unknown, but it is possible that the condition is caused by autoantibodies to skin or aberrant C3 expression in epidermal keratinocytes

Linkage analysis of HLA and candidate genes for celiac disease in a North American family-based study

BACKGROUND: Celiac disease has a strong genetic association with HLA. However, this association only explains approximately half of the sibling risk for celiac disease. Therefore, other genes must be involved in susceptibility to celiac disease. We tested for linkage to genes or loci that could play a role in pathogenesis of celiac disease. METHODS: DNA samples, from members of 62 families with a minimum of two cases of celiac disease, were genotyped at HLA and at 13 candidate gene regions, including CD4, CTLA4, four T-cell receptor regions, and 7 insulin-dependent diabetes regions. Two-point and multipoint heterogeneity LOD (HLOD) scores were examined. RESULTS: The highest two-point and multipoint HLOD scores were obtained in the HLA region, with a two-point HLOD of 3.1 and a multipoint HLOD of 5.0. For the candidate genes, we found no evidence for linkage. CONCLUSIONS: Our significant evidence of linkage to HLA replicates the known linkage and association of HLA with CD. In our families, likely candidate genes did not explain the susceptibility to celiac disease

Two Groups of Bullous Pemphigoid Antigens Are Identified by Affinity-Purified Antibodies

The bullous pemphigoid antigen was originally described as a 240-kD protein extracted from human epidermis, but a subsequent report has described patients' sera which react with epidermal proteins of molecular masses 240, 200, 180, 97, and 77 kD. We have evaluated the heterogeneity of the pemphigoid antigens identified by the sera of 10 patients with clinically typical bullous pemphigoid. We used indirect immunofluorescence and Western immunoblots of epidermal extracts prepared from epidermis separated by either 1M salt or 20mM EDTA to characterize the reactivity of both crude sera and affinity-purified antibodies. Affinity purification of antibodies was performed with either normal human epidermis or protein bands blotted onto nitrocellulose as immunoabsorbents. The anti-basement membrane antibody titers determined by indirect immunofluorescence on the saline- and EDTA- separated epidermis were identical. Despite this, Western blots of extracts prepared from EDTA-separated epidermis demonstrated greater amounts of the 240-kD antigen than saline split skin. Multiple antigens were recognized in epidermal extracts on Western blots by most crude BP sera, including bands at 240, 200, 160, and 100 kD. Different sera reacted with these antigens with a markedly different intensity, falling into two major groups, those bearing antibodies to the 240- 200-kD antigens and those with antibodies to the 160-1 00-kD components. When epidermis was used as a substrate for affinity purification of bullous pemphigoid anti- bodies, the eluted antibodies reacted with multiple bands on Western blots, demonstrating the reactivity of anti-basement membrane zone antibodies with multiple proteins. Antibodies eluted from several individual bands of immunoblots were found to react with the basement membrane on indirect immunofluorescence. When these nitrocellulose-purified antibodies were reapplied to Western blots, they cross-reacted within two groups, the 240-200 kD anigens and the 160-100 kD antigens. We conclude that perphigoid antigens are best demonstrated when EDTA-split skin is used for extraction and that different pemphigoid sera may contain antibodies to two separate groups of basement membrane zone antigens