Functional studies of postional candidate genes in vitiligo and associated autoimmune diseases

Generalized vitiligo is a common autoimmune disease characterized by white patches of skin and hair due to loss of melanocytes from the involved areas. Vitiligo is often associated with other autoimmune disorders, including autoimmune thyroid disease, Addison's disease, pernicious anemia, systemic lupus erythematosis, rheumatoid arthritis, psoriasis, and latent autoimmune diabetes of the adult. Genetic linkage analysis and association studies in our laboratory have identified several genes involved in vitiligo pathogenesis, including FOXD3 and NALP1. Notwithstanding genetic evidence that these genes are involved in vitiligo, little is known about the biological role these genes play in disease. This work was undertaken to conduct functional studies aimed at elucidating the roles FOXD3 and NALP1 play in vitiligo pathogenesis.;FOXD3 encodes a forkhead transcription factor that is a primary regulator of melanoblast differentiation in the embryonic neural crest. We identified a large family affected with vitiligo and other autoimmune diseases that had a -639G>T promoter mutation in FOXD3 which significantly increased transcriptional activity of the gene. A microarray study examining melanocytes from family members with vitiligo and this FOXD3 variant versus normal control melanocytes showed dysregulation of many genes involved in controlling cell cycle, cell division, and cell growth and proliferation. This suggests that the FOXD3 variant in this family may result in primary, cell-autonomous dysregulation of melanocyte growth, leading to vitiligo.;NALP1 is a member of the NLR family of proteins and is a key component of the inflammasome, a complex that regulates an IL-1beta inflammatory response. NALP1 is also thought to play an important role in apoptosis and may be part of the APAF1 apoptosome. Development of an antibody to NALP1 showed highest expression of NALP1 protein in B cells. Functional studies examining a high-risk vitiligo susceptibility haplotype in the NALP1 gene (tagged by the non-synonymous SNP rs12150220) show NALP1 mRNA and protein expression and inflammasome function are apparently not dysregulated. However, spontaneous apoptosis and IL-1beta release after stimulation may be dysregulated in the high-risk haplotype, suggesting a functional role for NALP1 in vitiligo pathogenesis.;Together, this work provides important insights into possible biological mechanisms leading to vitiligo and associated autoimmunity.