Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) is a monogenic autosomal disease with recessive inheritance. It is characterized by multiple autoimmune endocrinopathies, chronic mucocutaneous candidiasis, and ectodermal dystrophies. The defective gene responsible for this disease was recently isolated, and several different mutations in the novel gene, AIRE, have been identified, by us and by others, in patients with APECED. We have shown that the APECED protein is mainly localized, both in vitro and in vivo, to the cell nucleus, where it forms distinct speckles. This accords with the predicted structural features of the protein, which suggest involvement of AIRE in the regulation of gene transcription. Here, we report the results of mutational analyses of a series of 112 patients with APECED who were from various ethnic backgrounds. A total of 16 different mutations, covering 91% of disease alleles, were observed; of these, 8 were novel. The mutations are spread throughout the coding region of AIRE, yet four evident mutational hotspots were observed. In vitro expression of four different naturally occurring nonsense and missense mutations revealed a dramatically altered subcellular location of the protein in cultured cells. Interestingly, the wild-type APECED protein tethered to the Gal4 DNA-binding domain acted as a strong transcriptional activator of reporter genes in mammalian cells, whereas most of the analyzed mutant polypeptides had lost this capacity.

Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) is the only described systemic autoimmune disease with established monogenic background, and the first autoimmune disorder localized outside the major histocompatibility complex (MHC) region. The primary biochemical defect in APECED is unknown. We have isolated a novel gene, AIRE, encoding for a putative nuclear protein featuring two PHD-type zinc-finger motifs, suggesting its involvement in transcriptional regulation. Five mutations in AIRE are reported in individuals with this disorder. This is the first report of a single-gene defect causing a systemic human autoimmune disease, providing a tool for exploring the molecular basis of autoimmunity.

Autoimmune polyglandular disease type I (APECED) is an autosomal recessive autoimmune disease characterized by a variable combination of the failure of the endocrine glands. The pathogenesis of this unique autoimmune disease is unknown; unlike many other autoimmune diseases, APECED does not show association to specific HLA haplotypes. Unravelling the APECED locus will identify a novel gene outside the HLA loci influencing the outcome of autoimmune diseases. We have assigned the disease locus to chromosome 21q22.3 by linkage analyses in 14 Finnish families. Linkage disequilibrium studies have significantly increased the informativeness of the analyses and helped to locate the critical DNA region for the APECED locus to just 500 kilobases, a much more precise definition than linkage analyses alone could achieve.

Autoimmune-polyendocrinopathy-candidiasis-ecto-dermaldystrophy (APECED) is the only systemic autoimmune disease with a monogenic background known so far revealing no association with the major histocompatibility complex region. We have recently isolated the gene defective in this syndrome and characterized several different mutations in individuals with the disorder. The novel gene, AIRE, contains a putative bipartite nuclear targeting signal predicting a nuclear location of the corresponding protein. The presence of two PHD-type zinc finger domains as well as the newly described putative DNA-binding domain, SAND, in the amino acid sequence of the APECED protein implies that it may be involved in the regulation of gene expression. Using transient expression of AIRE cDNA in mammalian cells we demonstrate here the nuclear location of the APECED protein. Immunohistochemical staining of transfected cells revealed that most of the recombinant 58 kDa APECED protein is present in the form of nuclear dots. By double immuno-fluorescence labelling we further show that these APECED-containing structures and the previously described PML nuclear bodies are largely non-overlapping. The AIRE protein was also visualized in multiple human tissues: a subset of the cells in thymus, in spleen and in lymph node showed nuclear staining with APECED antiserum. Immunofluorescence labelling of peripheral blood mononuclear leukocytes also revealed a nuclear body-like staining pattern in a fraction of these cells. These data from both in vitro and ex vivo systems, together with the predicted structural features of the APECED protein, suggest that this protein is most probably involved in the regulation of gene expression.

The molecular background of human autoimmunity is poorly understood. Although many autoimmune diseases have a genetic basis, the actual disease appearance results from a complex interplay between genes and environment and thus these diseases represent typical multifactorial diseases. Even with molecular tools provided by the Human Genome Project, it still remains a challenge to identify the predisposing DNA variants behind such multifactorial traits. Two strategies have been suggested to provide short-cuts to the dissection of the genetic background of complex autoimmune diseases: (i) identification of genes in rare human diseases with a strong autoimmune component or (ii) unravelling loci causing phenotypes resembling autoimmune diseases in inbred mice strains. Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) is a monogenic autosomal disease with a recessive inheritance pattern, characterized by multiple autoimmune endocrinopathies, chronic mucocutaneous candidiasis and ectodermal dystrophies. Since it is the only known human autoimmune disease inherited in a Mendelian fashion, it provides an excellent model to analyse the genetic component of human autoimmunity. The causative gene for APECED was isolated recently by a traditional positional cloning strategy by two independent groups. The cDNA for the APECED gene proved to originate from a novel gene, AIRE , which is expressed prevalently in thymus, pancreas and adrenal cortex. Multiple mutations in AIRE have been identified in APECED patients. The predicted proline-rich AIRE polypeptide harbours two PHD-type zinc finger motifs and contains a putative nuclear targeting signal suggesting its involvement in the regulation of transcription. In the future, functional analysis of the AIRE protein both in vitro and in vivo will provide valuable insight not only into the molecular pathogenesis of APECED but also into the aetiology of autoimmunity in general.

Autoimmune–polyendocrinopathy–candidiasis–ectodermal dystrophy (APECED, PGD type I) is an autosomal recessive disease enriched in the Finnish population. Previously, we have assigned APECED to a 2.6-cM interval on chromosome 21q22.3 by linkage analysis in 14 Finnish families. This subtelomeric region of 21q22.3 seems to have sequence features resulting in its under-representation in large insert genomic libraries, and only a few large insert clones have been available for positional cloning to date. Here, we report the refined localization of the APECED gene and a visual physical map of 800 kb covering the critical chromosomal region for the gene. In the construction of the physical map, the recently developed fiber FISH techniques were essential for the orientation of the cosmid P1, PAC, and BAC clones in relation to each other. We also localized two cDNAs within this genomic region by fiber FISH combined with the highly sensitive tyramide-based detection method. These data will facilitate the final cloning of theAPECED gene and any other novel gene in this complex genomic region.[On-line supplement for primer sequences, PCR product size, and annealing temperatures is available athttp://www.cshl.org/gr.]

To evaluate the association of autoimmunity to glutamic acid decarboxylase (GAD) with insulin-dependent diabetes mellitus (IDDM) and IDDM-associated human leukocyte antigen (HLA) types, we studied a unique group of 47 patients with autoimmune polyendocrine syndrome type 1, a recessive disease not associated with HLA. GAD65 antibodies (GAD65-Ab), GAD67-Ab, islet cell antibodies, and HLA-DQA1, -DQB1, and -DRB1 were analyzed in relation to IDDM or a decreased insulin secretory capacity. GAD65-Ab were found in six of the eight diabetic patients 0.9-8.0 yr before the onset of IDDM and in 16 (41%) nondiabetic patients during a follow-up of 2.4-19.5 yr. Eleven (28%) nondiabetic patients had GAD67-Ab and islet cell antibodies. Fasting C peptide (mean +/- SD, 0.5 +/- 0.24 vs. 1.03 +/- 0.49 nmol/L; P = 0.003) and first phase insulin response (75.6 +/- 37.9 vs. 166.4 +/- 112.7 mU/L; P = 0.019) were lower in patients with than in those without GAD65-Ab. No HLA genotype predominated in the IDDM patients or GAD65-Ab-positive nondiabetic patients, but the IDDM high risk genotypes were decreased in frequency among the patients with GAD65-Ab. In conclusion, nondiabetic autoimmune polyendocrine syndrome type 1 patients frequently have GAD65-Ab together with a decreased insulin secretory capacity, suggesting subclinical islet cell inflammation not invariably progressing to diabetes. This is not associated with HLA haplotypes conferring susceptibility to or protection from IDDM.

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