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DNA breaks and chromatin structural changes enhance the transcription of Autoimmune Regulator target genes [FAIRE-Seq]

ABSTRACT: The Autoimmune Regulator (AIRE) protein is the key factor in thymic negative selection of autoreactive T-cells by promoting the ectopic expression of tissue-specific genes in thymic medullary epithelium. Mutations in AIRE cause a monogenic autoimmune disease called autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED). AIRE has been shown to promote DNA breaks via its interaction with topoisomerase 2 (TOP2). In this study, we investigated topoisomerase-induced DNA breaks and chromatin structural alterations in conjunction with AIRE-dependent gene expression. Using RNA-seq, we found that the inhibition of TOP2 religation activity by etoposide in AIRE-expressing cells had a synergistic effect on genes with low expression levels. AIRE-mediated transcription was not only enhanced by TOP2 inhibition but also by topoisomerase 1 (TOP1) inhibitor camptothecin. The transcriptional activation was associated with structural rearrangements in chromatin, notably the accumulation of γH2AX and the exchange of histone H1 with HMGB1 at AIRE target gene promoters. In addition, we found the transcriptional upregulation to co-occur with the chromatin structural changes within the genomic cluster of carcino-embryonic antigen-like cellular adhesion molecule (CEACAM) genes. Overall, our results suggest that the presence of AIRE can trigger molecular events leading to an altered chromatin landscape and the enhanced transcription of low-expressed genes.

ORGANISM(S): Homo sapiens

PROVIDER: GSE89892 | GEO | 2017/03/13

SECONDARY ACCESSION(S): PRJNA353659

REPOSITORIES: GEO

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Project description:Down syndrome (DS) patients frequently develop organ-specific autoimmune disorders, particularly endocrinopathies and coeliac disease, as well as an increased susceptibility to mucosal candidiasis. These clinical features resemble APECED (autoimmune-polyendocrinopathy-candidiasis-ectodermal-dystrophy), a monogenic condition due to mutations in the AIRE gene, located on 21q22.3 and already described as down-regulated in 21 trisomy. Here we investigated AIRE expression and global gene expression profiles in surgically removed thymuses from 14 DS infants and children with congenital heart defects and from 42 age-matched individuals with cardiac defect as an isolated malformation. Immunohistochemistry revealed significantly reduced AIRE expression in DS thymuses (70.48M-BM-149.59 positive cells/mm2 in DS X 154.70M-BM-161.16 in controls, p<0.0001). qPCR confirmed the lower expression of AIRE in DS thymuses. Global thymic RNA profiles from DS patients and controls revealed 407 genes significantly hypoexpressed in DS. Network transcriptional analysis showed that hypoexpressed genes are related to biological processes such as antigen processing and presentation of endogenous antigen (ERAP2, CD1D), negative (PRDX2) and positive (CD3D, CD74) thymic T-cell selection and homeostasis of number of cells (PRDX2). Altogether these findings may explain the high prevalence of autoimmune phenomena in DS patients. Moreover, our data are in accordance with previous findings of thymic abnormal development in DS patients, characterized by lymphocyte depletion, diminution of the cortex, and loss of corticomedullary demarcation. Global gene profiles indicate that in DS patients, the trisomic imbalance probably leads to thymic hypofunction. In conclusion, lower AIRE expression and the impairment of other crucial pathways for central tolerance could well explain the high prevalence of organ-specific autoimmune disorders in DS. Among the 14 DS infants and 42 age-matched individuals with cardiac defect, only 4 from each group provided enough biological material (thymus fragments) for isolation of high-quality RNA to perform array analysis. Eight thymic samples were analyzed: C1, C2, C3 and C4 are controls, and D1, D2, D3 and D4 are from patients with Down syndrome.

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DNA breaks and chromatin structural changes enhance the transcription of Autoimmune Regulator target genes [FAIRE-Seq]

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