Project description:Background: In order to become functionally competent but harmless mediators of the immune system, T cells undergo a strict educational program in the thymus, where they learn to discriminate between self and non-self. This educational program is, to a large extent, mediated by medullary thymic epithelial cells (mTECs) that have a unique capacity to express, and subsequently present a large fraction of body antigens. While the scope of promiscuously expressed genes by mTECs is well established, relatively little is known about the expression of variants that are generated by co- and post-transcriptional processes. Results: Our study reveals that in comparison to other cell types, mTECs display significantly higher levels of alternative splicing, as well as A-to-I and C-to-U RNA editing, which thereby further expand the diversity of their self-antigen repertoire. Interestingly, Aire, the key mediator of mTECs promiscuous gene expression, plays a limited role in the regulation of these transcriptional processes. Conclusions: Our results highlight RNA processing as another layer by which the immune system assures a comprehensive self-representation in the thymus which is required for the establishment of self-tolerance and prevention of autoimmunity. Identification of the number of genes expressed in Aire-KO MEChi
Project description:The aim of this study is to analyze the transcriptional effects of Aire deficiency in the thymus, using the Affymetrix MoGene platform to analyze variation in exon usage MECs were isolated from 4-6 wk-old WT or Aire KO ((B6xNOD)F1 background) mice. Three WT and three Aire-KO mice taken individually were used.
Project description:Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) is a life-threatening monogenic autoimmune disorder primarily caused by biallelic deleterious variants in the autoimmune regulator (AIRE) gene. We prospectively evaluated 104 patients with clinically diagnosed APECED syndrome and identified 17 patients (16%) from 14 kindreds lacking biallelic AIRE variants in exons or flanking intronic regions; 15 had Puerto Rican ancestry. Through whole-genome sequencing, we identified a deep intronic AIRE variant (c.1504-818 G>A) cosegregating with the disease in all 17 patients. We developed a culture system of AIRE-expressing primary patient monocyte-derived dendritic cells and demonstrated that c.1504-818 G>A creates a cryptic splice site and activates inclusion of a 109-base pair frame-shifting pseudoexon. We also found low-level AIRE expression in patient-derived lymphoblastoid cell lines (LCLs) and confirmed pseudoexon inclusion in independent extrathymic AIRE-expressing cell lines. Through protein modeling and transcriptomic analyses of AIRE-transfected human embryonic kidney 293 and thymic epithelial cell 4D6 cells, we showed that this variant alters the carboxyl terminus of the AIRE protein, abrogating its function. Last, we developed an antisense oligonucleotide (ASO) that reversed pseudoexon inclusion and restored the normal AIRE transcript sequence in LCLs. Thus, our findings revealed c.1504-818 G>A as a founder APECED-causing AIRE variant in the Puerto Rican population and uncovered pseudoexon inclusion as an ASO-reversible genetic mechanism underlying APECED.
Project description:The aim of this study is to analyze the transcriptional effects of Aire deficiency in the thymus, using the Affymetrix MoGene platform to analyze variation in exon usage
