Biology subjects

Irla, M.

Publications and source records attributed to Irla, M..

2 recordsLinked to original sources

bioRxiv2021

Aire-dependent transcripts escape H3K36me3 and Raver2 induced alternative splicing to sustain central immune tolerance

Aire allows medullary thymic epithelial cells (mTECs) to express and present a large number of self-antigens for central tolerance. Although mTECs express a high diversity of self-antigen splice isoforms, the extent and regulation of alternative splicing events (ASEs) included in their transcripts, notably in those induced by Aire, is unknown. Unexpectedly, and in contrast to Aire-neutral genes, we found that the Aire-sensitive genes exhibit in Aire-positive and negative mTECs, a weak inclusion of ASEs, with about a quarter present in peripheral tissues being excluded from the thymus. We identified Raver2, as a splicing-related factor overrepresented in mTECs and dependent on H3K36me3 marks. We discovered that both Raver2 and methylation of H3K36 promoted ASE inclusion for Aire-neutral genes, leaving Aire-sensitive genes unaffected. Profiling of H3K36me3 revealed its depletion at Aire-sensitive genes, supporting a mechanism, whose setup precedes Aires expression and by which Aire-sensitive genes exhibit weak ASE inclusion through the escape of Raver2s effect. Lack of ASEs in Aire-induced transcripts highlights a role for regulatory T cells in controlling the incomplete Aire-dependent negative selection.

immunology↗

bioRxiv2020

Thymocytes trigger self-antigen-controlling pathways in immature medullary thymic epithelial stages

Interactions of developing T cells with Aire+ medullary thymic epithelial cells expressing high levels of MHCII molecules (mTEChi) are critical for the induction of central tolerance. In turn, thymocytes regulate the cellularity of Aire+ mTEChi. However, it remains unknown whether thymocytes control Aire+ mTEChi-precursors that are contained in mTEClo cells or other mTEClo subsets that have recently been delineated or identified by single-cell transcriptomic analyses. Here, using three distinct transgenic mouse models, in which antigen-presentation between mTECs and CD4+ thymocytes is perturbed, we show by high-throughput RNA-seq that self-reactive CD4+ thymocytes induce in mTEClo the expression of tissue-restricted self-antigens, cytokines, chemokines and adhesion molecules important for T-cell development. This gene activation program is combined with a global increase of the active H3K4me3 histone mark. Finally, we show that these interactions induce key mTEC transcriptional regulators and govern mTEClo subset composition, including Aire+ mTEChi-precursors, post-Aire and tuft-like mTECs. Our genome-wide study thus reveals that self-reactive CD4+ thymocytes control multiple unsuspected facets from immature stages of mTECs, which determines their heterogeneity.

immunology↗