Genetic and epigenetic regulation of Treg cell fitness by autism-related chromatin remodeler CHD8.

Abstract

Background: Chromatin remodeler chromodomain helicase DNA-binding protein 8 (CHD8) defines a subtype of autism that is associated with immune disorders. It remains unknown whether CHD8 plays a cell-intrinsic role in immune cells such as regulatory T cells (Tregs) that maintain immune tolerance through suppressing CD4⁺ and CD8⁺ effector T cells.

Methods: Treg-specific conditional CHD8-deficient mice were generated by crossing Chd8^Flox/Flox mice with Foxp3^YFP-cre transgenic mice. Effects of CHD8 deficiency were investigated using hematoxylin and eosin (H&E) staining, flow cytometry, and multi-omics, including RNA-sequencing (RNA-seq), assay for transposase-accessible chromatin sequencing (ATAC-seq), and chromatin immunoprecipitation sequencing (CHIP-seq).

Results: We found that Treg-specific CHD8 deletion led to early, fatal inflammation owing to increased CD4⁺ and CD8⁺ effector T cells. CHD8 deletion did not alter Treg homeostasis but increased their functional plasticity with elevated expression of effector T cell cytokines. CHIP-seq of Tregs uncovered that CHD8 binding genes were enriched in phosphatidylinositol-3 kinase (PI3K)-protein kinase B (Akt)-mammalian target of rapamycin (mTOR) signaling and several other pathways. RNA-seq and ATAC-seq revealed that CHD8 deletion upregulated a number of pathways, notably mammalian target of rapamycin complex 1 (mTORC1) signaling and its mediated glycolysis that have been reported to promote Treg plasticity. Integrating RNA-seq data with CHIP-seq and ATAC-seq data identified a number of CHD8 target genes whose expression depends on CHD8 direct binding-mediated chromatin remodeling.

Conclusions: Our findings suggest that CHD8 plays an important role in maintaining Treg fitness through genetic and epigenetic mechanisms to control autoimmunity, which may have important implications in immune changes in autism.