ABSTRACT
Aire is a transcriptional regulator that induces promiscuous expression of thousands of genes encoding tissue-restricted antigens (TRAs) in medullary thymic epithelial cells (mTECs). While the target genes of Aire are well characterized, the transcriptional programs that regulate its own expression have remained elusive. Here we comprehensively analyzed both cis-acting and trans-acting regulatory mechanisms and found that the Aire locus was insulated by the global chromatin organizer CTCF and was hypermethylated in cells and tissues that did not express Aire. In mTECs, however, Aire expression was facilitated by concurrent eviction of CTCF, specific demethylation of exon 2 and the proximal promoter, and the coordinated action of several transcription activators, including Irf4, Irf8, Tbx21, Tcf7 and Ctcfl, which acted on mTEC-specific accessible regions in the Aire locus.
Subject(s)
Epithelial Cells/immunology , Gene Regulatory Networks , T-Lymphocytes/physiology , Thymus Gland/immunology , Transcription Factors/metabolism , Animals , Antigen Presentation/genetics , Autoantigens/metabolism , CCCTC-Binding Factor , Cell Differentiation , Cells, Cultured , Clonal Selection, Antigen-Mediated , DNA Methylation , Gene Expression Regulation , Interferon Regulatory Factors/genetics , Interferon Regulatory Factors/metabolism , Mice , Mice, Inbred C57BL , Mice, Knockout , Mice, Transgenic , Organ Specificity/genetics , Repressor Proteins/genetics , Repressor Proteins/metabolism , T-Box Domain Proteins/genetics , T-Box Domain Proteins/metabolism , Thymus Gland/cytology , Transcription Factors/genetics , AIRE ProteinABSTRACT
Autophagy is critical for homeostasis and cell survival during stress, but can also lead to cell death, a little understood process that has been shown to contribute to developmental cell death in lower model organisms, and to human cancer cell death. We recently reported 1 on our thorough molecular and morphologic characterization of an autophagic cell death system involving resveratrol treatment of lung carcinoma cells. To gain mechanistic insight into this death program, we performed a signalome-wide RNAi screen for genes whose functions are necessary for resveratrol-induced death. The screen identified GBA1, the gene encoding the lysosomal enzyme glucocerebrosidase, as an important mediator of autophagic cell death. Here we further show the physiological relevance of GBA1 to developmental cell death in midgut regression during Drosophila metamorphosis. We observed a delay in midgut cell death in two independent Gba1a RNAi lines, indicating the critical importance of Gba1a for midgut development. Interestingly, loss-of-function GBA1 mutations lead to Gaucher Disease and are a significant risk factor for Parkinson Disease, which have been associated with defective autophagy. Thus GBA1 is a conserved element critical for maintaining proper levels of autophagy, with high levels leading to autophagic cell death.