Project description:Steroid hormone receptors such as the Glucocorticoid Receptor (GR) mediate the transcriptional response to hormones and are frequently targeted in the treatment of human diseases. Experiments using bulk populations of cells have provided a detailed picture of the global transcriptional hormone response but are unable to interrogate cell-to-cell transcriptional heterogeneity. To examine the glucocorticoid response in individual cells, we performed single cell RNA sequencing (scRNAseq). The transcriptional response to hormone was robustly detected in individual cells and scRNAseq provided additional statistical power to identify over 100 GR-regulated genes that were not detected in bulk RNAseq. scRNAseq also revealed a large degree of cell-to-cell variability in the hormone response. On average, individual hormone-treated cells showed a response at only 30% of the total set of GR target genes. Understanding the basis of this heterogeneity will be critical for the development of more precise models of steroid hormone signaling.
Project description:Transcription-factor binding to cis-regulatory regions regulates the gene expression program of a cell, but occupancy is often a poor predictor of the gene response. Here, we show that glucocorticoid stimulation led to the reorganization of transcriptional coregulators MED1 and BRD4 within topologically associating domains (TADs), resulting in active or repressive gene environments. Indeed, we observed a bias toward the activation or repression of a TAD when their activities were defined by the number of regions gaining and losing MED1 and BRD4 following dexamethasone (Dex) stimulation. Variations in Dex-responsive genes at the RNA levels were consistent with the redistribution of MED1 and BRD4 at the associated cis-regulatory regions. Interestingly, Dex-responsive genes without the differential recruitment of MED1 and BRD4 or binding by the glucocorticoid receptor were found within TADs, which gained or lost MED1 and BRD4, suggesting a role of the surrounding environment in gene regulation. However, the amplitude of the response of Dex-regulated genes was higher when the differential recruitment of the glucocorticoid receptor and transcriptional coregulators was observed, reaffirming the role of transcription factor-driven gene regulation and attributing a lesser role to the TAD environment. These results support a model where a signal-induced transcription factor induces a regionalized effect throughout the TAD, redefining the notion of direct and indirect effects of transcription factors on target genes.
Project description:Diversity within or between a tumour and metastases, known as intra-patient tumour heterogeneity develops during disease progression, and is a serious hurdle for therapy1,2,3. Metastasis is the fatal hallmark of cancer and mechanisms of colonization, the most complex step of the metastatic cascade4,5, remain ill-defined. Better understanding of cellular and molecular processes underlying intra-patient tumour heterogeneity and metastasis are pivotal for the success of personalized cancer treatment. Here, transcriptional profiling of tumours and matched metastases showed cancer site-specific phenotypes, and identified increased glucocorticoid receptor (GR) activity in the distant metastases. GR has been shown to mediate the effects of stress hormones and of their synthetic derivatives, widely used in the clinic as anti-inflammatory and immunosuppressive.