Varticovski, L. | bioRxiv Science

bioRxiv2025

A Novel Patient-Derived Mutation in Glucocorticoid Receptor Reveals an Essential Role for DNA binding in Development and Endocrine Regulation

Glucocorticoid receptors (GRs) are vital transcription factors regulating stress responses, metabolism, and development. We report here a novel heterozygous NR3C1 c.1310C>T (p.T437I) variant within the GR DNA-binding domain found in a family exhibiting clinical and hormonal manifestations of partial glucocorticoid resistance. Patient-derived fibroblasts demonstrated an overall suppression in dexamethasone-induced transcription. To comprehensively assess the significance of the variant, we engineered a knock-in mouse model (Nr3c1+/T444I mice) using CRISPR-Cas9, providing an in vivo model of the patient-derived GR mutation at the orthologous residue. Heterozygous mice exhibited partial glucocorticoid resistance, dysregulated HPA axis activity and impaired dexamethasone suppression, closely recapitulating the patient phenotype. Homozygous Nr3c1T444I/T444I embryos were recovered at embryonic day 12.5 (E12.5) but did not survive to term, indicating mid-gestational lethality. Transcriptomic profiling of primary mouse embryonic fibroblasts revealed dosage-dependent effects with heterozygotes showing an intermediate response to dexamethasone compared to wild-type, while homozygotes showed a markedly blunted response. Our results challenge prior assumptions by demonstrating that GR DNA-binding is essential for embryogenesis, while offering a new preclinical platform to investigate glucocorticoid resistance pathophysiology and therapeutic interventions.

genetics↗

bioRxiv2025

Bile acids target an exposed cavity in the glucocorticoid receptor modulating receptor self-assembly, chromatin binding and transcriptional activity

The glucocorticoid receptor (GR) is an essential transcription factor that controls metabolism and homeostasis. Glucocorticoids (GCs) activate the GR upon occupying the internal ligand-binding pocket (LBP) of its ligand-binding domain (GR-LBD), which has been the focus of most previous structure-function studies. Synthetic GCs such as dexamethasone are widely used to treat inflammatory diseases, but their chronic use results in major side effects, whose molecular underpinnings remain unresolved. Here we present a thorough analysis of the topography of GR-LBD and its ability to bind small-molecule compounds, especially cholesterol derivatives. We show that one important class of steroids, bile acids, bind to previously unidentified and highly conserved, surface-exposed cavities on GR-LBD. We show that bile acids affect GR turnover and self-assembly in living cells, modulating receptor transcriptional activity. These findings reveal a previously unrecognized mechanism of GR regulation, with implications for the design of GCs with novel mechanisms of action. TeaserBile acids modulate the activity of the glucocorticoid receptor upon binding to an exposed allosteric pocket thereby influencing transcriptional regulation and receptor self-assembly in living cells.

molecular biology↗