MON-263 Decoding Glucocorticoid Sensitivity: Insights from a New Mouse Model

Abstract Disclosure: M. Laulhé: None. Y. Pelloux: None. S. Djellout: None. T. Rajkumar: None. J. Perrot: None. A. Arzel: None. P. Kamenicky: None. S. Viengchareun: None. L. Martinerie: None. Synthetic glucocorticoids are prescribed worldwide. Although they considerably improved the management of chronic inflammatory diseases, these treatments are also associated with numerous adverse effects, with a large inter-individual variability that remains poorly understood. Glucocorticoids exert their effects via an ubiquitous nuclear receptor, the glucocorticoid receptor (GR), encoded by the NR3C1 gene. Polymorphisms in the NR3C1 gene have been associated with variation in glucocorticoid sensitivity, ranging from resistance to increased sensitivity. While the polymorphisms associated with glucocorticoid resistance are well characterized, the molecular mechanisms involved in glucocorticoid sensitivity are not fully understood. The N363S variant, which encodes for a missense mutation within the N-terminal domain of the protein, has been associated with increased glucocorticoid sensitivity, but has never been thoroughly characterized. We performed in vitro studies demonstrating that maximal transactivation activity (GRWT 93,8% ± 5.1 vs GRN363S 142.6% ± 9,0, n=38, P<0.0001) and target gene expression were higher in response to dexamethasone in HEK 293T cells expressing the N363S variant. Next, we aim to assess the impact of the N363S variant using an innovative mouse model expressing the variant. Using the CRISPR/Cas9 system, we introduced a point mutation corresponding to the human variant into the coding sequence of the mouse Nr3c1 gene (c.1139 A>G), as the mutated amino acid is conserved across species. The genotype (Wild type: WT; heterozygous: HET; homozygous: HOM) was assessed by PCR. We evaluated the impact of the variant in unstimulated mice, evaluating weight, glucose metabolism, and HPA axis activity. Next, we studied its impact on susceptibility to adverse effects after treatment with dexamethasone (1 mg/kg/d) for 28 days via osmotic pumps. Expression of the N363S variant did not affect the viability or fertility of the mice. In the absence of dexamethasone treatment, we observed no significant differences between groups in adrenal gland weight, corticosterone secretion levels after a single intraperitoneal administration of dexamethasone (WT 9.4 ng/ml [3.5 ;12.2] ; HET 4.4 ng/ml [2.6 ;6.2] ; HOM 9.6 ng/ml [4.8 ; 12.6], n=4), glucose metabolism (fasting glycemia, WT 117 mg/dL[ 90 ;145], HET 107 mg/dL [95 ;121], HOM 96 mg/dL [83 ;138], n=3) or behavioral outcomes. The impact of genotype on the development of adverse effects, such as glucocorticoid-induced adrenal insufficiency, impaired glucose metabolism and depressive features, is currently being investigated after prolonged dexamethasone treatment. Overall, we developed an innovative transgenic mouse model that will provide new insights into glucocorticoid sensitivity and could emphasize the N363S variant as a predictive tool for personalized medicine. Presentation: Monday, July 14, 2025