The hippocampal response to acute corticosterone elevation is altered in a mouse model for Angelman syndrome

Angelman Syndrome (AS) is a severe neurodevelopmental disorder, caused by the neuronal absence of the ubiquitin protein ligase E3A (UBE3A). UBE3A promotes ubiquitin-mediated protein degradation and functions as a transcriptional coregulator of nuclear hormone receptors, including the glucocorticoid receptor (GR). Previous studies showed anxiety-like behavior and hippocampal-dependent memory disturbances in AS mouse models. Hippocampal GR is an important regulator of the stress response and memory formation, and we therefore investigated whether the absence of UBE3A in AS mice disrupted GR signaling in the hippocampus. We first established a strong cortisol-dependent interaction between the GR ligand binding domain and a UBE3A nuclear receptor box in a high-throughput interaction screen. In vivo, we found that UBE3A-deficient AS mice displayed significantly more variation in circulating corticosterone levels throughout the day compared to wildtypes (WT), with low to undetectable levels of corticosterone at the trough of the circadian cycle. Additionally, we observed an enhanced transcriptomic response in the AS hippocampus following acute corticosterone treatment. Surprisingly, chronic corticosterone treatment showed less contrast between AS and WT mice in the hippocampus and liver transcriptomic responses. This suggests that UBE3A limits the acute stimulation of GR signaling, likely as a member of the GR transcriptional complex. Altogether, these data indicate that AS mice are more sensitive to acute glucocorticoid exposure in the brain compared to WT mice. This suggests that stress responsiveness is altered in AS which could lead to anxiety symptoms. Gene expression profiling was performed using RNA-seq in hippocampus and liver tissue of wildtype (WT) and Angelman syndrome (AS) mice after acute or continuous corticosterone exposure. WT C57BL/6J male and female 129sv Ube3am+/p- mice (Ube3atm1Alb; MGI 2181811), were crossed to generate F1 hybrid WT and Ube3am-/p+ (AS) offspring. The Ube3atm1Alb strain resulted from the deletion of the exon 5 of Ube3a, leading to an out-of-frame mutation and loss of UBE3A protein expression in neurons. Adult 10-18-week-old male mice were used in the experiments.