The Impact of a Single Phosphorylation Site Mutation in the Glucocorticoid Receptor on the Molecular and Cellular Development of the Cerebral Cortex

Abstract

Premature birth leads to a significant increase in adverse clinical outcomes, including Respiratory Distress Syndrome, Bronchopulmonary Dysplasia, Necrotizing Enterocolitis and Intraventricular Hemorrhage. Synthetic Glucocorticoids (sGC) are administered prenatally to pregnant mothers at risk to reduce the chance of these complications. However, there is a correlation between long-term neurological defects in the infant and the clinical use of sGC prenatally. The use of the sGCs have been linked to the development of cerebral palsy and deficits in attention and concentration. To investigate the cellular basis of these abnormalities, we examined the consequences of sGC administration of the developing murine brain. Our studies demonstrated that premature exposure to sGC alters neural stem cell biology and has long term consequences for adult behavior in mice. In humans, site-specific phosphorylation of the Glucocorticoid Receptor (GR) on Serine 211 versus Serine 226 is associated with activated or repressed transcriptional states and clinical studies indicate that the ratio of S220/S226 phosphorylation is associated with increased predisposition to specific psychiatric disease states, including Major Depressive Disorder and Bipolar Disorder. To examine the role of these phosphorylation sites in the development of behavioral abnormalities, we utilized a knock-in mouse model where Serine 220 (equivalent to human Serine 211) was replaced with an alanine (S220A). In-vitro microarray analysis of neural stem cells and QPCR validation were performed to examine the expression changes in individual transcripts in critical pathways that may correlate with long-term neurologic disorders. Our results indicated that changing the phosphorylation status of GR alters the expression of 2570 genes. Ingenuity Pathway Analysis indicated that the major pathways altered include those involved in cellular proliferation, mitochondrial function, Valine degradation and G-coupled protein receptors involved in neurotransmission. Both in-vitro and in-vivo experiments indicated that the S220A mutation alters the cells response to sGC administration by impacting proliferation and differentiation. The long-term goal of these experiments was to demonstrate a role for S220 phosphorylation in the development of neuropsychiatric disorders.