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

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.

Betamethasone Induces a Unique Transcriptome in Neural Stem Cells

Twelve percent of pregnant women receive glucocorticoids (sGCs) to reduce the risks to reduce morbidity and mortality associated with preterm birth in infants. The two most commonly administered sGC are Dexamethasone (Dex) and Betamethasone (Beta) and they serve to decrease the severity of respiratory distress, intraventricular hemorrhage and necrotizing enterocolitis. However, repeated administration of sGC has been shown to be associated with adverse neurological outcome and depends on the type of sGCs used, dose, timing of sGCs administration and sex. We have previously shown that prenatal exposure to Dex in a murine model lead to sex specific changes in the transcription response and in the biological function of neural stem cells and to long-term changes in brain architecture and behavior. Beta is the predominant sGC used prenatally in the United States, therefore these studies investigated the cellular and molecular responses to beta exposure on the neural stem cells in-vitro and anatomical organization of the brain in-vivo. Murine NSCs were isolated from the E14.5 cerebral cortex and exposed to 10^-7 M Dex, 10^-7 M Beta, or Vehicle for 4 or 24 hours and the immediate and long-term impact on transcription, proliferation and neuronal, glial and oligodendrocyte differentiation examined. Affymetrix genome transcriptional analyses reveal sex specific responses to Dex vs Beta in 4 hours. In females 682 genes were differentially regulated by Dex compared to 576 by Beta. In contrast, 875 were altered by Dex and 576 by Beta in males (Fold change > +/- 1.5, P< 0.05). Select target genes were independently validated by QPCR. Ingenuity Pathway Analysis was used to identify unique and overlapping pathways that were altered by Dex vs Beta. In males, Dex uniquely altered 34 pathways including, Thyroid Hormone Metabolism, ERK5 Signaling and Opioid Signaling while Bata altered 33 pathways including, Phagasome formation, IL-7 Signaling and JAK STAT signaling. In Females, Dex altered 45 pathways including Calcium Signaling, Serotonin Receptor Signaling and Xenobiotic Signaling, while Beta altered 46 pathways including, FXR/RXR Activation, Tec Kinase Signaling and D-myo-Inositol-5-Phosphate Metabolism. Another 35 pathways were altered by both Dex and Beta but they showed differences in genes activated or repressed. Dex and Beta, both significantly altered genes involved in proliferation and differentiation therefore the biological response of NSC to sGCs stimulation in vitro and the long term consequences of sGC exposure in-vivo was compared. Distinct differences in cell proliferation, glial and oligodendrocyte differentiation were observed. These results reveal gene targets, cellular pathways and processes that are differentially altered by prenatal Dex vs Beta exposure. Our finds may provide insights into the sex specific neurological outcomes observed in children exposed to sGCs in-utero.

SUN-LB56 Steroid and Sex Specific Responses of Neural Stem Cells to Prenatal Dexamethasone versus Betamethasone Administration

Synthetic glucocorticoids (sGCs) are widely administered to pregnant women for their anti-inflammatory, immunosuppressive and organ maturation properties. Worldwide, Dexamethasone (Dex) and Betamethasone (Beta) are the two most commonly administered prenatal sGCs to reduce morbidity and mortality associated with respiratory distress, intraventricular hemorrhage and necrotizing enterocolitis. Preterm administration of sGCs is associated with reduced birthweight and increased risk for hypertension, cardiovascular, metabolic, and neurological problems later in life. Adverse neurological outcome has been shown to depend on the type of sGCs used, the dose, timing of sGCs administration and sex. We have previously shown that the glucocorticoid receptor (GR) is expressed in the developing brain in stem and progenitor cells, neurons and glia from early developmental stages, and that prenatal Dex alters neural stem cell (NSC) biology and the developmental trajectory of the cerebral cortex, hypothalamus and adult behavior. To identify the molecular and cellular basis of the sex and steroid specific responses in the developing brain, we compared the consequence of Dex versus Beta exposure on embryonic cerebral cortical NSC biology. Murine NSC were isolated from the E14.5 cerebral cortex and exposed to 10-7 M Dex, 10-7 M Beta, or Vehicle for 4 or 24 hours and the immediate and long-term impact on transcription, proliferation and neuronal, glial and oligodendrocyte differentiation examined. Affymetrix complete genome transcriptional analyses reveal sex specific responses to Dex versus Beta within 4 hours. At >+/-1.5-fold change 548 genes were differentially regulated by Dex, 452 by Beta and 256 were altered by both Dex and Beta (P < 0.05). Distinct sex specific responses to Dex versus Beta were observed. At >+/-2-fold change 126 genes were significantly different in the Dex versus Beta female transcriptome, 146 in the male transcriptome with 18 genes unique to both male and female transcriptome. Ingenuity Pathway Analysis revealed that the most significantly altered pathway altered (Z score >2) with both sGCs is Inositol Phosphate metabolism. Cardiac hypertrophy, Tec kinase, and Th1 pathways were unique to Beta stimulation, whereas Melatonin, Neuropathic Pain and IL6 signaling pathways were specific to Dex stimulation. Both Dex and Beta significantly alter genes implicated in proliferation and differentiation as also described in other studies, therefore the biological response of NSC to sGCs stimulation was compared. Only Dex significantly decreased the rate of proliferation over a 72 hour. In-vitro differentiation studies reveal that both Dex and Beta reduced oligodendrocyte differentiation without altering neuronal differentiation when cells were exposed to sGCs as progenitors. However, when cells were exposed to sGCs during differentiation, Dex increased oligodendrocyte and neuronal maturation while Beta only increased oligodendrocyte differentiation. These results reveal gene targets, cellular pathways and processes that are differentially altered by prenatal Dex versus Beta exposure. Prenatal sGCs administration provides clear benefits for neonatal outcome, however, a detailed understanding of their targets in the brain is required to identify alternative sGCs drug regimens to reduce adverse neurological effects. Our finds may provide insights into the sex specific neurological outcomes observed in children exposed to sGCs in-utero.