Luciferase reporter mice for in vivo monitoring and ex vivo assessment of hypothalamic signaling of Socs3 expression

Authors: CORDONIER, ELIZABETH - Children'S Nutrition Research Center (CNRC); LIU, TIEMIN - University Of Texas Southwestern Medical Center; SAITO, KENJI - Children'S Nutrition Research Center (CNRC); CHEN, SIYU - Children'S Nutrition Research Center (CNRC); XU, YONG - Children'S Nutrition Research Center (CNRC); FUKUDA, MAKOTO - Children'S Nutrition Research Center (CNRC)

Submitted to: Journal of the Endocrine Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/17/2019
Publication Date: 7/1/2019
Citation: Cordonier, E.L., Liu, T., Saito, K., Chen, S.S., Xu, Y., Fukuda, M. 2019. Luciferase reporter mice for in vivo monitoring and ex vivo assessment of hypothalamic signaling of Socs3 expression. Journal of the Endocrine Society. 3(7):1246-1260. https://doi.org/10.1210/js.2019-00077.
DOI: https://doi.org/10.1210/js.2019-00077

Interpretive Summary: The brain is a critical site for controlling body weight. How the brain reacts to excess nutrition and mediates obesity remains incompletely characterized. To better understand the underlying neural mechanisms of obesity, a new laboratory tool was developed to help identify a critical molecular pathway that potentially promotes obesity. Cellular imaging techniques were used in the new animal model, which in turn allowed visualization of the gene expression of a molecule that promotes obesity. This visualization resulted in identifying a neural pathway involved in the cellular process that may drive obesity. Neural levels of the gene were successfully altered by manipulating the activity of the signaling pathway. These findings provide a clue to mechanisms that determine body weight, and may potentially lead to a novel approach to control body weight by manipulating the pathway.

Technical Abstract: Suppressor of cytokine signaling-3 (SOCS3) is a negative regulator of actions of cytokines and the metabolic hormone leptin. In the hypothalamus, SOCS3 is induced in response to several conditions such as inflammation and high-fat diet feeding, modulates cellular signaling of cytokines and leptin, and mediates the effects of these biological conditions. However, signaling mechanisms controlling hypothalamic Socs3 expression remains to be fully established. To facilitate the identification of molecular pathways of Socs3 induction, we generated a real-time gene expression reporter mouse of Socs3 (Socs3-Luc mice). We successfully detected a remarkable increase in luciferase activity in various tissues of Socs3-Luc mice in response to a peripheral injection of lipopolysaccharide, a potent inducer of inflammation, reflecting expression levels of endogenous Socs3 mRNA. Using ex vivo hypothalamic explants of Socs3-Luc mice, we demonstrate that hypothalamic luciferase activity was significantly elevated in slices stimulated with known inducers of Socs3 such as proinflammatory cytokines IL-6, IL-1Beta, and TNF-alpha, lipopolysaccharide, and cAMP-inducing agent forskolin. Using the ex vivo model, we found glycogen synthase kinase-3 (GSK3)Beta-specific inhibitors to be potent inducers of Socs3. Furthermore, pharmacological inhibitors of Beta-catenin, a downstream mediator of GSK3Beta signaling, reduced Socs3 luciferase activity ex vivo. Finally, hypothalamic inhibition of GSK3Beta hindered leptin-induced phosphorylation of signal transducers and activators of transcription 3 in hypothalamic explants. These results suggest that the Socs3-luciferase mouse is useful for in vivo monitoring of Socs3 gene expression and for ex vivo slice-based screening to identify signaling pathways that control Socs3 in the hypothalamus.