Stress plays a significant role in neural development and brain function. To better understand the mechanisms underlying the impact of stress on brain development and neuroendocrine function, this study focuses on the phenylethanolamine-N-methyltransferase (Pnmt) enzyme as a key mediator of stress hormone signaling. Pnmt is activated as part of a positive feedback mechanism during stress to convert norepinephrine to epinephrine and amplify the sympathetic response. Most of our knowledge about Pnmt is derived from its role in the systemic production of epinephrine from adrenal chromaffin cells, but it is also known to be expressed in the central nervous system, including the brainstem, retina, hypothalamus, and cerebellum.
Given the importance of the central nervous system in modulating stress responses, this project sought to investigate cellular Pnmt expression in the central nervous system using a genetic-marking strategy with a Pnmt-Cre-recombinase knock-in driver strain (Pnmt+/Cre) and a β-galactosidase (βGal) reporter strain (R26R+/βGal) in parallel with Pnmt-specific immunofluorescent histochemical staining to identify Pnmt+ cells in the adult mouse cerebellum, hypothalamus, and cerebral cortex. The results show extensive patterns of active and historical Pnmt protein expression throughout the cerebellum and hypothalamus, with significant neuropeptide Y co-expression in the hypothalamus and considerable historical Pnmt expression throughout the cerebral cortex.
To quantify baseline Pnmt mRNA levels across embryonic and postnatal neural development and elucidate differential Pnmt isoform expression through tissue-specific regulation in the developing brain, quantitative polymerase chain reaction (qPCR) was performed in the brainstem, cerebellum, and cerebral cortex with isoform-specific primers. Initial results show a developmental, tissue-specific Pnmt isoform shift between embryonic and postnatal neural development by an intron-retention alternative splicing mechanism. Ultimately, these findings provide an anatomical "blueprint" for investigating the role of central nervous system Pnmt expression in health and disease, and emphasize the role of Pnmt in early neural development, illustrating how stress impacts the formation of neural connections during formative periods of brain maturation.
Bachelor of Science (B.S.)
College of Medicine
Burnett School of Biomedical Sciences
Length of Campus-only Access
Mehta, Meeti, "Epinephrine Synthesizing Enzyme Expression in the Developing Central Nervous System: Implications for the Impact of Stress on Formative Brain Maturation" (2021). Honors Undergraduate Theses. 994.