Phenylethanolamine N-methyltransferase (Pnmt) is the enzyme that N-methylates norepinephrine to produce the stress hormone/neurotransmitter, epinephrine, which is abundantly expressed in adrenal glands. Developmental studies have also identified Pnmt expression in the embryonic heart and several areas of the brain, including brainstem, cerebellum, and hypothalamus. Thus, we hypothesize that selective ablation of Pnmt+ cells will have detrimental effects on cardiovascular, neuromuscular, and metabolic processes. To uncover the importance of Pnmt+ cells in vivo, we generated a novel Diphtheria Toxin A (DTA) suicide model (Pnmt+/Cre; R26+/DTA) to selectively ablate Pnmt-expressing (Pnmt+) cells in mice. Appearing normal at birth, Pnmt-Cre/DTA mice began to develop apparent cardiovascular, neurological, and metabolic impairments soon thereafter. To measure cardiac function, we performed quantitative echocardiography, electrocardiography (ECG), and blood pressure measurements. Key findings from these assessments indicated decreased left-ventricular performance, slowed atrioventricular conduction, and increased pulse pressure in the Pnmt-Cre/DTA ablation mice. These mice also showed signs of motor control deficits as early as one month, which progressively worsened with age. To assess these effects, we performed standard motor tests including hind-limb clasping, grip strength, and rotarod balance tests. Moreover, we found that the Pnmt-Cre/DTA mice ceased to gain weight shortly after puberty. The motor and metabolic deficits apparent in these animals suggested potential neurological impairments, and we thus undertook immunohistochemical staining experiments to determine the localization of Pnmt+ cells in the brain. Staining revealed Pnmt expression in the Purkinje cells of the cerebellum (motor), paraventricular nucleus of the hypothalamus (metabolic), and surprisingly extensive staining in the cerebral cortex. These results demonstrate that Pnmt+ cell contributions in the brain are much more extensive than previously thought. Overall, this work opens new pathways that will have substantial impacts on our understanding of the roles Pnmt+ cells play in normal development and disorders affecting cardiovascular, motor, and metabolic functions.
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Master of Science (M.S.)
College of Medicine
Length of Campus-only Access
Masters Thesis (Campus-only Access)
Manja, Sanjana, "Unraveling the Role of Phenylethanolamine N-methyltransferase (Pnmt+) Cells In-vivo" (2019). Electronic Theses and Dissertations. 6385.