Neural Regulation of Gene Expression

Ph.D., University of Washington, Seattle
Postdoctoral, Roche Institute of Molecular Biology
Postdoctoral, Columbia University College of P&S

The ability of neural stimuli to regulate gene expression provides one means of integrating the many types of information typically received by a single neuron. Often the production of mRNA serves as the first step in gene regulation. Frequently transcriptional regulatory sites on DNA function as focal points to coordinate a gene's response to these influences. Currently I am investigation regulation of the gene encoding phenylethanolamine N-methyltransferase (PNMT), the final enzyme in the catecholamine biosynthetic pathway. The objective of our research is to learn how neural stimuli, primarily neurotransmitters, can regulate the expression of other neural genes, using transcription of the PNMT gene as a model system.

Physiologically, it has been established that catecholamine enzymes are stimulated by "chronic stress", a general term encompassing the ability of neurotransmitters and/or neural impulses to induce PNMT expression transynaptically. We have determined that cholinergic stimuli (e.g., acetylcholine) induce production of PNMT mRNA through two separate receptor systems, i.e. nicotinic and muscarinic, which involve distinct second messenger intermediates.

Knowing that neural influences affect transcription of the PNMT gene has served as the basis for mapping the cis-active elements on this gene that convey responsiveness to nicotinic, muscarinic, and depolarizing stimuli. We explore the response of PNMT regulatory elements by transfecting and expressing upstream regulatory regions of this gene in homogeneous populations of adrenal chromaffin cells. We are currently mapping multiple sites on the PNMT promoter that are specifically responsive to neural stimuli. Our strategy is to confirm the functionality of these sites using site-directed mutagenesis to abolish transmitter-mediated responses.

Regulatory sites encoded within the PNMT promoter are likewise instrumental in restricting expression of this gene.  Therefore, we are also characterizing sequences responsible for neural, adrenergic, and chromaffin cell-specific expression of PNMT.

Our future research directions involve identification of those nuclear proteins that interact with neurally and cell-specific responsive sites on the PNMT gene. These studies should contribute significantly toward understanding the molecular basis of transmitter production and regulation in the central and peripheral nervous systems.

Selected Publications

• Lee, Y-S. E., Raia, G., Tonshoff, C., and Evinger, M.J. Neural regulation of phenylethanolamine N-methyl-transferase (PNMT) gene expression in bovine chromaffin cells differs from other catecholamine biosynthetic enzyme genes.  J. Mol. Neurosci. 12(1). Feb., 1999. 53-68.
  
  
• Evinger M.J. (1998). Determinants of phenylethanolomin N-methyl transferase espression. Adv. Pharmacol. 42: 73-76.
  
  
• Tonshoff, C., Hemmick, L., and Evinger, M.J. .  Pituitary adenylate cyclase activating polypeptide (PACAP) regulates expression of catcholamine biosynthetic enzyme genes in bovine adrenal chromaffin cells.  J. Mol. Neurosci. 9(2). Oct., 1997. 127-140.
  
  
• Evinger, M.J., Ernsberger, P., Regunathan, S., Joh, T.H., and Reis, D.J. (1994) A single transmitter regulates gene expression through two separate mechanisms: Cholinergic regulation of phenylethanolamine N-methyltransferase mRNA via nicotinic and muscarinic pathways. J. Neurosci. 14: 2106-2116.