Pharmacological Sciences

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.