Biomedical Engineering Reference
In-Depth Information
12
Analysis of Gene Expression in Striatal Tissue
by Multiprobe RNase Protection Assay
Neil M. Richtand
1. Introduction
Studies of RNA expression within the central nervous system (CNS) have
contributed signifi cantly to increased understanding of both the acute and
long-term neurological effects of drugs of abuse. Before beginning such an
investigation, however, one must fi rst determine the method of RNA analysis
most applicable to the problem at hand. The four most commonly used
techniques include
in situ
hybridization, Northern blot, reverse transcriptase-
polymerase chain reaction (RT-PCR), and ribonuclease (RNase) protection
assay. Each method has its own strengths and limitations, and these factors
must be evaluated carefully to determine the method most appropriate for
the given problem.
A major but frequently overlooked limitation of all four methods is the fact
that these methodologies measure mRNA expression. In contrast, the scientifi c
question of greatest interest in determination of the neurological effect of a
given drug is often determination of the effect on protein, rather than mRNA
expression. There are several known examples of single proteins in the mam-
malian CNS in which changes in mRNA level reliably predict later change in
protein expression
(1)
. Evaluation of large numbers of yeast genes for which
both mRNA and protein expression data are available, however, demonstrates
little correlation between mRNA and protein expression levels, with protein
expression changing 20-fold, in some cases, in the absence of any appreciable
change in mRNA level
(2)
. Whether the same is true in mammalian systems
has not been clearly determined. The importance of information regarding both
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