Characterization of RNA - Animal Models of Acute Neurological Injuries: Injury and Mechanistic Assessments - page 138

Fig. 1. The RIN cannot predict the usefulness of gene expression data without prior validation. In addition, RIN values
acceptable for RT-PCR may not be useable for genome-wide microarray experiments. Correlate the RIN with downstream
experiments and determine the threshold RIN for meaningful results.

fl uorescence detection, which provides a platform to record the
size distribution of RNA molecules in a digital format. The RNA
integrity number (RIN) takes the entire electrophoretic trace into
account ( 37 ). The RIN algorithm is based on fi ve features that
contribute information about the RNA integrity, including the
ribosomal ratio. RIN values range from 10 (intact) to 1 (totally
degraded).
Figure 1 represents electropherograms of RNA at varying
stages of degradation.

3. Methods
for RNA
Characterization

Gene expression profi ling using microarray allows the user to obtain
a relative assessment of the quantity of expressed gene products in a
given tissue at a given time. This refl ects an estimate of the biologi-
cal environment of the cell(s) and cellular response under a given
circumstance. The technology evolved out of a need to examine the
complexity of biological interactions in parallel. In a single experi-
ment, information can be obtained for thousands of genes repre-
sented on a microarray chip or array. The fi rst microarrays contained
about 1,000 transcripts or RNA targets; whereas today's technol-
ogy allows for the assessment of greater than 48,000 (this includes
the >25,000 curated genes along with duplicate transcripts of genes,
secondary to alternative splicing and other probes targeting
unknown mRNA sequences). Over the course of 10-15 years, the

3.1. Microarrays