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International cooperation and technology transfer
Mussio, Luigi

Luciano Milanesi
Consiglio Nazionale delle Ricerche - ITBA
E-mail: milanesi@itba.mi.cnr.it
Raffaella Rizzi
Politecnico of Milan
E-mail: rizzi@itba.mi.cnr.it
KEYWORDS: gene expression, hybridization, oligonucleotide, cDNA, microarray.
Recently a new methodology based on gene expression studies has been developed to understand the role
of genes in regulating the biological activity in living organisms. The expression profiles in a living cell
(e.g. which genes are active and which genes are suppressed) are derived by investigating the images
produced by fluorescent reactions on nylon membranes or from microscope glass slides. The digitization
of expression images, by means of digital cameras or flatbed and drum scanners, generates the signal to be
analyzed. This method is highly parallel and at the same time allows to monitor a high-density panel of
genes by analyzing single-color and dual-color images (respectively for one cellular population and for
two different cellular populations). A brief description of the gene expression studies used for microarray
gene functional mapping and some procedure for the digital image analysis will be presented.
The first part of the Genome Project will
probably conclude in year 2003 (Schena et al.,
1996) with the sequencing of the complete
genome of all living organisms; at present this
purpose has been settled for a unique eukariotyc
organism: the yeast Saccharomyces cerevisiae
(Wodicka et al., 1997).
The second part of the project will concern the
investigation of the genome-wide expression of
living cells (particularly for the 80,000-100,000
genes of the human cells) to understand the
protein role in the cellular function thoroughly.
The traditional gene mapping consists in
determining the chromosome, which contains
the particular gene, and the reciprocal positions
between genes. Types of maps are cytogenetic
maps (gene is mapped in region which is some
megabases wide), physical maps (localization of
identifiable limits) and linkage maps
(polymorphism of a population).
The new techniques for gene expression profile
studies initiate a new kind of mapping: the gene
functional mapping.
The gene expression pattern of a single living
cell in peculiar conditions, is useful to
acknowledge, on one hand, the health state of
the cell and, on the other hand, its function.
That’s why it is very important to study gene
expression on a suitably wide scale, to monitor
at the same time, a great number of genes (in the
future for the entire human genome as biologists
hope) of several tissue cells, in different
development phases, in different physiological
and environmental conditions, treated with
various chemical substances (to experiment new
pharmacological targets) and in different states
of health (cancer cellular lines to determine
oncogenes and tumor suppresser genes) (Chen et
al., 1998; Schena et al., 1995, 1996; DeRisi et al.,
1996, 1997; Nguyen et al., 1995; Bernard et al.,
1996; Lockhart etal., 1996; et al., 1997; Wodicka
etal., 1997).
The following methods will be based on the
hybridization reaction of cellular messenger RNA
with high-density arrays of cDNA clones (Chen
et al., 1998; Bernard et al., 1996; DeRisi et al.,
1997), even with unknown sequences (Schena et
al., 1995, 1996), or synthetic oligonucleotide