Address for correspondence: Bertrand Jordan, Marseille-Génopole, Case 901, 13288 Marseille, France. Voice: 33 (0)4 91 82 94 70; fax: 33 (0)4 91 82 94 71.
jordan{at}genopole.univ-mrs.fr
Ann. N.Y. Acad. Sci. 975: 24-32 (2002).
Expression profiling using DNA arrays is often believed to have
appeared during the second half of the 1990s, and to be based
exclusively on nonisotopic methods. In fact, the first article
describing the application of cDNA arrays to expression analysis
was published in 1992, relied on radioactive labeling, and was
a new development of "high-density" membranes used until then
essentially for efficient screening of libraries. Several papers
described the use of this technology for simultaneous expression
measurement of thousands of genes at the time when the first
glass microarrays were published. Simultaneously, oligonucleotide
chips, originally developed for resequencing and mutation detection
applications, were shown to be capable of expression measurement
as well. The three approaches have developed over the years
and still coexist, as each of them has specific advantages (and
drawbacks); the major issues have become those of data quality,
data analysis and storage (ideally in a common public database).
Meanwhile, the technology continues to evolve. The most obvious
trend is a shift towards using arrays of relatively long oligonucleotides
that combine most of the advantages of very long (cDNA) and
very short (25-mer) DNA segments. The search for better detection
methods, ideally without labeling of the sample, is continuing,
although it seems difficult to reach the required sensitivity.
New materials for microarray manufacture and new implementations
of existing methods have appeared. In addition, the field is
progressively becoming segmented into high gene number, low
volume (research) applications on the one hand, and low gene
number, high throughput (diagnostic) uses on the other.
