are used by Genex Laboratory to screen the entire human genome
(60 000 gene sequences).
RNAs extracted from cells or tissues are transformed into complementary DNAs (cDNA) by the reverse transcription technique (RT) and labeled with the cyanin fluorochrome (cyanin-3 : green coloring, cyanin-5 red coloring). Labeled cDNAs are hybridized on spots containing DNA fragments, along with the control cDNA.
The fluorescence intensity is quantified after a high-resolution scanner analysis. Comparison of intensities between a treated sample versus a control sample will allow us to identify whether the expression of a gene is activated or inhibited. When a gene is activated in response to treatment, it synthesizes a messenger (mRNA) responsible for protein synthesis.
What is the interest of large-scale screening?
Genes and proteins work together
and a single gene cannot alone account for the activation of a process.
Substantiating a claim involves identifying a "functional network
" in which several genes will interact directly or indirectly. The function of these genes may have never been documented in skin tissue but the involvement of these genes, highlighting the specificity of the product, is a source of innovation.
From total RNA, it is possible to extract miRNAs (23-25 nucleotides) and quantify them through the use of miRNA chips. This quantification is used to evaluate the modulation of the expression of miRNAs present in a treated sample versus a control sample and therefore to identify the impact of a product on their synthesis. The human genome consist of approximately 1000 genes responsible for the synthesis of miRNAs that would regulate about 60% of the genes (see Newsletter # 2 for more information).