From DNA arrays to transcriptional regulatory networks

"Whole genome" expression profiles can be used as molecular signatures or p ortraits characteristic of a tumour or of the physiological state of a cell . This global description also provides a new, approach for the study of th e transcriptional regulation, and this review is dedicated to this fundamen tal aspect of the transcriptome. Gene expression studies will be first cons idered at the single cell level. In situ analyses reveal that transcription is a stochastic phenomenon, indicating that the transcriptome contains flu ctuating regions. The transcriptional response of a cell population to an e xternal stimulus has been used to evaluate the contribution of the various signalling pathways and transcription factors. One of the emerging themes i s the co-ordinate expression of genes associated with the same physiologica l process. Im the spirit of this analysis of the transcriptional regulatory networks, it is becoming possible to design artificial biological networks to implement desired functions, paving the way to new therapeutic approach es.