Global gene expression analysis of developing neocortex using SAGE.

The mammalian brain is estimated to contain about a hundred billion neurons, making it the most complex biological structure on earth. Trying to understand the assembly and function of this elaborate organ is a formidable task. Yet the information to build a brain is encoded by no more than a subset of the 80,000 genes present in the genome, a more manageable number. This review describes the use of SAGE technology (Serial Analysis of Gene Expression) to decode the genetic repertoire of genes that are differentially expressed in time and in space during development of the neocortex, the part of the mammalian brain responsible for complex traits. We demonstrate that SAGE is not only powerful for generating comprehensive molecular portraits from the developing cortex but can also assist in discovering new genes.