Determination of Transcriptional Initiation Sites and Their Usage in the Nervous System

The appearance and maintenance of differentiated neural cell types in eukaryotic organisms can be largely attributed to characteristic spa- tial and temporal regulatory cascades evoking cell-specific gene expres- sion. Since gene expression causes information passage from DNA to RNA to proteins and since most mammalian brain protein coding DNA is expressed as messenger RNA (mRNA) (1 ,2 ), it appears that the con- trol of mRNA levels is a critical intermediate step in producing brain- specific patterns of gene expression. Of the many transcriptional mechanisms known, RNA initiation is recognized as an important modulator of expression (3 –5 ).