Brain-specific gene expression.

The brain of an adult rat expresses approximately 30,000 different brain-specific mRNAs. To investigate their encoded proteins, we have selected cDNA clones corresponding to mRNAs expressed exclusively in rat brain, determined their nucleotide sequences and generated antisera against synthetic peptides mimicking short regions of the deduced protein sequences. The clone plB236 encodes a protein that defines a widely distributed neuronal system and may be the precursor for a family of novel neuropeptides. A second clone, plB208, encodes rat brain proteolipid protein, the major protein component of central nervous system myelin. These studies have also identified an 82 nucleotide genetic element called an ID (identifier) sequence that may be involved in the regulation of transcription of brain-specific genes.