Chapter 2.2.3 Brain region-specific genes: the hippocampus

The chapter discusses four approaches along with their merits and drawbacks, and possible means to the identification of genes and transcripts whose expression is restricted to the hippocampus, and the advantages and drawbacks of the techniques employed. Unexpectedly, each approach highlights a different and non-overlapping subset of genes, but the expression of at least some of these was largely if not exclusively restricted to the hippocampus. The most important method is differential hybridization. This yielded a gene, Cyp7b, whose expression is largely but not exclusively restricted to the hippocampal formation and encoding a novel enzyme metabolizing neurosteroids. The candidate gene family approach yielded a new serine protease, BSP1 with a highly restricted pattern of expression that permits exploitation in a transgenic context, and protein tyrosine phosphatase (PTP) gamma, whose restricted pattern of expression warrants further study.