Cell-specific expression of Epac2 in the subventricular and subgranular zones.

In the V-SVZ of the lateral ventricle, most GFAP-positive adult neural stem cells (NSC, defined as type B cells) and 75% of DCX-positive migrating neuroblasts (type A cells) expressed Epac2 proteins. Ninety-three percent of beta-catenin-positive ependymal cells (type E cells), which are in direct contact with NSCs and the ventricles, also expressed Epac2 protein. Similarly, in the SGZ of the hippocampus, Epac2-immunopositive signals were shown by 83% of GFAP-positive radial-glia-like NSCs (type 1 cells), 86% of DCX-positive transiently amplifying cells (type 2 and type 3 cells), and 71% of DCX-positive immature neurons. The present data suggest that a PKA-independent cAMP signaling pathway via Epac2 may be party to adult neurogenesis in the V-SVZ and the SGZ.