Fibroblast growth factor-2 (FGF-2) promotes proliferation of neuroprogenitor cells in culture and is up-regulated within brain after injury. Using mice genetically deficient in FGF-2 (FGF-2 ؊/؊ mice), we addressed the importance of endogenously generated FGF-2 on neurogenesis within the hippocampus, a structure involved in spatial, declarative, and contextual memory, after seizures or ischemic injury. BrdUrd incorporation was used to mark dividing neuroprogenitor cells and NeuN expression to monitor their differentiation into neurons. In the wild-type strain, hippocampal FGF-2 increased after either kainic acid injection or middle cerebral artery occlusion, and the numbers of BrdUrd͞NeuN-positive cells significantly increased on days 9 and 16 as compared with the controls. In FGF-2 ؊/؊ mice, BrdUrd labeling was attenuated after kainic acid or middle cerebral artery occlusion, as was the number of neural cells colabeled with both BrdUrd and NeuN. After FGF-2 ؊/؊ mice were injected intraventricularly with a herpes simplex virus-1 amplicon vector carrying FGF-2 gene, the number of BrdUrd-labeled cells increased significantly to values equivalent to wild-type littermates after kainate seizures. These results indicate that endogenously synthesized FGF-2 is necessary and sufficient to stimulate proliferation and differentiation of neuroprogenitor cells in the adult hippocampus after brain insult.fibroblast growth factor ͉ cerebral ischemia ͉ seizure ͉ gene delivery

Upon transforming growth factor-␤ (TGF-␤) binding to its cognate receptor, Smad3 and Smad4 form heterodimers and transduce the TGF-␤ signal to the nucleus. In addition to the Smad pathway, another pathway involving a member of the mitogen-activated protein kinase kinase kinase family of kinases, TGF-␤-activated kinase-1 (TAK1), is required for TGF-␤ signaling. However, it is unknown how these pathways function together to synergistically amplify TGF-␤ signaling. Here we report that the transcription factor ATF-2 (also called CRE-BP1) is bound by a hetero-oligomer of Smad3 and Smad4 upon TGF-␤ stimulation. ATF-2 is one member of the ATF/CREB family that binds to the cAMP response element, and its activity is enhanced after phosphorylation by stress-activated protein kinases such as c-Jun N-terminal kinase and p38. The binding between ATF-2 and Smad3/4 is mediated via the MH1 region of the Smad proteins and the basic leucine zipper region of ATF-2. TGF-␤ signaling also induces the phosphorylation of ATF-2 via TAK1 and p38. Both of these actions are shown to be responsible for the synergistic stimulation of ATF-2 trans-activating capacity. These results indicate that ATF-2 plays a central role in TGF-␤ signaling by acting as a common nuclear target of both Smad and TAK1 pathways.

Sphingosine-1-phosphate (S1P) is a lipid mediator that exerts multiple cellular functions through activation of G-proteincoupled receptors. Although the role of S1P on angiogenesis is well established, its role in neurogenesis is unknown. We examined the effects of S1P on G-protein activation in brain sections of rat embryo and on neural progenitor cells in culture. Intense S1P-stimulated [35 S]GTPcS labeling was observed as early as E15 in the neuroepithelium and differentiating fields throughout the brain, suggesting that functional S1P receptors are expressed in brain areas with active neurogenesis. mRNA transcripts for several S1P receptor subtypes (S1P 1 , S1P 2 , S1P 3 and S1P 5 ) were expressed in neural progenitor cells prepared from embryonic rat hippocampus. S1P induced phosphorylation of extracellular signal-regulated kinase (ERK) and proliferation of neural progenitor cells as determined by BrdU incorporation in a pertussis toxin-sensitive manner. These effects were prevented by the ERK signaling inhibitor U0126. S1P augmented telomerase activity in neural progenitor cells with similar potency as that of FGF-2. Furthermore, S1P induced cell-cell aggregation. This morphological change was transient and prevented by Y-27632, an inhibitor of Rhoassociated kinase. These results suggest that S1P plays a pleiotropic role in neurogenesis via pathways involving S1P receptors, MAP kinases and Rho kinase.