FIBROBLAST-GROWTH-FACTOR-2 INCREASES OTX2 EXPRESSION IN PRECURSOR CELLS FROM MAMMALIAN TELENCEPHALON

Dissociated primary cultures from rat telencephalon at different devel opmental stages were used to study the effect of basic fibroblast grow th factor (FGF2) on Otx2, Dlx1, and Emx1, three homeobox genes express ed in different regions of the developing mammalian forebrain. At embr yonic day (E)13.5, the regional pattern of expression of Otx1, Otx2, D lx1, Dlx2, Dlx5, and Emx1 is maintained in primary culture, suggesting that cells are already committed to a regional identity at this stage . In these cultures, Otx2 is expressed by precursor cells, whereas Dlx 1 and Emx1 are predominantly expressed by postmitotic cells. We found that FGF2 increased Otx2 expression within precursor cells and the tot al number of Otx2-expressing cells. This effect was gene-specific, dos e-dependent, and temporally regulated, with larger effects at earlier stages of development (E11.5). At E13.5, the effect of FGF2 on Otx2 ex pression was restricted to the basal telencephalon. Our results sugges t that a restricted population of neuroblasts respond to FGF2 in a tem porally regulated fashion by proliferating and increasing Otx2 express ion. This interaction between FGF2 and Otx2 may be important for the r egulation of neurogenesis in the forebrain.