Figure 2.

The apoptotic response of subgranular cells in the SGZ of the dentate gyrus after irradiation is attenuated in smpd1-deficient mice. Caspase-3 immunoreactive cells (red, a–i) are seen in the SGZ of the smpd1+/+ mouse dentate gyrus after 5 and 17 Gy (a–c). The response is decreased in smpd1+/– mice (d–f), and further attenuated in smpd1–/– mice (g–i). A caspase-3 positive cell (arrow, j) shows characteristic nuclear condensation of apoptosis (DAPI, k; merged, l). A similar dependence of the apoptotic response of subgranular cells on smpd1 status is observed using TUNEL to identify apoptotic cells (green, m–x). A TUNEL-positive apoptotic cell (arrow, v) demonstrates nuclear condensation after DAPI nuclear staining (arrow, w; merged, x). A significant reduction in caspase-3 (y) or TUNEL-positive subgranular cells (z) is observed in smpd1–/– mice compared with smpd1+/+ mice after irradiation (*P<0.01, t-test). The number of apoptotic cells in a minimum of three mice is estimated by stereology. Data represent means±S.E.M