Selective apoptosis within the rat subependymal zone: a plausible mechanism for determining which lineages develop from neural stem cells.
During development, the output of the subventricular zone (SZ) becomes increasingly restricted, yet it still harbors multipotential progenitors. The output of the SZ could be gated by selectively eliminating inappropriately specified progenitors. Using in situ end-labeling (ISEL) to identify apoptotic cells, nearly 60% of the ISEL(+) cells in the juvenile forebrain were localized to the SZ. Of these dying cells, at least 9% could be identified as neurons, 4% as astrocytes, and 12% as oligodendrocytes. The remainder were negative for the stem cell marker nestin, as well as other markers evaluated. To test the hypothesis that committed progenitors were under selective pressures, neural stem/progenitor cells were allowed to differentiate in vitro in the presence or absence of the caspase 3 inhibitor z-DEVD-fmk. DEVD increased neuronal production 10-fold over control cultures. By contrast, the development of astrocytes and oligodendrocytes was not affected. Altogether, these data support the hypothesis that selective forces within the postnatal rat forebrain control the types of precursors that emerge from the germinal matrix. Furthermore, they suggest that different mechanisms control neuronal versus glial cell numbers.
Levison
S W
SW
Department of Neuroscience, Pennsylvania State University College of Medicine, Hershey, Pa., USA. slevison@psu.edu
Rothstein
R P
RP
Brazel
C Y
CY
Young
G M
GM
Albrecht
P J
PJ
D000818:Animals; D000831:Animals, Newborn / Q000502:physiology; D017209:Apoptosis / Q000502:physiology*; D015415:Biomarkers; D053148:Caspase 3; D061945:Caspase Inhibitors; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004805:Ependyma / Q000166:cytology / Q000502:physiology*; D020287:In Situ Nick-End Labeling; D009457:Neuroglia / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism
D015415:Biomarkers; D061945:Caspase Inhibitors; D004791:Enzyme Inhibitors; C505410:Casp3 protein, rat; D053148:Caspase 3