mCD24 regulates proliferation of neuronal committed precursors in the subventricular zone.

We previously showed that deletion of the cell surface molecule mCD24 resulted in an increased proliferation in adult subventricular zone (SVZ). Here, we report an increased PSA-NCAM+/TuJ1- population in the mCD24-/- in vivo SVZ as well as in vitro neurospheres. Isolated in vitro, these cells were able to generate neurospheres. Proliferation studies, using BrdU incorporation, showed an increased proliferation in P7 mCD24-/- SVZ and neurospheres. Using electron microscopy, the same cell types were identified in the in vivo SVZ as well as in vitro neurospheres from the WT and mCD24-/- mice. In mixed neurospheres, formed with WT and EGFP/KO cells (enhanced green fluorescent protein mCD24-/-), the WT environment was able to control the proliferation rate of the mCD24-/- cells, but was unable to regulate their differentiation. We concluded that mCD24 acts cell nonautonomously to regulate transit-amplifying cells proliferation and/or differentiation.