Expression of GAP-43 in fibroblast cell lines influences the orientation of cell division

The orientation (vertical or horizontal) of cell division is known to be critical for neural cell fate determination during neurogenesis. At the onset of neurogenesis, neurogenic progenitor cells are dividing with the cleavage plane parallel to the ventricular surface (horizontal division), which would lead to critical apical components being unequally distributed to both their two daughter cells. The daughter cells lack of inheritance is going to differentiate into the neuron. Recent studies have shown that GAP-43 is highly expressed in horizontally dividing neural progenitor cells in the forebrain of mammals. Based on findings from in vivo studies, GAP-43 is locally associated with the centrosome and is required for centrosome positioning, suggesting that GAP-43 may be involved in neurogenesis through regulating the orientation of cell division. With a fibroblast cell model, our results show that both GFP expressing and control cells had the same potential (p>0.05) with regard to dividing orientation (either vertical or horizontal to the cells long axis). On the other hand, we found that GAP-43 was localized on the membrane instead of the centrosome during all phases of mitosis within GAP-43 transgenic cells, but expressing of GAP-43 could make the cells dividing more likely along their long axis (p<0.05). Our observations suggest that GAP-43 might link the cell membrane and spindle pole and consequently participate in controlling cleavage orientation during cell division.