Figure 5.

FlnA loss causes a prolongation of cell cycle length in vivo. a, Cumulative BrdU labeling estimates the time required for neural progenitors in the VZ to complete each phase of the cell cycle. With loss of FlnA function, fewer progenitors incorporated BrdU at 3 and 9 h, consistent with an overall prolongation of the cell cycle. By 14 h, virtually all VZ progenitors were labeled in both mutant and WT mice. b, Costaining for PH3 at various times after BrdU labeling enabled determination of the time required to complete G2 to M phase (T_G2+M, when all PH3+ cells were BrdU positive). Mitotic BrdU labeling indexes were calculated from the proportion of BrdU+ and PH3+ nuclei to total PH3+ nuclei along the ventricular surface. The ratio of M-phase cells to the total cells in ventricular zone was measured by direct cell count. Scale bars: b (for a, b), 50 μm. c, The labeling index, obtained from the cumulative BrdU experiments, allowed for determination of the entire cell cycle length (T_c), as well as time required to complete S phase (T_s). Time to complete M phase (T_M) was estimated by taking the ratio of cells along the ventricular lining, compared to the total number of progenitors within the VZ. V, Ventricle; CP, cortical plate. Based on the labeling index at each time interval, BrdU labeling curves for FlnA^y/+ (■) and FlnA^y/− (▴) neural progenitors were developed by linear fit. *p < 0.05.