rTg(tau_wt) neurospheres contain more human tau expressing cells than rTg(tau_P301L) neurospheres.

<p>Undifferentiated single cells (shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0039328#pone-0039328-g002" target="_blank">Figure 2</a>) stained with DAPI and nestin were counted and the proportion co-expressing Tau13 was determined. (A) Consistently the proportion of cells co-expressing Tau13 was significantly higher in rTg(tau_wt) cultures than rTg(tau_P301L) cultures. Four independent experiments consisting of 11 independent rTg(tau_wt) cultures and 11 independent rTg(tau_P301L) cultures are shown here (ANOVA: variation due to experiment F = 5.5, P = .01; ANOVA mutant versus wild type F = 65.9, P<0.0001. Interaction between experiment and tau genotype was marginally significant: F = 3.8, P = 0.035.) Following Bonferonni/Dunn correction, the mutant versus wild type comparison remained significant at P<0.0001. Paired t test also indicated a significant difference between rTg(tau_P301L) and rTg(tau_wt) neurospheres (P<0.0001). Closed circles represent tau_wt; open circles represent tau_P301L. (B, C) Fluorescence intensity histograms from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0039328#pone-0039328-g003" target="_blank">Figure 3A</a>’s Experiment 3 cells revealed heterogeneity in transgene expressing cells. Transgene positive cells were binned (1 to >10) based on fluorescence intensity. “1” indicates a “dim” cell with low transgene expression (open arrow from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0039328#pone-0039328-g002" target="_blank">Figure 2</a>), and bins 6 through >10 indicated “bright” cells with high transgene expression (closed arrow from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0039328#pone-0039328-g002" target="_blank">Figure 2</a>); proportion of cells is on the y-axis. The left-skewed rTg(tau_wt) histogram (B) indicated that most Tau13-positive cells expressed human tau at low levels. In contrast, the bimodal rTg(tau_P301L) histogram indicated two distinct cell populations: one comparable to rTg(tau_wt) and one with higher transgene expression levels. TRE cell lines, TRE-tau_P301L in this experiment, expressed human tau at low levels; all cells fell in bins 1 and 2.