ABC Transporters in Neurogenesis Figure 3. ABC transporter-deficiency did not lead to impairments of neuronal differentiation in vitro. ABCG20/0 cells showed a significant increase in proliferation capacity (+62%, A) quantified by detection of BrdU uptake using immunofluorescence (B). The differentiation capacity was not impaired by loss of ABC expression (C) as revealed by quantification of neuronal cells positive for Tuj1 (D). Error bar: SEM; Scale bar: 50 mm. doi:10.1371/journal.pone.0035613.g003 in altered cortical architecture, we determined the thickness of the cortical layers I-VI. The NeuN-stained paraffin slices were measured according to Manuel and colleagues [42] for layer thickness (Figure 7A). By comparing the proportional size of layer I, II–IV (combined), V and VI, we found significant effects of deficient ABC transporter expression on cortical architecture in ABCB10/0 and ABCC10/0 strains. The loss of ABCB1 resulted in a decreased size (212%) of layer I (Figure 7C), while all other layers were unaffected. The other significant effect showed ABCC10/0 mice where only the size of layer VI was increased by 15% (Figure 7C). ABCG20/0 animals showed no significant alterations in the cortical architecture. Layers I and VI represent the least cellular layers of the cortex with mostly interconnecting dendrites and axons. ABC transporter-deficiency influences activity and anxiety levels Because the hippocampus functions as a main interface between different cortical inputs and is important for memory consolida- tion, we wanted to determine whether the absence of specific ABC transporters results in behavioral changes. To assess potential alterations in overall activity, exploratory behavior, or the level of anxiety, we used Y- and elevated plus mazes as well as the light/ dark box setup [43,44,45,46]. First, the animals were analyzed for Figure 4. Expression of ABCB1b and ABCG2 are co-regulated in NSPCs in vitro. Relative mRNA expression of ABCB1b, ABCG2 and ABCC1 was measured against mRNA expression of GAPDH using TaqManH assays. Expression of ABCB1b was significantly impaired (228%) in ABCG20/0 cells (A). In reverse, expression of ABCG2 was increased significantly (+71%) in animals lacking ABCB1 expression, while a comparable effect on ABCC10/ 0 cells did not reach statistical significance (B). For ABCC1 mRNA expression, no significant changes were observed in the other cell lines (C). Error bar: SEM; * p,0.05; **p,0.01. doi:10.1371/journal.pone.0035613.g004 PLoS ONE | www.plosone.org 5 April 2012 | Volume 7 | Issue 4 | e35613