Figure 5

Quantification of neuronal number in specific cortical populations, apoptosis and cell density during development in C57Bl/6 and BTBR mice. Coronal sections of P7 C57Bl/6 and BTBR brains were processed for immunohistochemistry using anti-Satb2, anti-Ctip2 and anti-Tbr1 antibodies to label neurons in different cortical layers. Satb2 is highly expressed in layers 2/3 and less highly expressed in deep layers; Ctip2 is highly expressed in neurons in layer 5 and weakly expressed in layer 6, and Tbr1 is highly expressed in layer 6 (A, C). The expression patterns of Ctip2, Tbr1 and Satb2 are indistinguishable in both S1 and V1 between mouse strains, indicating normal cortical neuronal distribution and normal cortical lamination in BTBR mice. This was confirmed by analysis of the number of labelled cells per 500 μm of cortex, which was found to be unchanged between strains in both S1 and V1 (B, D). Caspase3 staining revealed that the degree of apoptotic cell death (quantified by number of labelled cells, green, in a 500-μm segment of DAPI-stained (purple) V1 cortex) was not significantly different between strains at this age (E, F). The density of DAPI-stained cells per 1 mm² of cortex was found to be no different between C57Bl/6 and BTBR mice in S1 (G) and V1 (H). n = 7 animals for each strain and condition. Scale bar = 100 μm for (A), (C) and (E); 20 μm for (E) insert. Ctip2 = chicken ovalbumin upstream promoter transcription factor-interacting proteins 2, Tbr1 = T-box brain gene 1, Satb2 = special AT-rich sequence-binding protein 2, BTBR = BTBR T + tf/J, DAPI = 4′,6-diamidino-2-phenylindole, dihydrochloride, n.s. = not significant.