Fig. 2. Reduced thickness of the neuronal layers, but not the progenitor layers, in the Dicer-ablated E13.5 dorsal telencephalon. Comparison of the dorsal telencephalon of control (Emx1^Cre/wt Dicer^flox/wt) and conditional Dicer knockout (Dicer KO, Emx1^Cre/wt Dicer^flox/flox) littermate mouse embryos. (A-C) β III-tubulin (Tuj1) immunofluorescence confocal microscopy (3-µm single optical sections) of 10-µm coronal cryosections at E12.5 (A, top), E13.5 (B, top) and E14.5 (C); the E12.5 and E13.5 cryosections were co-stained with DAPI (A,B, bottom). Note the similar thickness of the neuronal layers in the control and Dicer KO cortex at E12.5 (A, arrowheads), the reduced thickness in the E13.5 Dicer KO cortex (B, arrowheads), and the absence of a recognizable structure of the neuronal layers (NL) in the E14.5 Dicer KO cortex (C). IZ, intermediate zone; SP, subplate; CP, cortical plate; MZ, marginal zone; Ec, ectoderm. (D) Tbr1 immunofluorescence microscopy of 10-µm coronal cryosections at E13.5. Dotted lines, basal boundary of SVZ; NL, neuronal layers; dashed lines, basal lamina. (E) Quantification of the area of the progenitor layers (VZ plus SVZ, black bars) and of the neuronal layers (NL, white bars), as indicated by the dashed white lines in D. Data are the mean of two embryos; for each embryo, the sum of the respective area of nine cryosections along the rostrocaudal axis (one field per cryosection) was calculated; bars indicate the variation of the two embryos from the mean. ^**P<0.01. (F) DAPI staining of 70 µm coronal Vibratome-prepared sections at E13.5. The length of the ventricular surface between the two arrowheads was quantitated (see G). (G) Quantification of the length of the surface of the lateral ventricle. Data are the mean of two embryos; for each embryo, the sum of the length of the ventricular surface in each of 12 consecutive sections along the rostrocaudal axis was calculated; bars indicate the variation of the two embryos from the mean. Asterisks (A-C,D,F) indicate the ventricular lumen. Scale bars: 500 µm in F; 200 µm in A,B; 100 µm in D; 50 µm in C.