FIG. 6.

The anterior commissure is absent in Trio-null embryos. (A) Neuropilin 2 (Nrp2) immunostaining on horizontal serial brain sections from E17 +/+ (a), +/− (b), or −/− (c) embryos (n = 6 for +/+ and −/− embryos; n = 4 for +/− embryos). In the heterozygous embryos, the anterior branch of the commissure (AC) is defasciculated, which is illustrated by several roots exiting the cortex at lateral positions (arrows in frame b). In the Trio-null embryos, the commissure is absent (c). Scale bar, 80 μm. (B) Eosin staining on coronal brain sections from E17 +/− (a, b, and c) and −/− (d, e, and f) embryos. Defasciculated fibers are present in the heterozygous embryos (b, white arrows), whereas they are absent in the Trio-null embryos (e). In more posterior sections, anterior commissural fibers are detected in the heterozygous (c, black arrows) but not in Trio-null brains (f). Scale bar, 300 μm.