Fig. 6. Dorsal neural cell patterning is largely normal in netrin 1 mutant mice. Cellular patterning in the dorsal spinal cord demonstrated by Nissl staining (A,B) and in situ hybridization for Pax3 (C,D) and Lmx1b (E,F) on transverse sections from the E12.5 spinal cord. (G-K) BrdU labeling experiment. (A,C,E,G,I) Wild-type mice. (B,D,F,H,J) Netrin 1 mutant mice. (A) In wild-type mice, Nissl staining reveals a three-layered structure, and few cells are observed in the marginal zone (dorsal funiculus) which shows a sharp inner border (arrowheads). (B) In netrin 1 mutant mice, an ectopic small island is observed in the marginal zone (arrows in B,D,F), although a three-layered structure is formed. VZ, ventricular zone; ML, mantle layer; MZ, marginal zone. (C-F) Pax3 labels dorsal ventricular cells (C,D), and Lmx1b expression is found in cells in the dorsal mantle layer (E,F), both of which show few differences between wild-type and netrin 1 mutant mice. (G-J) The distribution of E10.5 (G,H) or E11.5 (I,J) BrdU-labeled cells in the E12.5 spinal cord. Many BrdU-labeled cells are observed in the dorsal mantle layer. (K) Quantification analysis of BrdU-labeled cells between the dorsal half and the ventral half of the dorsal spinal cord. Scale bar: 100 µm in A,B; 200 µm in C-J.