Fig. 4. The optic nerves of ThyCreShh^n/c embryos are hypocellular and covered by a thick layer of melanotic cells. (A,B,F,G) RNA in situ hybridization for Ntn1 (A,F) and Pax2 (B,G) expression in sections through the eye and optic nerve of E16 wild-type (A,B) and ThyCreShh^n/c (F,G) embryos. Note the expression of Ntn1 and Pax2 (arrows in F,G) in only proximal optic stalks of ThyCreShh^n/c mice. Although RGC axons invaded the optic nerves of ThyCreShh^n/c mice, as evidenced by anti-neurofilament-3A10 immunostaining (compare C and H), neuroepithelial cells in the nerve failed to differentiate as glial cells, resulting in the hypocellularity of the optic nerves (compare D,E with I,J). (E,J) High magnifications of the boxed areas in D and I. Dashed lines (E,J) outline the optic nerves, and arrowheads (I) indicate nuclei of some cells in optic nerves of ThyCreShh^n/c mice.