Fig. 1.

DCC and netrin expression in the E12 mouse hypothalamus. The schematicdiagrams on the left show the eyes, optic nerves, and ventral hypothalamus. The redrectangle indicates the anterior–posterior hypothalamic level at which tissue sections were obtained for netrin (middle) and DCC (right) immunostaining. Tissue sections separated by 20–30 μm were used for netrin and DCC immunostaining at each level. In all panels, dorsal is at the top.a–f, Netrin (arrowheads) was found in bilateral patches at different sites along the anterior–posterior length of the hypothalamus. a, Netrin expression at the ventral medial septal and diagonal band region is shown. Thearea of the dottedrectangle is shown at higher magnification in theinset at the topright. Staining in blood cells and vessels is nonspecific. b,Note the absence of netrin at the ventral midline region. c, d, Netrin is expressed at the ventral–lateral hypothalamic regions corresponding approximately to where axons of chiasm neurons (see Fig. 2) grow dorsally to join the TPOC and where the initial portions of the optic tract will later develop. There is no apparent ventral midline netrin expression. e, Netrin expression in the ventricular zone is shown. The area of thedottedrectangle is shown at higher magnification in the inset at the topright. Such bilateral patches of netrin were found in the ventricular zone region scattered throughout the anterior–posterior length of the hypothalamus. f,Netrin expression in the presumptive lateral posterior ME region is shown. g–l, DCC expression at different levels along the anterior–posterior length of the hypothalamus is shown. DCC was found in specific domains distributed throughout the hypothalamus but was absent from the ventricular zones. D, Dorsal;DB, diagonal band; ME, median eminence;MS, medial septum; OC, future chiasm region; OT, future region of the optic tract;POA, preoptic area. Scale bar, 200 μm.