Wild-type cyclops gene function is required for anterior movement of ventral diencephalic precursors. (A-D) Dorsal views, anterior to the top. (E,F) Side views, anterior to the left, dorsal to the top. e, eye; mhb, mid-hindbrain boundary. (A,B) Single cells in corresponding regions of the neural plate of wild-type (A, arrowhead) and cyclops mutant embryos (B, arrowhead) were injected with rhodamine dextran. The first group of embryos (n=9 wild type; n=3 cyclops) was immediately fixed and labeled for mar expression by mRNA in situ hybridization. (C,D) The second group of embryos (n=7 wild type; 2 cyclops) was fixed 2 hours later and labeled for mar expression. (C) By this time the injected cell (arrowhead) had shifted anteriorly, and had stopped expressing mar in wild-type embryos. (D) In cyclops mutant embryos, the injected cell failed to move anteriorly and remained near the anterior border of the mar expression domain. (E,F) The third group (n=6 wild type; n=3 cyclops) was fixed 4 hours after injection. These embryos were labeled (black) to detect the expression of pax2 in the prospective optic stalk region, emx1 in the prospective telencephalon, eng3 in the prospective midbrain hindbrain border and krx20 in the prospective hindbrain. In wild-type embryos (E), the injected cell (red, arrowhead) was found anterior and ventral to the eye primordia. The ventral diencephalon had formed. (F) In cyclops mutants, the injected cell failed to move forward and remained posterior to the eye (arrowhead). cyclops mutants lacked ventral diencephalon. Scale bar, 200 μm.
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