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Fig. 9 Accumulation of pax2-positive cells in six3 mRNA-injected embryos. pax2 expression in globin (A,C,E,G) or six3 (B,D,F,H) mRNA-injected embryos was analyzed at the 10-somite stage (A,B) or at 24 hours (C-H). (A,B) pax2 mRNA-expressing cells in the anlage of the optic vesicles are increased in six3 mRNA-injected embryos, while expression at the prospective midbrain-hindbrain boundary and at the otic placode is unchanged. (C,D) In control embryos pax2-positive optic stalk cells (arrow) are located in the ventral diencephalon, while these cells are located more dorsally in six3 mRNA-injected embryos. (E,F) In the eye, the pax2-positive region at the choroid fissure, i.e., the base of the optic stalk (arrow), is enlarged in six3 mRNA-injected embryos. Since the lens is unaffected, a gap arose between lens and retina (thin arrow). (G,H) Oblique ventral-lateral views of the optic stalk and eyes show that the base of optic stalk is substantially enlarged in six3 mRNA injected embryos. Schematic views show six3 expression as blue areas. Circles drawn in solid and dotted lines indicate the proximal and distal eyes, respectively. Scale bars, 100 μm. Additional abbreviations: l′, lens in the distal eye; mh, midbrain-hindbrain boundary; r′, retina in the distal eye.