Fig. 7. pac mutants exhibit severe coloboma. (A,B) Lateral views of 4 dpf wild-type (A) and pac^fr7 (B) heads. The choroid fissure does not close (red arrowheads) in pac^fr7. (C,D) High magnification of the optic nerve exit point/choroid fissure in 4 dpf wild-type (C) and pac^fr7 (D). Retinal cells spill out of the open fissure (D, red arrowheads) and spread to the diencephalon in pac^fr7. (E-J) pax2.1 labeling of optic stalks in wild-type and pac mutants. (E,F) Dorsal views of 19.5 hpf embryos showing pax2.1 (blue) and pax6 expression (red). Broader expression of pax2.1 in the optic vesicles of the pac mutant is indicated (arrows/lines) (G,H) Lateral views of 24 hpf optic cups showing expanded pax2.1 expression in the ventral retina of the pac mutant. (I,J) Ventral view of 48 hpf heads. pax2.1 expression is present in prospective astrocytes of the optic nerve. Additionally in the pac mutant, pax2.1-expressing cells are present in the ventronasal and ventrotemporal retina and spread from the optic nerves into the brain (arrowheads). (K) Lateral views of the choroid fissure in wild-type and pac^fr7 eyes. Light blue indicates the neural retina and dark blue shows pax2.1⁺ prospective astrocytes. a, amacrine cell layer; b, bipolar cell layer; di, diencephalon; r.ax, retinal axon; pl, photoreceptor layer.

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