Zebrafish islr2 mutants do not display widespread axon guidance defects and are morphologically normal. a Acetylated tubulin staining of 24 hpf embryos showing central axon tracts at the level of the medial longitudinal fasciculus (MLF). Thinner axon bundles were observed only in a subset of islr2 mutant animals. The general spacing and directionality of nerve fibers was unaltered compared to controls, indicating absence of guidance defects in these axons. Maximum intensity projections of confocal Z-stacks. Dorsal views. Anterior is to the left. Scale bar: 50 μm. b Transverse sections through the retina of 5 dpf islr2 mutants. Normal size, gross anatomy and layering of the retina were observed in islr2 mutants. RGC number may be decreased in some islr2−/− larvae. L: lens. GCL: ganglion cell layer. IPL: inner plexiform layer. INL: inner nuclear layer. ONL: outer nuclear layer. RPE: retinal pigmented epithelium. ON: optic nerve. Scale bar: 50 μm. c Transverse sections at the level of the optic chiasm in islr2 mutants and siblings. The chiasmatic and ventral diencephalic tissue appears normal in size and patterning, suggesting that the axon guidance phenotype of islr2 larvae does not originate from mispatterning effects. OC: optic chiasm. Scale bar: 100 μm
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