alx1 and alx3 functions are dispensable for retinal ganglion cell differentiation and retinal function in zebrafish larvae. Embryos derived from wildtype or alx1;alx3/+ incrosses were fixed at 2 dpf and stained with zn5, a retinal ganglion cell (RGC) marker, and DAPI, a nuclear co-stain (A-H). (A,B) A representative wildtype eye shows strong zn5-labeled RGCs and a characteristic layered nuclear organization (of four embryos). (C,D) Normal RGC and nuclear patterns in an alx1 mutant (of two embryos). (E,F) Normal RGC and nuclear patterns in a representative alx1;alx3/+ retina (of four embryos). (G,H) Normal RGC and nuclear patterns in a representative alx1;alx3 retina (of two embryos). Left eyes are shown in lateral views, anterior to the left. Scale bar, 25 µm. (I) Diagram summarizing the dark flash assay, with a lights-off stimulus eliciting O-bend turn responses in 5 dpf larval zebrafish. (J) Mean frequency of O-bend initiations to a series of 10 dark flash stimuli was measured in larvae derived from wildtype or alx1;alx3/+ crosses, and larvae were genotyped post-hoc. n.s.: P>0.9999 versus wildtype control; ****P<0.0001 versus wildtype control. ANOVA with Kruskal–Wallis test. Error bars indicate s.e.m.
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