Meis1-depleted embryos exhibit a partial temporal-to-nasal shift in retinal identity. (A, B, F, G) mRNA in situ hybridization (ISH) for the nasal marker foxg1a (A, B) and the temporal marker foxd1 (F, G) in 15-hpf wild-type and meis1 morphant (meis1MO) embryos. Dotted lines outline the optic vesicle. The black brackets in (A, B) indicate the proximal-distal extent of foxg1a expression, while the red brackets indicate the foxg1a-free region. Arrows in (F, G) indicate the dorsal leaflet of the optic vesicle. Transverse sections are oriented dorsal up. (C, D, H, I) mRNA ISH for the nasal marker foxg1a (C, D) and the temporal marker foxd1 (H, I) in dissected, flat-mounted eyes from 28-hpf wild-type and meis1 morphant embryos. The arrows indicate the approximate limit of the gene expression domain. (E, J) The domains of gene expression were quantified by determining a 360° profile of in situ staining intensity and graphing the radial position at which gene expression intensity falls to the halfway point between its minimum and maximum values. The nmax/2 and tmax/2 values are given as the mean radial position in degrees ± one standard deviation. Asterisks indicate regions in which there are statistically significant differences in axial identity between wild type and meis1 morphants as determined by an unpaired, two-tailed t-test using a P-value of 0.01 as a cutoff for significance. Representative dissected eyes are shown. Scale bars = 50 μm.
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