Fig. 2

Distribution of DSCAM in the optic nerve and chiasm along the posterior-to-anterior axis of stage 45/46 Xenopus tadpoles. a High magnification horizontal section at the level of the optic nerve shows differential distribution of DSCAM immunoreactivity (red) along retinal axon fibers. A gradual distribution of DSCAM immunoreactive fibers is observed from posterior to anterior while most 3A10 immunopositive fibers localize more anteriorly. White arrows identify a subset of axon fibers within the optic nerve that are immunopositive for both DSCAM and 3A10. b Horizontal section at the level of the optic chiasm imaged by confocal microscopy (stitched tiled scan) shows DSCAM immunoreactivity in fibers that organize caudally (posterior; empty white arrowhead) to most 3A10 immunopositive fibers. c, d Fluorescence intensity of DSCAM (red) and 3A10 (green) immunoreactivity was measured using a 3.5 μm ROI at six positions along the posterior to anterior axis tool as for Fig. 1, with five sets of measurements made at distinct locations along the optic nerve or optic chiasm (n = 4 tadpoles, with at least two tissue sections per tadpole). For each tissue sample, fluorescence intensity was normalized to the mean fluorescence intensity for each channel and is shown as percent of the mean with the x-axis designating the optic nerve or optic chiasm from the posterior to anterior regions. c A high-posterior to low-anterior distribution of DSCAM fluorescent signal is found along the width of the optic nerve, while 3A10 fluorescent signal is higher in the anterior portion of the optic nerve (difference for Distance p = 0.008; Distance x Fluorescent Channel p ≤ 0.0001; two-way ANOVA). d DSCAM and 3A10 fluorescence showed high-posterior to low-anterior DSCAM immunoreactivity within the optic chiasm, while 3A10 immunofluorescent signal was low posterior and increased anteriorly (difference for Distance p = 0.002; Distance x Fluorescent Channel p ≤ 0.0001; two-way ANOVA). Scale bars: 10 μm for a; 50 μm c