Figure 6

Alterations to RGC axon trajectories within the PAX77^+/+ retina at E16.5. (A-F) Wild-type (G-L) PAX77^+/+: panels show flatmounted retinae in which retinal axons are detected using (A,B,G.H) L1 immunostaining, (C,I) neurofilament immunostaining, or (D-F, J-L) DiI labelling following focal injection of DiI into the peripheral retina. In wild-type embryos retinal axons grow directly towards the optic nerve head in the centre of the retina. In PAX77^+/+ embryos, although this radial organisation is grossly preserved, the retinal axons take a more erratic route. (B,C) In the wild-type axon bundles are uniformly spaced and appear parallel when viewed at high magnification. (D,E) DiI focal injections label cohorts of axons which grow straight towards the optic nerve head (demarcated by dotted circle in E,K). In contrast in PAX77^+/+ embryos axon bundles are less evenly distributed and avoid some parts of the retina altogether (arrows in H,I,K). (F,L) Higher magnification of DiI labelled axons in the retina showing individual axons. (F) In the wild-type these run parallel to one another but (L) in the PAX77^+/+ retina they do not. Scale bars: (A,D,E,G,J,K), 100 μm; (B,C,F,H,I,L), 50 μm.