Fig. 8. Misrouting at the optic nerve head under NrCAM inhibition. Two typical examples of E4.5 eyes organ-cultured in presence of non-specific F(ab) fragments (A,B) and two in presence of NrCAM F(ab) fragments (C,D). Inset in A shows three DiO crystals placed on a retina flat-mount, which label groups of RGC axons. Dashed line indicates the position of the optic fissure (OF); arrow indicates the optic nerve head. The majority of axons had already reached the OF and dived into the optic nerve head before the inhibition treatment. (A,B) Under control conditions, all RGC axons grow towards the OF, enter the OF, and leave the retina at the optic nerve head. (C,D) In presence of NrCAM F(ab) fragments, axons fail to enter the optic nerve; they stray away from the pre-existing axons (which leave the retina) and extend onto the opposite side of the retina towards the periphery. Scale bars: (A-D) 50 µm; (inset) 500 µm.