Figure 5. Targets of GFP-positive RGCs in the brain of SPIG1^gfp/+ mice.

A, Coronal section showing that the MTN begins to be innervated by the GFP-positive fibers at E17.5. B, Schematic drawing of the injection of CTB into the eye. All RGC axons from an eye had been labeled anterogradely by CTB-Alexa 555 one day before the mice were killed at P1 (C) or at P10 (D–K). Except for (H–J), only the contralateral side is shown. C, MTN projection at P1. MTN is already innervated by the GFP-positive retinal fibers extensively. D, MTN projection at P10. The middle and right panels in (D) are enlargements of the dorsal region of the MTN boxed in the left panel. E, Coronal section at the level of the caudal LGN and pretectum. F, Enlargements of the LGN boxed in (E). GFP-positive RGC fibers predominantly innervate the ventro-medial part of the dLGN and are absent from the vLGN and the IGL. Inset is the enlargement of the boxed region in the vLGN, showing that intrinsic GFP-positive neurons are sparsely distributed in this region. G, Enlargements of the OPN boxed in (E). Inset is the enlargement of the boxed region, showing that a small number of GFP-positive RGC fibers innervate the ventromedial part of the OPN. H, Projection to the SC. GFP-positive RGC fibers predominantly innervate the lateral part of the SC. I, Coronal section just posterior to the optic chiasm. The right panel in (I) is the enlargement of the SCN boxed in the left panel, showing that the retinal axon projection to the SCN is devoid of axonal GFP. J, MTN projection in mice enucleated unilaterally at P2, injected with CTB into the remaining eye at P9, and killed at P10. GFP axons contralateral to the enucleated eye selectively disappeared (arrowheads). K, Enlargements of the dorsal region boxed in (J) of the MTN contralateral to the enucleated eye. A small number of GFP-positive RGC fibers remain after enucleation. MTN, medial terminal nucleus; SC, superior colliculus; LGN, lateral geniculate nucleus; dLGN, dorsal LGN; vLGN, ventral LGN; IGL, intergeniculate leaflet; OPN, olivary pretectal nucleus; SCN, suprachiasmatic nucleus. Scale bars: 50 µm (A, D, K); 200 µm (C, F–J).