Fig. 2. In Foxd1 (BF-2 in figure) deficient embryos, RGCs that project ipsilaterally arise from the entire retina, rather than exclusively from the ventrotemporal quadrant. (A) Schematic indicates that after retrograde labeling from one optic tract at E17.5, RGCs in Foxd1^+/+ embryos are labeled over the entire contralateral retina (left), whereas in the ipsilateral eye, RGCs are labeled only in the peripheral ventrotemporal retina (right). (B) Wholemounts of retina after retrograde labeling from the contralateral optic tract at E17.5. (a) In Foxd1^+/+ retina, contralateral-projecting RGCs come from all retinal quadrants except the VT crescent. (b) In Foxd1 deficient retina contralateral RGCs also arise from all the quadrants, including the VT crescent (asterisks). Overall, there are fewer contralateral labeled cells in Foxd1^lacZ/lacZ retina than in Foxd1^+/+ retina, probably because many axons stall at the optic chiasm. (C) Retinal wholemounts after retrograde labeling from the ipsilateral optic tract at E17.5. In Foxd1 deficient embryos (b), RGCs that project ipsilaterally arise from all retinal quadrants, not only from the VT crescent (a). Red lines in the contralateral retina delimit the VT crescent, where contralateral RGCs are not found in wild-type retina. Red lines in the ipsilateral retina mark the VT crescent, where ipisilateral RGCs are located. Note that both sectors are not equivalent in size; this is because at E17.5, when the backfill labeling is performed, both populations (ipsi- and contralaterally-projecting RGCs) partially intermingle, and the boundary segregating both populations is more peripheral at this time than at E14.5-E16.5. Scale bar: 500 µm.