Figure 1.

Characterization of Retino-retinal Cells in Mice

(A) Labeled axons from embryos monocularly electroporated with EGFP-encoding plasmids at E13.5 were analyzed at E16.5 or E18.5.

(B–D) At E16.5, EGFP-labeled axons are present within the contralateral optic nerve (cON) (arrowheads, B) and by E18.5 have reached the contralateral optic disc (asterisk, C and D).

(E) Targeted cells (green dots) in retinas electroporated at E13.5 (white flat-mounted retinas) and tracings of EGFP-labeled axons in the contralateral retina (gray flat-mounted retinas) at E18.5–P4.

(F) Mean (± SEM) number of R-R axons in E18.5–P4 retinas after electroporation of the opposite eye at E13.5. These numbers do not represent the total number of R-R neurons, as not all cells are targeted by electroporation.

(G) Diagram of a P2 retina containing R-R axons labeled from the opposite eye. (G’–G’’’) Image of boxed area in (G) showing an EGFP R-R axon and starburst amacrine cells labeled with ChAT antibodies.

(H) 3D reconstruction of z-projection with a z-step of 1.5 μm captured from boxed region in (G) showing ChAT⁺ cells embracing the axon terminal (red arrows).

(I) Middle: diagram of monocular injection of CTB. Left: retinal sections of injected P3 and P30 mice injected with CTB 2 days earlier are shown. Right: retinal sections of contralateral retinas from same animals are shown. Note two retrogradely labeled cells in the RGC layer at P3.

(J) Top: diagrams of whole-mount retinas retrogradely labeled with CTB at P3, P5, or P30. Boxed region of P3 retina shows retrogradely labeled cells (red) combined with antibody staining for Brn3a or Islet1/2 (green). Graph shows mean (± SEM) number of labeled cells/retina quadrant. At perinatal stages, most CTB-positive cells are in the ventral quadrants (ventronasal [VN] and ventrotemporal [VT]). At P30, no CTB cells were found.

(K) CTB-488 (green) and CTB-647 (red) were injected in the retina and the ipsilateral superior colliculus (SC), respectively, of newborn mice. The opposite whole-mounted retina was analyzed 2 days later. Right: images from the boxed area show a representative CTB-488 cell negative for CTB-647.

Error bars indicate ± SEM.

See also Figure S1.