Figure S1. Zic2 Is Necessary for Ventrotemproal (VT) RGCs to Respond Negatively to Cues from the Chiasm Midline In Vitro. (A) Retinal explants grown on dissociated chiasm cells and immunostained with α-neurofilament. Representative images of dorsotemporal (DT) (a–d) and VT (e–h) retinal explants that were untransfected (a and e) or incubated with lipofectamine (b and f), Zic2 decoy oligos (c and g), or Zic2-mutant-decoy oligos (d and h) and subsequently cocultured with dissociated chiasm cells. Scale bar: 100 μm. (B) Quantification of area occupied by axons of DT (black columns) or VT (white columns) retinal explants that were untransfected or incubated with lipofectamine, Zic2-decoy oligos, or mutant-Zic2-decoy oligos, and then cocultured with dissociated chiasm cells. Left panels and graph: transfection of Zic2-decoy oligos does not affect the outgrowth in DT neurites (p > 0.2). Right panels and graph: transfection of Zic2-decoy oligos leads to increased growth of VT neurites. (*p < 0.05 compared with VT explants incubated with the lipofection agent alone or transfected with Zic2M-decoy). Number above bars indicates number of explants.

Experimental Procedures for Supplemental Figure: Double-stranded Zic2 and Zic2 mutant decoy DNA were prepared by annealing complementary single strands with the follow sequences: 5′-TCTTGGGTGGTCTCCGGAGACCACCCAAGA (for Zic2 decoy) and 5′-TCTTGAGTGAACTCCGGAGTTCACTCAAGA (for Zic2M decoy) as a negative control (Mizugishi et al., 2001). We utilized unlabeled and also Texas-red-tagged oligonucleotides (Invitrogen) to monitor DNA entry into cells. The terminal four bases on either site of the molecule were linked by phosphorothioate esters for added stability. Retinal explants were exposed to serial concentrations (0, 10, 100, and 200 μM) of decoy DNA combined with serial concentrations of serum-free medium (SFM) plus Fungene 6 transfection reagent (Roche) and incubated for 1 hr 30 min at 37°C. The explants were then washed several times in SFM, plated on D-polylysine/laminin, and incubated at 37°C, and dissociated chiasm cells were added to the cultures 2 hr later. They were then immunolabeled with α-neurofilament and explant outgrowth quantified, as indicated in Experimental Procedures.

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