Fig. 8

The effect of irx1a knockdown on shh-GFP expression is both cell-autonomous and non-cell-autonomous. Lateral view of 48 hpf retina. Ventral to the bottom, anterior to the left. Blastomere transplantations were carried out to determine the cell-autonomy of the effects of irx1a knockdown. The donor embryos, which carry the shh-GFP transgene, were labeled with rhodamine-dextran. Donor cells were transplanted into wild-type shh-GFP hosts at blastula stages. The shh-GFP expression in retinas with transplanted irx1a-MO cells was severely reduced (D–I), while control-MO injected donor cells had no effect on shh-GFP expression (A–C). Transplanted cells failed to express the shh-GFP transgene in all cases (red stain panels D–F) suggesting a cell-autonomous requirement of irx1a. However, shh-GFP expression was also reduced in areas that were not occupied by irx1a-MO containing cells. Host retinas with large irx1a-MO clones (G–I) lacked almost entirely GFP expression in areas derived from host cells. These results indicate an additional non-cell-autonomous effect of irx1a knockdown. A microphthalmia phenotype was also observed in the irx1a-MO transplanted hosts with large clones of irx1a-MO cells.