Based on expansion of Wnt8b expression in the Foxg1−/− OS at E10.5 (Fig. 3) and the previously described repressor activity of foxg1 on wnt8b in the zebrafish telencephalon (Danesin et al., 2009), we hypothesized that upregulated Wnt8b expression in the OS causes coloboma in the Foxg1−/− mutant. The gene discussed is FOXG1; the disease is coloboma.