Fig. 2. Effects of RA signaling overexpression on eye DV polarity. (A) Low RA doses (0.1 µM) expand Pax2, Vax1b and Raldh3 expression domains, but do not significantly affect Vax2- and ET-positive regions in stage 33 Xenopus embryos. Pax2-hybridized embryos are also shown in frontal view (right column). (B) High RA doses (10 µM) upregulate Vax2 in the DR and repress Vent2, Pax2, Vax1b and Raldh3, but do not change Pax6 expression. (C) Schematic representation of the results shown in A and B. Low RA levels enlarge the OS. High RA levels ventralize the retina and repress OS formation.