Fig. 8. Retinoic acid treatment between 24 and 33 hpf does not affect the anterioposterior pattern of the hindbrain. (A-H) Analysis of the hoxa2, hoxb2, hoxb3 and hoxd3 expression patterns did not reveal any changes in anterioposterior patterning of the hindbrain when embryos were exposed to RA between 24 and 33 hpf. (I,J) In situ hybridization for epha4 expression did not reveal any anterioposterior shifts in the hindbrain rhombomere pattern of 33hpf embryos after RA treatment. (K,L) At 48 hpf, embryos treated with retinoic acid show a loss of the lateral expression domains of epha4 in rhombomere 3 and 5. cont, control embryos exposed to DMSO; r, rhombomere; RA, retinoic acid. (A-L) Dorsal views of flat-mount preparations, anterior towards the left.