Fig. 3

lmx1b.1, lmx1b.2, wnt1 and pax2.1 are expressed in overlapping domains at the isthmus. (A) Dorsal view, with anterior leftwards. At the one-somite stage, lmx1b.1 is expressed in the midline and in the precursors of the MMR and the otic placodes. At the presumptive IsO, pax 2.1 expression completely overlaps with lmx1b.1 expression and the pax2.1 domain is slightly broader. (B-G) Lateral views, with dorsal upwards and anterior leftwards. (B,C) At the 13-somite stage, pax2.1 expression at the IsO overlaps the expression of lmx1b.1 (B) and lmx1b.2 (C), and extends posteriorly. (D-F) At 24 hpf, the expression domains of lmx1b.1 (D), lmx1b.2 (E) and wnt1 (F) are found in the posterior mesencephalic vesicle, abutting the metencephalic vesicle. (G,H)At 24 hpf, pax2.1 expression overlaps both wnt1 (G) and lmx1b.1 (H, dorsolateral view), and extends more posteriorly. Red arrowheads indicate the MMR.