Fig. 1. Expression of Hoxb1 and Hoxb2 in the developing mouse hindbrain. (A-C) Ventricular views of flat-mounted wild-type mouse hindbrains stained with a Hoxb1 riboprobe at 10.5 dpc (A), 11.5 dpc (B) and 12.5 dpc (C). (D-H) Ventricular views of flat-mounted wild-type mouse hindbrains stained with a Hoxb2 riboprobe at 10.5 dpc (E), 11.5 dpc (F), 12.5 dpc (G), 13.5 dpc (H) and 14.5 dpc (D). (A-C) Between 10.5 dpc and 12.5 dpc, expression of Hoxb1 was restricted to rhombomere 4. It was upregulated in ventral and dorsal columns (black arrows). At 11.5 dpc (B), the ventral expression domain was further subdivided into two adjacent stripes. At 12.5 dpc (C), Hoxb1 expression was generally downregulated, but remained stronger in the ventral and dorsal columns. (D-H) Between 10.5 and 14.5 dpc, expression of Hoxb2 resolved into a series of longitudinal stripes that persisted longer than that of Hoxb1. At 10.5 dpc, Hoxb2 expression was stronger in the r4, r5 and r6 territories, where it was upregulated in specific ventral and dorsal columns (black arrows, E) that persisted to 11.5 dpc (black arrows, F). At 11.5 dpc (F), expression in the ventral domain resolved into two adjacent stripes similar to those of Hoxb1. At 12.5 dpc (G), Hoxb2 expression was absent in a ventral territory corresponding to the path of facial branchial motoneuron (fbm) migration (white arrows). From 13.5 dpc, expression was downregulated throughout the hindbrain (H), whereas at 14.5 dpc (D), expression was upregulated in a region close to the final position of the facial motor nucleus (black arrows).