| |
Fig. 4. Developmental expression of hoxa3. A: hoxa3 expression at stage 22 (A,B) and stage 24 (C,D) was restricted to the spinal cord with an anterior boundary of expression corresponding to rhombomere 5. hoxa3 was also expressed in the migrating NC cells. At stage 32 (E) and stage 34 (I), NC cells had colonized the third and fourth pharyngeal arches (IIIV) where they still expressed hoxa3. At this stage, hoxa3 was also detected in the pharyngeal endoderm epithelium of the arches, but was excluded from the mesoderm core. The level of the sections is indi- cated by a black line in F, J, N. At stage 41 (M), the primordium of the thymus emerging from the second pharyngeal pouch was surrounded by hoxa3-negative NC cells (arrows). For whole mount in situ hybridization, anterior to left, dorsal to top except for A, C, which are dorsal view. G, H, K, L are longitudinal sections, anterior towards the top. O, P are transverse sections, dorsal to top. ph, pharynx; pp, pharyngeal pouches; IIV, pharyngeal arches. In each panel, the stage is indicated in the lower left corner. The scale bars in (A, I, and M) 1⁄4 500 mm; (F, J, and N) 1⁄4 250 mm; (G, K, and O) 1⁄4 200 mm; (H, L, and P) 1⁄4 100 mm. |
