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Fig. 4. Developmental expression of X-dll4, 3 and 2 by whole- mount in situ hybridization. In all panels apart from these on the top row, anterior is to the leftand dorsal to the top. A, C, E, G, H, K and M show the ontogenesis of X-dll3 while F, I, J, L and N show the ontogenesis of X-dll4. (A) Frontal view of X-dll3 expression at the open neural plate stage (stage 16). Staining is observed in the cement gland and the anterior transverse rim of the neural plate. (B) Frontal view of X-twi expression in the premigratory cranial neural crest at the same stage (stage 16). InA and B, arrows indicate the lateral limits of expression. Note that X-twi and X-dll3 expression is not overlapping and if superimposed would label most of the anterior and anterolateral rim of the neural plate. (C) Frontal view of a non-cleared embryo showing the external expression of X-dll3 a few stages later, after neural tube closure. Expression externally is detected in a band of cells, probably representing the olfactory placode (arrow) and the cement gland (cg). (D) Rear view of the same embryo as inC, showing expression of X-dll3 around the closed blastopore lip, the prospective proctodeum (arrowhead). (E,F) Side views of cleared tailbud stage (stage 25) Xenopus, showing expression of X-dll3 (E) and X-dll4 (F). (G,I) Higher magnification of E and F. X-dll3 is expressed in the prosencephalon, olfactory placode, otic vesicle and cement gland (E,G) and X-dll4 is expressed in what appears to be the same region of the prosencephalon and, in addition, in the branchial arches and cement gland (F,I). The A-P limits of expression in the prosencephalon are delimited by arrows. The contour of the brain has been traced by a dashed line inG but is also visible in I. (H) Expression of X-dll3 in the brain of a cleared stage 33 embryo. (J) expression of X-dll4 at the same stage. Note that, in addition to the sites of expression at stage 25, X-dll3 is now also expressed in the branchial arches (H) and X-dll4 is also expressed in the eye (J). (K,L) Whole cleared tadpoles showing that X-dll3 (K) and X-dll4 (L) are expressed in the forebrain and all of the branchial arches. (M,N) Higher magnifications of X-dll3 and X-dll4 expression respectivelyat the same stage as in K and L. In M, small arrows point to the telencephalic-diencephalic boundary. In M and N, arrowheads point to the dorsal limit of expression in the telencephalon and diencephalon. Note that expression in the tadpole brain appears more extensive relative to expression at the tailbud stage (compare M and N with G and I; see text for details). The asterisk inN indicates a staining artifact. Abbreviations: ba, branchial arches; bl, blastopore; cg, cement gland; di, dienecephalon; dt, dorsal telencephalon; e, eye; fb, forebrain; op, olfactory placode; os, optic stalk; ov, otic vesicle; vt, ventral telencephalon. |
