XB-ART-3438Dev Dyn July 1, 2004; 230 (3): 461-7.
Independent induction and formation of the dorsal and ventral fins in Xenopus laevis.
It has been known since the 1930s that the dorsal fin is induced by the underlying neural crest. The inducer of the ventral fin, however, has remained elusive. We have investigated the source of the inducer of the ventral fin in Xenopus and show that it is the ventral mesoderm and not the neural crest. This induction takes place during mid-neurula stages and is completed by late neurulation. In terms of cell composition, the dorsal fin mesenchyme core arises from neural crest cells, while the mesenchyme of the ventral fin has a dual origin. The ventral fin contains neural crest cells that migrate in from the dorsal side of the embryo, but a contribution is also made by cells from the ventral mesoderm.
PubMed ID: 15188431
Article link: Dev Dyn
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|Fig. 1. Diagram representing the stages of fin induction and formation. A: Stage 25. B: Stage 28. C: Stage 31. D: Stage 32.|
|Fig. 2. Role of the neural crest. A: Schematic of neurula embryo stage 13. Dorsal and side view. Red areas represent the posterior neural crest ablated in C. Green areas represent the posterior dorsal fin epidermis ablated in D. Blue areas represent the ventral region. Pink areas represent the lateral region. B: Control embryo stage 41. C: Ablation of the posterior neural crest at stage 13. Embryo cultured to stage 41. Embryo shows loss of the dorsal fin from arrow, except at the very tip. The ventral fin remains unaffected. D: Ablation of the dorsal fin epidermis at stage 13. Embryos cultured to stage 41. No fin defect is observed. n 35 for C, n 30 for D.|
|Fig. 3. Explant cocultures. A: Uninduced epidermis from alongside the neural folds and under the blastopore, extirpated at stage 13 and cultured until controls reached stage 40. See green and blue areas in Figure 2A. B: Lateral, ventral, and dorsal epidermis cocultured as a sandwich with neural folds. See green, blue, and pink areas, plus red area, in Figure 2A. Note the ruffles of fin induced around the explant. C: Lateral, ventral, and dorsal epidermis cocultured with lateral mesoderm and endoderm. See green, blue, and pink areas, plus underlying pink area in Figure 2A. No fin induction is observed. D: Fluorescein dextran amineabeled non-fin epidermis grafted at stage 20 above the posterior neural tube and incorporated into the development of a normal dorsal fin by stage 40. Fin is outlined by dashed white line. E,F: Ventral tissue explanted at stage 13 and cultured until controls reached stage 40. See blue area in Figure 2A. Arrow in E points to fin-like structures. n 20 for A and B, n 30 for C and E.|
|Fig. 4. Location of the ventral fin inducer. A: Stage 41 embryos. A,C,E,G,I,K,M,O: Side views of fins. B,D,F,H,J,L,N,P: Frontal sections through developing tails. A,B: Operations carried out at stage 13. C,M: Operations carried out at stage 15. K,L: Operations carried out at stage 20. A,B: Square of tissue ventral to blastopore was ablated, resulting in reduction of the ventral fin. C,D: Similar ablation at stage 15, resulting in complete loss of the ventral fin. E,F: Similar-sized piece of lateral tissue ablated. No effect on fin development. G,H: Ventral epidermis only ablated, resulting in no fin defect. I,J: Ventral mesoderm and endoderm ablated, resulting in defects in the ventral fin. K,L: Ventral mesoderm and endoderm ablated at late neurula stage, showing only limited defect in the ventral fin. M,N: Ventral endoderm alone ablated, resulting in no ventral fin defect. O,P: Ventral mesoderm alone ablated, resulting in ventral fin defects. N 300 for each extirpation.|
|Fig. 5. Orthotopic grafting of fluorescein dextran amineabeled ventral tissue at stage 13. Embryos grown to stage 41. A: Schematic of stage 41 tail. B: Ventral endoderm only labeled. Label is restricted to the ventral site near the proctodaeum. C: Ventral epidermis only labeled. Label found throughout ventral fin epithelium. D: Ventral mesoderm and epidermis labeled. Label is seen in the fin epithelium (as in C). In addition, label was observed in the ventral somites and in cells within the fin core, see arrows. Fin is outlined by dashed white line. n 15 for each.|