XB-IMG-151493
Xenbase Image ID: 151493
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Fig. 1. Summary of lens induction and cornea-lens transdifferentia- tion. (A) During the early phase of lens induction (gastrula and neural plate stages 11.5–14), inductive signals (dashed arrows) originating from the neural plate act in a planar fashion, and from the underlying mesoderm and endoderm, in a vertical manner, on the presumptive lens ectoderm. (B) During the late phase of lens induction the optic vesicle contacts the head ectoderm and further signals from the optic cup act on the lens ectoderm to pinpoint the site of lens formation (beginning at stage 19). (C and D) The developing lens grows into the cavity that forms in the optic vesicle. (E) The lens eventually detaches from the overlying head ectoderm and continues to undergo differentiation in the optic cup. The inner cornea is derived from migrating neural crest cells while the outer cornea is derived from the remaining head ectoderm overlying the eyecup. (F) The cornea of a premetamorphosed tadpole has the ability to undergo transdifferentiation to form a new lens if the original lens is removed during larval stages. (G) Signals from the neural retina (dashed arrow) act on the inner layer of the outer cornea where the new lens initially forms (H). (I) This tissue ultimately develops into a fully differenti- ated lens, which resides in the optic cup. All stages follow those of Nieuwkoop and Faber (1956).
Image published in: Schaefer JJ et al. (1999) Copyright © 1999. Image reproduced with permission of the Publisher, John Wiley & Sons. Larger Image Printer Friendly View |