Eye primordium transplantation in Xenopus embryo.

A part of the eye primordium, the presumptive retinal anlage, was transplanted from stage-23/24 Xenopus borealis to replace the removed olfactory anlage of Xenopus laevis. Cells of the two species can be distinguished under fluorescence microscopy, and we used the resulting chimeras to determine whether the transplanted eye primordium would inhibit the regeneration of the olfactory anlage, whether it would connect with its usual target, the diencephalon, and whether migration of cells would occur from the transplant to the host CNS or from the host CNS to the transplant. In all cases, the olfactory anlage regenerated promptly, and normal olfactory bulbs developed. Omission of the eye stalk in the transplant resulted in failure of an optic nerve to develop from the developing retina. A cellular bridge containing the optic axons connected the transplanted retina to the diencephalon. Cells from the transplant migrated freely through the cellular bridge to several CNS regions. Their morphology, topographic arrangement, number, and relations with other host elements are consistent with the hypothesis that these cells belong to both glia and neuron types.