Retinal ganglion cell death and regeneration of abnormal retinotectal projections after removal of a segment of optic nerve in Xenopus tadpoles

Totally or partially disorganized visuotectal projections have been reported to develop following surgical manipulations in embryonic and larval Anura. Here it is shown that these are associated with a thin optic nerve arising from a retinal ganglion cell layer containing 20–30% of normal cell numbers, and entering the brain by the oculomotor nerve root. Such abnormal patterns of nerve growth have been found to result when a segment of optic nerve is removed. It is suggested that the abnormality represents a process of retinal ganglion cell death rather than a misprogramming of ganglion cell specificities as was previously hypothesized.