Meeting Abstract
The brittle star Ophioderma brevispinum is an emerging model in regenerative biology. This highly regenerative echinoderm readily autotomizes and grows backs its body appendages called arms. Each arm contains a radial nerve cord (a major component of the central nervous system) and an elaborate system of peripheral nerves. This highly complex nervous system is completely restored in the regenerated arm. The early post-injury phase (day 2-3 post injury) involves dedifferentiation of the neuroepithelium of the radial nerve cord in the vicinity of the autotomy plane. The nervous processes disappear while the remaining glial cells dedifferentiate and re-organize themselves to form a blunt-ended epithelial tube. The cells of the glial tube give rise to new segments of the radial nerve cord in the regenerating arm through extensive cell proliferation. Initially, the regenerating sections of the radial nerve cord are completely devoid of neuronal elements, but as soon as on day 11 post-autotomy the first neuronal progenitors differentiate within the glial tube. They are marked by the expression of the transcription factor Brn1/2/4 and the RNA-binding protein ELAV. At the same time, the regenerating segments of the radial nerve cord start developing their neuropil with axons immunolabeled with neuronal markers, such as synaptotagmin B, acetylated tubulin, and the neuropeptide GFSKLYFamide. The injured radial nerve cord of the brittle star therefore regenerates from its own glial cells, rather from undifferentiated pluripotent progenitors, as was suggested earlier.
