Kuscha, V., Frazer, S.L., Dias, T.B., Hibi, M., Becker, T., and Becker, C.G. (2012) Lesion-induced generation of interneuron cell types in specific dorso-ventral domains in the spinal cord of adult zebrafish. The Journal of comparative neurology. 520(16):3604-3616.
In contrast to mammals, adult zebrafish regenerate neurons in the the lesioned spinal cord. For example, motor neurons are generated from an olig2 expressing population of pMN-like ependymo-radial glial cells in a ventro-lateral position at the central canal. However, the extent of neuronal regeneration is unclear. Here we show, using a transgenic fish in which V2 interneurons are labeled by green fluorescent protein (GFP) under the control of the vsx1 promoter, that after a complete spinal cord transection, large numbers of V2 interneurons are generated in the vicinity of the lesion site. Tg(vsx1:GFP)+ cells are not present in the unlesioned spinal cord and label with the proliferation marker BrdU after a lesion. Some medio-laterally elongated Tg(vsx1:GFP)+ cells contact the central canal in a medial position. These cells likely arise from a p2-like domain of ependymo-radial glial progenitor cells, indicated by co-expression of Pax6 and Nkx6.1, but not DsRed driven by the olig2 promoter in these cells. We also present evidence that Pax2+ interneurons are newly generated after a spinal lesion, whereas the generation rate for a dorsal population of parvalbuminergic interneurons is comparatively low. Our results identify the regenerative potential of different interneuron types for the first time and support a model in which different progenitor cell domains in distinct dorso-ventral positions around the central canal are activated by a lesion to give rise to diverse neuronal cell types in the adult zebrafish spinal cord.