The acute transcriptome response of the midbrain/diencephalon to injury in the adult mummichog (Fundulus heteroclitus)

Adult fish produce new cells throughout their central nervous system during the course of their lives. Furthermore, they maintain a tremendous capacity to repair damaged neural tissue. Much of the focus on understanding brain repair and regeneration in fish has been directed at regions of the brainstem and forebrain; however, the mesencephalon (midbrain) and diencephalon have received comparatively little attention. We sought to characterize differential gene expression in the midbrain/diencephalon in response to injury in the adult fish using RNA-seq. Using the mummichog (Fundulus heteroclitus), we administered a mechanical lesion traversing the midbrain optic tectum, tegmentum and underlying hypothalamus of the diencephalon and examined differential gene expression at an acute recovery time of 1hr post-injury. Comparisons of whole transcriptomes derived from isolated RNA of intact and injured midbrain/diencephalic tissue identified over 400 differentially expressed genes with the vast majority being upregulated. Using qPCR, we validated the upregulation of three differentially expressed genes, pim-2-like, syndecan-4-like, and cd83. Based on genes both familiar and novel regarding the adult brain response to injury, these data provide an extensive molecular profile giving insight into a range of cellular processes putatively involved in the injury response of a brain regenerative-capable vertebrate.