Expression and regulation of the gefiltin gene during zebrafish development

Neurogenesis is correlated with the progressive expression of diverse neuronal intermediate filaments (IF) proteins. The apparent developmental regulation of IF protein expression suggests that specific neurofilament proteins impart unique structural attributes that support the staged growth of the neuron. In the teleost visual pathway, the sequential expression of two IF proteins, plasticin and gefiltin, is linked to the age of retinal ganglion cells (RGCs) and to the regeneration of optic axons after nerve injury. Based on these observations I hypothesized that plasticin and gefiltin would be sequentially expressed during retinal development. In fact, gefiltin is expressed after plasticin, during the later stages of zebrafish retinal development when axons grow past the optic chiasm and innervate their targets. Outside of the visual pathway, gefiltin is predominantly expressed in axonal tracts of the central nervous system and the motor neurons of the spinal cord. To identify and characterize potential regulatory elements and their binding proteins in the milieu of an intact, I utilized transient transgenic technology in zebrafish embryos. Additionally, I used a statistical approach to analyze the effect of deleting two regions that are conserved between zebrafish and goldfish gefiltin promoters. I determined that one region positively regulates the level of gefiltin expression in the hindbrain while the second conserved region negatively regulates gefiltin expression outside the CNS. In addition, these two regions appear to work together to regulate gefiltin expression in the forebrain.