CLONING OF ZEBRAFISH NEUROFILAMENT CDNAS FOR PLASTICIN AND GEFILTIN -INCREASED MESSENGER-RNA EXPRESSION IN GANGLION-CELLS AFTER OPTIC-NERVE INJURY

During retinal growth and optic axon regeneration, the differential ex pression of the neuronal intermediate filament proteins, plasticin and gefiltin, in the goldfish visual pathway suggests that these proteins support programmed axonal growth. To investigate plasticin and gefilt in during axonogenesis, we turned to the zebrafish, a system that is m ore amenable to mutational analysis. As a first step, we demonstrated that the intermediate filament compositions of goldfish and zebrafish are similar. In addition, the cDNAs for zebrafish plasticin and gefilt in were cloned and characterized. Using in situ hy bridization in reti na, we show increased mRNA levels for these proteins following optic n erve crush. Zebrafish plasticin and gefiltin peak and return to baseli ne levels of expression more rapidly than in goldfish. Furthermore, in the unoperated eye of experimental fish, there was a moderate increas e in the levels of plasticin and gefiltin mRNA, suggesting that solubl e factors influence the expression of these proteins. The successive e xpression of plasticin and gefiltin suggests that these neuronal inter mediate filament proteins are integral components of axonogenesis. The cloning and characterization of cDNAs for plasticin and gefiltin perm it mutational analyses of these proteins during zebrafish axonogenesis .