Identification of c-fos related genes and their induction by neural activation in rainbow trout brain.
A number of studies have shown that the induction of c-fos gene is an indicator of the responses of cells and tissues to the environmental stimuli. In the present study, using RT-PCR-based strategy, we isolated, from the brain of the rainbow trout, two partial cDNA clones (RT-fos1 and RT-fos2) that code proteins homologous to c-Fos proteins of higher vertebrates. Sequence analysis of the two clones indicated that the two rainbow trout clones are very similar to each other over the entire cloned region (88% amino acid identity) and showed moderate similarity to c-Fos proteins of higher vertebrates (40% amino acid identity with human c-Fos). Two functionally important domains (i.e. the leucine zipper and zinc finger) are highly conserved among all the vertebrate species analyzed, although the region between the two domains was highly variable between different species. Intraperitoneal administration of kainic acid, a stable agonist of glutamate receptors, transiently induced the mRNAs for both RT-fos1 and RT-fos2 in the rainbow trout brain. These results indicate that the expression pattern of the two clones can be utilized as a suitable anatomical marker for the increased neural activities in salmonid fish brain to investigate the higher order behavior such as the learning and imprinting of odors of the home river.