Bulk isolation and identification of fish genes by cDNA clone tagging

The fish has long been a popular research model for various disciplines in the life sciences, but its molecular biology remains largely unexplored, and the number of fish genes identified at present is still limited. To increase the repertoire of fish genes to facilitate further research, we have embarked on cDNA clone tagging studies in several teleosts. The basic procedure is partial sequencing of randomly selected cDNA clones by a single sequencing reaction to obtain nucleotide sequences of about 200 to 300 bp for each clone. These partial DNA sequences can be used as tags to identify fish homologous genes by searching for sequence similarity in DNA databases. By this method, we have sequenced a total of 265 clones from pituitary and liver cDNA libraries from five species of fish and identified 83 clones encoding 55 different genes. These 55 genes are described for the first time in their species, and 37 of them are described for the first time in fish. These preliminary data indicate that cDNA clone tagging is useful for rapidly increasing the number and availability of genes in teleosts. Several applications of these tagged random clones are discussed.