Structure and expression of activin genes in rainbow trout.

Activins are dimeric members of the transforming growth factor-beta (TGF-beta) superfamily. By using the polymerase chain reaction (PCR), we have cloned and sequenced activin beta A and beta B genes encoding the mature region of the peptides from the rainbow trout genomic DNA. Two forms of beta A and a single form of beta B-subunits were found. There is high identity with mammalian counterparts; the two rainbow trout beta A-subunits have more than 75% nucleotide sequence identity with the human beta A-subunit, and the beta B-subunit had 82% sequence identity with the human beta B-subunit. Expression of rainbow trout activin genes was examined by reverse transcription-PCR (RT-PCR). The major expression tissue of rainbow trout activin was ovary and brain at the messenger RNA level, and the major expression subunit of rainbow trout activin was the beta B subunit.