Molecular cloning and expression of a TNF receptor and two TNF ligands in the fish ovary

Using degenerative primers, partial cDNAs of a TNF (tumor necrosis factor) receptor and two TNF ligands were obtained by PCR of zebrafish and trout cD NAs, or cDNA libraries. These fragments were then used to screen cDNA libra ries of appropriate tissues to obtain clones containing full coding sequenc es. A zebrafish cDNA was obtained that presumably codes for a 438 amino aci d ovarian TNF receptor (OTR) that was identified as a death-domain-containi ng member of the TNF receptor family. On Northern blots, the OTR cDNA hybri dized with a 3.4-kb transcript that is abundant in the zebrafish ovary but lightly detected in all other tissues tested. A zebrafish cDNA presumably c oding for a 214 amino acid protein with sequence similarity to mammalian TR AIL (TNF-related apoptosis inducing ligand), was also isolated. In addition , a fragment of the brook trout TRAIL homologue was obtained. Finally, a fu ll-length brook trout cDNA, that presumably codes for a 255 amino acid prot ein with sequence similarity to mammalian TNF-alpha and lymphotoxin-alpha, was isolated. This study is the first report of a death-domain-containing T NF receptor and the first published report of a TNF ligand in fish. (C) 200 1 Elsevier Science Inc. All rights reserved.