Cloning and expression of a myc family member from the pituitary gland of the Rainbow trout, Oncorhynchus mykiss

Molecular markers of cancer in cartilaginous fish: immunocytochemical study of PCNA, p-53, myc and ras expression in neoplastic and hyperplastic tissues from free ranging blue sharks, Prionace glauca (L.)

Archival formalin-fixed tissues from wild-caught adult blue sharks, Prionace glauca (L.), were used for immunocytochemical detection of proliferating cell nuclear antigen (PCNA), two oncoproteins from the oncogenes c-myc and pan-ras, and a protein product from the tumour suppressor gene p-53. All sharks were caught during summer months between 2000 and 2006 by recreational fishermen off the USA coast in the northwestern Atlantic. The sharks were necropsied on landing and selected organ samples were collected into elasmobranch formalin and processed for paraffin embedding and light microscopy. Paraffin-embedded sections from collected tissue were both stained with haematoxylin and eosin and processed by immunocytochemical techniques using antibodies raised against the PCNA, p-ras, c-myc and p-53 proteins. The lesions examined in this study included two well differentiated adenomatous gastric polyps, a testicular capsular mesothelioma, a gingival fibropapilloma with elements of ameloblastoma, three liver tumours, two pericardial fibropapillomas and six cases of proliferative serositis (pericarditis and peritonitis). Normal and hyperplastic tissues from blue sharks, and human neoplastic tissues served as negative and positive controls, respectively. We detected upregulation of PCNA in many neoplastic, one dysplastic and in some hyperplastic lesions, and positive p-ras and c-myc signals in some of the neoplastic lesions. None of the examined tissues showed positive p-53 signalling. This is the first literature report on immunocytochemical detection of molecular markers of cancer in sharks and in fish of the class Chondrichthyes.

A consolidated linkage map for rainbow trout (Oncorhynchus mykiss)

Androgenetic doubled haploid progeny produced from a cross between the Oregon State University and Arlee clonal rainbow trout (Oncorhynchus mykiss) lines, used for a previous published rainbow trout map, were used to update the map with the addition of more amplified fragment length polymorphic (AFLP) markers, microsatellites, type I and allozyme markers. We have added more than 900 markers, bringing the total number to 1359 genetic markers and the sex phenotype including 799 EcoRI AFLPs, 174 PstI AFLPs, 226 microsatellites, 72 VNTR, 38 SINE markers, 29 known genes, 12 minisatellites, five RAPDs, and four allozymes. Thirty major linkage groups were identified. Synteny of linkage groups in our map with the outcrossed microsatellite map has been established for all except one linkage group in this doubled haploid cross. Putative homeologous relationships among linkage groups, resulting from the autotetraploid nature of the salmonid genome, have been revealed based on the placement of duplicated microsatellites and type I loci.

Expression and regulation of the myc proto-oncogene in the pituitary gland of rainbow trout

We have isolated two c-myc cDNA clones from a trout pituitary gland (PG). One of these clones (tmyc2) is expressed as a 1.9-2.0 kb transcript in the PG, brain and heart, but not in the liver and codes for a protein of 398 amino acids. The second clone (tmyc3) is expressed in the PG (1.6 kb), but not in brain, liver or heart and codes for a protein of 401 amino acids. The expression level of tmyc3 in the PG is 10-fold greater than that of tmyc2. This profile is markedly different from a previously isolated genomic c-myc clone (tmyc1) that is expressed primarily in the liver (2.4 kb) and codes for a larger protein consisting of 417 amino acids. In situ hybridization and Northern blot analysis showed that tmyc3 is expressed primarily in somatolactotrophs of the intermediate lobe (IL) of the PG. Tmyc2 is expressed at similar levels in both the IL and the pars distalis (PD). In vitro stimulation experiments show that releasing factors, known to control cells in the PD, failed to stimulate tmyc2 or tmyc3. However, dopamine and norepinephrine (two neurotransmitters known to control hormone release from the IL) increased tmyc3 expression two to five times. Two other neurotransmitters (GABA and serotonin) failed to stimulate tmyc3 expression. None of the neurotransmitters tested affected tmyc2 expression. These results suggest that tmyc3 is involved in regulating hypertrophy of somatolactotrophs and may have a role in stimulating production of somatolactin, the only hormone known to be synthesised by these cells.