Damselfish neurofibromatosis (DNF) is a naturally occurring, neoplastic disease affecting bicolor damselfish (Pomacentrus partitus) living on coral reefs in southern Florida, USA. The disease consists of multiple neurofibromas, neurofibrosarcomas and chromatophoromas and has been proposed as an animal model for neurofibromatosis type 1 in humans. DNF is transmissible by injection of crude tumour homogenates, cell-free filtrates of homogenates or cells from tumour cell lines. An analysis of tumorigenic cell lines derived from fish with spontaneous or experimentally induced DNF revealed virus particles budding from cells and present in conditioned media. The 90-110 nm particles resembled type C retroviruses. This virus exhibited a buoyant density of 1.14-1.17 g/cm2 in sucrose, at least six virus proteins of 15 to 80 kDa and reverse transcriptase (RT) activity. RT activity was maximized with a poly(rC)·oligo(dG) template·primer combination and Mn2+ at a concentration of 0.5-1.0 mM. The optimum temperature for RT was determined to be 20°C, a finding consistent with the ambient temperatures encountered by this species. This retrovirus, tentatively named damselfish neurofibromatosis virus (DNFV) may be the aetiological agent of DNF. Whether DNFV or another, as yet unidentified, virus is the cause of DNF, this agent may be unique in virus oncogenesis; neoplastic transformation of the cell types involved in DNF, Schwann cells and chromatophores, has not been documented in any other transmissible tumour.
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