Oncogene-related sequences in xiphophorin fish prone to hereditary melanoma formation

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Abstract
In certain xiphophorin fish a whole spectrum of melanomas of varying severity can be produced on a genetic basis, from benign melanomas composed of almost fully differentiated (mature) pigment cells to malignant melanomas composed of very incompletely differentiated (immature) pigment cells. This feature should provide an excellent basis for the study of the role of oncogenes in this melanoma formation and in cell development. This is a preliminary study reporting the screening of the genomes of Xiphophorus helleri (swordtail) and 4 different strains of X. maculatus (platyfish) for the presence of oncogenic sequences using cloned probes of v-src, v-rasKi, c-mys and c-mos in Southern blot analysis. Under high stringency conditions, a very complex hybridization pattern was observed in the DNA of the fish when probed with v-src and v-rasKi; it was less complex when probed with c-myc. No hybridization pattern was found in any DNA with c-mos, even under low stringency conditions. The complex patterns suggest a relatively high copy number of v-src and v-rasKi related sequences in the genomes of the fish. The patterns obtained for the DNA of the 2 spp. are very similar, if not identical, with 2 interesting exceptions. X. helleri DNA shows a more complex v-src pattern than the DNA of the X. maculatus strains, perhaps indicating a higher copy number. The DNA of 2 X. maculatus strains, one a deletion mutant of the other, show a single v-src related band difference in their patterns.