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Tumor suppression in Xiphophorus by an accidentally acquired promoter
D Adam1, N Dimitrijevic, M Schartl
1Genzentrum, Max-Planck-Institut für Biochemie, Martinsried, Germany.
Abstract:
Melanoma formation in the teleost Xiphophorus is caused by a dominant genetic locus, Tu. This locus includes the Xmrk oncogene, which encodes a receptor tyrosine kinase. Tumor induction is suppressed in wild-type fish by a tumor suppressor locus, R. Molecular genetic analyses revealed that the Tu locus emerged by nonhomologous recombination of the Xmrk proto-oncogene with a previously uncharacterized sequence, D. This event generated an additional copy of Xmrk with a new promoter. Suppression of the new Xmrk promoter by R in parental fish and its deregulation in hybrids explain the genetics of melanoma formation in Xiphophorus.
Insights
Melanoma in Xiphophorus fish arises from the Tu genetic locus, containing the Xmrk oncogene. A tumor suppressor locus, R, normally prevents tumor formation, but its deregulation in hybrids drives melanoma development.
Area of Science:
- Genetics
- Oncology
- Developmental Biology
Background:
- Melanoma formation in Xiphophorus fish is a well-studied genetic trait.
- The Tu locus, encoding the Xmrk oncogene, is central to melanoma development.
- Tumor suppression is mediated by a locus denoted as R in wild-type fish.
Purpose of the Study:
- To elucidate the molecular mechanisms underlying melanoma formation in Xiphophorus.
- To understand the genetic interaction between the Tu and R loci.
- To investigate the origin and regulation of the Xmrk oncogene in melanoma development.
Main Methods:
- Molecular genetic analyses were employed.
- Recombination events involving the Xmrk proto-oncogene and sequence D were investigated.
- Gene promoter activity and regulatory interactions were assessed.
Main Results:
- The Tu locus originated from nonhomologous recombination between the Xmrk proto-oncogene and an uncharacterized sequence D.
- This recombination event created an additional Xmrk copy with a novel promoter.
- The R locus suppresses the new Xmrk promoter in parental fish, but this suppression is lost in hybrids, leading to melanoma.
Conclusions:
- The emergence of the Xmrk oncogene via recombination and its altered regulation by the R locus are key drivers of melanoma in Xiphophorus.
- Understanding these genetic mechanisms provides insights into oncogene activation and tumor suppression.
- This model system offers valuable perspectives on the genetic basis of cancer in vertebrates.