A Transgenic Zebrafish model for Melanoma using BRAF and other cell cycle mutan

Children's Hospital Boston
posted on 02/10/2012

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This work has created a zebrafish model of both benign nevi and malignant melanoma, a model that offers faithful recreation of the human melanomagenesis and attractive adaptability for investigative research. Transgenic zebrafish bearing human, mutated BRAF (V599E) cDNA, expressed in under the melanocytes-specific mitfa (nacre) gene promoter, develop benign, ectopic melanocyte proliferation, resembling human nevi. In a genetic background carrying a p53 mutation [homozygous Met246Lys missense mutation of the zebrafish zp53 gene, corresponding to a mutation seen in human cancers and demonstrated to inhibits radiation-induced apoptosis in the fish], expression of the V599E BRAF in melanocytes leads to the development of melanomas in the fish, arising over time from nevi and displaying characteristic similar to human malignant melanoma. This research has defined a valuable platform for the study of both pre-malignant nevi and malignant melanoma. Zebrafish represent a genetically tractable species, allowing experiments on genetically identical individuals, allowing introduction of new mutations at will, and allowing genetic screens for novel mutations that result in a desired phenotype. Their short generation time and large numbers of offspring allow rapid expansion of new genetic lineages. Zebrafish are large enough to be surgically manipulated (allowing excision of tumors, implantation, transplantation, etc.) yet are small enough to be raised economically in large numbers. The advantage of rearing large numbers of genetically identical fish is manifest both in large scale population studies (where large numbers of identical individuals can be exposed to a limited number of treatments to accurately evaluate weak environmental variables) and in screening (where fish can be exposed to a large number of potential therapeutic compounds for in vivo, high throughput, drug screening). As vertebrates, zebrafish shared the same developmental program of melanocyte generation from neural crest progenitors as seen in mammals, and the mammalian and zebrafish melanocytes share biochemical and cell biological features and share expression of many homologous genes. The fish nevi and melanomas are relevant models for their human counterparts, sharing histological similarities and showing involvement of mutations in homologous genes in melanomagenesis.