ASSIGNMENT OF THE TP53 ORTHOLOGUE TO A NEW LINKAGE GROUP (LG-XIV) IN FISH OF THE GENUS XIPHOPHORUS (TELEOSTEI, POECILIIDAE)

Using a p53 encoding cDNA fragment of rainbow trout (Oncorhynchus myki ss) as probe, a lambda clone from a platyfish (Xiphophorus maculatus) genomic library was isolated. DNA sequencing of the insert from this c lone revealed that it contained the highly conserved domains IV and V of the p53 polypeptide. To map the Xiphophorus p53 gene, joint segrega tion analysis of the inheritance of a PstI-generated DNA restriction f ragment length polymorphism (RFLP) and the inheritance of 36 polymorph ic protein and DNA markers was performed in backcross hybrids of X. cl emenciae x (X. clemenciae x X. milleri) and X. helleri x X. (helleri x X. maculatus Jp 163 B) using Oncorhynchus cDNA and Xiphophorus genomi c p53 probes, respectively. The p53-hybridizing sequence (TP53) was li nked to the ACO1 (cytosolic aconitase) locus in both crosses, and defi nes a new Xiphophorus linkage group, designated LG XIV. This is the fi rst mapping assignment of a known human tumor suppressor gene in fish. Since ACO1 is not Iinked with melanoma severity in X. helleri x X. ma culatus Jp 163 A backcross hybrids, these data indicate that homozygos ity for the X. helleri TP53 genotype in backcross hybrids of the cross type is not associated with genetically regulated malignant melanoma formation in the Gordon-Kosswig hybrid melanoma model.