CHARACTERIZATION OF A TYROSINE KINASE-PEPTIDASE A SYNTENY IN LINKAGE GROUP-XIII OF XIPHOPHORUS FISHES (TELEOSTEI, POECILIIDAE) - IMPLICATIONS FOR VERTEBRATE CHROMOSOME EVOLUTION

We exploited the extensive protein and DNA polymorphisms in genetic hy brids made between Xiphophorus species to genetically map two loci to linkage group (LG) XIII oi Xiphophorus. One of these loci, designated FYNL1, has sequence homology to the src gene family of tyrosine kinase s, members of which have been mechanistically implicated in the format ion of spontaneous tumors in the classical Gordon-Kosswig hybrid melan oma model in Xiphophorus fishes. FYNL1 differs from the Xiphophorus fy n and yes sequences previously cloned, but synteny between yes and pep tidase A on human chromosome 18 suggests that the linkage of FYNL 1 an d PEPA on LG XIII represents an ancestral vertebrate gene arrangement. This observation, as well as other evidence, suggest that the src gen e family of tyrosine kinases may have arisen through chromosome duplic ations during the evolution of the vertebrate genome.