High-resolution FISH mapping of the rat alpha(2u)-globulin multigene family

The rat alpha(2u)-globulins are a group of similar proteins that are encode d by a family of approximately 20 genes located a single locus of less than or equal to 880 kbp on Chromosome (Chr) 5q. Individual members of this gen e family demonstrate complex tissue, hormonal, and developmental expression patterns despite a high degree of sequence similarity among the members an d consequently provide an interesting system for studying the evolution of differential gene expression. Hybridization analysis indicated that gene cl asses, similar to those identified at the homologous MUP locus in the mouse , do not exist within the rat alpha(2u)-globulin locus. Furthermore, cross- hybridization analysis revealed the presence of conserved sequences in the 5' and 3' regions flanking the alpha(2u)-globulin genes, some of which were present in an inverted orientation. We have used high-resolution fiber FIS H to examine the structural organization of the alpha(2u)-globulin locus, a nd found the genes to be arranged as an array of both direct and inverted r epeats. The organization of the rat alpha(2u)-globulin genes differs from t he MUP genes and suggests different evolutionary events have reorganized th ese homologous sets of genes.