The C-MYB story--is it definitive?

T he MYB gene family has provided examples that bear on two interesting questions in evolutionary biology. Why do duplicated genes persist in the face of purifying selection? How do new organs arise? All vertebrate animal species are believed to have three closely related MYB genes (C-MYB/ MYB, A-MYB/MYBL1, and B-MYB/ MYBL2) (1). Most invertebrate animal species examined thus far have a single MYB gene, an exception being the nematode Caenorhabditis elegans. Genetic studies in the laboratory mouse and in Drosophila have provided important clues about the functional evolution of the MYB gene family (Fig. 1) (2–6). However, two recent reports of C-MYB mutants in two species of teleosts (bony fish) have raised new questions (7, 8).