FATE OF A REDUNDANT GAMMA-GLOBIN GENE IN THE ATELID CLADE OF NEW-WORLD MONKEYS - IMPLICATIONS CONCERNING FETAL GLOBIN GENE-EXPRESSION

Conclusive evidence was provided that gamma 1, the upstream of the two linked simian gamma-globin loci (5'-gamma(1)-gamma 2-3'), is a pseudo gene in a major group of New World monkeys. Sequence analysis of PCR-a mplified genomic fragments of predicted sizes revealed that all extant genera of the platyrrhine family Atelidae [Lagothrix (woolly monkeys) , Brachyteles (woolly spider monkeys), Ateles (spider monkeys), and Al ouatta (howler monkeys)] share a large deletion that removed most of e xon 2, all of intron 2 and exon 3, and much of the 3' flanking sequenc e of gamma(1). The fact that two functional gamma-globin genes were no t present in early ancestors of the Atelidae (and that gamma(1) was th e dispensible gene) suggests that for much or even all of their evolut ion, platyrrhines have had gamma(2) as the primary fetally expressed g amma-globin gene, in contrast to catarrhines (e.g., humans and chimpan zees) that have gamma(1) as the primary fetally expressed gamma-globin gene. Results from promoter sequences further suggest that all three platyrrhine families (Atelidae, Cebidae, and Pitheciidae) have gamma(2 ) rather than gamma(1) as their primary fetally expressed gamma-globin gene. The implications of this suggestion were explored in terms of h ow gene redundancy, regulatory mutations, and distance of each gamma-g lobin gene from the locus control region were possibly involved in the acquisition and maintenance of fetal, rather than embryonic, expressi on.