No abstract

Conclusive evidence was provided that y', the upstream of the two linked simian y-globin loci (5'-y'-'y2-3'), is a pseudogene in a major group of New World monkeys. Sequence analysis of PCR-amplified 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 Alouafta (howler monkeys)] share a large deletion that removed most of exon 2, all of intron 2 and exon 3, and much of the 3' flanking sequence of y. The fact that two functional 'y-globin genes were not present in early ancestors of the Atelidae (and that y1 was the dispensible gene) suggests that for much or even all of their evolution, platyrrhines have had ly2as the primary fetally expressed 'y-globin gene, in contrast to catarrhines (e.g., humans and chimpanzees) that have 'y' as the primary fetally expressed y-globin gene. Results from promoter sequences further suggest that all three platyrrhine families (Atelidae, Cebidae, and Pitheciidae) have y2 rather than y' as their primary fetally expressed y-globin gene. The implications of this suggestion were explored in terms of how gene redundancy, regulatory mutations, and distance of each 'y-globin gene from the locus control region were possibly involved in the acquisition and maintenance of fetal, rather than embryonic, expression.

The genus Alouatta (howler monkeys) is the most widely distributed of New World primates, and has been arranged in three species groups: the Central American Alouatta palliata group and the South American Alouatta seniculus and Alouatta caraya groups. While the latter is monotypic, the A. seniculus group encompasses at least three species (A. seniculus, A. belzebul and A. fusca). In the present study, approximately 600 base pairs of the γ 1 -globin pseudogene were sequenced in the four Brazilian species (A. seniculus, A. belzebul, A. fusca and A. caraya). Maximum parsimony and maximum likelihood methods yielded phylogenetic trees with the same arrangement: {A. caraya [A. seniculus (A. fusca, A. belzebul)]}. The most parsimonious tree had bootstrap values greater than 82% for all groupings, and strength of grouping values of at least 2, supporting the sister clade of A. fusca and A. belzebul. The study also confirmed the presence of a 150-base pair Alu insertion element and a 1.8-kb deletion in the γ 1 -globin pseudogene in A. fusca, features found previously in the remaining three species. The cladistic classification based on molecular data agrees with those of morphological studies, with the monospecific A. caraya group being clearly differentiated from the A. seniculus group.