Fate of a redundant gamma-globin gene in the atelid clade of New World monkeys: implications concerning fetal globin gene expression.

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.

A Maximum Likelihood Method for Detecting Functional Divergence at Individual Codon Sites, with Application to Gene Family Evolution

“…Fitch et al (1991) suggested that the initial gene duplication event was followed by divergence of e and c for different ''embryonic niches.'' Later (35 to 55 MYA), a second case of genetic co-option occurred when embryonically expressed c was recruited for fetal expression in the early simian lineage Tagle et al 1988;Meireles et al 1995;Johnson et al 1996). The objective of our analysis was, first, to test for divergence in selective pressure between e and c and, second, to identify sites consistent with this type of selective pressure if they existed.…”

“…Here we describe a model that allows variation in d N /d S among sites, with a fraction of sites evolving under divergent selective pressures between two clades following a co-option event. We implement the model in the maximum likelihood framework and apply it to two cases of evolution by gene duplication: (i) the e and c globin gene family (Meireles et al 1995;Johnson et al 1996;Fitch et al 1991) and (ii) the eosinophil cationic protein (ECP) and eosinophil-derived neurotoxin (EDN) gene family (Zhang et al 1998;Zhang and Rosenberg 2002).…”

Phylogenetic relationships among Brazilian howler monkeys, genus Alouatta (Platyrrhini, Atelidae), based on <FONT FACE=Symbol>g</FONT>1-globin pseudogene sequences

“…All genes in this cluster have three exons and two introns (Lawn et al, 1980). In the atelids, γ 1 is a pseudogene (Meireles et al, 1995(Meireles et al, , 1998, whereas in the platyrrhine genera Aotus and Saimiri, the two loci are combined into a hybrid gene (Chiu et al, 1996).…”

“…In the present study, sequences of the γ 1 -globin pseudogene were used in a molecular analysis of the phylogenetic relationships among Brazilian howler monkeys. The aligned sequences were also used to estimate divergence times based on a local molecular clock, and to investigate the presence of the Alu insertion -found in other Alouatta species (Meireles et al, 1995(Meireles et al, , 1998 …”

“…The γ 1 fragment was obtained using the PCR protocol described in Meireles et al (1995), and consisted of an initial denaturation of 3 min at 1 -globin pseudogene is amplified exhibiting the primers R1 and R2 used in this study and also the 1.8-kb deletion shared by all four Alouatta species as well as by the ateline group (Meireles et al, 1995(Meireles et al, , 1998). …”