Divergent evolution and purifying selection of the H (FUT1) gene in New World monkeys (Primates, Platyrrhini)

Abstract

In the present study, the coding region of the H gene was sequenced and analyzed in fourteen genera of New World primates (Alouatta, Aotus, Ateles, Brachyteles, Cacajao, Callicebus, Callithrix, Cebus, Chiropotes, Lagothrix, Leontopithecus, Pithecia, Saguinus, and Saimiri), in order to investigate the evolution of the gene. The analyses revealed that this coding region contains 1,101 nucleotides, with the exception of Brachyteles, the callitrichines (Callithrix, Leontopithecus, and Saguinus) and one species of Callicebus (moloch), in which one codon was deleted. In the primates studied, the high GC content (63%), the nonrandom distribution of codons and the low evolution rate of the gene (0.513 substitutions/site/MA in the order Primates) suggest the action of a purifying type of selective pressure, confirmed by the Z-test. Our analyses did not identify mutations equivalent to those responsible for the H-deficient phenotypes found in humans, nor any other alteration that might explain the lack of expression of the gene in the erythrocytes of Neotropical monkeys. The phylogenetic trees obtained for the H gene and the distance matrix data suggest the occurrence of divergent evolution in the primates.

Evolution of the SEC1 gene in New World monkey lineages (Primates, Platyrrhini)

“…The average GC content was 63.8% and the GC:AT proportion was 1.76. These values are similar to those described for the FUT1 gene (Borges and Harada, 2004) and suggest that SEC1 is located in a GC-rich isochore, similar to that proposed by Sharp et al (1995) for humans. The analysis of nucleotide substitution patterns revealed a predominance of transitions over transversions, with an average ratio of 2.73.…”

“…The transition/transversion rates and nucleotide sequence alignment support the hypothesis that primate SEC1 evolved by divergent evolution, as proposed for the origin of fucosyltransferases (Breton et al, 1998;Oriol et al, 1999;Barreaud et al, 2000;Bureau et al, 2001;Borges and Harada, 2004). In contrast, multiple stop codons and amino acid changes present in different species suggest convergent inactivation events in apes, Callitrichinae, Aotus and Pithecia.…”

“…Nevertheless, no mutation was found in the FUT1 gene that could explain the lack of expression (Borges and Harada, 2004). Apoil et al (2000) suggest that an Alu-like element inserted in a region crucial for regulation is responsible for expression of the H enzyme in human and ape erythroid lineages.…”

“…lower than the evolutionary rates of pseudogenes (Borges and Harada, 2004). The SEC1-like family presents higher evolutionary rates than the FUT2-like family due to accumulation of mutations, such as premature stop codons, in the SEC1 pseudogene (Apoil et al, 2000).…”