Boissinot S, Tan Y, Shyue S K, Schneider H, Sampaio I, Neiswanger K, Hewett-Emmett D, Li W H
Human Genetics Center, School of Public Health, University of Texas, P.O. Box 20334, 6901 Bertner Avenue, Houston, TX 77225, USA.
Proc Natl Acad Sci U S A. 1998 Nov 10;95(23):13749-54. doi: 10.1073/pnas.95.23.13749.
It is known that the squirrel monkey, marmoset, and other related New World (NW) monkeys possess three high-frequency alleles at the single X-linked photopigment locus, and that the spectral sensitivity peaks of these alleles are within those delimited by the human red and green pigment genes. The three alleles in the squirrel monkey and marmoset have been sequenced previously. In this study, the three alleles were found and sequenced in the saki monkey, capuchin, and tamarin. Although the capuchin and tamarin belong to the same family as the squirrel monkey and marmoset, the saki monkey belongs to a different family and is one of the species that is most divergent from the squirrel monkey and marmoset, suggesting the presence of the triallelic system in many NW monkeys. The nucleotide sequences of these alleles from the five species studied indicate that gene conversion occurs frequently and has partially or completely homogenized intronic and exonic regions of the alleles in each species, making it appear that a triallelic system arose independently in each of the five species studied. Nevertheless, a detailed analysis suggests that the triallelic system arose only once in the NW monkey lineage, from a middle wavelength (green) opsin gene, and that the amino acid differences at functionally critical sites among alleles have been maintained by natural selection in NW monkeys for >20 million years. Moreover, the two X-linked opsin genes of howler monkeys (a NW monkey genus) were evidently derived from the incorporation of a middle (green) and a long wavelength (red) allele into one chromosome; these two genes together with the (autosomal) blue opsin gene would immediately enable even a male monkey to have trichromatic vision.
已知松鼠猴、狨猴以及其他相关的新大陆（NW）猴在单个X连锁光色素位点上拥有三个高频等位基因，并且这些等位基因的光谱敏感性峰值处于人类红色和绿色色素基因所界定的范围内。松鼠猴和狨猴中的这三个等位基因此前已被测序。在本研究中，在僧面猴、卷尾猴和绢毛猴中发现了这三个等位基因并进行了测序。尽管卷尾猴和绢毛猴与松鼠猴和狨猴属于同一科，但僧面猴属于不同的科，并且是与松鼠猴和狨猴差异最大的物种之一，这表明许多NW猴中存在三基因座系统。对所研究的这五个物种的这些等位基因的核苷酸序列分析表明，基因转换频繁发生，并且已部分或完全使每个物种中等位基因的内含子和外显子区域同质化，这使得在这五个所研究的物种中似乎每个物种都独立出现了一个三基因座系统。然而，详细分析表明，三基因座系统在NW猴谱系中仅出现过一次，源自一个中波长（绿色）视蛋白基因，并且等位基因在功能关键位点的氨基酸差异在NW猴中通过自然选择得以维持超过2000万年。此外，吼猴（一种NW猴属）的两个X连锁视蛋白基因显然是通过将一个中（绿色）和一个长波长（红色）等位基因整合到一条染色体中而产生的；这两个基因与（常染色体）蓝色视蛋白基因一起将立即使即使是雄性猴子也能拥有三色视觉。
