Lipscombe R J, Beatty D W, Ganczakowski M, Goddard E A, Jenkins T, Lau Y L, Spurdle A B, Sumiya M, Summerfield J A, Turner M W
Molecular Immunology Unit, Institute of Child Health, London, UK.
Eur J Hum Genet. 1996;4(1):13-9. doi: 10.1159/000472164.
Mannose-binding protein (MBP; mannan-binding protein, mannan-binding lectin) is a member of the collectin family of proteins and is thought to be important in innate immunity. We have previously shown high frequencies of two distinct mutations in codon 54 and codon 57 of exon 1 of the MBP gene in non-African and African populations, respectively. These result in low levels of the protein and an opsonic deficiency but the frequencies also suggest some selective advantage for low MBP levels. A third mutation in codon 52 occurs at a much lower frequency. We have now extended our earlier studies to other populations. In the south-west Pacific (Papua New Guinea and Vanuatu) neither the codon 52 nor the codon 57 mutation was detected and the codon 54 mutation was significantly less common (gene frequencies of 0.07 and 0.01, respectively) than in other non-African populations (gene frequencies 0.11-0.16). This could be explained by relatively recent admixture. The ancestral Melanesian population probably diverged some 50,000-60,000 years ago and our data suggest that the codon 54 mutation may have occurred after that even but before the divergence of European-Asian groups (40,000 years ago). Two further sub-Saharan populations were also studied: a group of Xhosa from South Africa were similar to Gambians, with a high gene frequency for the codon 57 mutation (0.27) and no evidence of the codon 52 or 54 mutations. In contrast, San Bushmen from Namibia had low frequencies of both the codon 57 mutation (0.07) and the codon 54 mutation (0.03). Again the codon 52 mutation was not found. This pattern is unique amongst sub-Saharan populations studied to date and suggests that this population may have been subjected to different selective pressures.
甘露糖结合蛋白（MBP；甘露聚糖结合蛋白、甘露聚糖结合凝集素）是胶原凝集素家族蛋白的成员，被认为在固有免疫中起重要作用。我们之前分别在非非洲人群和非洲人群的MBP基因外显子1的第54密码子和第57密码子中发现了两种不同突变的高频率情况。这些突变导致该蛋白水平降低和调理素缺陷，但这些频率也表明低MBP水平具有某种选择性优势。第52密码子中的第三种突变出现频率要低得多。我们现在已将早期研究扩展到其他人群。在西南太平洋地区（巴布亚新几内亚和瓦努阿图），未检测到第52密码子或第57密码子的突变，且第54密码子突变的发生率明显低于其他非非洲人群（基因频率分别为0.07和0.01）（基因频率为0.11 - 0.16）。这可以用相对较新的混合情况来解释。美拉尼西亚祖先人群可能在约5万至6万年前分化，我们的数据表明第54密码子突变可能在那之后但在欧亚人群分化（4万年前）之前发生。还研究了另外两个撒哈拉以南人群：一组来自南非的科萨人与冈比亚人相似，第57密码子突变的基因频率较高（0.27），且没有第52或54密码子突变的证据。相比之下，纳米比亚的桑族布须曼人第57密码子突变（0.07）和第54密码子突变（0.03）的频率都较低。同样未发现第52密码子突变。在迄今研究的撒哈拉以南人群中，这种模式是独特的，表明该人群可能受到了不同的选择压力。
