African-American mitochondrial DNAs often match mtDNAs found in multiple African ethnic groups
African-American mitochondrial DNAs often match mtDNAs found in multiple African ethnic groups
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DOI：
10.1186/1741-7007-4-34
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发表时间：
2006-10-12
期刊：
影响因子：
5.4
通讯作者：
Jackson, Bruce A.
中科院分区：
文献类型：
--
作者：
Ely, Bert;Wilson, Jamie Lee;Jackson, Bruce A.
背景：线粒体DNA(MtDNA)单倍型已成为追踪母系祖先的流行工具，有几家公司向公众提供这项服务。大量研究表明，人类mtDNA单倍型可以用来确定单倍型起源的大陆。理想情况下，mtDNA单倍型还可以用来确定母系祖先来自的特定国家或民族。然而，线粒体DNA单倍型的地理分布受个体和群体迁移的影响很大。因此，常见的mtDNA单倍型在多个种族之间是共享的。我们研究了mtDNA单倍型在西非种族群体中的分布，以确定mtDNA单倍型可用于将非洲裔美国人与非洲母系祖先的国家或民族重新联系起来的频率。线粒体DNA高变片段I(HVS-I)的核苷酸序列通常提供了足够的信息来将特定的mtDNA分配给合适的单倍群，它包含了可用于区分特定mtDNA单倍型和密切相关的单倍型的大部分变异。本研究将一般非洲裔美国人和特定的Gullah/Geechee HVS-I单倍型样本与撒哈拉以南非洲的两个HVS-I单倍型数据库进行比较，并记录每个样本的完美匹配率。结果：当分析两个独立的非洲裔美国人样本时，超过一半的样本HVS-I mtDNA单倍型与多个非洲种族共享的常见单倍型完全匹配。另有40%的序列与数据库中的任何序列都不匹配，只有不到10%的序列与单一非洲种族的序列完全匹配。在非洲数据库中观察到单倍型的地区分布差异，非洲裔美国人的单倍型更有可能与西非或中西部非洲族群的单倍型匹配，而不是东部或南部非洲的单倍型。只有不到14%的非洲裔美国人的mtDNA序列与仅来自西非或仅来自中非西部的序列匹配。结论：我们的撒哈拉以南地区mtDNA序列数据库包括非洲多个地区的种族之间共享的最常见的单倍型。这些常见的单倍型已经在一半的撒哈拉以南非洲人身上发现。超过60%的剩余单倍型不同于人类免疫缺陷病毒I区单核苷酸位置上的常见单倍型，它们可能在撒哈拉以南非洲地区以不同的频率出现。然而，所分析的40%的非裔美国人mtDNA在数据库中没有匹配的发现表明，只有一小部分非洲单倍型被识别出来。此外，只有不到10%的非洲裔美国人的线粒体DNA与单一非洲地区的线粒体DNA序列匹配，这一发现表明，很少有非洲裔美国人能够将他们的线粒体DNA谱系追溯到非洲的特定地区，能够将他们的线粒体DNA追溯到单一种族群体的人更少。然而，在一个更大的数据库可用之前，不应该得出任何确定的结论。然而，很明显，当来自非洲不同地区的许多民族共享相同的mtDNA单倍型时，不可能根据mtDNA序列确定哪个单一民族是特定母系祖先的来源。
Background: Mitochondrial DNA (mtDNA) haplotypes have become popular tools for tracing maternal ancestry, and several companies offer this service to the general public. Numerous studies have demonstrated that human mtDNA haplotypes can be used with confidence to identify the continent where the haplotype originated. Ideally, mtDNA haplotypes could also be used to identify a particular country or ethnic group from which the maternal ancestor emanated. However, the geographic distribution of mtDNA haplotypes is greatly influenced by the movement of both individuals and population groups. Consequently, common mtDNA haplotypes are shared among multiple ethnic groups. We have studied the distribution of mtDNA haplotypes among West African ethnic groups to determine how often mtDNA haplotypes can be used to reconnect Americans of African descent to a country or ethnic group of a maternal African ancestor. The nucleotide sequence of the mtDNA hypervariable segment I (HVS-I) usually provides sufficient information to assign a particular mtDNA to the proper haplogroup, and it contains most of the variation that is available to distinguish a particular mtDNA haplotype from closely related haplotypes. In this study, samples of general African-American and specific Gullah/Geechee HVS-I haplotypes were compared with two databases of HVS-I haplotypes from sub-Saharan Africa, and the incidence of perfect matches recorded for each sample.Results: When two independent African-American samples were analyzed, more than half of the sampled HVS-I mtDNA haplotypes exactly matched common haplotypes that were shared among multiple African ethnic groups. Another 40% did not match any sequence in the database, and fewer than 10% were an exact match to a sequence from a single African ethnic group. Differences in the regional distribution of haplotypes were observed in the African database, and the African-American haplotypes were more likely to match haplotypes found in ethnic groups from West or West Central Africa than those found in eastern or southern Africa. Fewer than 14% of the African-American mtDNA sequences matched sequences from only West Africa or only West Central Africa.Conclusion: Our database of sub-Saharan mtDNA sequences includes the most common haplotypes that are shared among ethnic groups from multiple regions of Africa. These common haplotypes have been found in half of all subSaharan Africans. More than 60% of the remaining haplotypes differ from the common haplotypes at a single nucleotide position in the HVS-I region, and they are likely to occur at varying frequencies within sub-Saharan Africa. However, the finding that 40% of the African-American mtDNAs analyzed had no match in the database indicates that only a small fraction of the total number of African haplotypes has been identified. In addition, the finding that fewer than 10% of African-American mtDNAs matched mtDNA sequences from a single African region suggests that few African Americans might be able to trace their mtDNA lineages to a particular region of Africa, and even fewer will be able to trace their mtDNA to a single ethnic group. However, no firm conclusions should be made until a much larger database is available. It is clear, however, that when identical mtDNA haplotypes are shared among many ethnic groups from different parts of Africa, it is impossible to determine which single ethnic group was the source of a particular maternal ancestor based on the mtDNA sequence.