Prospects for DNA from Neandertals

最近，慕尼黑的S. PÞÞbo博士从尼安德特人类型的标本中确定了线粒体DNA序列，并在我们的实验室得到了独立的证实。序列分析表明，尼安德特人不太可能为当代人类贡献mtDNA；然而，这个结论是建立在这个单一序列上的。更明确的论证需要对尼安德特人mtDNA变异的范围进行评估。这样的分析需要成功地从更多的尼安德特人遗骸中提取真实的DNA。因此，这项研究的目的是对从至少另外10具尼安德特人遗骸中提取DNA的前景进行全面评估。这将通过两步程序分析一些遗骸来完成。首先，将对少量骨粉进行氨基酸外消旋化分析，这已被证明是DNA的合理替代品。其次，对于那些外消旋程度足够低的样本，表明DNA可能以足够的数量和质量存活以进行分析，DNA将被提取，并针对先前确定的尼安德特人mtDNA序列使用特异性引物进行PCR扩增。所有产生预期大小的PCR产物的扩增反应，并且扩增和提取控制为适当的阴性，将被克隆，并确定至少10个克隆的序列。PÞÞbo博士在慕尼黑的实验室将同时进行类似的工作。产生类似尼安德特人序列的标本（通过与从尼安德特人类型标本中获得的序列进行比较来判断），并在两个实验室中复制，将被判断为产生可靠和真实的尼安德特人DNA。这些标本将成为未来分析的主题，以确定额外的mtDNA序列信息。使用尼安德特人特有的引物，这直到现在才成为可能，这意味着缺乏成功不能归因于无意中使用了与任何真正的尼安德特人DNA相违背的引物。因此，不能产生类似尼安德特人序列的标本确实可以说缺乏足够的DNA进行分析。通过这种方式，这项工作的目标，即获得额外的真实尼安德特人mtDNA序列的可能性的可靠评估，将实现。

Recently, Dr. S. PÞÞbo of Munich determined a mitochondrial DNA sequence from the Neandertal type specimen, and it was independently confirmed in our laboratory. Sequence analysis indicates that it is unlikely that Neandertals contributed mtDNA to contemporary human populations; however, this conclusion rests on this single sequence. A more definitive demonstration requires an assessment of the range of mtDNA variation in Neandertals. Such analyses require the successful retrieval of authentic DNA from additional Neandertal remains. The objective of this research is, therefore, to provide a thorough assessment of the prospects for retrieval of DNA from at least 10 additional Neandertal remains. This will be accomplished by analyzing a number of remains by a two-step procedure. First, a small quantity of bone powder will be analyzed for amino acid racemization, which has been shown to be a reasonable proxy for DNA. Second, for those specimens for which the degree of racemization is low enough to suggest DNA might survive in sufficient quantity and quality for analysis, DNA will be extracted and primers specific for the previously-determined Neandertal mtDNA sequence will be used in PCR amplifications. All amplification reactions which yield a PCR product of the expected size, and for which amplification and extraction controls are suitably negative, will be cloned and the sequence of at least 10 clones determined. Similar work will be carried out in parallel by Dr. PÞÞbo's laboratory in Munich. Specimens that yield a Neandertal-like sequence (as judged by comparison with the sequence obtained from the Neandertal type specimen), and which are replicated in both laboratories, will be judged as yielding reliable and authentic Neandertal DNA. These specimens would then be the subject of future analysis to determine additional mtDNA sequence information. The use of Neandertal-specific primers, which is only now possible, means that a lack of success cannot be attributed to the inadvertent use of primers that select against any authentic Neandertal DNA. Hence, specimens that do not yield Neandertal-like sequences can be truly said to lack sufficient DNA for analysis. In this way, the goal of this work, namely a robust assessment of the likelihood of obtaining additional authentic Neandertal mtDNA sequences, will be achieved.