Impact of selection and demography on the diffusion of lactase persistence.
Impact of selection and demography on the diffusion of lactase persistence.
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DOI：
10.1371/journal.pone.0006369
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发表时间：
2009-07-24
期刊：
影响因子：
3.7
通讯作者：
Sanchez-Mazas A
中科院分区：
文献类型：
--
作者：
Gerbault P;Moret C;Currat M;Sanchez-Mazas A
乳糖酶可以消化新鲜牛奶中的乳糖。在大多数人中，其活性在断奶阶段后强烈下降，但在欧洲和一些游牧民族中以高频率持续存在。通常提出两种假说来解释乳糖酶持续表型的特殊分布。基因-文化协同进化假说假设牧区人群乳糖消化的营养优势。钙同化假说表明，乳糖酶持久性等位基因（LCT*P）的携带者在高纬度地区更受欢迎，那里的阳光不足，无法准确合成维生素D。在这项工作中，我们使用几种互补的方法来测试这两个假设的有效性在一个大型的全球乳糖酶持久性频率数据集。我们首先分析了乳糖酶持久性在各大洲的地理变异，畜牧业水平，和其他独立的多态性观察到的遗传模式的分布。然后，我们使用计算机模拟和引入驯化的大型考古日期数据库，根据不同的人口情景和选择强度来探索这些频率在欧洲的演变。我们的研究结果表明，基因文化协同进化是一个可能的假设在非洲高LCT*P频率优先发现在牧区人口。在欧洲，我们表明，人口的历史发挥了重要作用，乳糖酶持久性在大陆的扩散。此外，乳糖酶持续性的选择压力一直很高，在西北部的大陆，相比之下，东南部的遗传漂变可以单独解释观察到的频率。这种选择压力随纬度的增加是高度兼容的钙同化假说，而基因文化协同进化假说不能排除，如果积极选择乳糖酶基因进行在前面的扩张波在欧洲新石器时代的过渡。
The lactase enzyme allows lactose digestion in fresh milk. Its activity strongly decreases after the weaning phase in most humans, but persists at a high frequency in Europe and some nomadic populations. Two hypotheses are usually proposed to explain the particular distribution of the lactase persistence phenotype. The gene-culture coevolution hypothesis supposes a nutritional advantage of lactose digestion in pastoral populations. The calcium assimilation hypothesis suggests that carriers of the lactase persistence allele(s) (LCT*P) are favoured in high-latitude regions, where sunshine is insufficient to allow accurate vitamin-D synthesis. In this work, we test the validity of these two hypotheses on a large worldwide dataset of lactase persistence frequencies by using several complementary approaches. We first analyse the distribution of lactase persistence in various continents in relation to geographic variation, pastoralism levels, and the genetic patterns observed for other independent polymorphisms. Then we use computer simulations and a large database of archaeological dates for the introduction of domestication to explore the evolution of these frequencies in Europe according to different demographic scenarios and selection intensities. Our results show that gene-culture coevolution is a likely hypothesis in Africa as high LCT*P frequencies are preferentially found in pastoral populations. In Europe, we show that population history played an important role in the diffusion of lactase persistence over the continent. Moreover, selection pressure on lactase persistence has been very high in the North-western part of the continent, by contrast to the South-eastern part where genetic drift alone can explain the observed frequencies. This selection pressure increasing with latitude is highly compatible with the calcium assimilation hypothesis while the gene-culture coevolution hypothesis cannot be ruled out if a positively selected lactase gene was carried at the front of the expansion wave during the Neolithic transition in Europe.
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发表时间：
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影响因子：
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