Perry George H, Dominy Nathaniel J, Claw Katrina G, Lee Arthur S, Fiegler Heike, Redon Richard, Werner John, Villanea Fernando A, Mountain Joanna L, Misra Rajeev, Carter Nigel P, Lee Charles, Stone Anne C
School of Human Evolution and Social Change, Arizona State University, Tempe, Arizona 85287, USA.
Nat Genet. 2007 Oct;39(10):1256-60. doi: 10.1038/ng2123. Epub 2007 Sep 9.
Starch consumption is a prominent characteristic of agricultural societies and hunter-gatherers in arid environments. In contrast, rainforest and circum-arctic hunter-gatherers and some pastoralists consume much less starch. This behavioral variation raises the possibility that different selective pressures have acted on amylase, the enzyme responsible for starch hydrolysis. We found that copy number of the salivary amylase gene (AMY1) is correlated positively with salivary amylase protein level and that individuals from populations with high-starch diets have, on average, more AMY1 copies than those with traditionally low-starch diets. Comparisons with other loci in a subset of these populations suggest that the extent of AMY1 copy number differentiation is highly unusual. This example of positive selection on a copy number-variable gene is, to our knowledge, one of the first discovered in the human genome. Higher AMY1 copy numbers and protein levels probably improve the digestion of starchy foods and may buffer against the fitness-reducing effects of intestinal disease.
食用淀粉是农业社会以及干旱环境中的狩猎采集者的一个显著特征。相比之下，雨林地区和环北极地区的狩猎采集者以及一些牧民食用的淀粉要少得多。这种行为差异增加了一种可能性，即不同的选择压力作用于淀粉酶，这种酶负责淀粉水解。我们发现，唾液淀粉酶基因（AMY1）的拷贝数与唾液淀粉酶蛋白水平呈正相关，并且来自高淀粉饮食群体的个体平均比传统低淀粉饮食群体的个体拥有更多的AMY1拷贝。对这些群体中的一部分与其他基因座的比较表明，AMY1拷贝数分化的程度非常不寻常。据我们所知，这种对拷贝数可变基因的正选择例子是在人类基因组中首次发现的之一。更高的AMY1拷贝数和蛋白水平可能会改善淀粉类食物的消化，并可能缓冲肠道疾病对健康的不良影响。
