Department of Behavioural Ecology and Evolutionary Genetics, Max Planck Institute for Ornithology, Eberhard-Gwinner-Strasse, D-82319 Seewiesen, Germany.
Proc Biol Sci. 2010 Nov 7;277(1698):3353-61. doi: 10.1098/rspb.2010.1007. Epub 2010 Jun 9.
In vertebrates, including humans, the relative length of the second to the fourth digit correlates with sex hormone-dependent behavioural, psychological and physiological traits. However, despite a decade of research, the underlying mechanism linking digit ratio to these sex hormone-dependent traits remains unclear. Previous work suggests that during embryo development, circulating levels of plasma androgens or oestrogens may act through their receptors to affect transcription levels of posterior HOX genes in the developing digits, thereby possibly influencing their relative length. The correlation between digit ratio and sex hormone-dependent traits might thus stem from variation in expression or sensitivity of the sex hormone receptors, or from variation in sex hormone levels in the embryo. Here, we show that in a population of 1156 zebra finches Taeniopygia guttata, a polymorphism in the oestrogen receptor α gene (ESR1) explains 11.3 per cent of the variation in digit ratio, and is also associated with male and female-mating behaviour. By contrast, we found no associations between digit ratio or mating behaviours and polymorphisms in the androgen receptor gene. Thus, our results (i) provide an explanation for the observed significant genetic covariance between digit ratio and male and female mating behaviour and (ii) strongly confirm the indicator function of digit ratio through the oestrogen pathway. Finally, we note that the commonly invoked effect of foetal testosterone on human digit ratio seems to be substantially weaker than the effect described here.
在包括人类在内的脊椎动物中，第二至第四指的相对长度与性激素依赖性的行为、心理和生理特征相关。然而，尽管已经进行了十年的研究，将数字比例与这些性激素依赖性特征联系起来的潜在机制仍不清楚。先前的工作表明，在胚胎发育过程中，循环中的血浆雄激素或雌激素水平可能通过其受体作用，影响发育中的手指中后部 HOX 基因的转录水平，从而可能影响其相对长度。因此，数字比例与性激素依赖性特征之间的相关性可能源于性激素受体的表达或敏感性的变化，或胚胎中性激素水平的变化。在这里，我们表明，在 1156 只斑胸草雀 Taeniopygia guttata 的群体中，雌激素受体 α 基因（ESR1）的一个多态性解释了数字比例变化的 11.3%，并且与雄性和雌性交配行为有关。相比之下，我们没有发现雄激素受体基因的多态性与数字比例或交配行为之间存在关联。因此，我们的结果：(i) 解释了观察到的数字比例与雄性和雌性交配行为之间存在显著遗传协方差的原因；(ii) 通过雌激素途径强烈证实了数字比例的指示功能。最后，我们注意到，胎儿睾丸激素对人类数字比例的通常影响似乎比这里描述的影响要小得多。
