Eizirik Eduardo, Yuhki Naoya, Johnson Warren E, Menotti-Raymond Marilyn, Hannah Steven S, O'Brien Stephen J
Laboratory of Genomic Diversity, NCI-Frederick, National Institutes of Health, Frederick, MD 21702-1201, USA.
Curr Biol. 2003 Mar 4;13(5):448-53. doi: 10.1016/s0960-9822(03)00128-3.
Melanistic coat coloration occurs as a common polymorphism in 11 of 37 felid species and reaches high population frequency in some cases but never achieves complete fixation. To investigate the genetic basis, adaptive significance, and evolutionary history of melanistic variants in the Felidae, we mapped, cloned, and sequenced the cat homologs of two putative candidate genes for melanism (ASIP [agouti] and MC1R) and identified three independent deletions associated with dark coloration in three different felid species. Association and transmission analyses revealed that a 2 bp deletion in the ASIP gene specifies black coloration in domestic cats, and two different "in-frame" deletions in the MC1R gene are implicated in melanism in jaguars and jaguarundis. Melanistic individuals from five other felid species did not carry any of these mutations, implying that there are at least four independent genetic origins for melanism in the cat family. The inferred multiple origins and independent historical elevation in population frequency of felid melanistic mutations suggest the occurrence of adaptive evolution of this visible phenotype in a group of related free-ranging species.
黑化毛色是37种猫科动物中11种的常见多态性现象，在某些情况下其种群频率很高，但从未完全固定下来。为了研究猫科动物黑化变异的遗传基础、适应性意义和进化历史，我们对两个假定的黑化候选基因（ASIP[刺鼠信号蛋白]和MC1R）的猫同源基因进行了定位、克隆和测序，并在三种不同的猫科动物中鉴定出与深色相关的三个独立缺失。关联分析和传递分析表明，ASIP基因中的一个2bp缺失决定了家猫的黑色毛色，而MC1R基因中的两个不同的“框内”缺失与美洲豹和美洲狮猫的黑化有关。来自其他五种猫科动物的黑化个体没有携带这些突变中的任何一种，这意味着猫科动物的黑化至少有四个独立的遗传起源。猫科动物黑化突变推断的多个起源和种群频率的独立历史升高表明，这种可见表型在一组相关的自由放养物种中发生了适应性进化。
