Physical mapping of the elephant X chromosome: conservation of gene order over 105 million years.

Claudia Leticia Rodríguez Delgado, Paul D Waters, Clément Gilbert, Terence J Robinson, Jennifer A Marshall Graves
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引用次数: 69

Abstract

All therian mammals (eutherians and marsupials) have an XX female/XY male sex chromosome system or some variant of it. The X and Y evolved from a homologous pair of autosomes over the 166 million years since therian mammals diverged from monotremes. Comparing the sex chromosomes of eutherians and marsupials defined an ancient X conserved region that is shared between species of these mammalian clades. However, the eutherian X (and the Y) was augmented by a recent addition (XAR) that is autosomal in marsupials. XAR is part of the X in primates, rodents, and artiodactyls (which belong to the eutherian clade Boreoeutheria), but it is uncertain whether XAR is part of the X chromosome in more distantly related eutherian mammals. Here we report on the gene content and order on the X of the elephant (Loxodonta africana)-a representative of Afrotheria, a basal endemic clade of African mammals-and compare these findings to those of other documented eutherian species. A total of 17 genes were mapped to the elephant X chromosome. Our results support the hypothesis that the eutherian X and Y chromosomes were augmented by the addition of autosomal material prior to eutherian radiation. Not only does the elephant X bear the same suite of genes as other eutherian X chromosomes, but gene order appears to have been maintained across 105 million years of evolution, perhaps reflecting strong constraints posed by the eutherian X inactivation system.

大象X染色体的物理图谱:1.05亿年来基因顺序的保存。
所有兽类哺乳动物(真兽类和有袋类)都有XX雌性/XY雄性性染色体系统或其变体。自从兽类哺乳动物从单孔动物分化出来以来,在1.66亿年的时间里,X和Y从一对同源常染色体进化而来。比较真动物和有袋动物的性染色体,确定了这些哺乳动物进化分支物种之间共享的一个古老的X保守区域。然而,真兽X(和Y)被最近的添加(XAR)增加,这是有袋动物的常染色体。XAR是灵长类动物、啮齿动物和偶蹄动物(它们属于真动物分支Boreoeutheria) X染色体的一部分,但不确定XAR是否在更远亲的真动物中是X染色体的一部分。在这里,我们报告了非洲象(Loxodonta africana)的X染色体的基因含量和序列,并将这些发现与其他记录在案的真兽物种进行了比较。非洲象是非洲哺乳动物的基础地方性分支。共有17个基因被定位到大象X染色体上。我们的研究结果支持这样的假设,即真卵X染色体和Y染色体在真卵放射前通过常染色体物质的添加而扩增。大象的X染色体不仅与其他真动物的X染色体具有相同的基因套件,而且基因顺序似乎在1.05亿年的进化中得以维持,这可能反映了真动物X失活系统所构成的强烈限制。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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