Evolution of the avian sex chromosomes from an ancestral pair of autosomes
Evolution of the avian sex chromosomes from an ancestral pair of autosomes
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DOI：
10.1073/pnas.95.14.8147
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发表时间：
1998-07-07
影响因子：
11.1
通讯作者：
Ellegren, H
中科院分区：
文献类型：
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作者：
Fridolfsson, AK;Cheng, H;Ellegren, H
在动物性别决定的机制中，染色体性别决定在许多遥远的分类群中都有发现。染色体性别决定的广泛而不是普遍存在，甚至在谱系中也没有，这表明性染色体在动物辐射期间独立进化了几次，但缺乏确凿的证据。这个过程最受欢迎的模型是祖先常染色体对的逐渐分化，正如我们所知，哺乳动物的性染色体可能有一个非常古老的起源，甚至有人推测哺乳动物和鸟类的性染色体可能有一个共同的染色体祖先。在本研究中，我们暂时排除了目前分配到鸟类雌性特异性W染色体上的两个基因ATP5A1和CHD1都存在于Z染色体上一个非常密切相关的拷贝中，但不是假常染色体，这表明这两个性染色体具有共同的祖先，与一对常染色体的进化一致。然而，比较定位表明，ATP5A1和CHD1在真兽哺乳动物中没有性别连锁；到目前为止，鸟类Z染色体上的大多数其他基因也不是这样。我们的研究结果表明，性染色体的进化在哺乳动物和鸟类中是独立发生的。
Among the mechanisms whereby sex is determined in animals, chromosomal sex determination is found in a wide variety of distant taxa. The widespread but not ubiquitous occurrence, not even within lineages, of chromosomal sex determination suggests that sex chromosomes have evolved independently several times during animal radiation, but firm evidence for this is lacking. The most favored model for this process is gradual differentiation of ancestral pairs of autosomes, As known for mammals, sex chromosomes may have a very ancient origin, and it has even been speculated that the sex chromosomes of mammals and birds would share a common chromosomal ancestry. In this study we shelved that the two genes, ATP5A1 and CHD1, so far assigned to the female-specific W chromosome of birds both exist in a very closely related copy on the Z chromosome but are not pseudoautosomal, This indicates a common ancestry of the two sex chromosomes, consistent with the evolution from a pair of autosomes. Comparative mapping demonstrates, however, that ATP5A1 and CHD1 are not sex-linked among eutherian mammals; this is also not the case for the majority of other genes so far assigned to the avian Z chromosome. Our results suggest that the evolution of sex chromosomes has occurred independently in mammals and birds.