How to manage without a Y chromosome.
How to manage without a Y chromosome.
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没有Y染色体如何生存。
DOI：
10.1073/pnas.2218839120
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发表时间：
2023-01-10
影响因子：
11.1
通讯作者：
Lamatsch, Dunja K.
中科院分区：
文献类型：
--
作者：
Schartl, Manfred;Lamatsch, Dunja K.
哺乳动物的Y染色体在遗传上是退化的，并且与其对应的X染色体相比很小。X和Y从一对常染色体进化了大约180 Mya。虽然X或多或少地保持了其原始结构，但Y停止了重组，导致其退化（1，2）;它失去了97%的基因内容，大小不到X的三分之一。只有决定雄性的Sry基因和其他一些基因，主要是精子发生基因，留在Y染色体上。哺乳动物的Y染色体，特别是人类的Y染色体，是否已经达到了退化的终点，或者它们是否会在完全消失之前继续萎缩（3-6）是有争议的。反对这一观点的一个主要论点是，完全失去Y染色体将使男性灭绝。因此，进化的力量会强烈反对这种损失。然而，一些已经失去Y染色体的啮齿动物物种反驳了这一论点。在奄美多刺鼠Tokudaia osimensis中，人们早就知道雄性没有Y染色体（图1）;然而，从那以后，这个物种的性别决定机制一直是个谜。在PNAS中，Terao et al. (7)现在，通过显示一个新的性别决定基因是由一个关键途径基因上游调控区的微小变化产生的，为Y染色体的丢失提供了一个解决方案。奄美刺鼠T. Osimensis是一种小型啮齿动物，生活在日本的奄美大岛。它被认为是濒危的破坏其自然环境和增加其天敌（www。红色名单org/）。这个物种在大约50年前引起了人们的注意，当时人们发现它丢失了典型的哺乳动物Y染色体（8，9）。雄性和雌性都具有N= 25 X 0的染色体结构;然而，在一个相关物种T中没有Y染色体的痕迹。muenninki（10）。提出了T. Osimensis的一个重要特征是Sry基因从原始Y染色体转移到另一条染色体上，但易位区域太小，无法在染色体扩散上检测到。这与某些男性的情况类似，他们的染色体核型为XX，没有Y染色体，但SRY基因易位到X染色体上（11）。然而，尽管进行了广泛的努力，在多刺大鼠中没有发现Sry基因的痕迹（12，13）。精子发生基因在哺乳动物Y染色体上的积累被认为是导致其进化分化和退化的原因（14）。而且，这些对男性有益的基因应该能保证Y染色体的维持。那么，除了Sry基因外，这只Amami多刺大鼠是如何失去Y染色体的呢？Y染色体上的基因对精子的产生和功能性雄性是必不可少的。前Tokudaia Y染色体的常染色质区域，包括精子发生的基因，现在被发现在男性和女性共享的单个X染色体上（15），这表明转移发生在Y丢失之前。在两种鱼类中，也观察到了以前位于退化Y染色体上的基因转移到其他染色体上的情况，就像“老鼠离开沉船”一样。在普通的孔雀鱼中，只有部分退化的Y，性拮抗的颜色基因占据了Y（MSY）的男性特异性区域。但在一个相关物种，沼泽孔雀鱼，其中有一个极端退化的Y，他们已经离开了MSY，现在是常染色体或假常染色体（16）。Terao et al. (7)现在提供了令人信服的证据的机制，如何性别是决定在奄美多刺大鼠。他们的基因方法首先...
The mammalian Y chromosome is genetically degenerated and small compared with its counterpart, the X chromosome. The X and Y evolved approximately 180 Mya from an autosome pair. While the X has more or less maintained its original structure, the Y stopped recombining, resulting in its degeneration (1, 2); it lost 97% of its gene content and is less than one-third the size of the X. Only the maleness-determining Sry gene and a few other genes, mostly spermatogenesis genes, remain on the Y chromosome. Whether mammalian Y chromosomes, and in particular the human Y, have reached an end point of degradation or whether they will continue to shrink before entirely disappearing (3–6) is controversial. One major argument against this idea is that total loss of the Y would wipe out males. Thus, evolutionary forces would strongly act against such a loss. However, a few rodent species, which have lost the Y chromosome contradict this argument. In the Amami spiny rat, Tokudaia osimensis, it was long known that males have no Y (Fig. 1); however, the mechanism of how sex is determined in this species has remained a mystery ever since. In PNAS, Terao et al.(7) now provide a solution to the loss of Y by showing that a new sex-determining gene was created by a tiny change in the regulatory region upstream of a key pathway gene. The Amami spiny rat, T. osimensis, is a small rodent that lives on the Amami-Oshima Island in Japan. It is considered endangered by the deconstruction of its natural environment and an increase in its natural enemies (www. redlist. org/). This species attracted attention about 50 y ago, when it was found to have lost the typical mammalian Y chromosome (8, 9). Both, males and females have a N= 25 X0 chromosome constitution; however, no trace of the Y chromosome that is present in a related species, T. muenninki (10), was detected. A hypothesis to explain the aberrant karyotype of T. osimensis has been that the Sry gene was transferred from the original Y to another chromosome, but the translocated region was too small to be detected on chromosome spreads. This would be similar to the situation in certain human males who have an XX karyotype without a Y chromosome but the SRY gene is translocated to the X (11). However, despite extensive efforts, no trace of the Sry gene was found in the spiny rat (12, 13). Accumulation of spermatogenesis genes on the mammalian Y is thought to have driven its evolutionary divergence and degeneration (14). Also, these male beneficial genes should guarantee the maintenance of the Y. So, how could the Amami spiny rat lose the Y chromosome that in addition to the Sry gene has harbored genes that are essential for sperm production and thus functional maleness? The euchromatic regions of the former Tokudaia Y chromosome including the genes for spermatogenesis are now found on the single X chromosome shared by males and females (15), suggesting that the transfer happened before the Y was lost. The situation that genes previously placed on the degenerating Y chromosome had moved to other chromosomes—like “rats leaving a sinking ship”—was also observed in two fish species. In the common guppy, which has an only partially degenerated Y, the sexually antagonistic color genes populate the male-specific regions of the Y (MSY). But in a related species, the swamp guppy, which has an extremely degenerated Y, they have left the MSY and are now autosomal or pseudoautosomal (16). In their manuscript in PNAS, Terao et al.(7) provide now compelling evidence for the mechanism of how sex is determined in the Amami spiny rat. Their genetic approach first …
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影响因子：
6
作者：
Nanda I;Schories S;Simeonov I;Adolfi MC;Du K;Steinlein C;Alsheimer M;Haaf T;Schartl M
通讯作者：
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影响因子：
1.6
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影响因子：
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作者：
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通讯作者：
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影响因子：
2.5
作者：
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通讯作者：
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影响因子：
3.1
作者：
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通讯作者：
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