The multicopy gene Sly represses the sex chromosomes in the male mouse germline after meiosis.-猫眼课题宝

DOI：

10.1371/journal.pbio.1000244

发表时间：

2009-11

期刊：

PLoS biology

影响因子：

9.8

通讯作者：

中科院分区：

生物学1区

文献类型：

作者：

Cocquet J;Ellis PJ;Yamauchi Y;Mahadevaiah SK;Affara NA;Ward MA;Burgoyne PS

来源链接：

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2770110/?report=classic

小干扰RNA被用来干扰小鼠Y染色体上100多个拷贝的Sly基因的功能，导致精子细胞分化过程中性染色体抑制缺陷，从而导致精子畸形和近乎不育。对Y染色体长臂缺陷小鼠的研究表明，男性特异区(MSYq)编码精子分化和减数分裂后性染色质抑制(PSCR)所需的信息。已经在MSYq上发现了几个基因，但因为它们每个都有40多个拷贝，所以它们的功能不能用传统的基因打靶来研究。在这里，我们产生了产生小干扰RNA的转基因小鼠，这些小干扰RNA专门针对MSYq编码的多拷贝基因Sly(类似Sycp3的Y连锁)的转录产物。对这些缺乏Sly的男性和缺乏MSYq的男性进行的微阵列分析显示，精子细胞中的性染色体基因显著上调。在正常男性精子细胞中，Sly蛋白与X和Y染色质共存，Sly缺乏会导致性染色质抑制标记的缺陷，如异染色质蛋白CBX1和赖氨酸9处甲基化的组蛋白H3水平降低。Sly缺陷小鼠与MSYq缺陷小鼠一样，精子分化严重受损，接近不育。我们认为它们的精子发生表型是Sly缺乏后精子细胞基因表达改变的结果。据我们所知，这是第一次成功地靶向干扰多拷贝基因(或任何Y基因)的功能。这表明Sly在PSCR中具有主要作用，它通过与精子细胞性染色质直接相互作用或通过与性染色质蛋白伴侣相互作用而发挥作用。Sly缺乏是17年前在MSYq缺陷男性中发现的一系列异常的主要潜在原因。我们的结果还表明，小鼠性相关精子细胞表达基因的扩增是伴随Sly扩增的PSCR增强的结果。在雄鼠的减数分裂过程中，X和Y染色体在转录上是沉默的，并在减数分裂后保留了显著程度的抑制。因此，在减数分裂后期，X和Y染色体编码的基因表达水平较低，但以许多副本存在的基因除外，这可以实现较高水平的表达。基因扩增是X和Y染色体的一个显著特征，有人认为这是为了补偿减数分裂后的抑制。小鼠Y染色体的长臂(MSYq)有多拷贝基因，这些基因在几个百万碱基上以簇的形式组织。在对携带MSYq缺失的小鼠进行分析的基础上，我们提出MSYq编码的遗传信息对于减数分裂后抑制性染色体和精子分化至关重要。然而，负责这些功能的基因(S)尚不清楚。在这项研究中，使用转基因传递的小干扰RNA，我们干扰了Sly的功能，Sly是一种存在于MSYq上的100多个拷贝的基因。SLY缺陷的男性有严重的精子分化问题，同时X和Y染色体上编码的基因在减数分裂后显著降低。此外，通常与性染色体抑制相关的表观遗传修饰也发生了改变。因此，我们的数据表明，Sly蛋白是介导X和Y染色体减数分裂后抑制所必需的。Sly缺陷男性的精子分化问题很可能主要是精子细胞中性染色体抑制的结果。我们认为，Sly对X和Y染色体上编码的基因的减数分裂后抑制作用推动了它们在小鼠体内的大量扩增。

Small-interfering RNAs have been used to disrupt the function of the more than 100 copies of the Sly gene on the mouse Y chromosome, leading to defective sex chromosome repression during spermatid differentiation and, as a consequence, sperm malformations and near-sterility. Studies of mice with Y chromosome long arm deficiencies suggest that the male-specific region (MSYq) encodes information required for sperm differentiation and postmeiotic sex chromatin repression (PSCR). Several genes have been identified on MSYq, but because they are present in more than 40 copies each, their functions cannot be investigated using traditional gene targeting. Here, we generate transgenic mice producing small interfering RNAs that specifically target the transcripts of the MSYq-encoded multicopy gene Sly (Sycp3-like Y-linked). Microarray analyses performed on these Sly-deficient males and on MSYq-deficient males show a remarkable up-regulation of sex chromosome genes in spermatids. SLY protein colocalizes with the X and Y chromatin in spermatids of normal males, and Sly deficiency leads to defective repressive marks on the sex chromatin, such as reduced levels of the heterochromatin protein CBX1 and of histone H3 methylated at lysine 9. Sly-deficient mice, just like MSYq-deficient mice, have severe impairment of sperm differentiation and are near sterile. We propose that their spermiogenesis phenotype is a consequence of the change in spermatid gene expression following Sly deficiency. To our knowledge, this is the first successful targeted disruption of the function of a multicopy gene (or of any Y gene). It shows that SLY has a predominant role in PSCR, either via direct interaction with the spermatid sex chromatin or via interaction with sex chromatin protein partners. Sly deficiency is the major underlying cause of the spectrum of anomalies identified 17 y ago in MSYq-deficient males. Our results also suggest that the expansion of sex-linked spermatid-expressed genes in mouse is a consequence of the enhancement of PSCR that accompanies Sly amplification. During meiosis in the male mouse, the X and Y chromosomes are transcriptionally silenced, and retain a significant degree of repression after meiosis. Postmeiotically, X and Y chromosome–encoded genes are consequently expressed at a low level, with the exception of genes present in many copies, which can achieve a higher level of expression. Gene amplification is a notable feature of the X and Y chromosomes, and it has been proposed that this serves to compensate for the postmeiotic repression. The long arm of the mouse Y chromosome (MSYq) has multicopy genes organized in clusters over several megabases. On the basis of analysis of mice carrying MSYq deletions, we proposed that MSYq encodes genetic information that is crucial for postmeiotic repression of the sex chromosomes and for sperm differentiation. The gene(s) responsible for these functions were, however, unknown. In this study, using transgenically delivered small interfering RNA, we disrupted the function of Sly, a gene that is present in more than 100 copies on MSYq. Sly-deficient males have major sperm differentiation problems together with a remarkable postmeiotic derepression of genes encoded on the X and Y chromosomes. Furthermore, the epigenetic modifications normally associated with sex chromosome repression are altered. Our data thus show that the SLY protein is required to mediate postmeiotic repression of the X and Y chromosomes. It is likely that the sperm differentiation problems in Sly-deficient males are largely a consequence of the derepression of the sex chromosomes in spermatids. We propose that the postmeiotic repressive effect of Sly on genes encoded on the X and Y chromosomes drove their massive amplification in the mouse.