Germline X chromosomes exhibit contrasting patterns of histone H3 methylation in Caenorhabditis elegans
Germline X chromosomes exhibit contrasting patterns of histone H3 methylation in Caenorhabditis elegans
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DOI：
10.1006/dbio.2002.0634
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发表时间：
2002-05-01
影响因子：
2.7
通讯作者：
Lin, R
中科院分区：
文献类型：
--
作者：
Reuben, M;Lin, R
在哺乳动物中，雌性的两条体细胞X染色体中的一条失活，从而使两种性别的X染色体衍生的转录平衡，这一过程称为剂量补偿。然而，在生殖系中，情况却大不相同。两个X染色体在雌性卵子发生过程中转录活跃，而X和Y染色体在雄性精子发生过程中转录沉默。以往的研究表明，秀丽隐杆线虫生殖系X染色体可能有不同的转录活性，在两种性别的方式类似于在哺乳动物。使用特异于H3甲基化的抗体，我们发现，位点特异性H3甲基化的模式是不同的X染色体和常染色体之间以及生殖系X染色体之间的两个性别在C。优雅我们发现，粗线期生殖系X染色体在两性缺乏Me（K4）H3相比，常染色体，与他们的转录不活跃。生殖系X染色体的这种转录失活在雌雄同体中显然是短暂的，因为在生殖细胞核退出粗线期后，两条X染色体都对Me（K4）H3染色明亮。另一方面，男性单个X染色体在整个生殖系中仍然缺乏Me（K4）H3染色。相反，雄性生殖系X染色体表现出高水平的Me（K9）H3，其在任一性别的任何其他染色体上均未检测到，这与该染色体的稳定沉默一致。使用缺陷的性别决定途径的突变体，我们表明，X-染色体Me（K9）H3染色是由性表型，而不是核型，动物。我们在雄性小鼠XY体中检测到类似的高水平Me（K9）H3，这表明在雄性生殖系中特异性沉默X染色体的进化保守机制。(C)2002 Elsevier Science（美国）。
In mammals, one of the two somatic X chromosomes in the female is inactivated, thereby equalizing X chromosome-derived transcription in the two sexes, a process known as dosage compensation. In the germline, however, the situation is quite different. Both X chromosomes are transcriptionally active during female oogenesis, whereas the X and Y chromosomes are transcriptionally silent during male spermatogenesis. Previous studies suggest that Caenorhabditis elegans germline X chromosomes might have different transcriptional activity in the two sexes in a manner similar to that in mammals. Using antibodies specific to H3 methylated at either lysine 4 or lysine 9, we show that the pattern of site-specific H3 methylation is different between X chromosomes and autosomes as well as between germline X chromosomes from the two sexes in C. elegans. We show that the pachytene germline X chromosomes in both sexes lack Me(K4)H3 when compared with autosomes, consistent with their being transcriptionally inactive. This transcriptional inactivity of germline X chromosomes is apparently transient in hermaphrodites because both X chromosomes stain brightly for Me(K4)H3 after germ nuclei exit pachytene. The male single X chromosome, on the other hand, remains devoid of Me(K4)H3 staining throughout the germline. Instead, the male germline X chromosome exhibits a high level of Me(K9)H3 that is not detected on any other chromosomes in either sex, consistent with stable silencing of this chromosome. Using mutants defective in the sex determination pathway, we show that X-chromosomal Me(K9)H3 staining is determined by the sexual phenotype, and not karyotype, of the animal. We detect a similar high level of Me(K9)H3 in male mouse XY bodies, suggesting an evolutionarily conserved mechanism for silencing the X chromosome specifically in the male germline. (C) 2002 Elsevier Science (USA).