Germ line-limited and somatic chromosomes of Acricotopus lucidus differ in distribution and timing of alterations of histone modifications in male gonial mitosis and meiosis
Germ line-limited and somatic chromosomes of Acricotopus lucidus differ in distribution and timing of alterations of histone modifications in male gonial mitosis and meiosis
复制标题
DOI：
10.1007/s10577-012-9308-x
复制
发表时间：
2012-08-01
影响因子：
2.6
通讯作者：
Staiber, Wolfgang
中科院分区：
文献类型：
--
作者：
Staiber, Wolfgang
特殊的染色体限于生殖系（=Ks）和特殊的遗传事件，如消除有丝分裂和单极迁移的Ks在最后的生殖细胞有丝分裂是具体的功能复杂的染色体周期发生在摇蚊Acricotopus lucidus。在男性中，这种不平等的差别生殖腺有丝分裂的结果在一个正常的精母细胞拥有所有的Ks除了体细胞染色体（=Ss）和一个异常的精母细胞只包含Ss。在进化过程中，Ks是从SS进化而来的，由常染色质S同源片段和异染色质片段组成。关于Ks的功能和转录活性知之甚少。已知特定的翻译后组蛋白修饰与染色质的转录活性和非活性状态相关。在免疫荧光研究中，分析了A雄性生殖器有丝分裂和减数分裂中Ks和Ss组蛋白H3和H4中下列乙酰化（ac）、甲基化（me）和磷酸化（ph）氨基酸的分布。H3 K18 ac和H4 K8 ac，H3 K4 me 3和H3 K9 me 3，H3 S10 ph，H3 S28 ph和H3 T3 ph。Ks和Ss在生殖细胞和减数分裂中期的H3 S28 ph分布上明显不同。H3 S28 ph标记覆盖了整个Ss，而Ks仅在含有生殖系特异性重复DNA序列的着丝粒周围异染色质条带上显示此标记。同一细胞内Ks和Ss的H3 S10 ph、H3 S28 ph和H3 T3 ph的去磷酸化存在时间差异。的去磷酸化发生在Ks迁移第一极，比后来同样分离的Ss。在连接的初级精母细胞中，在中期I，异常精母细胞的未分离的Ss中发生了程序性的快速组蛋白脱乙酰化和脱磷酸化，这与这些Ss在中期样凝聚状态下的永久失活的开始相关。在减数分裂中，磷酸化的H3 T3只能在中期II染色体的内着丝粒的连接姐妹染色单体检测。最近报道，在该区域的H3 T3 ph标记在有丝分裂中对于染色体乘客复合体的组分的正确沉积以及因此对于染色体的正确比对、姐妹染色单体凝聚和分离是必需的（Wang et al.，Science 330：231-235，2010; Curr Biol 21：1061-1069，2011）。重要的是，在精母细胞，常染色质部分的Ks强烈乙酰化H3 K18和H4 K8，并在H3 K4三甲基化减数分裂I和II期间，而减数分裂Ss的常染色质hypoacetylated和hypomethylated在这些网站。这一结果表明，沉默的SS在精母细胞减数分裂。在常染色质K切片中检测到的高水平的活性组蛋白修饰支持了A.透明细胞在生殖细胞系中具有转录活性。
Special chromosomes limited to the germ line (=Ks) and exceptional genetic events such as elimination mitoses and a monopolar migration of the Ks in the last gonial mitosis are specific features of the complex chromosome cycle occurring in the chironomid Acricotopus lucidus. In the male, this unequal differential gonial mitosis results in a regular spermatocyte possessing all the Ks in addition to the somatic chromosomes (=Ss) and an aberrant spermatocyte containing only Ss. During evolution, the Ks have developed from the Ss and are composed of euchromatic S-homologous sections and heterochromatic segments. Less is known about the function and the transcriptional activity of the Ks. Specific post-translational histone modifications are known to be associated with transcriptionally active and inactive states of the chromatin. In an immunofluorescence study, the distribution of the following acetylated (ac), methylated (me) and phosphorylated (ph) amino acids in the histones H3 and H4 was analysed in Ks and Ss in male gonial mitoses and meiosis of A. lucidus, namely H3K18ac and H4K8ac, H3K4me3 and H3K9me3, H3S10ph, H3S28ph and H3T3ph. Ks and Ss clearly differ in the distribution of H3S28ph in gonial and meiotic metaphases. The H3S28ph mark covered the entire Ss, while the Ks showed this label only on their pericentromeric heterochromatin bands containing germ line-specific repetitive DNA sequences. A differential timing in the dephosphorylation of H3S10ph, H3S28ph and H3T3ph between Ks and Ss within the same cell was detected in the last gonial mitosis. The dephosphorylation occurred earlier in the Ks migrating first to the pole, than in the later equally segregating Ss. A programmed rapid histone deacetylation and dephosphorylation happened in the unseparated Ss of the aberrant spermatocyte at metaphase I in the connected primary spermatocyte, which correlated with the beginning of a permanent inactivation of these Ss in a metaphase-like condensed state. In meiosis, phosphorylated H3T3 could be detected only in metaphase II chromosomes at the inner centromeres of the attached sister chromatids. The H3T3ph labelling at this region was recently reported to be essential in mitosis for correct deposition of components of the chromosomal passenger complex and so for proper alignment, sister chromatid cohesion and segregation of chromosomes (Wang et al., Science 330:231-235, 2010; Curr Biol 21:1061-1069, 2011). Importantly, in spermatocytes, the euchromatic sections of the Ks were strongly acetylated at H3K18 and H4K8, and trimethylated at H3K4 during meiosis I and II, while the euchromatin of the meiotic Ss was hypoacetylated and hypomethylated at these sites. This result suggests a silencing of the Ss during spermatocyte meiosis. The high levels of active histone modifications detected in the euchromatic K sections support the idea that the Ks of A. lucidus are transcriptionally active in the germ line.