C. elegans Germ Cells Show Temperature and Age-Dependent Expression of Cer1, a Gypsy/Ty3-Related Retrotransposon
C. elegans Germ Cells Show Temperature and Age-Dependent Expression of Cer1, a Gypsy/Ty3-Related Retrotransposon
复制标题
DOI：
10.1371/journal.ppat.1002591
复制
发表时间：
2012-03-01
期刊：
影响因子：
6.7
通讯作者：
Priess, James R.
中科院分区：
文献类型：
--
作者：
Dennis, Shannon;Sheth, Ujwal;Priess, James R.
在小杆线虫生殖细胞中没有观察到病毒样颗粒（VLP），尽管线虫基因组含有少量的逆转录转座子和逆转录病毒序列。我们使用电子显微镜在各种小杆线虫野生株中寻找VLP，并在一些菌株中观察到非常罕见的候选VLP，包括小杆线虫的标准实验室菌株。elegans，N2.我们鉴定了N2 VLP为Cer 1产生的衣壳，Cer 1是Gypsy/Ty 3逆转录病毒/逆转录转座子家族中的一种逆转录转座子。Cer 1的表达是年龄和温度依赖性的，在15 ℃时表达丰富，在25 ℃时没有可检测的表达，这解释了VLP如何在以前的研究中逃脱检测。类似的年龄和温度依赖性的Cer 1反转录转座子的表达，观察其他几个野生菌株，表明这些属性是常见的，如果不是完整的，这个retroelement的功能。反转录转座子，与DNA转座子相反，在复制中具有细胞质阶段，并且那些感染非分裂细胞的转座子必须使其基因组物质通过核孔。在大多数C.在线虫生殖细胞中，核孔大部分被称为P颗粒的生殖细胞特异性细胞器覆盖。我们的研究结果表明，铈1衣壳的目标退出粗线期减数分裂生殖细胞，当自由核孔被添加到核膜和现有的P颗粒开始被删除。在粗线期生殖细胞中，Cer 1衣壳集中在远离细胞核的微管子集上，这些微管对微管抑制剂具有特殊的抗性;衣壳可以在老年人中聚集这些稳定的微管，这些微管表现出温度依赖性的卵子活力降低。当生殖细胞退出粗线期时，稳定的微管消失，衣壳重新分布到具有无P颗粒核孔的细胞核附近。这种重新分布是微管依赖性的，这表明从稳定的微管释放的衣壳转移到新的动态微管上，以跟踪到细胞核。这些研究介绍了C. elegans作为研究retroelements和生殖细胞生物学之间相互作用的模型。
Virus-like particles (VLPs) have not been observed in Caenorhabditis germ cells, although nematode genomes contain low numbers of retrotransposon and retroviral sequences. We used electron microscopy to search for VLPs in various wild strains of Caenorhabditis, and observed very rare candidate VLPs in some strains, including the standard laboratory strain of C. elegans, N2. We identified the N2 VLPs as capsids produced by Cer1, a retrotransposon in the Gypsy/Ty3 family of retroviruses/retrotransposons. Cer1 expression is age and temperature dependent, with abundant expression at 15 degrees C and no detectable expression at 25 degrees C, explaining how VLPs escaped detection in previous studies. Similar age and temperature-dependent expression of Cer1 retrotransposons was observed for several other wild strains, indicating that these properties are common, if not integral, features of this retroelement. Retrotransposons, in contrast to DNA transposons, have a cytoplasmic stage in replication, and those that infect non-dividing cells must pass their genomic material through nuclear pores. In most C. elegans germ cells, nuclear pores are largely covered by germline-specific organelles called P granules. Our results suggest that Cer1 capsids target meiotic germ cells exiting pachytene, when free nuclear pores are added to the nuclear envelope and existing P granules begin to be removed. In pachytene germ cells, Cer1 capsids concentrate away from nuclei on a subset of microtubules that are exceptionally resistant to microtubule inhibitors; the capsids can aggregate these stable microtubules in older adults, which exhibit a temperature-dependent decrease in egg viability. When germ cells exit pachytene, the stable microtubules disappear and capsids redistribute close to nuclei that have P granule-free nuclear pores. This redistribution is microtubule dependent, suggesting that capsids that are released from stable microtubules transfer onto new, dynamic microtubules to track toward nuclei. These studies introduce C. elegans as a model to study the interplay between retroelements and germ cell biology.