Dynamic redistribution of vasa homolog and exclusion of somatic cell determinants during germ cell specification in Ciona intestinalis
Dynamic redistribution of vasa homolog and exclusion of somatic cell determinants during germ cell specification in Ciona intestinalis
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DOI：
10.1242/dev.02446
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发表时间：
2006-07-15
期刊：
影响因子：
4.6
通讯作者：
Nakamura, Akira
中科院分区：
文献类型：
--
作者：
Shirae-Kurabayashi, Maki;Nishikata, Takahito;Nakamura, Akira
海鞘类胚胎在后极隔离一种特殊的细胞质，称为后质，在那里积累了许多母体RNA和蛋白质。虽然后质被认为是生殖质，但它也高度富含体细胞发育所必需的几种因子，并且后质成分如何调控生殖细胞和体细胞分化仍然是个谜。使用VasA同系物、CiVH和其他胞质后成分作为标记，我们发现含有胞质后的卵裂球，即B7.6细胞，在原肠形成过程中经历了不对称的细胞分裂，产生了两个不同的子细胞：B8.11和B8.12。大多数后质组分只分离到B8.11细胞中，而B8.11细胞永远不会融合到性腺中。相比之下，母体CiVH RNA和蛋白质专门分布在B8.12细胞中，B8.12细胞进一步分裂，并被合并到幼体的性腺中。在B8.12细胞中，CiVH的产生来自母体RNA来源，导致核周CiVH颗粒的形成，这可能是许多动物生殖细胞的标志。我们认为，特定的母体分子重新分布到B8.12细胞中，对于海鞘生殖细胞的指定是必不可少的。
Ascidian embryos sequester a specific cytoplasm, called the postplasm, at the posterior pole, where many maternal RNAs and proteins accumulate. Although the postplasm is thought to act as the germ plasm, it is also highly enriched in several factors essential for somatic cell development, and how the postplasm components regulate both germ and somatic cell differentiation remains elusive. Using a vasa homolog, CiVH, and other postplasmic components as markers, we found that the postplasm-containing blastomeres, the B7.6 cells, undergo an asymmetric cell division during gastrulation to produce two distinct daughter cells: B8.11 and B8.12. Most of the postplasmic components segregate only into the B8.11 cells, which never coalesce into the gonad. By contrast, the maternal CiVH RNA and protein are specifically distributed into the B8.12 cells, which divide further and are incorporated into the gonad in juveniles. In the B8.12 cells, CiVH production is upregulated from the maternal RNA source, resulting in the formation of perinuclear CiVH granules, which may be the nuage, a hallmark of germ cells in many animal species. We propose that the redistribution of specific maternal molecules into the B8.12 cells is essential for germ-cell specification in ascidians.