Ozhan-Kizil Günes, Havemann Johanna, Gerberding Matthias
Max-Planck-Institut für Entwicklungsbiologie, Spemannstr. 35, 72076 Tübingen, Germany.
Dev Biol. 2009 Mar 1;327(1):230-9. doi: 10.1016/j.ydbio.2008.10.028. Epub 2008 Nov 5.
Germ cells are a population of cells that do not differentiate to form somatic tissue but form the egg and sperm that ensure the reproduction of the organism. To understand how germ cells form, holds a key for identifying what sets them apart from all other cells of the organism. There are large differences between embryos regarding where and when germ cells form but the expression of Vasa protein is a common trait of germ cells. We studied the role of vasa during germ cell formation in the crustacean Parhyale hawaiensis. In a striking difference to the posterior specification of the group of germ cells in the arthropod model Drosophila, all germ cells in Parhyale originate from a single germ line progenitor cell of the 8-cell stage. We found vasa RNA ubiquitously distributed from 1-cell to 16-cell stage in Parhyale and localized to the germ cells from 32-cell stage onwards. Localization of vasa RNA to the germ cells is controlled by its 3'UTR and this could be mimicked by fluorescently labeled 3'UTR RNA. Vasa protein was first detectable at the 100-cell stage. MO-mediated inhibition of vasa translation caused germ cells to die after gastrulation. This means that in Parhyale Vasa protein is not required for the initial generation of the clone of germ cells but is required for their subsequent proliferation and maintenance. It also means that the role of vasa changed substantially during an evolutionary switch in the crustaceans by Parhyale from the specification of a group of germ cells to that of a single germ line progenitor. This is the first functional study of vasa in an arthropod beyond Drosophila.
生殖细胞是一类不会分化形成体细胞组织，而是形成卵子和精子以确保生物体繁殖的细胞群体。要了解生殖细胞是如何形成的，是识别它们与生物体所有其他细胞区别所在的关键。不同胚胎在生殖细胞形成的位置和时间上存在很大差异，但Vasa蛋白的表达是生殖细胞的一个共同特征。我们研究了Vasa在甲壳类动物夏威夷缺角蜣螂生殖细胞形成过程中的作用。与节肢动物模型果蝇中生殖细胞群体的后部特化形成显著差异的是，夏威夷缺角蜣螂的所有生殖细胞都起源于8细胞期的单个生殖系祖细胞。我们发现，在夏威夷缺角蜣螂中，Vasa RNA在1细胞期到16细胞期普遍分布，从32细胞期开始定位于生殖细胞。Vasa RNA定位于生殖细胞是由其3'非翻译区（3'UTR）控制的，这可以通过荧光标记的3'UTR RNA来模拟。Vasa蛋白在100细胞期首次可检测到。MO介导的Vasa翻译抑制导致生殖细胞在原肠胚形成后死亡。这意味着在夏威夷缺角蜣螂中，Vasa蛋白对于生殖细胞克隆的初始产生不是必需的，但对于它们随后的增殖和维持是必需的。这也意味着，在夏威夷缺角蜣螂所代表的甲壳类动物进化转变过程中，Vasa的作用发生了很大变化，从一组生殖细胞的特化转变为单个生殖系祖细胞的特化。这是除果蝇之外在节肢动物中对Vasa进行的首次功能研究。
