The diversity of nanos expression in echinoderm embryos supports different mechanisms in germ cell specification.
The diversity of nanos expression in echinoderm embryos supports different mechanisms in germ cell specification.
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DOI：
10.1111/ede.12197
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发表时间：
2016-07
影响因子：
2.9
通讯作者：
Wessel GM
中科院分区：
文献类型：
--
作者：
Fresques T;Swartz SZ;Juliano C;Morino Y;Kikuchi M;Akasaka K;Wada H;Yajima M;Wessel GM
所有动物有性生殖都需要生殖细胞谱系的说明。然而，生殖细胞分化的时间和机制在动物发育中是非常不同的。棘皮动物，如海胆和海星，是研究生殖细胞特化的分子和细胞机制的良好模型系统。在一些被测试的棘皮动物胚胎中，生殖细胞因子Vasa在早期发育期间广泛积累，并在原肠胚形成后被限制为生殖细胞谱系的细胞。然而，在海胆中，生殖细胞因子Vasa在32细胞阶段被限制在一个特定的谱系中。因此，我们假设，在海胆/拟锦胆谱系中，生殖细胞规范程序已经进化到一个更早的发育时间点。为了验证这一假设，我们确定了第二种生殖细胞因子Nanos在5个现存棘皮动物分支中的4个中的表达模式。在这里，我们发现Nanos mRNA直到囊胚阶段才积累，或者在所有其他棘皮动物胚胎的发育过程中，除了那些属于棘皮类谱系的胚胎。相反，Nanos在棘球蚴胚胎的32-128细胞阶段在一个有限的区域表达。我们的研究结果支持了生殖细胞特异性程序在棘蚴谱系中发生异慢性转移的模型。比较棘球蚴和非棘球蚴的生殖细胞特化机制将有助于我们理解这些机制在动物进化过程中是如何变化的。
Specification of the germ cell lineage is required for sexual reproduction in all animals. However, the timing and mechanisms of germ cell specification is remarkably diverse in animal development. Echinoderms, such as sea urchins and sea stars, are excellent model systems to study the molecular and cellular mechanisms that contribute to germ cell specification. In several echinoderm embryos tested, the germ cell factor Vasa accumulates broadly during early development and is restricted after gastrulation to cells that contribute to the germ cell lineage. In the sea urchin, however, the germ cell factor Vasa is restricted to a specific lineage by the 32-cell stage. We therefore hypothesized that the germ cell specification program in the sea urchin/Euechinoid lineage has evolved to an earlier developmental time point. To test this hypothesis we determined the expression pattern of a second germ cell factor, Nanos, in four out of five extant echinoderm clades. Here we find that Nanos mRNA does not accumulate until the blastula stage or later during the development of all other echinoderm embryos except those that belong to the Echinoid lineage. Instead, Nanos is expressed in a restricted domain at the 32–128 cell stage in Echinoid embryos. Our results support the model that the germ cell specification program underwent a heterochronic shift in the Echinoid lineage. A comparison of Echinoid and non-Echinoid germ cell specification mechanisms will contribute to our understanding of how these mechanisms have changed during animal evolution.