Key Laboratory of Freshwater Aquatic Genetic Resources, Ministry of Agriculture; National Demonstration Center for Experimental Fisheries Science Education; Shanghai Engineering Research Center of Aquaculture, Shanghai Ocean University, 999 Hucheng Ring Road, Shanghai, 201306, China.
College of Fisheries and Life Science, Pudong New Area, Shanghai Ocean University, 999 Hucheng Ring Road, Shanghai, 201306, China.
Cell Tissue Res. 2021 Dec;386(3):559-569. doi: 10.1007/s00441-021-03534-4. Epub 2021 Oct 2.
Germ plasm is a special cytoplasmic component containing special RNAs and proteins, and is located in specific regions of oocytes and embryos. Only the blastomeres inheriting the germ plasm can develop into primordial germ cells (PGCs). By using Vasa mRNA as a germline marker, we previously demonstrated that germline specification followed the preformation mode in the prawn Macrobrachium nipponense. In this study, we raised the Vasa antibody to identify germ plasm in the oocyte and trace the origin and migration of PGCs. In previtellogenic oocytes, Vasa protein was detected in the perinuclear region, in which electron-dense granules associated with numerous mitochondria were mostly visualized under a transmission electron microscope. In mature oocytes, immunosignal was localized to a large granule under the plasma membrane. During early embryogenesis, the granule was inherited by a single blastomere from 1-cell to 16-cell stages, and thereafter was segregated into two daughter blastomeres at the 32-cell stage. In gastrula, the Vasa-positive cells were large with typical PGC characteristics, containing a big round nucleus and a prominent nucleolus. The immunosignal was localized to the perinuclear region again. In the zoea stage, the Vasa-positive cells migrated toward the genital ridge and clustered in the dorsomedial region close to the yolk portion. Accordingly, we concluded that the prawn PGCs could be specified from the 16-cell stage by inheriting the germplasm. To our knowledge, this is the first report on the identification of the prawn germ plasm and PGCs. The continuous expression of Vasa protein throughout oogenesis and embryogenesis suggests that Vasa protein could be an important factor in germ plasm that functions in early germ cell specification.
生殖质是一种特殊的细胞质成分，含有特殊的 RNA 和蛋白质，位于卵母细胞和胚胎的特定区域。只有继承生殖质的卵裂球才能发育成原始生殖细胞（PGC）。我们之前使用 Vasa mRNA 作为生殖系标记证明，在对虾 Macrobrachium nipponense 中，生殖系的特化遵循预定模式。在这项研究中，我们制备了 Vasa 抗体来识别卵母细胞中的生殖质，并追踪 PGC 的起源和迁移。在卵黄发生前期卵母细胞中，Vasa 蛋白在核周区被检测到，在透射电子显微镜下，电子致密颗粒与大量线粒体相关联。在成熟卵母细胞中，免疫信号定位于质膜下的一个大颗粒。在早期胚胎发生过程中，从 1 细胞到 16 细胞阶段，单个卵裂球继承了这个颗粒，然后在 32 细胞阶段，这个颗粒被分成两个子卵裂球。在原肠胚阶段，阳性细胞体积较大，具有典型的 PGC 特征，包含一个大圆形核和一个明显的核仁。免疫信号再次定位于核周区。在幼体阶段，阳性细胞迁移到生殖嵴，聚集在靠近卵黄部分的背内侧区域。因此，我们得出结论，对虾 PGC 可以从 16 细胞阶段通过继承生殖质来特化。据我们所知，这是首次报道对虾生殖质和 PGC 的鉴定。Vasa 蛋白在卵发生和胚胎发生过程中的持续表达表明，Vasa 蛋白可能是生殖质中的一个重要因素，在早期生殖细胞特化中起作用。
