Pitt J N, Schisa J A, Priess J R
Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington, 98109, USA.
Dev Biol. 2000 Mar 15;219(2):315-33. doi: 10.1006/dbio.2000.9607.
The germ cells, and germ cell precursors, in the nematode Caenorhabditis elegans contain distinctive granules called P granules. During early embryogenesis, P granules are segregated asymmetrically into those blastomeres that eventually produce the germ line. Because of the correlation between P granule distribution and the development of the germ line, P granules are widely thought to function in some aspect of germ line specification or differentiation. Most of the analysis of P granule structure and localization has focused on the early embryo, when P granules are located in the cytoplasm. However, during most of development P granules are associated with germ cell nuclei. We report here an ultrastructural analysis of the nuclear-associated P granules in the germ cells of the adult hermaphrodite gonad. We show that P granules are tightly associated with nuclear pores and that the positions of certain structures within the P granules correspond to the positions of pores on the nuclear envelope. We present immunocytochemical and ultrastructural data suggesting that P granules can associate, or remain associated, with pore-like structures even after they detach from the nuclear envelope during oogenesis. Finally, we show that nuclear-associated P granules in the gonad contain RNA, complementing previous studies showing that cytoplasmic P granules in embryos contain RNA.
线虫秀丽隐杆线虫中的生殖细胞和生殖细胞前体含有称为P颗粒的独特颗粒。在早期胚胎发生过程中，P颗粒不对称地分离到那些最终产生生殖系的卵裂球中。由于P颗粒分布与生殖系发育之间的相关性，人们普遍认为P颗粒在生殖系特化或分化的某些方面发挥作用。对P颗粒结构和定位的大多数分析都集中在早期胚胎上，此时P颗粒位于细胞质中。然而，在大多数发育过程中，P颗粒与生殖细胞核相关联。我们在此报告对成年雌雄同体性腺生殖细胞中与核相关的P颗粒的超微结构分析。我们表明，P颗粒与核孔紧密相关，并且P颗粒内某些结构的位置与核膜上孔的位置相对应。我们提供的免疫细胞化学和超微结构数据表明，即使在卵子发生过程中P颗粒从核膜脱离后，它们仍可与孔状结构结合或保持结合。最后，我们表明性腺中与核相关的P颗粒含有RNA，这补充了先前的研究，即胚胎中的细胞质P颗粒含有RNA。
