Updike Dustin, Strome Susan
Molecular Cell and Developmental Biology, University of California Santa Cruz, Santa Cruz, CA 95064, USA.
J Androl. 2010 Jan-Feb;31(1):53-60. doi: 10.2164/jandrol.109.008292. Epub 2009 Oct 29.
Germ granules are large, non-membrane-bound, ribonucleoprotein (RNP) organelles found in the germ line cytoplasm of most, if not all, animals. The term germ granule is synonymous with the perinuclear nuage in mouse and human germ cells. These large RNPs are complexed with germ line-specific cytoplasmic structures such as the mitochondrial cloud, intermitochondrial cement, and chromatoid bodies. The widespread presence of germ granules across species and the associated germ line defects when germ granules are compromised suggest that germ granules are key determinants of the identity and special properties of germ cells. The nematode Caenorhabditis elegans has been a very fruitful model system for the study of germ granules, wherein they are referred to as P granules. P granules contain a heterogeneous mixture of RNAs and proteins. To date, most of the known germ granule proteins across species, and all of the known P granule components in C elegans, are associated with RNA metabolism, which suggests that a main function of germ granules is posttranscriptional regulation. Here we review P granule structure and localization, P granule composition, the genetic pathway of P granule assembly, and the consequences in the germ line when P granule components are lost. The findings in C elegans have important implications for the germ granule function during postnatal germ cell differentiation in mammals.
生殖颗粒是存在于大多数（即便不是所有）动物生殖系细胞质中的大型、无膜包裹的核糖核蛋白（RNP）细胞器。在小鼠和人类生殖细胞中，生殖颗粒这一术语与核周的生殖质同义。这些大型核糖核蛋白与生殖系特异性细胞质结构如线粒体云、线粒体间基质和类染色质体结合。生殖颗粒在物种间广泛存在，且当生殖颗粒受损时会出现相关的生殖系缺陷，这表明生殖颗粒是生殖细胞特性和特殊性质的关键决定因素。线虫秀丽隐杆线虫是研究生殖颗粒的一个非常有成效的模式生物，在其中生殖颗粒被称为P颗粒。P颗粒包含RNA和蛋白质的异质混合物。迄今为止，跨物种的大多数已知生殖颗粒蛋白以及秀丽隐杆线虫中所有已知的P颗粒成分都与RNA代谢相关，这表明生殖颗粒的主要功能是转录后调控。在此我们综述P颗粒的结构和定位、P颗粒的组成、P颗粒组装的遗传途径以及当P颗粒成分缺失时在生殖系中的后果。秀丽隐杆线虫的研究结果对哺乳动物出生后生殖细胞分化过程中的生殖颗粒功能具有重要意义。
