C. elegans germ granules regulate both germline and somatic RNAome [RNA-Seq]

Germ granules are membrane-less organelles essential for small RNA biogenesis and germline development. Among the conserved properties of germ granules is their association with the nuclear membrane. Recent studies demonstrated that LOTUS domain proteins, EGGD-1 and EGGD-2 (also known as MIP-1 and MIP-2 respectively), promote the formation of perinuclear germ granules in C. elegans. This finding presents a unique opportunity to evaluate the significance of perinuclear localization of germ granules. Here we show that loss of eggd-1 causes the coalescence of germ granules and formation of abnormal cytoplasmic aggregates. Impairment of perinuclear granules affects certain germline classes of small RNAs including Piwi-interacting RNAs. Transcriptome profiling reveals overexpression of spermatogenic and cuticle-related genes in eggd-1 hermaphrodites. We further demonstrate that disruption of germ granules activates HLH-30-mediated transcriptional program in somatic tissues. Collectively, our findings underscore the essential role of EGGD-1 in germ granule organization and reveal an unexpected germ granule-to-soma communication. Overall design: Gene expression analysis of wild type and eggd-1 C. elegans mutants by mRNA sequencing

生殖颗粒（germ granules）是一类对小RNA生物发生与生殖系发育至关重要的无膜细胞器。生殖颗粒的保守特性之一是其与核膜的结合。近期研究表明，LOTUS结构域蛋白（LOTUS domain proteins）EGGD-1与EGGD-2（分别又名MIP-1与MIP-2）可促进秀丽隐杆线虫（C. elegans）中核周生殖颗粒的形成。这一发现为评估生殖颗粒核周定位的生物学意义提供了独特的研究契机。本研究发现，eggd-1基因缺失会导致生殖颗粒发生融合，并形成异常的细胞质聚集体。核周生殖颗粒的功能受损会影响特定生殖系小RNA类群，包括Piwi互作RNA（Piwi-interacting RNAs）。转录组分析显示，eggd-1突变型雌雄同体个体中，精子发生相关基因与表皮相关基因呈现过表达现象。本研究进一步证实，生殖颗粒的破坏会激活体细胞中由HLH-30介导的转录程序。综上，本研究结果明确了EGGD-1在生殖颗粒组装中的核心功能，并揭示了一条此前未被发现的生殖颗粒-体细胞通讯通路。实验设计：通过mRNA测序对野生型与eggd-1突变型秀丽隐杆线虫进行基因表达分析。