Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan.
Department of Pathology, Osaka University, Suita, Osaka, Japan.
EMBO Rep. 2018 Mar;19(3). doi: 10.15252/embr.201744957. Epub 2018 Feb 14.
PIWI-interacting RNAs (piRNAs) are germ cell-specific small RNAs essential for retrotransposon gene silencing and male germ cell development. In piRNA biogenesis, the endonuclease MitoPLD/Zucchini cleaves long, single-stranded RNAs to generate 5' termini of precursor piRNAs (pre-piRNAs) that are consecutively loaded into PIWI-family proteins. Subsequently, these pre-piRNAs are trimmed at their 3'-end by an exonuclease called Trimmer. Recently, poly(A)-specific ribonuclease-like domain-containing 1 (PNLDC1) was identified as the pre-piRNA Trimmer in silkworms. However, the function of PNLDC1 in other species remains unknown. Here, we generate mutant mice and analyze small RNAs in their testes. Our results demonstrate that mouse PNLDC1 functions in the trimming of both embryonic and post-natal pre-piRNAs. In addition, piRNA trimming defects in embryonic and post-natal testes cause impaired DNA methylation and reduced MIWI expression, respectively. Phenotypically, both meiotic and post-meiotic arrests are evident in the same individual mutant mouse. The former and latter phenotypes are similar to those of MILI and MIWI mutant mice, respectively. Thus, PNLDC1-mediated piRNA trimming is indispensable for the function of piRNAs throughout mouse spermatogenesis.
PIWI 相互作用 RNA（piRNA）是一类生殖细胞特异性的小 RNA，对于逆转座子基因沉默和雄性生殖细胞发育至关重要。在 piRNA 生物发生过程中，内切核酸酶 MitoPLD/Zucchini 切割长的单链 RNA，生成前体 piRNA（pre-piRNA）的 5' 末端，这些 pre-piRNA 随后被称为 Trimmer 的外切核酸酶在 3' 端进行修剪。最近，多聚腺苷酸特异性核糖核酸酶样结构域包含蛋白 1（PNLDC1）被鉴定为家蚕中的 pre-piRNA 修剪酶。然而，PNLDC1 在其他物种中的功能仍然未知。在这里，我们生成了 PNLDC1 敲除小鼠，并分析了其睾丸中的小 RNA。我们的结果表明，小鼠 PNLDC1 参与了胚胎期和出生后 pre-piRNA 的修剪。此外，胚胎期和出生后睾丸中 piRNA 修剪缺陷分别导致 DNA 甲基化受损和 MIWI 表达降低。表型上，同一 PNLDC1 敲除小鼠中同时存在减数分裂和减数分裂后停滞。前者和后者的表型分别与 MILI 和 MIWI 突变小鼠的表型相似。因此，PNLDC1 介导的 piRNA 修剪对于 piRNA 在整个小鼠精子发生过程中的功能是不可或缺的。
