Somatic activity of the piRNA pathway in the mouse

The piRNA pathway is necessary for the suppression of retrotransposon activity in germ cells and the maintenance of germ cell populations, but the existence of the pathway in adult somatic cells has not been demonstrated. This study investigates the activity of the piRNA pathway in somatic cells of the adult mouse. We find that the PIWI protein MIWI2 is expressed in a variety of somatic tissues. Immunoprecipitation of MIWI2 from extracts of spleen cells and Friend virus-transformed mouse erythroblasts (MEL cells) identifies abundant piRNAs encoded by multiple intergenic clusters. In comparison to MIWI2-bound testis piRNAs, the somatic piRNAs are slightly smaller, and markedly deficient in repeat-derived sequences, but they have the same preference for a uracil at the 5' end; "ping-pong" amplification is absent. Determination of MIWI2-bound piRNAs in mouse erythropoietic cellspiRNA通路（piRNA pathway）对于抑制生殖细胞内反转录转座子（retrotransposon）的活性以及维持生殖细胞群的稳定必不可少，但目前尚无证据表明该通路存在于成体体细胞中。本研究针对成年小鼠体细胞中的piRNA通路活性展开探究。研究发现，PIWI蛋白MIWI2在多种体细胞组织中均有表达。通过对脾脏细胞与弗氏病毒转化的小鼠成红细胞（MEL细胞）提取物中的MIWI2进行免疫沉淀，可鉴定出由多个基因间簇编码的大量piRNA。与MIWI2结合的睾丸piRNA相比，体细胞piRNA的长度略短，且显著缺乏重复序列来源的序列，但二者在5'端偏好尿嘧啶的特征保持一致；且未检测到乒乓扩增（ping-pong amplification）现象。本研究同时完成了小鼠红细胞生成细胞中结合MIWI2的piRNA的鉴定。