Editorial on “PNLDC1 is essential for piRNA 3' end trimming and transposon silencing during spermatogenesis in mice”

Piwi-interacting RNA (piRNA) are a class of small non-coding RNAs expressed in the germline. These piRNAs are processed to a mature piRNA by endonucleases and exonucleases that are bound to PIWI family proteins (1-3). In mouse, three Piwi proteins have been shown to be critical for spermatogenesis, namely Miwi, Mili and Miwi2 (4-6). Mili and Miwi show different temporal expression during testes development.