1c of 1 histone cluster in mutant F12 (higher -panel) or treated with RNAi (lower -panel). Among different classes of endogenous little RNAs in pets, PIWI-interacting RNAs (piRNAs) play a conserved function in repressing transposons and various other repetitive components (REs)1, and in a number of pet species the increased loss of piRNAs causes sterility2. […]