TEX15 is an essential executor of MIWI2-directed transposon DNA methylation and silencing.

The PIWI protein MIWI2 and its associated PIWI-interacting RNAs (piRNAs) instruct DNA methylation of young active transposable elements (TEs) in the male germline. Here we show that MIWI2 associates with TEX15 in foetal gonocytes. TEX15 is predominantly a nuclear protein that is not required for piRNA biogenesis but is essential for piRNA-directed TE de novo methylation and silencing. In summary, TEX15 is an essential executor of mammalian piRNA-directed DNA methylation. Examination of piRNA expression profiles in control (Tex15+/-) and Tex15-/- foetal testes, RNA expression profiles in wildtype and Tex15-/- P20 testis, and RNA expression profiles in control (Tex15+/-) and Tex15-/- E16.5 gonocytes.