Plays a central role during spermatogenesis by repressing transposable elements and preventing their mobilization, which is essential for the germline integrity. Acts via the piRNA metabolic process, which mediates the repression of transposable elements during meiosis by forming complexes composed of piRNAs and Piwi proteins and governs the methylation and subsequent repression of transposons. Its association with piP-bodies suggests a participation in the secondary piRNAs metabolic process. Required for the localization of germ-cell factors to the meiotic nuage (By similarity). Interacts with SMARCB1, SIN3B and DDX4. Interacts with piRNA-associated proteins TDRD1, PIWIL1 and PIWIL2 (By similarity). Interacts with TEX19 (By similarity). Component of the meiotic nuage, also named P granule, a germ-cell-specific organelle required to repress transposon activity during meiosis. Specifically localizes to piP-bodies, a subset of the nuage which contains secondary piRNAs (By similarity). Testis-specific. Expressed in various cancer cell lines, probably due to demethylation of its promoter. Belongs to the maelstrom family.