Plays a central role during spermatogenesis by participating in the repression 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. Required for the localization of Piwi proteins to the meiotic nuage. Involved in the piRNA metabolic process by ensuring the entry of correct transcripts into the normal piRNA pool and limiting the entry of cellular transcripts into the piRNA pathway. May act by allowing the recruitment of piRNA biogenesis or loading factors that ensure the correct entry of transcripts and piRNAs into Piwi proteins (By similarity). Found in a mRNP complex, at least composed of TDRD1, TDRD6, TDRD7 and DDX4. Interacts with MAEL. Interacts with PIWIL1, PIWIL2 and PIWIL4 (when methylated on arginine residues). Interacts with TDRD12 (By similarity). Component of the meiotic nuage, also named P granule, a germ-cell-specific organelle required to repress transposon activity during meiosis. Also present in chromatoid body (By similarity). Testis and ovary specific. Also expressed in several cancers. Tudor domains 2 and 3 have higher affinity for arginine-methylated peptides, tudor domain 1 is a poor binder due to an impaired aromatic cage. Belongs to the TDRD1 family. Potential poly-A sequence. Truncated N-terminus. Contaminating sequence. Truncated N-terminus. Potential poly-A sequence.