ATP-dependent RNA helicase required during spermatogenesis to repress transposable elements and prevent their mobilization, which is essential for germline integrity (PubMed:20534472, PubMed:20547853, PubMed:23166510, PubMed:25762440). 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 (PubMed:20534472, PubMed:20547853, PubMed:23166510, PubMed:25762440). Involved in the primary piRNA metabolic process (PubMed:20534472, PubMed:20547853, PubMed:23166510, PubMed:25762440). Specifically binds to piRNA precursors and promotes the generation of intermediate piRNA processing fragments that are subsequently loaded to Piwi proteins (PubMed:25762440). Acts via its ATP-dependent RNA helicase activity: displays 5'-3' RNA unwinding activity and probably mediates unwinding and funneling of single-stranded piRNA precursor transcripts to the endonuclease that catalyzes the first cleavage step of piRNA processing to generate piRNA intermediate fragments that are subsequently loaded to Piwi proteins (PubMed:25762440). May act downstream of MEF2C during heart formation. Acts as a cardiac-specific suppressor of cardiomyocyte hypertrophy and cell cycle progression, suggesting that it may suppress these processes through the regulation of CDKN1A. Such results however require additional evidence. ATP + H2O = ADP + H(+) + phosphate Interacts with PIWIL1 (PubMed:20534472). Interacts with PIWIL2 (PubMed:20534472, PubMed:20547853). Interacts with PIWIL4 (PubMed:20534472, PubMed:20547853). Interacts with HSPA2 (PubMed:20547853). Interacts with PLD6 (PubMed:25762440). Component of the meiotic nuage, also named P granule, a germ-cell-specific organelle required to repress transposon activity during meiosis (PubMed:20534472, PubMed:23166510). Additional isoforms seem to exist. Isoform 1: Specifically expressed in testis (PubMed:12754203). Isoform 1: In testis, present in pachytene spermatocytes but absent in postmeiotic spermatids (at protein level) (PubMed:20534472, PubMed:20547853). Isoform 2: Present in cardiomyocytes (at protein level) (PubMed:11279525). Isoform 2: Heart specific (PubMed:11854500). Isoform 3: Heart specific and is specifically expressed in cardiac myocytes (PubMed:12754203). Expression is first observed in the linear heart tube at 8 dpc. The highest expression is in the region that will give rise to the ventricular segments. At 9.5 dpc, the ventricular expression is maintained in the looped heart tube. In the adult, expression is observed exclusively within myocardial cells. Isoform 2: Activated by MEF2C. Isoform 3: Activated by Nkx2-5. Mice are viable and healthy but show male sterility due to defects in spermatogenesis at early prophase of meiosis I (PubMed:20534472, PubMed:20547853, PubMed:23166510). Retrotransposons are derepressed due to DNA demethylation (PubMed:20534472). Defects are caused by impaired piRNA biogenesis during pachytene (PubMed:20534472, PubMed:20547853). The absence of pachytene piRNAs causes disruption of germ cell development and results in defects in post-meiotic genome integrity (PubMed:23166510). Mice do not show any cardiac abnormalities (PubMed:20547853). Belongs to the DNA2/NAM7 helicase family. SDE3 subfamily.