RNA-binding factor that positively regulates gene expression by prohibiting miRNA-mediated gene suppression (By similarity). Relieves miRNA repression in germline cells (By similarity). Prohibits the function of several miRNAs by blocking the accessibility of target mRNAs (By similarity). Sequence-specific RNA-binding factor that binds specifically to U-rich regions (URRs) in the 3' untranslated region (3'-UTR) of several mRNAs (By similarity). Does not bind to miRNAs (By similarity). Isoform 1 may play a role during primordial germ cell (PGC) survival. However, does not seem to be essential for PGC migration. Interacts with APOBEC3. Perinuclear germ granules, also called germ plasm or chromatoid body (By similarity). Colocalizes in perinuclear sites with APOBEC3. Isoform 1 and isoform 2 are expressed in testis. Isoform 1 is expressed continuously in post natal (PN) testis although levels are low between PN1 to PN6. Isoform 2 is expressed from PN 20 onwards. Isoform 2 is strongly expressed in meiotic and in post-meiotic germ cells of the testis with highest expression at the elongated spermatid stage (at protein level). Expressed in testis and heart. Expressed in germ cells and genital ridges. Not detected in testicular tumors. Isoform 1, but not isoform 2, is expressed in embryos at 13.5 and 15.5 dpc. Isoform 1, but not isoform 2, is expressed in primordial gonads at 13.5 and 15.5 dpc. Isoform 1, but not isoform 2, is expressed in ES cell lines. Isoform 1, but not isoform 2, is expressed in embryonic germ (EG) cells (at protein level). Detected in the embryo and allantoic bud at 7.5 dpc, in the neuroectoderm at 8.5 dpc, and widespread at 9.5 dpc, including the neural tube, head mesenchyme, first branchial arch and the hindgut, through which primordial germ cells are migrating. At 11.5 dpc, also expressed in the XY and XX genital ridges. Expressed in genital ridges at 13.5 dpc. Between 12.5 to 14.5 dpc, up-regulated in the testis cords of the XY gonads and down-regulated in XX gonads. Down-regulation occurs progressively as an anterior to posterior wave. Defects in Dnd1 are the cause of the Ter mutation phenotype. Ter mice are characterized by primordial germ cell loss and susceptibility to spontaneous testicular germ cell tumors (TGCT). They are sterile, but viable. Isoform 1 defects may be the cause of tumor development. May be due to intron retention.