Component of specific cytoplasmic RNA granules involved in post-transcriptional regulation of specific genes: probably acts by binding to specific mRNAs and regulating their translation. Required for lens transparency during lens development, by regulating translation of genes such as CRYBB3 and HSPB1 in the developing lens. Also required during spermatogenesis. Found in a mRNP complex, at least composed of TDRD1, TDRD6, TDRD7 and DDX4. Found in a complex containing CABLES1, CDK16 and CDK17. Interacts with CABLES1, CDK17 and PIWIL1. Localizes to cytoplasmic RNA granules. Present in chromatoid body (CB) of spermatids (mammalian counterpart of germplasm, pole plasm or polar granules in Drosophila germ cells), also named processing bodies (P-bodies) in somatic cells. Detected in the multilobular cytoplasmic CBs (also called intermitochondrial cementin) in pachytene spermatocytes and as a single perinuclear CB in haploid round spermatids. Mainly expressed in testis. Expressed in spermatogonia, spermatocytes and round spermatids (at protein level). Also expressed in the developing lens. At 12.5 dpc, it is expressed in differentiating fiber cells in the posterior lens, but not in the anterior epithelium of the lens (AEL). Mice develop cataracts and glaucoma and males are sterile. Within 4 weeks of birth, mice develop a posterior cataract that becomes severe with age. At later stages, the lens fiber cell compartment develops vacuoles with lens capsule rupture and extrusion of fiber cell mass into the vitreous. In addition, the mass of fiber cells passes through the pupil into the anterior chamber of the eye. By 4 months of age, iris flattening is detected and anterior chamber depth increased. By 6 months of age, the intraocular pressure (IOP) is elevated in some mutants, and the incidence of elevated IOP increases with age, leading to glaucome. Severe optic nerve atrophy characterized by retinal ganglion cell axon loss and excavative remodeling of the optic nerve are observed. In addition, males display sterility due to an arrest in spermatogenesis at the round spermatid stage, likely due to a chromatoid body defect. Belongs to the TDRD7 family.