USP30 and Infertility: USPs are well-known deubiquitinating enzymes with key roles in spermatogenesis: USP9 deletion has been discovered in infertile men (54), polymorphisms in USP26 have been associated with infertility (55), male mice lacking USP2 have severe defects in sperm motility (56), and USP30 regulates mitochondrial morphology (26).