TDRD1 and Azoospermia: Interestingly, we identified meiotic proteins a priori unrelated to the UPS such as DAZL (deleted in azoospermia), SPAG1 (Sperm-associated antigen 1), SPATA5/20 (Spermatogenesis-associated protein 5/20), the tudor domain proteins TDRD1/6/9, MAEL (repressor of transposable elements), and RNF17.