We found that STK33 is mutated in infertile patients with NOA, but Stk33-/KI and Stk33−/− mice were sterile with decreased number of sperm with oligoasthenoteratozoospermia, and Stk33KI/KI mice were subfertile with decreased number of sperm and asthenozoospermia. This evidence concerns the gene STK33 and Reduced sperm motility.