Because morphological defects in mitochondria are one cause of human asthenozoospermia [38, 39], revealing the mechanism is beneficial for developing new fertility treatments and male contraceptives.Recently, Chen et al., revealed that GK2 is specifically localized to the mitochondria in spermatids, and Gk2 KO male mice are infertile. Here, GK2 is linked to Reduced sperm motility.