GAK and Azoospermia: For instance, in 3M vs 1Y and 3M vs 3Y, 8 common DE circRNAs were generated from DAZL and BOLL that belong to deleted in azoospermia (DAZ) gene family associated with germ cell development and spermatogenesis (Fu et al., 2015); 29 DE circRNAs were derived from 15 genes coding for cell division cycle-related proteins (e.g., CDC14B, CDC20B, CDC6, GAK, CDK6, CDK12-13, CDK17, etc.).