DDX4 and Azoospermia: Additionally, germ cell-specific (DEAD-box helicase 4), seminal vesicle-specific (Semenogelin 1), and prostate-specific (Transglutaminase 4) mRNAs in seminal plasma could be markers for identifying the presence of germ cells or the rough localization of complete obstructive azoospermia (Li et al., 2012).