The expression levels of germ-cell-specific mRNAs such as protamine 1 (PRM1), protamine 2 (PRM2), deleted in azoospermia (DAZ), and A-kinase anchoring protein 4 (AKAP4) have also been associated with SRR outcomes, with detectable levels linked to higher SRR rates in some studies [67]. Here, AKAP4 is linked to Azoospermia.