Furthermore, ING2 expression was lower in testicular biopsy specimens from non-obstructive azoospermia (NOA) patients than those from obstructive azoospermia (OA) patients (GSE9210) [46], suggesting the functional involvement of reduced expression of ING2 in human male infertility due to defective germ cell development, but not that due to a physical obstruction. Here, ING2 is linked to male infertility.