IQUB and Azoospermia: As catalogued in Table 1, key members include: IQCH, which regulates testis-specific RNA splicing and is linked to azoospermia (7, 12, 31); IQCD, which binds Munc13 to mediate the acrosome reaction (13); IQUB, whose deficiency causes asthenozoospermia (14, 15); IQCN, essential for sperm equatorial segment translocation and fertilization (16, 34, 36); and IQGAP1/IQGAP2, which regulate actin cytoskeleton dynamics and cell adhesion (6, 18–21, 37, 38).