MAPK3 and Reduced sperm motility: In sperm function, IQUB modulates Ca2+/CaM-dependent inhibition of the p-ERK1/2/RSPH3 pathway to support flagellum radial spoke assembly, with mutations (e.g., c.842del, p.L281Pfs*28) causing asthenozoospermia despite normal sperm morphology; IQCN, by contrast, mediates acroplaxome stability and sperm head shaping, and its inactivation leads to acrosomal defects and fertilization failure due to impaired oocyte activation.