IQUB (IQ motif and ubiquitin domain containing) is an adapter protein that plays a critical role in flagellar and ciliary function by anchoring the radial spoke 1 (RS1) complex to the A microtubule of outer doublet microtubules in axonemes 1. The protein is essential for proper sperm flagellar motility, as IQUB deficiency causes male infertility characterized by asthenozoospermia despite normal sperm morphology 12. Mechanistically, IQUB functions by recruiting calmodulin in low calcium environments and inhibiting RSPH3/p-ERK1/2 activity to facilitate normal radial spoke assembly 1. The protein is specifically required for RS1 assembly but not RS2 or RS3, and its absence results in deficiency of RS1 while leaving other radial spokes intact 32. Beyond reproductive function, IQUB has been implicated in cancer biology, where upregulation promotes breast cancer cell proliferation and migration via the Akt/GSK3β/β-catenin signaling pathway 4. Mutations in IQUB cause structural defects in sperm flagella that can be addressed through assisted reproductive technologies like ICSI 2.