RSPH3 (radial spoke head 3) is a structural component of axonemal radial spokes essential for ciliary and sperm flagellar motility 1. The protein functions as a protein kinase A-anchoring protein (AKAP) that scaffolds the cAMP-dependent protein kinase holoenzyme and binds to ERK1/2, serving as a convergence point for MAPK and PKA signaling in cilia 1. RSPH3 localizes to the radial spoke head complex and is critical for proper radial spoke assembly and central complex integrity 2. Mutations in RSPH3 cause primary ciliary dyskinesia (PCD), characterized by near-absent radial spokes, variable central complex defects, and reduced ciliary beat amplitude 2. RSPH3 mutations also contribute to male infertility through asthenospermia with normal sperm morphology 3. The protein functions in conjunction with IQUB to regulate radial spoke assembly by inhibiting RSPH3/p-ERK1/2 activity 4. Patients with RSPH3 mutations causing severe asthenoteratospermia can achieve successful pregnancies through intracytoplasmic sperm injection (ICSI) 5. RSPH3 represents an important diagnostic marker in PCD cases with central complex/radial spoke defects, accounting for >10% of such cases 2.