LRRC23 (leucine rich repeat containing 23) is essential for sperm motility and male fertility, functioning as a critical component of the radial spoke 3 (RS3) head structure in sperm flagella 1. The protein plays a vital role in the proper assembly of RS3 and the bridge structure between RS2 and RS3, which are T-shaped multiprotein complexes that modulate flagellar motility 1. LRRC23 interacts with RS head protein RSPH9, and this interaction is crucial for RS3 head assembly 1. Loss-of-function mutations in LRRC23 cause asthenozoospermia (reduced sperm motility) and male infertility by disrupting RS3 assembly and flagellar structure 23. Cryo-electron tomography studies demonstrate that LRRC23 deficiency results in absence of the RS3 head and sperm-specific RS2-RS3 bridge structure 1. The protein has also been identified as a master regulator gene in severe persistent asthma, suggesting broader ciliary functions beyond reproduction 4. Clinically, LRRC23 mutations are associated with spermatogenic failure 92, but affected males can achieve successful fertility through assisted reproductive techniques like intracytoplasmic sperm injection 23.