RSPH6A (radial spoke head 6 homolog A) is a structural component of the radial spoke complex within the axoneme of sperm flagella. It functions as part of the radial spoke head, a T-shaped macromolecular complex that connects peripheral doublet microtubules to the central pair apparatus to regulate sperm flagellar beat frequency and amplitude 1. RSPH6A is testis-enriched and essential for proper flagellar assembly and male fertility; Rsph6a knockout mice produce short, immotile spermatozoa due to disrupted axoneme elongation and impaired manchette removal, with secondary loss of RSPH9 in flagella 2. Reduced RSPH6A expression is associated with asthenozoospermia (reduced sperm motility) 3. Genetic mutations in RSPH6A cause male infertility with normal sperm morphology in humans 4, and RSPH6A is a critical component of the radial spoke 1 head structure 1. Beyond fertility, RSPH6A variants show potential associations with blood pressure regulation through DNA methylation-mediated pathways 5 and shared genetic relationships with migraine and thyroid function traits 6. Testis-specific hypomethylation of RSPH6A supports tissue-specific expression patterns 7.