ODF1 (outer dense fiber of sperm tails 1) encodes a major structural protein component of the outer dense fibers in mammalian sperm tails, functioning as a small heat shock protein (HSPB10) with molecular chaperone activity 1. The protein is essential for maintaining the rigid junction between sperm head and tail, as demonstrated by targeted deletion studies in mice where Odf1-deficient males showed complete infertility due to sperm head detachment 1. ODF1 also plays a critical role in organizing the mitochondrial sheath and outer dense fiber structure within the sperm tail 1. Clinical significance is evident in human male infertility, where ODF1 expression is significantly decreased in asthenozoospermic men with reduced sperm motility compared to normozoospermic controls 2. Furthermore, ODF1 interacts with SUN5 and Nesprin3 to form a 'triplet' structure at the sperm neck region, and disruption of this complex contributes to acephalic spermatozoa syndrome 3. Even haplo-deficiency of ODF1 can cause subfertility through weakened head-to-tail coupling, suggesting its involvement in unexplained male infertility cases 4. The gene is specifically expressed in spermatids and contains conserved regulatory sequences for testis-specific expression 5.