| Modification Notes |
Mammalian sperm flagellum contain two cytoskeletal structures associated with the the axoneme: the outer dense fibers and the fibrous sheath. The outer dense fibers surround the axoneme in the midpiece and principal piece, whereas the fibrous sheath surrounds outer dense fibers of the tail of the principal piece. SPAG4 (sperm associated antigen 4), also known as outer dense fiber-associated protein SPAG4, is a 427 amino acid multi-pass membrane protein that may play a role in the organization and assembly of outer dense fibers (ODFs). Existing as a homodimer, SPAG4 interacts with Odf1 and is suggested to associate with microtubules. SPAG4 localizes to the transient manchette and axoneme of elongating spermatids and epididymal sperm. Containing one SUN domain, SPAG4 is considered a potential cancer marker. |