SPAG4

The mammalian sperm flagellum contains two cytoskeletal structures associated with the axoneme: the outer dense fibers surrounding the axoneme in the midpiece and principal piece and the fibrous sheath surrounding the outer dense fibers in the principal piece of the tail. Defects in these structures are associated with abnormal tail morphology, reduced sperm motility, and infertility. In the rat, the protein encoded by this gene associates with an outer dense fiber protein via a leucine zipper motif and localizes to the microtubules of the manchette and axoneme during sperm tail development. [provided by RefSeq]

sperm associated antigen 4

Involved in spermatogenesis. Required for sperm head formation but not required to establish and maintain general polarity of the sperm head. Required for anchoring and organization of the manchette. Required for targeting of SUN3 and probably SYNE1 through a probable SUN1:SYNE3 LINC complex to the nuclear envelope and involved in accurate posterior sperm head localization of the complex. May anchor SUN3 the nuclear envelope. Involved in maintenance of the nuclear envelope integrity. May assist the organization and assembly of outer dense fibers (ODFs), a specific structure of the sperm tail.

Biological Process cell differentiationIEA:UniProtKB-KW
Biological Process nuclear envelope organizationManual Assertion Based On ExperimentIBA:GO_Central
Biological Process spermatogenesisManual Assertion Based On ExperimentTAS:ProtInc

Membrane
Cytoplasm, cytoskeleton
Cytoplasm, cytoskeleton, flagellum axoneme
Nucleus envelope
Nucleus inner membrane
In spermatids, it is localized in the transient manchette and in the axoneme of elongating spermatids and epididymal sperm (By similarity).
Colocalized with SEPT12 at the nuclear periphery in round spermatids, at sperm neck in elongated spermatids and at midpiece regions in ejaculated spermatozoa (PubMed:25775403).