Sperm Specific Antigen 2 (SSFA2)

Sperm surface molecules have been shown to be transferred to the egg membrane during fertilization. Thus, the sperm cell can share in or impart antigenic specificities to fertilized ova and cleaving embryos. The molecules that are incorporated into the oocyte may provide an extranuclear signal to the oocyte to cleave. The sperm surface antigen involved in some step of early cleavage of the fertilized oocyte is a doublet of proteins of approximately 14 kD and 18 kD. Antibodies to this protein inhibit early cleavage of the oocyte without affecting pronuclear formation.No homology was found to any known sequence, indicating that CS1 is a unique protein. In a rabbit reticulocyte in vitro translation system, the transcribed CS1 RNA produced a 33-kD CS1 protein. The 2 parts of the antigen are presumably derived from 1 transcript.