Localization of a single sperm membrane autoantigen (RSA-1) on spermatogenic cells and spermatozoa

Area of Science:

• Reproductive immunology
• Spermatozoa biology
• Protein biochemistry

Background:

• RSA-1 is a rabbit sperm membrane autoantigen.
• It is a sialoglycoprotein with a molecular weight of 13,000 daltons.
• RSA-1 expression begins on pachytene spermatocytes.

Purpose of the Study:

• To localize the RSA-1 antigen on testicular cells and spermatozoa.
• To characterize the molecular forms of RSA-1 in testicular cells and ejaculated sperm.

Main Methods:

• Immunofluorescence and immunoperoxidase staining for antigen localization.
• Immunoadsorbent chromatography and SDS-PAGE for polypeptide identification.

Main Results:

• RSA-1 appears in patches on pachytene spermatocytes and round spermatids.
• Uniform distribution observed on late spermatids and spermatozoa, stopping at the equatorial segment-postacrosomal border.
• In testicular cells, anti-RSA-1 recognizes a 13,000-dalton form and a dye front component.
• In ejaculated sperm, anti-RSA-1 recognizes an 84,000-dalton major band and five minor components in a higher-molecular-weight complex.

Conclusions:

• RSA-1 undergoes changes in surface distribution and molecular form during sperm development and ejaculation.
• These alterations suggest a role for RSA-1 in sperm function or maturation.