Mitogenic polypeptide of the mammalian seminiferous epithelium: biochemical characterization and partial purification

Area of Science:

• Reproductive Biology
• Molecular Endocrinology
• Cellular Signaling

Background:

• A mitogenic polypeptide was previously identified in prepuberal mouse Sertoli cells.
• This factor, seminiferous growth factor (SGF), is crucial for testicular development.

Purpose of the Study:

• To determine the presence and characteristics of SGF in adult mammalian testes.
• To investigate the biochemical properties and purification of SGF.

Main Methods:

• Detection of SGF in adult mouse and other mammalian species (rat, guinea pig, calf).
• Biochemical analysis including molecular weight, isoelectric point (pI), and aggregation properties.
• Multi-step purification protocol involving precipitation, ion exchange, gel filtration, and hydrophobic chromatography.
• Analysis of purified SGF using SDS-PAGE and silver staining.

Main Results:

• SGF is present in Sertoli cells of adult mice and the seminiferous epithelium of other mammals.
• SGF levels are not significantly reduced in adult mouse testes after hypophysectomy.
• Purified SGF from adult mouse and calf has a molecular weight of approximately 15,700 Da and a pI between 4.8-5.8.
• SGF exhibits a propensity to aggregate into high molecular weight species.
• A purification process yielded over 350-fold enrichment of SGF activity from calf testes.
• SDS-PAGE revealed approximately 7 polypeptides in the purified SGF preparation, ranging from 14,000 to 20,000 Da.

Conclusions:

• Seminiferous growth factor (SGF) is conserved across adult mammalian species.
• SGF is an important component of the adult mammalian reproductive system.
• The purification protocol effectively isolates SGF based on its biochemical properties.