Cell Autonomous and Nonautonomous Function of CUL4B in Mouse Spermatogenesis

Area of Science:

• Reproductive Biology
• Molecular Genetics
• Cellular Biology

Background:

• CUL4B is a ubiquitin ligase with distinct roles in spermatogenesis compared to its homolog CUL4A.
• Previous studies showed CUL4A deficiency causes male infertility due to meiotic errors.

Purpose of the Study:

• To investigate the specific roles of CUL4B in spermatogenesis.
• To elucidate the mechanisms by which CUL4B affects male germ cells and somatic cells.

Main Methods:

• Generation of Cul4b germ cell-specific conditional knock-out (Cul4b(Vasa)) and global knock-out (Cul4b(Sox2)) mice.
• Analysis of sperm motility, mitochondrial activity, ATP production, and sperm structure.
• Mass spectrometry to identify CUL4B substrates.

Main Results:

• Germ cell-specific Cul4b deletion caused male infertility with impaired sperm motility, reduced mitochondrial activity, and defective sperm structures.
• CUL4B directly polyubiquitinates and degrades INSL6 in male germ cells.
• Global Cul4b knockout led to age-dependent germ cell loss, indicating a role in maintaining the spermatogonial stem cell niche.

Conclusions:

• CUL4B is crucial for spermatogenesis, acting cell-autonomously in germ cells for sperm motility and non-cell-autonomously in somatic cells for stem cell maintenance.
• CUL4B links sperm motility and stem cell maintenance via ubiquitin modification, underscoring its significance in male reproduction.