The testis-specific LINC component SUN3 is essential for sperm head shaping during mouse spermiogenesis

Area of Science:

• Reproductive Biology
• Cell Biology
• Molecular Genetics

Background:

• Sperm head shaping during spermiogenesis is vital for male fertility.
• Linker of nucleoskeleton and cytoskeleton (LINC) complexes are involved in nuclear shaping by transmitting mechanical forces.
• The precise role of LINC complexes in sperm head formation remains unclear.

Purpose of the Study:

• To investigate the function of SUN3, a testis-specific LINC component, in spermiogenesis and male fertility.
• To elucidate the molecular mechanisms underlying sperm head abnormalities associated with SUN3 deficiency.

Main Methods:

• CRISPR/Cas9 gene editing to generate Sun3 knockout mice.
• Phenotypic analysis of sperm counts, morphology (acrosome, head shape), and flagella.
• Assessment of manchette microtubules and perinuclear rings during spermiogenesis.
• Co-immunoprecipitation to study protein interactions (SUN3 and SUN4).

Main Results:

• Sun3 knockout male mice exhibit infertility with significantly reduced sperm counts.
• Mice lacking SUN3 display a globozoospermia-like phenotype, characterized by acrosomal defects and abnormal sperm flagella.
• Sperm head elongation failure and absence of manchette microtubules/perinuclear rings were observed in Sun3-null mice.
• SUN3 interacts with SUN4, and SUN4 protein levels are reduced in Sun3-deficient testes.

Conclusions:

• SUN3 is essential for proper sperm head shaping and male fertility.
• SUN3 likely functions within the LINC complex to transmit cytoskeletal forces for nuclear elongation.
• SUN3 deficiency leads to globozoospermia-like phenotypes, offering insights into related pathologies.