Fusion as the result of sperm-somatic cell interaction

Area of Science:

• Reproductive Biology
• Cell Biology
• Molecular Biology

Background:

• Sperm-oocyte fusion is crucial for fertilization.
• The molecular mechanisms underlying sperm-somatic cell fusion are not fully understood.

Purpose of the Study:

• To investigate if acrosome-reacted spermatozoa can fuse with somatic cells.
• To determine if molecular machinery involved in sperm-egg fusion plays a role in sperm-somatic cell fusion.

Main Methods:

• Boar spermatozoa were capacitated and induced to undergo acrosome reaction.
• Fusion was assessed by fluorescent dye diffusion after incubating spermatozoa with somatic cells (granulosa, CRFK, VERO, ESK4).
• Involvement of integrin alpha6 and tetraspanin CD9 was evaluated using antibodies and CD9-negative cells; their expression was confirmed by western blot and immunostaining.

Main Results:

• Acrosome-reacted boar spermatozoa successfully fused with granulosa cells and various somatic cell lines (CRFK, VERO, ESK4).
• Fusion efficiency varied among cell types and correlated with their expression of integrin alpha6 and CD9.
• Inhibition of integrin alpha6 or CD9 significantly reduced fusion incidence.

Conclusions:

• Boar spermatozoa can fuse with diverse somatic cell types from different species.
• Sperm-somatic cell fusion necessitates the co-expression of integrin alpha6 and tetraspanin CD9 on the somatic cell plasma membrane.