Motility and centrosomal organization during sea urchin and mouse fertilization

Area of Science:

• Cell Biology
• Developmental Biology
• Reproductive Biology

Background:

• Sperm and egg interactions are crucial for fertilization.
• The roles of cytoskeletal elements (microfilaments and microtubules) and centrosome inheritance in fertilization are not fully understood across different species.
• Mammalian fertilization mechanisms, particularly centrosome contribution, remain an area of active research.

Purpose of the Study:

• To investigate the roles of microfilaments and microtubules in sperm incorporation and pronuclear apposition during fertilization in sea urchins and mice.
• To examine the behavior and inheritance of centrosomes during fertilization in these species.

Main Methods:

• Utilized Latrunculin A, a microfilament assembly inhibitor, to test the requirement of microfilaments.
• Employed an autoimmune antibody against centrosomal material to detect and track centrosomes.
• Compared fertilization processes in sea urchins and mice at the molecular and cellular levels.

Main Results:

• Sperm incorporation in sea urchins requires microfilament activity, while mouse sperm incorporation occurs independently of microfilaments.
• Microfilament inhibitors arrested pronuclear apposition in mouse oocytes.
• Microtubules are essential for nuclear migrations in sea urchins (via sperm aster) and pronuclear apposition in mice (via egg cytoplasmic sites).
• Centrosomes were detected in sea urchin sperm but not unfertilized eggs, functioning in cell division.
• Mouse sperm lacked detectable centrosomal antigens; centrosomes were present in unfertilized oocytes.

Conclusions:

• Both microfilaments and microtubules are essential for fertilization in sea urchins and mice, but their specific functions and timing vary.
• Centrosomes are contributed by the sperm in sea urchins.
• Mammalian fertilization may involve maternal inheritance of centrosomes.