Peptides from sperm acrosomal protein that initiate egg development

Area of Science:

• Reproductive Biology
• Developmental Biology
• Marine Biology

Background:

• Sperm-egg interaction is crucial for initiating embryonic development.
• Previous research identified sperm acrosomal protein as an egg activator.
• The precise molecular mechanisms of sperm-induced egg activation remain under investigation.

Purpose of the Study:

• To identify and characterize the specific sperm component responsible for egg activation.
• To determine the sequence and biological activity of the active sperm peptide.
• To investigate the role of this peptide in initiating egg development and subsequent embryonic stages.

Main Methods:

• Enzymatic cleavage of sperm acrosomal protein into peptide fragments.
• Purification and sequencing of an active peptide (P23).
• Testing the biological activity of the purified and synthetic peptide on Urechis eggs, including experiments with sperm centrosome introduction and peptide conjugation.

Main Results:

• A peptide fragment, P23 (Val-Ala-Lys-Lys-Pro-Lys), was identified as responsible for egg activation.
• Synthetic P23 mimicked the activity of the natural peptide, inducing fertilization potential, meiosis completion, and DNA replication.
• P23-activated eggs, even with a sperm centrosome introduced separately, developed into trochophore larvae.
• P23 activated eggs externally and also induced germinal vesicle breakdown in oyster eggs, but not sea urchin eggs.

Conclusions:

• The peptide P23 is a key molecule in sperm-mediated egg activation in Urechis.
• P23 initiates a cascade of events mimicking fertilization, leading to embryonic development.
• The findings provide a molecular basis for understanding sperm-egg interactions and early development in marine invertebrates.