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#sperm guidance

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Regeneration -ll

The protein that provides direction for sperm toward eggs in sea urchins is:

Sea urchin eggs release diffusible peptides into surrounding jelly that establish chemical gradients guiding sperm navigation. Resact, a fourteen amino acid peptide purified from Arbacia punctulata jelly, serves as potent chemoattractant for conspecific sperm, while speract functions in Strongylocentrotus purpuratus. Resact binds to transmembrane guanylate cyclase receptor on sperm flagellum, boosting cGMP, activating cyclic nucleotide-gated K+ channels, causing hyperpolarization, intracellular alkalization, and periodic CatSper calcium influxes that steer flagellum toward higher gradient. Bindin mediates adhesion after arrival, hyalin supports embryonic adhesion, not chemotactic directionality.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 7: Egg-sperm chemotaxis - resact, speract and guanylate cyclase signaling.

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Sea urchin -l

The protein that provides direction for sperm toward eggs in sea urchins is:

Sea urchin eggs release small soluble peptides into surrounding seawater to actively guide sperm navigation. Speract modulates intracellular Ca2+ to increase flagellar beat frequency aiding vicinity search, while resact is definitive 14-amino-acid chemotactic peptide purified from Arbacia punctulata jelly that attracts sperm directionally. Resact binds receptor guanylate cyclase and elicits rapid cGMP-dependent Ca2+ bursts that transiently increase curvature and steer swimming up concentration gradient, analogous to bacterial chemotaxis. Bindin is sperm adhesion protein, hyalin mediates blastomere adhesion. Resact thus provides precise directional information orienting sperm toward egg center, greatly increasing encounter efficiency during broadcast spawning.

Ref: Ward et al., J Biol Chem 1985, Discovery of resact; Gilbert Chapter 7: Sperm chemotaxis by resact and speract.

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