Architecture of the Vertebrate Egg Coat and Structural Basis of the ZP2 Block to Polyspermy

Nishio, S.; Emori, C.; Wiseman, B.; Fahrenkamp, D.; Dioguardi, E.; Zamora-Caballero, S.; Bokhove, M.; Han, L.; Stsiapanava, A.; Lu, Y.; Kodani, M.; Bainbridge, R. E.; Komondor, K. M.; Carlson, A. E.; Landreh, M.; de Sanctis, D.; Yasumasu, S.; Ikawa, M.; Jovine, L.

doi:10.1101/2023.06.21.544075

bioRxiv · 10.1101/2023.06.21.544075

Architecture of the Vertebrate Egg Coat and Structural Basis of the ZP2 Block to Polyspermy

Nishio, S.·Emori, C.·Wiseman, B.·Fahrenkamp, D.·Dioguardi, E.·Zamora-Caballero, S.·Bokhove, M.·Han, L.·Stsiapanava, A.·Lu, Y.·Kodani, M.·Bainbridge, R. E.·Komondor, K. M.·Carlson, A. E.·Landreh, M.·de Sanctis, D.·Yasumasu, S.·Ikawa, M.·Jovine, L.

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Abstract

Post-fertilization cleavage of glycoprotein ZP2, a major subunit of egg zona pellucida (ZP) filaments, is crucial for mammalian reproduction by irreversibly blocking polyspermy. ZP2 processing is thought to inactivate a sperm-binding activity located upstream of the proteins cleavage site; however, its molecular consequences and connection with ZP hardening are unknown. Here we report X-ray crystallographic, cryo-EM and biochemical studies showing that cleavage of ZP2 triggers its oligomerization. Deletion of the ZP-N1 domain that precedes the cleavage site of mouse ZP2 allows it to homodimerize even without processing, and animals homozygous for this variant are subfertile by having a semi-hardened ZP that allows sperm attachment but hinders penetration. Combined with the structure of a native egg coat filament, which reveals the molecular basis of heteromeric ZP subunit interaction, this suggests that oligomerization of cleaved ZP2 cross-links the ZP, rigidifying it and making it physically impenetrable to sperm.

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Nishio, S., Emori, C., Wiseman, B., Fahrenkamp, D., Dioguardi, E., Zamora-Caballero, S., Bokhove, M., Han, L., Stsiapanava, A., Lu, Y., Kodani, M., Bainbridge, R. E., Komondor, K. M., Carlson, A. E., Landreh, M., de Sanctis, D., Yasumasu, S., Ikawa, M., Jovine, L.. 2023-06-22. Architecture of the Vertebrate Egg Coat and Structural Basis of the ZP2 Block to Polyspermy. https://doi.org/10.1101/2023.06.21.544075

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