The SPARK complex forms the molecular basis of vertebrate fertilization

Victoria E. Deneke; Johannes P Suwita; Haoting Wang; Shingo Tonai; Yonggang Lu; Karin Panser; Alexander Schleiffer; Jeremy A. Hollis; Maria Novatchkova; Gerhard Duernberger; Karel Stejskal; Gabriela Krššáková; Andreas Blaha; Aleq Adrianne R. Andresan; Muriel Mirus; Hana Marvanova; Hsin‐Yi Chang; Taichi Noda; Alejandro R. Burga; Elisabeth Roitinger; Masahito Ikawa; Andrea Pauli

doi:10.64898/2026.05.13.724128

Developmental BiologybioRxivMay 15, 2026

Preprint

The SPARK complex forms the molecular basis of vertebrate fertilization

Victoria E. Deneke iD, Johannes P Suwita iD, Haoting Wang iD, Shingo Tonai iD, Yonggang Lu iD, Karin Panser iD, Alexander Schleiffer iD, Jeremy A. Hollis iD, Maria Novatchkova iD, Gerhard Duernberger iD, Karel Stejskal iD, Gabriela Krššáková, Andreas Blaha iD, Aleq Adrianne R. Andresan, Muriel Mirus, Hana Marvanova, Hsin‐Yi Chang iD, Taichi Noda iD, Alejandro R. Burga iD, Elisabeth Roitinger iD, Masahito Ikawa iD, Andrea Pauli iD

Abstract

Fertilization requires gamete recognition and membrane fusion, yet the molecular basis of this process in vertebrates remains unknown. Here we identify SPARK (sperm protein assembly and receptor-binding key), a conserved multi-protein complex that integrates all known sperm fertilization factors, including TMEM81-IZUMO1-SPACA6 and DCST1/2, together with two newly identified components, TMDD1 and FAM187A. SPARK subunits are mutually dependent for stability in mature sperm, and disruption of any single component causes male sterility in zebrafish and mice. Incubating zebrafish sperm with soluble egg receptor Bouncer partially rescues fertilization of Bouncer-deficient eggs in a SPARK-dependent manner, consistent with egg receptor binding priming the complex for fusion. Thus, we propose SPARK as a con-served molecular machine that couples gamete recognition to membrane fusion.

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