Biology subjects

Deneke, V. E.

Publications and source records attributed to Deneke, V. E..

5 recordsLinked to original sources

bioRxiv2026

The SPARK complex forms the molecular basis of vertebrate fertilization

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.

developmental biology↗

bioRxiv2023

A conserved fertilization complex of Izumo1, Spaca6, and Tmem81 mediates sperm-egg interaction in vertebrates

Fertilization, the fusion of sperm and egg, is essential for sexual reproduction. While several proteins have been demonstrated to be essential for the binding and fusion of gametes in vertebrates, the molecular mechanisms driving this key process are poorly understood. Here, we performed a protein interaction screen using AlphaFold-Multimer to uncover protein-protein interactions in fertilization. This screen resulted in the prediction of a trimeric complex composed of the essential fertilization factors Izumo1 and Spaca6, and Tmem81, a protein previously not implicated in fertilization. We show that Tmem81 is a conserved, testis-expressed transmembrane protein that is evolutionarily related to Izumo1 and Spaca6 and is essential for male fertility in fish and mice. Consistent with trimer formation in vivo, zebrafish izumo1-/-, spaca6-/-, and tmem81-/- mutants exhibit the same sperm-egg binding defect and show co-depletion of all three proteins in sperm. Moreover, we provide experimental evidence that Izumo1, Spaca6, and Tmem81 interact in zebrafish sperm. Strikingly, the Izumo1-Spaca6 interaction is predicted to form a cleft that serves as a binding site for Bouncer, the only identified egg protein essential for fertilization in zebrafish. Together, these results provide compelling evidence for a conserved sperm factor complex in vertebrates that forms a specific interface for the sperm-egg interaction required for successful fertilization.

developmental biology↗

bioRxiv2021

The sperm protein Spaca6 is essential for fertilization in zebrafish

Fertilization is a key process in all sexually reproducing species, yet the molecular mechanisms that underlie this event remain unclear. To date, only a few proteins have been shown to be essential for sperm-egg binding and fusion in mice, and only some are conserved across vertebrates. One of these conserved, testis-expressed factors is SPACA6, yet its function has not been investigated outside of mammals. Here we show that zebrafish spaca6 encodes for a sperm membrane protein which is essential for fertilization. Zebrafish spaca6 knockout males are sterile. Furthermore, Spaca6-deficient sperm have normal morphology, are motile, and can approach the egg, but fail to bind to the egg and therefore cannot complete fertilization. Interestingly, sperm lacking Spaca6 have decreased levels of another essential and conserved sperm fertility factor, Dcst2, revealing a previously unknown dependence of Dcst2 expression on Spaca6. Together, our results show that zebrafish Spaca6 regulates Dcst2 levels and is required for binding between the sperm membrane and the oolemma. This is in contrast to murine SPACA6, which was reported not to be required for sperm-egg membrane binding but necessary for fusion. These findings demonstrate that Spaca6 is essential for zebrafish fertilization and is a conserved sperm factor in vertebrate reproduction.

developmental biology↗

bioRxiv2021

Sperm membrane proteins DCST1 and DCST2 are required for the sperm-egg fusion process in mice and fish

The process of sperm-egg fusion is critical for successful fertilization, yet the underlying mechanisms that regulate these steps have remained unclear in vertebrates. Here, we show that both mouse and zebrafish DCST1 and DCST2 are necessary in sperm to fertilize the egg, similar to their orthologs SPE-42 and SPE-49 in C. elegans and Sneaky in D. melanogaster. Mouse Dcst1 and Dcst2 single knockout (KO) spermatozoa are able to undergo the acrosome reaction and show normal relocalization of IZUMO1, an essential factor for sperm-egg fusion, to the equatorial segment. While both single KO spermatozoa can bind to the oolemma, they rarely fuse with oocytes, resulting in male sterility. Similar to mice, zebrafish dcst1 KO males are subfertile and dcst2 and dcst1/2 double KO males are sterile. Zebrafish dcst1/2 KO spermatozoa are motile and can approach the egg, but rarely bind to the oolemma. These data demonstrate that DCST1/2 are essential for male fertility in two vertebrate species, highlighting their crucial role as conserved factors in fertilization.

developmental biology↗

bioRxiv2019

CDK-regulated phase separation seeded by histone genes ensures precise growth and function of Histone Locus Bodies

Many membrane-less organelles form through liquid-liquid phase separation, but how their size is controlled and whether size is linked to function remain poorly understood. The Histone Locus Body (HLB) is an evolutionarily conserved nuclear body that regulates the transcription and processing of histone mRNAs. Here, we show that Drosophila HLBs form through phase separation of the scaffold protein multi-sex combs (Mxc). The size of HLBs is controlled in a precise and dynamic manner that is dependent on the cell cycle and zygotic gene activation. Control of HLB growth is achieved by a mechanism integrating nascent mRNAs at the histone locus, which catalyzes phase separation, and the nuclear concentration of Mxc, which is controlled by the activity of cyclin-dependent kinases. Reduced Cdk2 activity results in smaller HLBs and the appearance of nascent, misprocessed histone mRNAs. Our experiments thus identify a mechanism linking nuclear body growth and size with gene expression.

cell biology↗