Evolutionarily conserved sperm factors, DCST1 and DCST2, are required for gamete fusion.

Naokazu Inoue,Ikuo Wada,Yoshihisa Hagihara

doi:10.7554/elife.66313

Abstract

To trigger gamete fusion, spermatozoa need to activate the molecular machinery in which sperm IZUMO1 and oocyte JUNO (IZUMO1R) interaction plays a critical role in mammals. Although a set of factors involved in this process has recently been identified, no common factor that can function in both vertebrates and invertebrates has yet been reported. Here, we first demonstrate that the evolutionarily conserved factors dendrocyte expressed seven transmembrane protein domain-containing 1 (DCST1) and dendrocyte expressed seven transmembrane protein domain-containing 2 (DCST2) are essential for sperm-egg fusion in mice, as proven by gene disruption and complementation experiments. We also found that the protein stability of another gamete fusion-related sperm factor, SPACA6, is differently regulated by DCST1/2 and IZUMO1. Thus, we suggest that spermatozoa ensure proper fertilization in mammals by integrating various molecular pathways, including an evolutionarily conserved system that has developed as a result of nearly one billion years of evolution.

Highlights

Gamete recognition and fusion in mammals are considered to occur through a complex intermolecular interaction in which izumo sperm–egg fusion 1 (IZUMO1), sperm acrosome associated 6 (SPACA6), transmembrane protein 95 (TMEM95), fertilization influencing membrane protein (FIMP) and sperm–oocyte fusion required 1 (SOF1) on the sperm side and JUNO and cluster of differentiation 9 (CD9) on the ovum side are all involved in membrane fusion, as proven by gene disruption (Barbaux et al, 2020; Bianchi et al, 2014; Fujihara et al, 2020; Inoue et al, 2005; Kaji et al, 2000; Lamas-Toranzo et al, 2020; Le Naour et al, 2000; Lorenzetti et al, 2014; Miyado et al, 2000; Noda et al, 2020)
Mouse DCST1 is considered to be an orthologue of Caenorhabditis elegans spermatogenesis-defective 49 (SPE-49) (Wilson et al, 2018) and Drosophila SNEAKY (Wilson et al, 2006), whereas mouse DCST2 is considered to be an orthologue of C. elegans SPE-42 (Kroft et al, 2005) and Drosophila DCST2, the numbers of putative transmembrane regions appear different (Figure 1A,B)
Gamete fusion assay showed that Dcst1/2-/- spermatozoa were capable of binding to the plasma membranes of oocytes, but no Dcst1/2-/- spermatozoa had fused with the oocytes (Figure 3B)

Summary

Introduction

Gamete recognition and fusion in mammals are considered to occur through a complex intermolecular interaction in which izumo sperm–egg fusion 1 (IZUMO1), sperm acrosome associated 6 (SPACA6), transmembrane protein 95 (TMEM95), fertilization influencing membrane protein (FIMP) and sperm–oocyte fusion required 1 (SOF1) on the sperm side and JUNO ( known as IZUMO1 receptor) and cluster of differentiation 9 (CD9) on the ovum side are all involved in membrane fusion, as proven by gene disruption (Barbaux et al, 2020; Bianchi et al, 2014; Fujihara et al, 2020; Inoue et al, 2005; Kaji et al, 2000; Lamas-Toranzo et al, 2020; Le Naour et al, 2000; Lorenzetti et al, 2014; Miyado et al, 2000; Noda et al, 2020). Mouse DCST1 is considered to be an orthologue of Caenorhabditis elegans spermatogenesis-defective 49 (SPE-49) (Wilson et al, 2018) and Drosophila SNEAKY (Wilson et al, 2006), whereas mouse DCST2 is considered to be an orthologue of C. elegans SPE-42 (Kroft et al, 2005) and Drosophila DCST2, the numbers of putative transmembrane regions appear different (Figure 1A,B). These factors have been shown to be essential for fertilization. We here provide evidence that a common set of related factors between vertebrates and invertebrates actively participates in fertilization and appears to promote gamete merging in mammals

Results and discussion

Materials and methods

C Merged Hoechst 33342

Funding Funder