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Author Notes:

Correspondence: nishimura@lif.setsunan.ac.jp (H.N.), bioslh@emory.edu (S.W.L.)

We thank Andrew Singson (Rutgers University) for sharing unpublished data and for critical reading of our manuscript.

We are also grateful to Takeshi Ishihara (Kyushu University), Andrew Fire (Stanford University) and Masaru Okabe (Osaka University) for their kind gifts of pMW118, pPD118.20 and mouse Izumo1 cDNA, respectively.

Shozo Yokoyama (Emory University) and Naoyuki Iwabe (Kyoto University) provided helpful comments about spe-45 evolution.

Our gratitude is extended to Shohei Mitani as a representative of the National BioResource Project for providing spe-42(tm2421) and spe-45(tm3715) worms.

All experiments using worms were carried out under approval by the Institutional Animals Care and Use Committees of Setsunan University and Emory University.


Research Funding:

Some strains were provided by the Caenorhabditis Genetics Center, which is funded by the NIH Office of Research Infrastructure Programs (P40 OD010440).

This work was supported by MEXT KAKENHI Grant Number 24112716 (to H.N.) and JSPS KAKENHI Grant Number 24570241 (to H.N.), Japan.

We were also supported by grants from the NSF (to S.W.L., IOB-0544180) and the NIH (to S.W.L., GM082932 and HD066577) and by funds from Emory College, USA.

The Immunoglobulin-like Gene spe-45 Acts during Fertilization in Caenorhabditis elegans like the Mouse Izumo1 Gene


Journal Title:

Current Biology


Volume 25, Number 24


, Pages 3225-3231

Type of Work:

Article | Post-print: After Peer Review


The Caenorhabditis elegans spe-9 class genes, which show specific or predominant expression in the male germline, are indispensable for fertilization [ 1 and 2]. However, due to the rapid evolution of genes involved in reproduction, we do not currently know if there are spe-9 class genes in mammals that play similar roles during fertilization to those found in C. elegans. In mice, the Izumo1 gene encodes a sperm-specific transmembrane (TM) protein with a single immunoglobulin (Ig)-like domain that is absolutely required for gamete fusion [ 3 and 4]. In this study, we hypothesized that C. elegans has a new member of the spe-9 class genes coding for an IZUMO1-like protein. We screened C. elegans microarray data [ 5 and 6] to identify male germline-enriched genes that encode membrane proteins with Ig-like domains. A deletion (tm3715) in one such gene (F28D1.8) caused hermaphrodites to show a male germline-dependent self-sterility, so we have named it spe-45. Mutant spe-45 worms seemed to normally undergo spermatogenesis (spermatid production by meiosis) and spermiogenesis (spermatid activation into actively motile spermatozoa). spe-45 mutant spermatozoa, however, could not complete gamete fusion, which is a characteristic of all spe-9 class mutants [ 1 and 2]. Moreover, spe-45 self-sterile worms were rescued by a transgene expressing chimeric SPE-45 protein in which its Ig-like domain was replaced by the Ig-like domain from mouse IZUMO1. Hence, C. elegans SPE-45 and mouse IZUMO1 appear to have retained a common function(s) that is required during fertilization.

Copyright information:

© 2015 Elsevier Ltd. All rights reserved.

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