Proteomic characterization of sperm radial spokes identifies a novel spoke protein with an ubiquitin domain

Radial spokes are T-shaped protein complexes important for the regulation of axonemal dyneins in eukaryotic cilia and flagella. Using a functional proteomics approach, we identified six spoke proteins in sperm flagella of the ascidian Ciona intestinalis. Many of the domain/motif structures in spoke proteins are commonly found in flagella of both Ciona sperm and Chlamydomonas, but interestingly they often distribute over non-orthologous protein components. A novel 116 kDa protein named CMUB116 has both an ubiquitin domain and an IQ motif. It has orthologs in vertebrates, but not in Chlamydomonas. Furthermore, the results obtained by immunological analysis provide strong indication that CMUB116 is located at the stalk of radial spokes, where it is associated with MORN40

Generation of mutant mice by pronuclear injection of circular plasmid expressing Cas9 and single guided RNA

Mashiko, D., Fujihara, Y., Satouh, Y. et al. Generation of mutant mice by pronuclear injection of circular plasmid expressing Cas9 and single guided RNA. Sci Rep 3, 3355 (2013). https://doi.org/10.1038/srep0335

Sperm-borne phospholipase C zeta-1 ensures monospermic fertilization in mice

Sperm entry in mammalian oocytes triggers intracellular Ca2+ oscillations that initiate resumption of the meiotic cell cycle and subsequent activations. Here, we show that phospholipase C zeta 1 (PLCζ1) is the long-sought sperm-borne oocyte activation factor (SOAF). Plcz1 gene knockout (KO) mouse spermatozoa fail to induce Ca2+ changes in intracytoplasmic sperm injection (ICSI). In contrast to ICSI, Plcz1 KO spermatozoa induced atypical patterns of Ca2+ changes in normal fertilizations, and most of the fertilized oocytes ceased development at the 1-2-cell stage because of oocyte activation failure or polyspermy. We further discovered that both zona pellucida block to polyspermy (ZPBP) and plasma membrane block to polyspermy (PMBP) were delayed in oocytes fertilized with Plcz1 KO spermatozoa. With the observation that polyspermy is rare in astacin-like metalloendopeptidase (Astl) KO female oocytes that lack ZPBP, we conclude that PMPB plays more critical role than ZPBP in vivo. Finally, we obtained healthy pups from male mice carrying human infertile PLCZ1 mutation by single sperm ICSI supplemented with Plcz1 mRNA injection. These results suggest that mammalian spermatozoa have a primitive oocyte activation mechanism and that PLCζ1 is a SOAF that ensures oocyte activation steps for monospermic fertilization in mammals.Nozawa, K., Satouh, Y., Fujimoto, T. et al. Sperm-borne phospholipase C zeta-1 ensures monospermic fertilization in mice. Sci Rep 8, 1315 (2018). https://doi.org/10.1038/s41598-018-19497-

CABYR is essential for fibrous sheath integrity and progressive motility in mouse spermatozoa

Ca²⁺-binding tyrosine-phosphorylation-regulated protein (CABYR) has been implicated in sperm physiological function in several in vitro studies. It has also been implicated as a potential cause of and diagnostic tool in asthenozoospermic human males. CABYR is known to be localized to the fibrous sheath, an accessory structure in the flagellar principal piece. Utilizing the CRISPR–Cas9 technology, we have knocked out this gene in mice to understand its role in male fertility. <i>Cabyr</i>-knockout male mice showed severe subfertility with a defect in sperm motility as well as a significant disorganization in the fibrous sheath. Further, abnormal configuration of doublet microtubules was observed in the Cabyr-knockout spermatozoa, suggesting that the fibrous sheath is important for the correct organization of the axoneme. Our results show that it is the role of CABYR in the formation of the fibrous sheath that is essential for male fertility

Structural and functional insights into IZUMO1 recognition by JUNO in mammalian fertilization

Kato, K., Satouh, Y., Nishimasu, H. et al. Structural and functional insights into IZUMO1 recognition by JUNO in mammalian fertilization. Nat Commun 7, 12198 (2016). https://doi.org/10.1038/ncomms1219

CRISPR/Cas9-mediated rapid generation of multiple mouse lines identified Ccdc63 as essential for spermiogenesis

Spermatozoa are flagellated cells whose role in fertilization is dependent on their ability to move towards an oocyte. The structure of the sperm flagella is highly conserved across species, and much of what is known about this structure is derived from studies utilizing animal models. One group of proteins essential for the movement of the flagella are the dyneins. Using the advanced technology of CRISPR/Cas9 we have targeted three dynein group members; Dnaic1, Wdr63 and Ccdc63 in mice. All three of these genes are expressed strongly in the testis. We generated mice with amino acid substitutions in Dnaic1 to analyze two specific phosphorylation events at S124 and S127, and generated simple knockouts of Wdr63 and Ccdc63. We found that the targeted phosphorylation sites in Dnaic1 were not essential for male fertility. Similarly, Wdr63 was not essential for male fertility; however, Ccdc63 removal resulted in sterile male mice due to shortened flagella. This study demonstrates the versatility of the CRISPR/Cas9 system to generate animal models of a highly complex system by introducing point mutations and simple knockouts in a fast and efficient manner.Young, S.A.M.; Miyata, H.; Satouh, Y.; Kato, H.; Nozawa, K.; Isotani, A.; Aitken, R.J.; Baker, M.A.; Ikawa, M. CRISPR/Cas9-Mediated Rapid Generation of Multiple Mouse Lines Identified Ccdc63 as Essential for Spermiogenesis. Int. J. Mol. Sci. 2015, 16, 24732-24750. https://doi.org/10.3390/ijms16102473

Structural insights into tetraspanin CD9 function

Umeda, R., Satouh, Y., Takemoto, M. et al. Structural insights into tetraspanin CD9 function. Nat Commun 11, 1606 (2020). https://doi.org/10.1038/s41467-020-15459-