Testis-enriched kinesin KIF9 is important for progressive motility in mouse spermatozoa

Miyata, H., Shimada, K., Morohoshi, A., Oura, S., Matsumura, T., Xu, Z., . . . Ikawa, M. (2020). Testis-enriched kinesin KIF9 is important for progressive motility in mouse spermatozoa. FASEB Journal, 34(4), 5389-5400. doi:10.1096/fj.201902755

Nexin-Dynein regulatory complex component DRC7 but not FBXL13 is required for sperm flagellum formation and male fertility in mice

Nexin-Dynein regulatory complex component DRC7 but not FBXL13 is required for sperm flagellum formation and male fertility in mice. Morohoshi A, Miyata H, Shimada K, Nozawa K, Matsumura T, et al. PLOS Genetics. 2020. 16(1) doi:10.1371/journal.pgen.100858

RSPH6A is required for sperm flagellum formation and male fertility in mice

The flagellum is an evolutionarily conserved appendage used for sensing and locomotion. Its backbone is the axoneme and a component of the axoneme is the radial spoke (RS), a protein complex implicated in flagellar motility regulation. Numerous diseases occur if the axoneme is improperly formed, such as primary ciliary dyskinesia (PCD) and infertility. Radial spoke head 6 homolog A (RSPH6A) is an ortholog of Chlamydomonas RSP6 in the RS head and is evolutionarily conserved. While some RS head proteins have been linkedtoPCD, littleisknown about RSPH6A. Here, weshow that mouse RSPH6A is testis-enriched and localized in the flagellum. Rsph6a knockout (KO) male mice are infertile as a result of their short immotile spermatozoa. Observation of the KO testis indicates that the axoneme can elongate but is disrupted before accessory structures are formed. Manchette removal is also impaired in the KO testis. Further, RSPH9, another radial spoke protein, disappeared in the Rsph6a KO flagella. These data indicate that RSPH6A is essential for sperm flagellar assembly and male fertility in mice. This article has an associated First Person interview with the first author of the paper

A Germ Cell–Specific Gene of the ARGONAUTE Family Is Essential for the Progression of Premeiotic Mitosis and Meiosis during Sporogenesis in Rice[W]

The rice (Oryza sativa) genome contains 18 copies of genes of the ARGONAUTE (AGO) family. Although AGO members play important roles in RNA-mediated silencing during plant development, a family member that is specifically involved in sexual reproduction has not been identified in plants. We identified the rice AGO gene MEIOSIS ARRESTED AT LEPTOTENE1 (MEL1) from the analysis of seed-sterile mutants. In the mel1 mutant, chromosome condensation was arrested at early meiotic stages and irregularly sized, multinucleated, and vacuolated pollen mother cells (PMCs) frequently appeared in developing anthers. In addition, histone H3 lysine-9 dimethylation of pericentromeres was rarely reduced and modification of the nucleolar-organizing region was altered in mel1 mutant PMCs. The mutation also affected female germ cell development. These results indicate that the germ cell–specific rice MEL1 gene regulates the cell division of premeiotic germ cells, the proper modification of meiotic chromosomes, and the faithful progression of meiosis, probably via small RNA–mediated gene silencing, but not the initiation and establishment of germ cells themselves

Sperm IZUMO1 Is Required for Binding Preceding Fusion With Oolemma in Mice and Rats

Fertilization occurs as the culmination of multi-step complex processes. First, mammalian spermatozoa undergo the acrosome reaction to become fusion-competent. Then, the acrosome-reacted spermatozoa penetrate the zona pellucida and adhere to and finally fuse with the egg plasma membrane. IZUMO1 is the first sperm protein proven to be essential for sperm-egg fusion in mammals, as Izumo1 knockout mouse spermatozoa adhere to but fail to fuse with the oolemma. However, the IZUMO1 function in other species remains largely unknown. Here, we generated Izumo1 knockout rats by CRISPR/Cas9 and found the male rats were infertile. Unlike in mice, Izumo1 knockout rat spermatozoa failed to bind to the oolemma. Further investigation revealed that the acrosome-intact sperm binding conceals a decreased number of the acrosome-reacted sperm bound to the oolemma in Izumo1 knockout mice. Of note, we could not see any apparent defects in the binding of the acrosome-reacted sperm to the oolemma in the mice lacking recently found fusion-indispensable genes, Fimp, Sof1, Spaca6, or Tmem95. Collectively, our data suggest that IZUMO1 is required for the sperm-oolemma binding prior to fusion at least in rat