Biology subjects

Yasumasu, S.

Publications and source records attributed to Yasumasu, S..

4 recordsLinked to original sources

bioRxiv2024

Effect of Light and Water Agitation on Hatching Processes in Clown Anemonefish Amphiprion ocellaris

Clown anemonefish (Amphiprion ocellaris) exhibit an environmentally cued hatching strategy, wherein parents generate water flow to encourage embryos to hatch after sunset on the eighth day post spawning. Although previous studies have shown that hatching requires complete darkness and water agitation, the regulatory mechanisms underlying these environmental cues remain elusive. This study investigated the expression patterns of hatching enzymes and how darkness and water agitation affect their secretion and the digestion of the egg envelope (chorion) in clown anemonefish. We revealed that hatching enzymes were expressed from the early developmental stages and decreased towards hatching day, similar to other fish species. The hatching gland cells were located on the tail, which may be associated with egg shape and chorion breakage. On the day of hatching, chorion digestion occurred exclusively in complete darkness, regardless of water agitation. In addition, ionomycin, a Ca2+ ionophore and an inducer of hatching enzyme secretion, triggered chorion digestion even under light-on conditions. Furthermore, water agitation expedited chorion digestion in the dark. In conclusion, our findings indicate that darkness triggers the secretion of hatching enzymes mediated by changes in Ca2+ levels, whereas water agitation assists chorion digestion activity and/or hatching enzyme secretion. These responses to environmental cues contribute to the rapid and synchronised hatching in clown anemonefish. Summary statementLight conditions and water agitation regulate the secretion of hatching enzymes and the chorion digestion activity, thereby facilitating a rapid hatching response to environmental changes in clown anemonefish.

physiology↗

bioRxiv2023

Architecture of the Vertebrate Egg Coat and Structural Basis of the ZP2 Block to Polyspermy

Post-fertilization cleavage of glycoprotein ZP2, a major subunit of egg zona pellucida (ZP) filaments, is crucial for mammalian reproduction by irreversibly blocking polyspermy. ZP2 processing is thought to inactivate a sperm-binding activity located upstream of the proteins cleavage site; however, its molecular consequences and connection with ZP hardening are unknown. Here we report X-ray crystallographic, cryo-EM and biochemical studies showing that cleavage of ZP2 triggers its oligomerization. Deletion of the ZP-N1 domain that precedes the cleavage site of mouse ZP2 allows it to homodimerize even without processing, and animals homozygous for this variant are subfertile by having a semi-hardened ZP that allows sperm attachment but hinders penetration. Combined with the structure of a native egg coat filament, which reveals the molecular basis of heteromeric ZP subunit interaction, this suggests that oligomerization of cleaved ZP2 cross-links the ZP, rigidifying it and making it physically impenetrable to sperm.

biophysics↗

bioRxiv2020

Cryo-EM Structure of Native Human Uromodulin, a Zona Pellucida Module Polymer

Assembly of extracellular filaments and matrices mediating fundamental biological processes such as morphogenesis, hearing, fertilization and antibacterial defense is driven by a ubiquitous polymerization module known as zona pellucida (ZP) "domain". Despite the conservation of this element from hydra to human, no information is available on the filamentous conformation of any ZP module protein. Here we report the cryo-electron microscopy structure of uromodulin (UMOD)/Tamm-Horsfall protein, the most abundant protein in human urine and an archetypal ZP module-containing molecule, in its mature homopolymeric state. UMOD forms a one-start helix with an unprecedented 180-degree twist between subunits enfolded by interdomain linkers that have completely reorganized as a result of propeptide dissociation. Lateral interaction between filaments in the urine generates sheets exposing a checkerboard of binding sites to capture uropathogenic bacteria, and UMOD-based models of mammalian and avian heteromeric egg coat filaments identify a common sperm-binding region at the interface between subunits.

biophysics↗

bioRxiv2019

Genome sequence of the euryhaline Javafish medaka, Oryzias javanicus: a small aquarium fish model for studies on adaptation to salinity.

BackgroundThe genus Oryzias is constituted of 35 medaka-fish species each exhibiting various ecological, morphological and physiological peculiarities and adaptations. Beyond of being a comprehensive phylogenetic group for studying intra-genus evolution of several traits like sex determination, behaviour, morphology or adaptation through comparative genomic approaches, all medaka species share many advantages of experimental model organisms including small size and short generation time, transparent embryos and genome editing tools for reverse and forward genetic studies. The Java medaka, Oryzias javanicus, is one of the two species of medaka perfectly adapted for living in brackish/sea-waters. Being an important component of the mangrove ecosystem, O. javanicus is also used as a valuable marine test-fish for ecotoxicology studies. Here, we sequenced and assembled the whole genome of O. javanicus, and anticipate this resource will be catalytic for a wide range of comparative genomic, phylogenetic and functional studies.\n\nFindingsComplementary sequencing approaches including long-read technology and data integration with a genetic map allowed the final assembly of 908 Mbp of the O. javanicus genome. Further analyses estimate that the O. javanicus genome contains 33% of repeat sequences and has a heterozygosity of 0.96%. The achieved draft assembly contains 525 scaffolds with a total length of 809.7 Mbp, a N50 of 6.3 Mbp and a L50 of 37 scaffolds. We identified 21454 expressed transcripts for a total transcriptome size of 57, 146, 583 bps.\n\nConclusionsWe provide here a high-quality draft genome assembly of the euryhaline Javafish medaka, and give emphasis on the evolutionary adaptation to salinity.

genomics↗