Biology subjects

Kuwahara, M.

Publications and source records attributed to Kuwahara, M..

4 recordsLinked to original sources

bioRxiv2026

Bidirectional Extracellular Vesicle-Mediated Maternal-Embryonic Exchange in the Lecithotrophic Teleost Guppy

The placenta is defined as an organ that mediates the exchanges of nutrients, hormones, and other substances between the mother and embryo in viviparous animals. Its structure is diverse due to interspecific differences in fetal tissues and variation in the forms of maternal-fetal interfaces. Matrotrophic poeciliid teleosts, in which the embryo develops within the maternal ovarian follicle, possess functional placentas formed from maternal follicular and embryonic tissues. However, the physiological mechanisms underlying substrate exchange between mother and embryo remain unclear. Furthermore, although similar embryonic-maternal interfaces are observed in lecithotrophic poeciliids, it is unknown whether nutrient exchange occurs in these species. Therefore, this study investigated whether substance exchange occurs between the mother and embryo in the lecithotrophic teleost guppy (Poecilia reticulata) and identified the underlying physiological mechanisms. Histological analysis revealed that guppies have embryonic-maternal interfaces consisting of the maternal follicle and the embryonic yolk sac and pericardial sac. Additionally, tracking of 2,000 kDa fluorescein isothiocyanate-dextran injected into pregnant guppies confirmed its transport from mother to embryo. Immunofluorescence staining and electron microscopy revealed that substance transport from mother to embryo occurs via extracellular vesicles. Moreover, immunofluorescence staining and pharmacological experiments revealed exosome transport from embryo to mother. This study demonstrates that lecithotrophic guppies possess a functional placenta that mediates maternal-embryonic substrate transfer via extracellular vesicles. These findings provide fundamental insight into the evolution of placental strategies within the Poeciliidae family. Significance StatementViviparity, in which embryos develop within the maternal body, has evolved independently across diverse animal lineages. In lecithotrophic viviparity, embryos are thought to rely primarily on yolk-derived nutrients, with maternal-fetal exchange limited to small molecules such as gases. Here, using macromolecular tracer experiments and ultrastructural analyses in guppies, we show that large macromolecules (2000 kDa) are exchanged bidirectionally between mother and fetus via extracellular vesicles, despite the absence of direct tissue attachment. These findings challenge the conventional view of lecithotrophic viviparity and reveal a previously unrecognized mechanism of maternal-fetal communication. Our results suggest that extracellular vesicle-mediated exchange may represent a widespread and evolutionarily conserved strategy for maternal-fetal interaction across viviparous animals.

developmental biology↗

bioRxiv2024

Regional differences in cell characteristics in electric eel electric organs indicate electrocyte development with ventral to dorsal migration.

Electric eels (Electrophorus) are renowned for their ability to generate electric discharge, which is used for prey capture and defense. Their electric organs (EOs) are located along the lateral-ventral region of the tail and contain electrocytes, which are multinucleated syncytium cells. The developmental origin of the electrocyte is mesodermal lineage cells observed in the ventral part of the myotome. However, it is unclear whether these precursor cells are also maintained in later stages and contribute to electric organ growth in adulthood. In this study, we report regional differences in cell morphology within the main EO (mEO) and identify a candidate cell population for electrocyte progenitors at the juvenile stages of Electrophorus. The cell morphology and distribution from the ventral terminal to the dorsal region of the mEO suggest the segregation of progenitors from the ventral cluster and their gradual transformation into mature multinucleated electrocytes via cell fusion and layering along the dorsal axis. Immunohistochemistry revealed strong expression of sodium-potassium adenosine triphosphatase (Na+/K+-ATPase), a key component in generating electric discharge in the mEO, across most mEO regions, except in the ventral cluster cells. Based on these observations, we propose that electrocyte progenitors develop from ventral cluster cells in the mEO and differentiate into mature multinucleated cells as they migrate dorsally. This is the first report to approach the developmental process of Electrophorus electrocytes from cell morphology and genetic profiles. Our findings represent a breakthrough in understanding the differentiation of electrocytes during the growth stages of Electrophorus.

developmental biology↗

bioRxiv2023

Membrane molecule bouncer enables follicle fertilization in a viviparous teleost: Poecilia reticulata (guppy)

Fertilization is a fundamental mechanism of sexual reproduction. Generally, oocytes are ovulated from the ovarian follicles and contact the sperm outside the ovarian medulla. Unlike this, follicle fertilization which means the egg contact with sperm in the ovarian medulla without ovulation is known in the viviparous teleost species belonging to the Poeciliidae. In this study, we focused on a viviparous teleost species, Poecilia reticulata (guppy). Our sperm tracking assay indicated that the sperm reached the immature oocytes with a germinal vesicle, and the fertilized immature oocytes were presumed to contribute to littermates. The binding between immature oocytes and sperm is a specific trait in the guppy, which was not observed in Danio rerio (zebrafish) or Oryzias latipes (medaka). The loss- and gain-of-function assays indicated that bouncer plays a critical role in immature oocyte-to-sperm binding. This fertilization trait in immature oocytes may provide certain advantages for females with respect to nutrition or other gestation costs. Our findings shed light on the unique reproductive strategies of guppy and contribute to our understanding of the diverse reproductive mechanisms in vertebrates. Summary statementUnlike general vertebrates, guppys oocyte fertilizes with sperm in the ovarian medulla at the immature stages. The distinctive trait depends on the Ly6/uPAR protein bouncer.

developmental biology↗

bioRxiv2017

Glutamine metabolism regulates Th2 cell differentiation via the α-ketoglutarate-dependent demethylation of histone H3K27

The acquisition of T cell functions seems to be closely linked to the reprogramming of the metabolic pathway. However, the impact of metabolic changes on the differentiation of helper T cell subsets remains unclear. We found that TCR-mediated activation of glutamine metabolism regulates Th2 cell differentiation via the supplementation of -ketogulutalate (-KG) and histone H3K27 demethylation. Deprivation of glutamine or pharmacological inhibition of glutamine metabolism blocks the induction of Th2 cell differentiation without affecting Stat6 phosphorylation. The methylation status of H3K27 at the Th2 cytokine gene locus was significantly increased in Th2 cells cultured under glutamine-deprived conditions. The inhibitory effect of glutamine-deprivation was antagonized by -KG, and the -KG-dependent induction of Th2 cell differentiation was reduced in utx- and jmjd3-deficient naive CD4 T cells. These findings show that the glutamine-a-ketoglutarate axis is crucial to regulating the epigenetic status at the Th2 cytokine gene locus and subsequent Th2 cell differentiation.

immunology↗