Biology subjects

Kamei, Y.

Publications and source records attributed to Kamei, Y..

15 recordsLinked to original sources

bioRxiv2026

Extraocular Photoreception Controls nocturnal hatching via a neuroendocrine pathway in False Clownfish

Hatching is the transition from embryo to larva in oviparous animals. Birds, reptiles, and insects rupture the eggshell mechanically, whereas fish and amphibians digest the egg envelope using hatching enzymes. When and where larvae emerge influences their fitness. Many species regulate hatching timing using environmental cues, such as light, oxygen availability, and physical stimuli. In fish, hatching is driven by a neuroendocrine event that triggers hatching enzyme secretion; however, the mechanisms controlling this event are unknown. Using the false clownfish Amphiprion ocellaris, which hatches synchronously within 1-2 h after sunset, we showed that the role of thyrotropin-releasing hormone (TRH) as a hatching hormone, previously established in zebrafish and medaka, extended to clownfish, where TRH activated Ca2+; signaling in hatching gland cells through its receptor trhra, reinforcing the TRH-Ca2+-hatching enzyme axis as a conserved core module of teleost hatching. In clownfish, this module was additionally placed under upstream control by extraocular photoreception because dark-induced hatching persisted in eyeless embryos. This photoreceptive system was most sensitive to green light (550 nm), and several opsins with absorbance maxima in the corresponding middle- to long-wavelength range were expressed outside the eyes of pre-hatching embryos. Coupling extraocular photoreception to a conserved neuroendocrine module placed a critical life-history transition under stringent photic control, releasing larvae only in complete darkness, an adaptation that may have underpinned the success of this lineage in predator-rich coral reefs.

zoology↗

bioRxiv2026

Environment-specific mechanosensing preserves a common bleb-based migratory program across diverse embryonic environments

Cell migration frequently requires cells to traverse tissue environments with distinct physical and biochemical properties. How migrating cells preserve a common migratory program while adapting to these heterogeneous environments remains poorly understood. Here, we show that chick primordial germ cells (PGCs) preserve a common bleb-based migratory mode throughout embryogenesis despite migrating through mechanically distinct tissues. PGCs formed membrane blebs during both intravascular crawling and migration through the dorsal mesentery. However, nuclear envelope (NE) unfolding and activation of the NE-cPLA2 pathway occurred specifically during migration through the mechanically confined dorsal mesentery, where this pathway was required for bleb formation and efficient migration. In contrast, bleb formation during vascular crawling occurred independently of the NE-cPLA2 pathway, demonstrating that distinct molecular mechanisms can generate the same migratory behavior in different tissue environments. Together, these findings suggest that diverse environmental cues converge on a conserved bleb-forming machinery. We propose a hierarchical model in which migrating cells preserve a common migratory program by flexibly switching the upstream molecular mechanisms that initiate bleb formation according to the tissue environment.

developmental biology↗

bioRxiv2026

Oleuropein stimulates peripheral serotonin secretion via voltage-dependent Ca2+ channels and acutely regulates central function

Serotonin (5-HT) is a monoamine which regulates not only central functions but also various peripheral functions. Peripheral 5-HT is primarily derived from the gut, and its synthesis and secretion are regulated by enterochromaffin cells. Stimulation of enterochromaffin cells by food factors may regulate mental functions via the gut-brain axis. We studied whether oleuropein, an olive-derived polyphenol, regulates central functions by stimulating 5-HT secretion from enterochromaffin cells. In QGP-1 cells, which are enterochromaffin-like cells, 10 {micro}M oleuropein stimulated 5-HT secretion via Ca2+ influx through T-type and L-type voltage-dependent Ca2+ channels. Hydroxytyrosol, a metabolite of oleuropein, also promoted 5-HT secretion via the same mechanism. Furthermore, oleuropein stimulated 5-HT secretion from isolated mouse colon via voltage-dependent Ca2+ channels. Finally, oral administration of 200 mg/kg oleuropein acutely increased the depression-like behavior in the mice, which was inhibited by the prior administration of ramosetron, a 5-HT3 receptor antagonist. These findings suggest that oleuropein is a potent stimulant of gut 5-HT secretion, and show that food factors may act to regulate mental function via the secretion of gut 5-HT.

animal behavior and cognition↗

bioRxiv2025

Wntless interacts with Notch signaling to balance the generation of neurons and gliocytes in vertebrate dorsal diencephalon

Wnt chaperon Wntless (Wls) mediates the intracellular transport of Wnts and plays important roles in early vertebrate brain development. Spatially restricted induction of Wls denotes the earliest differentiation of non-telencephalic cells in human brain organoids. In zebrafish developing diencephalon, loss-of-Wls reduces the formation of habenula (HA) neurons but how Wls influences HA neurogenesis is unclear and whether Wls regulates gliocyte development is unknown. Here we report that the formations of cholinergic, substance P-ergic or glutamatergic neurons in HA are reduced differentially but the generation of gliocyte-derived choroid plexus (ChP) epithelia is increased in wls null mutants. At earlier stage, three-dimensional gene expression analyses revealed that while neurog1 expressions in HA progenitor zones are reduced, the expressions of Notch downstream effector her6 are increased and expanded into HA progenitor zones in wls mutants. Over-expressing Her6 in neurog1-positive cells reduced neurog1 expressions in HA progenitor zones. These results indicate that Wls restricts the expressions of Notch effector her6 to promote the specification of neurog1 proneurons and demotes the generation of ChP epithelia in zebrafish embryonic dorsal diencephalon.

developmental biology↗

bioRxiv2025

Heat-mediated manipulation of gene expression by IR-LEGO in the developing genitalia in Drosophila

Manipulating gene expression in a tissue-specific and temporally controlled manner is essential for understanding the function of the focal genes. Still, in many cases, the limited availability of specific promotors to drive ectopic manipulation remains a restricting factor in developing organs, even in Drosophila. Developing external genitalia is one such organ with a complex anatomical structure shaped by a joint regulatory network of many transcription factors. To overcome the restriction, we employed the infrared laser-evoked gene operator system (IR-LEGO), in which infrared laser (1,480 nm) irradiation induces gene expression under the control of a heat shock promoter. Pupal genital structures were irradiated at approximately 24 or 48 hours after puparium formation. We tested a range of laser power and depth to the target structure by a reporter assay using green fluorescent protein, which was induced under the control of the heat shock protein 70 promoter (hs-GAL4). In previous studies, the IR-LEGO has been used as a tool to induce ectopic transgene expression. In this study, we attempted to knock down genes such as yellow (y) and odd-paired (opa) ectopically by RNAi using the GAL4/UAS system. The results demonstrated that this technique has a high potential in manipulating transcript abundance levels in small groups of cells in specific genital structures to unravel novel functions of genes involved in the morphogenesis of species-specific and rapidly evolving anatomical structures. Article summaryManipulating gene expression is essential for understanding the function of the genes at specific regions of the body. In particular, knowing how different genes contribute to shaping complex anatomical structures, such as insect external genitalia, is an intriguing question. While manipulating gene expression precisely at a specific time and space remains challenging, we show that we can knock down a gene in a specific group of cells in the developing genitalia of Drosophila pupae, using infrared laser irradiation. This is a new approach to investigating how activity of genes shapes the rapidly evolving male genitalia in insects.

genetics↗

bioRxiv2025

Excessive chondrogenesis in the blastema initiates during hypomorphic limb regeneration in Xenopus froglet, but not during patterned limb regeneration in Xenopus tadpoles and newts

Xenopus laevis tadpoles and newts regenerate a limb almost completely after amputation, with recapitulation of the patten formation of the limb. Metamorphosed Xenopus froglets form a cone-shaped regenerating blastema, similar to tadpoles and newts, but ultimately regenerate only a hypomorphic cartilaginous spike. Previous study suggested that excessive chondrogenesis, distinct from Xenopus tadpoles, may occur in the regenerating limb of a froglet and may prevent pattern formation during regeneration. However, it remains unclear whether excessive chondrogenesis actually occurs in froglet blastemas. If it does, when does it initiate and how does it progress in the blastemas? To answer these questions, we examined the extent of chondrogenesis in regenerating blastemas which have the common morphological shapes observed in newts (Pleurodeles waltl), Xenopus laevis tadpoles, and froglets. To evaluate excessive chondrogenesis, we developed a simplified procedure using immunofluorescence for cartilage markers (Sox9 or Col2a1) and quantitative image analysis. Our analysis revealed that signs of excessive chondrogenesis were detected not in newts and tadpoles but in froglets blastemas. During limb regeneration in froglets, the first sign of excessive chondrogenesis was detected in the cone-shaped blastema at the medium bud (MB) stage, and excessive chondrogenesis progressed to a more severe state as the blastema grew. These results indicate that excessive chondrogenesis initiates specifically in froglet blastemas at the MB stage at the latest and progresses in a definite spatio-temporal manner. Further elucidation of the mechanisms underlying froglet-specific excessive chondrogenesis in the blastema may lead to the recovery of patterned limb regeneration in froglets with adequate inhibition of chondrogenesis.

developmental biology↗

bioRxiv2024

Novel function of Hox13 in regulating outgrowth of the newt hindlimb bud through interaction with Fgf10 and Tbx4

5Hox genes regulate pattern formation along the axes of the limb. Previously, we showed that Hoxa13/Hoxd13 double mutant newts lacked all digits of the forelimbs during development and regeneration, showing that newt Hox13 is necessary for digit formation in development and regeneration. In addition, we found another unique phenotype. A part of the Hox13 crispant newts showed hindlimb defects, in which whole or almost whole hindlimbs were lost, suggesting a novel function of Hox13 in limb development. Using germline mutants, we showed that mutation in Hox13 led to hindlimb defects. The limb buds of Hox13 crispants formed, however, did not show outgrowth. Expression of Fgf10 and Tbx4, which are involved in limb outgrowth, decreased in the hindlimb buds of Hox13 crispants. In addition, hindlimb defects were observed in both Fgf10 and Tbx4 crispant newts. Finally, Fgf10 and Tbx4 interacted with Hox13 genetically. Our results revealed a novel function of Hox13 in regulating the outgrowth of the newt hindlimb bud through interaction with Fgf10 and Tbx4.

developmental biology↗

bioRxiv2024

Neuroestrogens facilitate male-typical behaviors by potentiating androgen receptor signaling in medaka

In rodents, estrogens aromatized from androgens in the brain are essential for the development of male-typical behaviors. In many other vertebrates including humans and teleost fish, however, androgens facilitate these behaviors directly via the androgen receptor without aromatization into estrogens. Here we report that mutagenesis-derived male medaka fish lacking Cyp19a1b (a subtype of aromatase predominantly expressed in the brain) exhibit severely impaired male-typical mating and aggression, despite elevated brain androgen levels. These phenotypes can be rescued by estrogen administration, indicating that brain-derived estrogens are pivotal for male-typical behaviors even in teleosts. Our results further suggest that these estrogens facilitate male-typical behaviors by potentiating androgen action in the brain via the direct stimulation of androgen receptor transcription. Taken together, these findings reveal a previously unappreciated mode of action of brain-derived estrogens in shaping male-typical behaviors.

physiology↗

bioRxiv2023

Optineurin deficiency impairs autophagy to cause interferon beta overproduction and increased survival of mice following viral infection

BackgroundOptineurin (OPTN) is associated with several human diseases, including amyotrophic lateral sclerosis (ALS), and is involved in various cellular processes, including autophagy. Optineurin regulates the expression of interferon beta (IFN{beta}), which plays a central role in the innate immune response to viral infection. However, the role of optineurin in response to viral infection has not been fully clarified. It is known that optineurin-deficient cells produce more IFN{beta} than wild-type cells following viral infection. In this study, we investigate the reasons for, and effects of, IFN{beta} overproduction during optineurin deficiency both in vitro and in vivo. MethodsTo investigate the mechanism of IFN{beta} overproduction, viral nucleic acids in infected cells were quantified by RT-qPCR and the autophagic activity of optineurin-deficient cells was determined to understand the basis for the intracellular accumulation of viral nucleic acids. Moreover, lethal viral infection experiments using optineurin-disrupted (Optn-KO) animals were performed. ResultsIFN{beta} overproduction following viral infection was observed not only in several types of optineurin-deficient cell lines but also in Optn-KO mice and human ALS patient cells carrying mutations in OPTN. IFN{beta} overproduction in Optn-KO cells was revealed to be caused by excessive accumulation of viral nucleic acids, which was a consequence of reduced autophagic activity caused by the loss of optineurin. Additionally, IFN{beta} overproduction in Optn-KO mice suppressed viral proliferation, resulting in increased mouse survival following lethal viral challenge. ConclusionOur findings indicate that the combination of optineurin deficiency and viral infection leads to IFN{beta} overproduction in vitro and in vivo. The effects of optineurin deficiency are elicited by viral infection, therefore, viral infection may be implicated in the development of optineurin-related diseases.

immunology↗

bioRxiv2022

The shh limb enhancer is activated in patterned limb regeneration but not in hypomorphic limb regeneration in Xenopus laevis

Xenopus young tadpoles regenerate a limb with the anteroposterior (AP) pattern, but metamorphosed froglets regenerate a hypomorphic limb after amputation. The key gene for AP patterning, shh, is expressed in a regenerating limb of the tadpole but not in that of the froglet. Genomic DNA in the shh limb-specific enhancer, MFCS1 (ZRS), is hypermethylated in froglets but hypomethylated in tadpoles: shh expression may be controlled by epigenetic regulation of MFCS1. Is MFCS1 specifically activated for regenerating the AP-patterned limb? We generated transgenic Xenopus laevis lines that visualize the MFCS1 enhancer activity with a GFP reporter. The transgenic tadpoles showed GFP expression in hoxd13- and shh-expressing domains of developing and regenerating limbs, whereas the froglets showed no GFP expression in the regenerating limbs despite having hoxd13 expression. Genome sequence analysis and co-transfection assays using cultured cells revealed that Hoxd13 can activate Xenopus MFCS1. These results suggest that MFCS1 activation correlates with regeneration of AP-patterned limbs and that re-activation of epigenetically inactivated MFCS1 would be crucial to confer the ability to non-regenerative animals for regenerating a properly patterned limb.

developmental biology↗

bioRxiv2022

Epigenetically distinct synaptic architecture in clonal compartments in the teleostean dorsal pallium

The dorsal telencephalon (i.e. the pallium) exhibits high anatomical diversity across vertebrate classes. The mammalian dorsal pallium accommodates a six layered-structure, the neocortex, whereas the teleostean dorsal pallium possesses various compartmentalized structures among species. The development, function and evolution of the fish dorsal pallium remain unillustrated. Here, we analyzed the structure and epigenetic landscapes of cell lineages in the telencephalon of medaka fish (Oryzias latipes) which possesses a clearly delineated dorsal pallium (the Dd2 region). We found that different pallial regions, including Dd2, are formed by mutually exclusive clonal units, and that each pallium compartment exhibits a distinct epigenetic landscape. In particular, Dd2 possesses a unique open chromatin pattern that preferentially targets synapse-related genes. Indeed, Dd2 shows a high density of synapses, which might reflect strong plasticity. Finally, we identified several transcription factors as candidate regulators for the Dd2, which are partially shared with the human neocortex and hippocampus.

neuroscience↗

bioRxiv2022

Diaphorin, a polyketide produced by a bacterial symbiont of the Asian citrus psyllid, inhibits the growth of Bacillus subtilis but promotes the growth of Escherichia coli

Diaphorin is a polyketide produced by Candidatus Profftella armatura (Gammaproteobacteria: Burkholderiales), an obligate symbiont of a notorious agricultural pest, the Asian citrus psyllid Diaphorina citri (Hemiptera: Psyllidae). Diaphorin belongs to the pederin family of bioactive agents found in various host-symbiont systems, including beetles, lichens, and sponges, harboring phylogenetically diverse bacterial producers. Previous studies showed that diaphorin has inhibitory effects on various eukaryotes, including the natural enemies of D. citri. However, little is known about its effects on prokaryotic organisms. To address this issue, the present study assessed the biological activities of diaphorin on two model prokaryotes, Escherichia coli (Gammaproteobacteria: Enterobacterales) and Bacillus subtilis (Firmicutes: Bacilli). The analyses revealed that diaphorin inhibits the growth of B. subtilis but moderately promotes the growth of E. coli. This finding implies that diaphorin functions as a defensive agent of the holobiont (host + symbionts) against some bacterial lineages but is beneficial for others, which potentially include obligate symbionts of D. citri. ImportanceCertain secondary metabolites, including antibiotics, evolve to mediate interactions among organisms. These molecules have distinct spectra for microorganisms and are often more effective against Gram-positive bacteria than Gram-negative ones. However, it is rare that a single molecule has completely opposite activities on distinct bacterial lineages. The present study revealed that a secondary metabolite synthesized by an organelle-like bacterial symbiont of psyllids inhibits the growth of Gram-positive Bacillus subtilis but promotes the growth of Gram-negative Escherichia coli. This finding not only provides insights into the evolution of symbiosis between animal hosts and bacteria but may also potentially be exploited to promote the effectiveness of industrial material production by microorganisms.

microbiology↗

bioRxiv2021

Appropriate tension sensitivity of α-catenin ensures rounding morphogenesis of epithelial spheroids

The adherens junction (AJ) is an actin filament-anchoring junction. It plays a central role in epithelial morphogenesis through cadherin-based recognition and adhesion among cells. The stability and plasticity of AJs are required for the morphogenesis. An actin-binding -catenin is an essential component of the cadherin-catenin complex and functions as a tension transducer that changes its conformation and induces AJ development in response to tension. Despite much progress in understanding molecular mechanisms of tension sensitivity of -catenin, its significance on epithelial morphogenesis is still unknown. Here we show that the tension sensitivity of -catenin is essential for epithelial cells to form round spheroids through proper multicellular rearrangement. Using a novel in vitro suspension culture model, we found that epithelial cells form round spheroids even from rectangular-shaped cell masses with high aspect ratios without using high tension and that hypersensitive mutants affected this morphogenesis. Analyses of AJ formation and cellular tracking during rounding morphogenesis showed cellular rearrangement, probably through AJ remodeling. The rearrangement occurs at the cell mass level, but not single-cell level. Hypersensitive -catenin mutant-expressing cells did not show cellular rearrangement at the cell mass level, suggesting that proper AJ plasticity requires appropriate tension sensitivity of -catenin.

cell biology↗

bioRxiv2021

All-trans retinoic acid induces GADD34 gene expression via transcriptional regulation by Six1-TLE3 and post-transcriptional regulation by p38-TTP in skeletal muscle

All-trans retinoic acid (ATRA) increases the sensitivity to unfolded protein response (UPR) in differentiating leukemic blasts. The downstream transcriptional factors of PERK, a major arm of UPR, regulates muscle differentiation. However, the role of growth arrest and DNA damage-inducible protein 34 (GADD34), one of the downstream factors of PERK, and the effects of ATRA on GADD34 expression in muscle remain unclear. In this study, we identified ATRA increased the GADD34 expression independent of the PERK signal in the gastrocnemius muscle of mice. ATRA up-regulated GADD34 expression through the transcriptional activation of it via inhibiting the interaction of homeobox Six1 and transcription co-repressor TLE3 with the MEF3-binding site on the GADD34 gene promoter in myoblasts. ATRA also inhibited the interaction of TTP, which induces mRNA degradation, with AU-rich element on GADD34 mRNA via p38 MAPK, resulting in the instability of GADD34 mRNA. Overexpressed GADD34 in myoblasts changes the type of myosin heavy chain in myotubes. These results suggest ATRA increases GADD34 expression via transcriptional and post-transcriptional regulation in myoblasts, which changes muscle fiber type in myotubes.

biochemistry↗

bioRxiv2020

Hoxa10 mediates positional memory to govern stem cell function in adult skeletal muscle

Skeletal muscle stem cells (satellite cells) are distributed throughout the body with heterogeneous properties that corresponds to region-specific pathophysiology. However, topographical genes that have functions remain unidentified in satellite cells of adult muscle. Here, we showed that expression of Homeobox (Hox)-A cluster genes, key regulators of the embryonic body plan, was robustly maintained in both muscles and satellite cells in adult mice and humans, which recapitulates their embryonic origin. We observed that regionally specific expressed Hox genes were linked to hypermethylation of the Hox-A locus. We examined Hoxa10 inactivation in satellite cells and found it led to genomic instability and mitotic catastrophe, which resulted in a decline in the regionally specific regenerative ability of muscles in adult mice. Thus, our results showed that Hox gene expression profiles instill the embryonic history in satellite cells as positional memory, potentially modulating the region-specificity in adult skeletal muscles.

developmental biology↗