For over a century, developmental phase transitions such as metamorphosis and puberty have been presumed to be triggered by instantaneous spatial size thresholds1-9. Here we overturn this paradigm, demonstrating that biological size and life-history progression are governed by continuous temporal integration. Diverse biological transitions can be understood as manifestations of a single integral threshold mechanism. Our genetic analysis of Myoglianin (Myo), which is a muscle- and glia-derived TGF-β factor10 inducing metamorphosis in the cricket Gryllus bimaculatus, reveals a striking paradox: partial reduction leads to gigantism11,12, whereas complete myo knockout causes permanent developmental arrest13. This proves Myo acts as an essential temporal licensing signal. We formulate the Epigenetic Integration Clock (EIC) model, wherein systemic signals are continuously integrated into an epigenetic state. Phase transitions occur only upon reaching a critical threshold, yielding the Area-Constancy Rule of Epigenetics (Size × Duration ≈ constant). During vertebrate evolution, this temporal integration was decoupled from spatial constraints via the subfunctionalization of Myo into Myostatin (GDF8)14 and GDF1115, enabling extreme body size allometries. This rule naturally derives the quarter-power scaling law of lifespan and resolves the vernalization and the source-sink paradox in plant agronomy. Ultimately, the EIC reveals temporal epigenetic integration as the fundamental principle coupling growth, aging, and biological time across taxa.

Mutations in the fibroblast growth factor 10 (FGF10) gene in humans cause aplasia of the lacrimal and salivary glands (ALSG). In patients with ALSG, heterozygous loss-of-function mutations are found, and FGF10 haploinsufficiency results in the absence of these secretory organs. Lacrimal glands (LGs) are formed through epithelial thickening, budding, and branching morphogenesis. To compare the variable phenotypes of the Fgf10+/- Harderian glands (HGs) previously reported, we examined the development of LGs in wild-type (WT), Fgf10+/-, and Fgf10-null mice. Pax6 immunostaining was performed to visualize the LG primordia from embryonic day 15.5 (E15.5) onwards. In situ hybridization of the genes encoding the epithelial receptor of FGF10, FGFR2b, and its other ligands was performed to determine their potential involvement in LG development. LG primordia were not observed in Fgf10+/- mice bilaterally at E16.5 or later stages. At E15.5, budding from the developing conjunctival epithelium (CE) was observed in a small fraction of the Fgf10+/- LG primordia. In contrast, the Fgf10-null CE failed to promote budding. Among Fgf1, Fgf3, Fgf7, Fgf10, and Fgf22, Fgf10 was expressed in the mesenchyme surrounding developing LG epithelial cells, whereas Fgf1 was expressed in the LG epithelium of WT mice. Fgf7 was initially expressed in the mesenchyme surrounding the nascent LG epithelium, but its expression subsequently became diffused. Thus, we conclude that among the FGFR2b ligands, initial LG formation is dependent on the mesenchymal factors FGF10 and FGF7, and FGF1 is likely to function as an epithelial factor in the LG primordia. A single allele of Fgf10 was found to be insufficient to support the budding process during LG morphogenesis.

Although numerous biological phenomena have been elucidated at the molecular level, a unifying principle explaining fundamental phenomena such as why organisms grow to defined sizes, mature, and die after species-specific lifespanis still lacking. To resolve these mysteries, here we propose the Epigenetic Integration Clock (EIC), an hourglass model wherein environmental and physiological signals accumulate as molecular memory until threshold-dependent phase transitions occur. A central prediction is the Epigenetic Area-Constancy (EAC) rule: different combinations of signal intensity and duration trigger the transition once their integrated area reaches a fixed threshold. Molecularly, this threshold may be implemented by chromatin mechanisms—including histone modification[1], Polycomb-mediated memory[2,3], and liquid–liquid phase separation (LLPS)[4,5], which can convert gradual accumulation into switch-like commitment. Applying this framework to the mystery of animal size reveals muscle-derived systemic factors as the primary integration inputs dictating final body mass. This paradigm shift from spatial thresholds to temporal integration unifies plant vernalization[6], insect metamorphosis[7,8], vertebrate maturation[9,10], aging[11,12], cellular reprogramming[12,13], and allometric scaling laws[14] through a shared architecture. The EIC posits not a universal molecule, but a conserved logic—integration, area constancy, threshold detection, phase transition, and memory—through which living systems generate, limit, and reset their own time.

To achieve efficient bone resorption by osteoclasts, the specialized innate immune cells, it is important not only to promote osteoclast differentiation and activation but also to maintain their survival. C-type lectin (CLEC) receptors recognize pathogen ligands and altered self-tissues, comprising activating and inhibitory types whose balance eliminates pathogens while preventing excessive immune responses. However, roles of CLEC receptors in osteoclast differentiation, function, and survival remain unclear. We established knockout (KO) mice of CLEC receptor genes highly expressed by osteoclast and analyzed osteoclast features and bone morphology. We conducted comprehensive in silico screening of osteoclast lineage-specific CLEC receptors utilizing a mouse gene expression dataset and generated single and double KO (DKO) mice of Clec4a2 and Clec4d using a multi-targeted CRISPR-Cas9 system. Clec4a2 KO and DKO enhanced osteoclast differentiation in vitro, and Clec4a2 KO also stimulated enlargement of osteoclasts. Clec4d KO slightly reduced trabecular bone thickness in the femur, while Clec4a2 KO and DKO did not affect bone morphology under physiological conditions. Contrary to conventional understanding that enhanced osteoclast differentiation leads to increased bone resorption, our time-lapse analysis revealed that Clec4a2 KO paradoxically increased osteoclast formation while reducing resorption efficiency due to cell death of osteoclasts and its daughter cells after fission. Clec4a2 KO provided protection against inflammatory bone loss induced by lipopolysaccharide, demonstrating the first evidence that Clec4a2 could serve as therapeutic targets for inflammatory osteolytic diseases. This study introduces a novel paradigm that osteoclast survival regulation by Clec4a2 is fundamental for efficient bone resorption.

The recent discovery of nonvisual photoreceptors in various organs has raised expectations for uncovering their roles and underlying mechanisms. In this work, we identified a previously unrecognized hormone-releasing mechanism in the pituitary of the Japanese rice fish (medaka) induced by light. Ca 2+ imaging analysis revealed that melanotrophs, a type of pituitary endocrine cell that secretes melanocyte-stimulating hormone, robustly increase the concentration of intracellular Ca 2+ during short-wavelength light exposure. Moreover, we identified Opn5m as the key molecule that drives this response. Knocking out opn5m attenuated melanogenesis by reducing tyrosinase expression in the skin. Our findings suggest a mechanism in which direct reception of short-wavelength light by pituitary melanotrophs triggers a pathway that might contribute to protection from ultraviolet radiation in medaka.

The teleost whole-genome duplication (TGD) contributed to functional diversification of opsins. Some TGD paralogs, including those of parapinopsin (PP), Vertebrate Ancient (VA) opsin, and long wavelength-sensitive (LWS) opsin, show different absorption spectra and/or expression patterns. However, our knowledge of detailed evolutionary processes and mechanisms by which TGD contributed to opsin diversification is still limited. Here, we report that TGD paralogs of parietopsin (PT1 and PT2) are retained in extant species. While most species, including the zebrafish, have only PT1, several characins, including the red piranha ( Pygocentrus nattereri ), retain both PT1 and PT2. The Mexican tetra ( Astyanax mexicanus ) and catfishes have only PT2. To assess the degree of functional diversification between PT1 and PT2, we characterized spectral properties and expression patterns. Maximum absorption spectra differ slightly among PTs. Those of red piranha PT1, PT2, Mexican tetra PT2, and Japanese catfish ( Silurus asotus ) PT2 were located at 517 nm, 528 nm, 517 nm, and ∼535 nm, respectively. Fluorescence in situ hybridization showed that (1) piranha PT1 and PT2 are expressed in the same pineal cells, and (2) they are also co-expressed with PP1 . Based on these findings, functional diversification of opsins after gene duplication is discussed. ### Competing Interest Statement The authors have declared no competing interest.

Medicines used for cancer treatment often cause serious side effects by damaging normal cells due to nonspecific diffusion. To address this issue, we previously developed an optical method to induce apoptotic cell death via intracellular pH alkalinization using the outward proton pump rhodopsin, Archaerhodopsin-3 (AR3) in various noncancer model cells in vitro and in vivo. In this study, we applied this method to cancer cells and tumors to evaluate its potential as an anticancer therapeutic strategy. First, we confirmed that AR3-expressing murine cancer cell lines (MC38, B16F10) showed apoptotic cell death upon green light irradiation, as indicated by increased levels of cell death and apoptosis-related markers. Next, we established stable AR3-expressing MC38 and B16F10 cells by using viral vectors. When these AR3-expressing cells were subcutaneously transplanted into C57BL/6 mice, the resulting tumors initially grew at a rate comparable to that of control tumors lacking AR3 expression or light stimulation. However, upon green light irradiation, AR3-expressing tumors exhibited either a marked reduction in size or significantly suppressed growth, accompanied by the induction of apoptosis signals and decreased proliferation signals. These results demonstrate that AR3-mediated cell death has potent antitumor effects both in vitro and in vivo. This optical method thus holds promise as a novel cancer therapy with potentially reduced side effects.

Fluorescent in situ hybridization (FISH) enables highly sensitive, high-resolution detection of gene transcripts. Moreover, by employing multiple probes, this technique allows multiplexed, simultaneous detection of distinct gene expression patterns in a spatiotemporal manner, making it a valuable spatial transcriptomics approach. Owing to these advantages, FISH techniques are rapidly being adopted across diverse areas of basic biology. However, conventional protocols often rely on volatile, toxic reagents such as formalin or methanol, posing potential health risks to researchers. Here, we present a safer protocol that replaces these chemicals with low-toxicity and commercially available alternatives, without compromising the high detection sensitivity of FISH. We validated this protocol using both in situ hybridization chain reaction (HCR) and signal amplification by exchange reaction (SABER)-FISH in frozen sections of amphibians, Pleurodeles waltl and Xenopus laevis , as well as the teleost medaka ( Oryzias latipes ). Our results demonstrate successful multiplexed detection of various morphogenetic genes in these amphibian models and cell-type marker genes in the medaka using this safer protocol. The protocol has the additional advantage of requiring no proteolytic enzyme treatment. This protocol retains the benefits of high-sensitivity detection afforded by in situ HCR and SABER-FISH while providing a safer option for researchers, thereby offering a valuable tool for both basic biological and medical studies. ### Competing Interest Statement The authors have declared no competing interest. JST CREST, JPMJCR2025 to K.T.S. JSPS KAKENHI, 21H03829 to K.T.S. JSPS KAKENHI, 23K05850 to K.S. NIBB Collaborative Research Program, 24NIBB328 to M.M. Joint Research of the Exploratory Research Center on Life and Living Systems (ExCELLS), 23-S6 and 22-S3 to K.T.S. the Japan Foundation for Applied Enzymology, to K.S.

AIMS:Edible insects, including crickets, represent a promising protein source, yet concerns over foodborne pathogens limit consumer acceptance. This study investigated whether gut microbiota modulates colonization by Salmonella enterica subsp. enterica serovar Enteritidis (SE) in the two-spotted cricket (Gryllus bimaculatus). METHODS AND RESULTS:Under standard conditions, SE was undetectable in crickets despite prolonged exposure; however, antibiotic-induced dysbiosis enabled stable SE colonization. Long-read 16S rRNA sequencing revealed significant microbiota shifts, notably a reduction in Lactococcus garvieae. In vitro assays showed strong inhibitory effects of L. garvieae against SE, and supplementation of dysbiotic crickets with L. garvieae reduced SE colonization by ∼1000-fold. CONCLUSIONS:The native cricket gut microbiota, especially L. garvieae, plays a protective role against SE colonization. Enhancing beneficial gut bacteria could mitigate pathogen risks and promote edible insects as a sustainable protein.

Unlike terrestrial environments, where humans reside, there is no sunlight in the deep sea. Instead, dim visible light from black-body radiation and bioluminescence illuminates hydrothermal vent areas in the deep sea. A deep-sea hydrothermal vent shrimp, Rimicaris hybisae, is thought to detect this dim light using its enlarged dorsal eye; however, the molecular basis of its photoreception remains unexplored. Here, we characterized the molecular properties of opsins, universal photoreceptive proteins in animals, found in R. hybisae. Transcriptomic analysis identified six opsins: three Gq-coupled opsins, one Opn3, one Opn5, and one peropsin. Functional analysis revealed that five of these opsins exhibited light-dependent G protein activity, whereas peropsin exhibited the ability to convert all-trans-retinal to 11-cis-retinal like photoisomerases. Notably, all the R. hybisae opsins, including Opn5, convergently show visible light sensitivity (around 457-517 nm), whereas most opsins categorized as Opn5 have been demonstrated to be UV sensitive. Mutational analysis revealed that the unique visible light sensitivity of R. hybisae Opn5 is achieved through the stabilization of a protonated Schiff base by a counterion residue at position 83 (Asp83), which differs from the position identified in other opsins. These findings suggest that the vent shrimp R. hybisae has adapted its photoreceptive devices to dim deep-sea hydrothermal light by selectively maintaining a repertoire of visible light-sensitive opsins, including the uniquely tuned Opn5.

Many animals regenerate lost body parts through several signalling pathways; however, the triggers that initiate regeneration remain unclear. In the present study, we focused on the role of reactive oxygen species (ROS) produced by the NADPH oxidase Dual oxidase (Duox) during cricket leg regeneration. The results showed that ROS levels were upregulated during leg regeneration and decreased by DUOXRNAi. In DUOXRNAi nymphs, wound closure and scab formation were incomplete 2 days after amputation, and hypertrophy occurred in the distal region of the regenerating legs at 5 days after amputation. In addition, the hypertrophic phenotype was induced by DUOXARNAi and NADPH oxidase inhibitor treatment. During hypertrophy, haemocytes, including plasmatocytes, oenocytoids and granulocytes, accumulated. Proliferation of haemocytes in regenerating legs was not increased by DUOXRNAi; however, haemocyte accumulation was regulated by the Spatzle (Spz) family molecules, which are Toll receptor ligands. As the exoskeleton of DUOXRNAi nymphs was thinner than that of the control, excessive haemocyte accumulation can cause hypertrophy in DUOXRNAi nymphs. Thus, Duox-derived ROS are involved in wound healing and haemocyte accumulation through the Spz/Toll signalling pathway during leg regeneration in crickets.

Opsins are photoreceptive proteins responsible for visual and non-visual photoreceptions in animals. In general, vertebrates have multiple visual and non-visual opsins whose spectral sensitivities range from the UV to the red region. Among these opsins, Opn5 has been widely identified in vertebrates from fishes to primates and functions as a non-visual opsin in various tissues, including the retina and brain. Vertebrate Opn5 has been characterized as a UV-sensitive bistable opsin. Thus, Opn5 provides one of the molecular mechanisms determining the short wavelength limit that vertebrates can detect. In this study, we searched for the amino acid residue responsible for the UV light sensitivity of Opn5. Our mutational analysis revealed that Opn5 acquired visible light sensitivity by the substitution of Lys91 with an amino acid other than an arginine or tyrosine residue. In addition, the mutations at Lys91 altered the preferential binding of the retinal isomers in Opn5. Therefore, the conservation of Lys91 among vertebrate Opn5 proteins would be necessary to enable Opn5 to work as the shortest wavelength sensor in various tissues.

Some forms of Sjögren’s syndrome (SS) follow a clinical course accompanied by systemic symptoms caused by lymphocyte infiltration and proliferation in the liver, kidneys, and other organs. To better understand the clinical outcomes of SS, here we used minor salivary gland tissues from patients and examine their molecular, biological, and pathological characteristics. A retrospective study was performed, combining clinical data and formalin-fixed paraffin-embedded (FFPE) samples from female patients over 60 years of age who underwent biopsies at Okayama University Hospital. We employed direct digital RNA counting with nCounter® and multiplex immunofluorescence analysis with a PhenoCycler™ on the labial gland biopsies. We compared FFPE samples from SS patients who presented with other connective tissue diseases (secondary SS) with those from stable SS patients with symptoms restricted to the exocrine glands (primary SS). Secondary SS tissues showed enhanced epithelial damage and lymphocytic infiltration accompanied by elevated expression of autophagy marker genes in the immune cells of the labial glands. The close intercellular distance between helper T cells and B cells positive for autophagy-associated molecules suggests accelerated autophagy in these lymphocytes and potential B cell activation by helper T cells. These findings indicate that examination of FFPE samples from labial gland biopsies can be an effective tool for evaluating molecular histological differences between secondary and primary SS through multiplexed analysis of gene expression and tissue imaging.

Animal opsin is a G-protein coupled receptor (GPCR) and binds retinal as a chromophore to form a photopigment. The Opsin 5 (Opn5) group within the animal opsin family comprises a diverse array of related proteins, such as Opn5m, a protein conserved across all vertebrate lineages including mammals, and other members like Opn5L1 and Opn5L2 found in non-mammalian vertebrate genomes, and Opn6 found in non-therian vertebrate genomes, along with Opn5 homologs present in invertebrates. Although these proteins collectively constitute a single clade within the molecular phylogenetic tree of animal opsins, they exhibit markedly distinct molecular characteristics in areas such as retinal binding properties, photoreaction, and G-protein coupling specificity. Based on their molecular features, they are believed to play a significant role in physiological functions. However, our understanding of their precise physiological functions and molecular characteristics is still developing and only partially realized. Furthermore, their unique molecular characteristics of Opn5-related proteins suggest a high potential for their use as optogenetic tools through more specialized manipulations. This review intends to encapsulate our current understanding of Opn5, discuss potential manipulations of its molecular attributes, and delve into its prospective utility in the burgeoning field of animal opsin optogenetics.

Most vertebrates have a rhodopsin gene with a five-exon structure for visual photoreception. By contrast, teleost fishes have an intron-less rhodopsin gene for visual photoreception and an intron-containing rhodopsin (exo-rhodopsin) gene for pineal photoreception. Here, our analysis of non-teleost and teleost fishes in various lineages of the Actinopterygii reveals that retroduplication after branching of the Polypteriformes produced the intron-less rhodopsin gene for visual photoreception, which converted the parental intron-containing rhodopsin gene into a pineal opsin in the common ancestor of the Teleostei. Additional analysis of a pineal opsin, pinopsin, shows that the pinopsin gene functions as a green-sensitive opsin together with the intron-containing rhodopsin gene for pineal photoreception in tarpon as an evolutionary intermediate state but is missing in other teleost fishes, probably because of the redundancy with the intron-containing rhodopsin gene. We propose an evolutionary scenario where unique retroduplication caused a “domino effect” on the functional diversification of teleost visual and pineal opsin genes.

OBJECTIVES:The advancement of laparoscopic surgery has allowed surgeons to see finer anatomical structures during surgery. As a result, several issues have arisen regarding Gerota fascia that cannot be explained by previous interpretations, such as its various forms observed during surgery. To address these issues, we histologically examined the structure of Gerota fascia. METHODS:Specimens for study were prepared from kidneys with Gerota fascia from four cadavers, and the structure was studied histologically. Its thickness and collagen fiber area ratios were measured using ImageJ and compared to those of the epimysium of the rectus abdominis muscle. RESULTS:Connective tissue that appeared to be Gerota fascia was observed in 26 specimens. Histologically, the basic structure of Gerota fascia was a sandwich-like structure with a thin layer of thick, long collagen fibers in the central layer, and small granular collagen fibers scattered at the edges. However, not all areas observed had a similar structure; eight specimens were composed only of small granular collagen fibers. The average thickness of the Gerota fascia was 466 μm, and the area ratio of collagen was 27.1%. In contrast, the epimysium was much thicker than Gerota fascia, and its collagen fibers were much thicker and denser. CONCLUSIONS:Gerota fascia, unlike the epimysium, was a very thin and fragile layer of collagen fibers, and its structure was diverse. This explains why Gerota fascia was observed in various states during surgery. It is important for surgeons to understand the properties of Gerota fascia and to treat it appropriately.

The mouse Harderian gland (HG) is a secretory gland that covers the posterior portion of the eyeball, opening at the base of the nictitating membrane. The HG serves to protect the eye surface from infection with its secretions. Mice open their eyelids at about 2 weeks of age, and the development of the HG primordium mechanically opens the eye by pushing the eyeball from its rear. Therefore, when HG formation is disturbed, the eye exhibits enophthalmos (the slit-eye phenotype), and a line of Fgf10+/− heterozygous loss-of-function mice exhibits slit-eye due to the HG atrophy. However, it has not been clarified how and when HGs degenerate and atrophy in Fgf10+/− mice. In this study, we observed the HGs in embryonic (E13.5 to E19), postnatal (P0.5 to P18) and 74-week-old Fgf10+/− mice. We found that more than half of the Fgf10+/− mice had markedly degenerated HGs, often unilaterally. The degenerated HG tissue had a melanized appearance and was replaced by connective tissue, which was observed by P10. The development of HGs was delayed or disrupted in the similar proportion of Fgf10+/− embryos, as revealed via histology and the loss of HG-marker expression. In situ hybridization showed Fgf10 expression was observed in the Harderian mesenchyme in wild-type as well as in the HG-lacking heterozygote at E19. These results show that the Fgf10 haploinsufficiency causes delayed or defective HG development, often unilaterally from the unexpectedly early neonatal period.

The vertebrate body comprises four distinct cell populations: cells derived from (1) ectoderm, (2) mesoderm, (3) endoderm, and (4) neural crest cells, often referred to as the fourth germ layer. Neural crest cells arise when the neural plate edges fuse to form a neural tube, which eventually develops into the brain and spinal cord. To date, the embryonic origin of exocrine glands located in the head and neck remains under debate. In this study, transgenic TRiCK mice were used to investigate the germinal origin of the salivary and lacrimal glands. TRiCK mice express fluorescent proteins under the regulatory control of Sox1, T/Brachyury, and Sox17 gene expressions. These genes are representative marker genes for neuroectoderm (Sox1), mesoderm (T), and endoderm (Sox17). Using this approach, the cellular lineages of the salivary and lacrimal glands were examined. We demonstrate that the salivary and lacrimal glands contain cells derived from all three germ layers. Notably, a subset of Sox1-driven fluorescent cells differentiated into epithelial cells, implying their neural crest origin. Also, these Sox1-driven fluorescent cells expressed high levels of stem cell markers. These cells were particularly pronounced in duct ligation and wound damage models, suggesting the involvement of neural crest-derived epithelial cells in regenerative processes following tissue injury. This study provides compelling evidence clarifying the germinal origin of exocrine glands and the contribution of neural crest-derived cells within the glandular epithelium to the regenerative response following tissue damage.

Mammalian type opsin 5 (Opn5m), a UV-sensitive G protein-coupled receptor opsin highly conserved in vertebrates, would provide a common basis for UV sensing from lamprey to humans. However, G protein coupled with Opn5m remains controversial due to variations in assay conditions and the origin of Opn5m across different reports. Here, we examined Opn5m from diverse species using an aequorin luminescence assay and Gα-KO cell line. Beyond the commonly studied major Gα classes, Gαq, Gα11, Gα14, and Gα15 in the Gq class were individually investigated in this study, as they can drive distinct signaling pathways in addition to a canonical calcium response. UV light triggered a calcium response via all the tested Opn5m proteins in 293T cells, which was abolished by Gq-type Gα deletion and rescued by cotransfection with mouse and medaka Gq-type Gα proteins. Opn5m preferentially activated Gα14 and close relatives. Mutational analysis implicated specific regions, including α3-β5 and αG-α4 loops, αG and α4 helices, and the extreme C terminus, in the preferential activation of Gα14 by Opn5m. FISH revealed co-expression of genes encoding Opn5m and Gα14 in the scleral cartilage of medaka and chicken eyes, supporting their physiological coupling. This suggests that the preferential activation of Gα14 by Opn5m is relevant for UV sensing in specific cell types.