Biology subjects

Hasegawa, E.

Publications and source records attributed to Hasegawa, E..

8 recordsLinked to original sources

bioRxiv2026

Radiocarbon dating of bird and mammal eye lenses reveals long-term chronology

Time-series isotope analysis using eye lenses has recently gained attention as a low-cost method for reconstructing long-term information from a single sampling event, with potential applications across diverse taxonomic groups. However, information from eye lenses in birds and mammals remains limited, particularly during early growth stages, and the eye-lens time axis over extended periods should be reconstructed. This study measured the radiocarbon (14C) isotope ratios of eye lenses to examine the temporal framework recorded in the eye lenses of birds and mammals. The calibrated 14C ages of the central lens sections closely matched the known birth years or years preceding their introduction to Japan. 14C ages increased progressively from the center toward the periphery of the eye lens. The Siberian tiger allowed information reconstruction spanning from 2002.4 {+/-} 1.6 to 2017.8 {+/-} 2.0, whereas the ring-tailed lemur yielded reconstructed ages from 2000.2 {+/-} 1.6 to 2019.2 {+/-} 0.0. Calendar ages for all individuals after approximately 2019 could not be resolved using the radiocarbon calibration approach applied in this study. The sulphur-crested cockatoo demonstrated the longest reconstructed time span, covering 27.4 years from 1968.7 {+/-} 1.3 to 1996.1 {+/-} 1.4. Our results indicate that eye lenses can reconstruct long-term information spanning much of the lifespan in mammals examined, whereas avian lenses can preserve information spanning several years to decades after birth. Lens growth patterns may differ according to life history; thus, future studies should examine a wider range of species and taxonomic groups with diverse life histories.

zoology↗

bioRxiv2026

Visualization of neuronal morphology of the suprachiasmatic nucleus vasopressin neurons by Cre/FLPe-based genetic two-step sparse labelling - GT-SPARCL

Resolving the morphology of individual neurons in densely packed brain regions remains challenging. Sparse labeling is essential for delineating cellular architecture, yet achieving reproducible low-density labeling e.g. < 1% has been a persistent technical hurdle/problem. We present a genetically encoded two-step strategy, GT-SPARCL (Genetic Two-Step Sparse Cre/FLPe Combination Labeling), which leverages two independent stochastic recombination events to deliver stable, tunable low-density labeling in mice. As a proof of concept, we applied this method to visualizing arginine vasopressin (AVP) neurons in the suprachiasmatic nucleus (SCN), the master circadian pacemaker composed of [~]10,000 neurons per side in mice. Using two-photon imaging of whole-mount SCN blocks, we reconstructed individual AVP neurons and uncovered previously under-resolved morphological heterogeneity. Based on axonal trajectories, we distinguished five structural types, including subclasses with commissural projections to the contralateral SCN and others extending projections beyond the nucleus. The majority ([~]70%) exhibited projections both within and outside the ipsilateral SCN, whereas the second most dominant subset ([~]20%) projected exclusively outside the SCN, representing an output-biased type. In contrast, neurons projecting exclusively within the ipsilateral SCN were exceptionally rare, suggesting that "dedicated" local-circuit AVP neurons do not form a major structural subtype. Collectively, our data indicate that AVP neurons are not structurally uniform but instead comprise diverse projection-defined subtypes, implying subtype-depen-dent contributions to intra-SCN communication, bilateral coupling, and circadian output. Beyond the SCN, our GT-SPARCL method may be applicable for achieving low-density labelling of neurons that can be defined by other specific Cre mouse lines.

neuroscience↗

bioRxiv2026

The slow-acting G-protein Gz defines the duration of circadian rest time

Duration of nightly rest is a trait that varies between individuals, influenced by a complex interplay between multiple genetic and environmental factors. The central circadian clock that orchestrates daily rhythm in behavior/sleep resides in the suprachiasmatic nucleus (SCN). Yet, how the SCN encodes the "length" of the circadian rest phase ({rho}) remains an open question. Here we demonstrate that the unique G-protein-subtype Gz contributes to this process by sculpting the waveform of the circadian cAMP-PKA activity rhythm within the SCN. Genetic deletion and subsequent rescue of Gz expression reversibly altered the {rho} duration, shifting it from [~]10 h in Gz+/+ mice to [~]7.5 h in Gz-/-; mice, accompanied by proportional changes in peak cAMP-PKA activity duration and transcriptome remodeling in the SCN. Notably, intra-SCN cAMP activation led to behavioral rest, with Gz specifically shaping this response without affecting 24-h rhythmicity. These findings suggest that the SCN is not merely a rhythm-generator, but actively allocates the {rho}-rest period via Gz signaling.

neuroscience↗

bioRxiv2026

NAD boosting mediated by CD38 inhibition drives reversal of a pathological vicious cycle of intracrine activity and inflammation in eyelid meibomian gland dysfunction

Vicious cycles--reciprocal cause-and-effect loops that progressively intensify dysfunction--are implicated in many diseases. Here, we examined whether "intracrine" steroidogenesis, a tissue-local mode of hormone production, participates in a pathological vicious cycle in eyelid meibomian gland dysfunction (MGD), the most common cause of evaporative dry eye disease with incidence increasing with age. We show that loss of meibomian intracrine androgen production triggers inflammatory remodeling of the eyelid tarsal plate. Conversely, inflammation suppresses nicotinamide adenine dinucleotide (NAD)-dependent 3{beta}-hydroxysteroid dehydrogenase activity in the meibomian gland, thereby further weakening intracrine steroidogenesis. Mechanistically, we identified inflammation-associated accumulation of the NAD-degrading enzyme CD38 as a key down-regulator for the NAD-dependent intracrine activity. Accordingly, pharmacological inhibition of CD38 (using 78c) in aged mice, restores meibomian cellular NAD levels, rescues intracrine activity, suppresses inflammatory signatures, and promotes recovery of gland size. Thus, our data suggest that boosting NAD availability not only ameliorates meibomian gland dysfunction but also induces a reciprocal "virtuous" cycle, in which suppression of inflammation and restoration of intracrine activity mutually reinforce each other. These findings constitute a previously unknown example in which the reversal of a pathological vicious cycle into a beneficial virtuous cycle underlies the therapeutic effects of NAD boosting and may help combat age-associated meibomian gland disorder.

pathology↗

bioRxiv2026

Translational regulation of GAD1 identified by circadian and light-responsive ribosome-bound transcriptome analysis in the mouse hypothalamic suprachiasmatic nucleus

The suprachiasmatic nucleus (SCN) serves as the master circadian pacemaker, integrating regulation of clock genes in the SCN has been extensively studied, whether gene expression in the SCN is regulated at the level of mRNA translation has remained largely unexplored. Here, we report the first ribosome-profiling (Ribo-seq) dataset generated from the mouse SCN, enabling a genome-wide assessment of translational regulation in this central circadian clock. Combined time-series Ribo-seq and RNA-seq analyses identified 385 genes that exhibit rhythmic ribosome binding without corresponding oscillations in mRNA abundance, revealing widespread translational regulation in the SCN. Among these, light stimulation induced an approximately twofold increase in ribosome binding of Gad1, which encodes the major GABA-synthetic enzyme Gad67, despite only marginal changes in Gad1 mRNA levels. Importantly, immunohistochemical analyses demonstrated light-dependent accumulation of Gad67 protein selectively in light-activated SCN neurons, establishing that translational regulation of Gad1 gives rise to overt protein-level changes. In contrast, canonical clock genes were regulated predominantly at the transcriptional level and showed little evidence of translational modulation. Our data allow a systematic comparison between transcriptionally and translationally regulated genes, including their relative rhythm-amplitudes and phases, and thereby revealed translational control as a distinct modulatory layer shaping time-of-day-dependent and light-dependent gene expression in the SCN.

neuroscience↗

bioRxiv2024

Male contributions to female-male mutualism overcome the twofold cost of sex.

The increasing rate of anisogamy (fusion between eggs and sperm) against asexual thelytoky is necessarily halved under a 1:1 sex ratio because males lay no eggs. The present dominance of anisogamy despite this twofold cost of male production is the greatest enigma in evolutionary biology. Various benefits of sex are insufficient to overcome this cost. How can anisogamy be maintained? Here, we propose hypotheses that anisogamy evolved as a female-male mutualism in which females produce large eggs to ensure zygote development and males produce many sperm to ensure fertilisation. In the real world with finite resources, thelytoky cannot express its twofold increasing potential, and various male functions reduce the thelytokys performance. Thus, the twofold cost is an artefact of the infinite resource assumption. Simple mathematical models and simulations showed that when males and thelytokous females are equally competitive and acquire the same amount of resources but males can develop with fewer resources than females, anisogamy outcompetes thelytoky. When males need more growth costs than females, as in sexually selected species, the excess mating activity of "harmful" males reduces the fitness of thelytokous females. The significance of sexes, a question since Aristotles time, is explained by male contribution to sustaining mutualism.

evolutionary biology↗

bioRxiv2022

Synchronous multi-segmental activity between metachronal waves controls locomotion speed in Drosophila larvae

The ability to adjust the speed of locomotion is essential for survival. In limbed animals, the frequency of locomotion is modulated primarily by changing the duration of the stance phase. The underlying neural mechanisms of this selective modulation remain an open question. Here, we report a neural circuit controlling a similarly selective adjustment of locomotion frequency in Drosophila larvae. Drosophila larvae crawl using peristaltic waves of muscle contractions. We find that larvae adjust the frequency of locomotion mostly by varying the time between consecutive contraction waves, reminiscent of limbed locomotion. A specific set of muscles, the lateral transverse (LT) muscles, co-contract in all segments during this phase, the duration of which sets the duration of the interwave phase. We identify two types of GABAergic interneurons in the LT neural network, premotor neuron A26f and its presynaptic partner A31c, which exhibit segmentally synchronized activity and control locomotor frequency by setting the amplitude and duration of LT muscle contractions. Altogether, our results reveal an inhibitory central circuit that sets the frequency of locomotion by controlling the duration of the period in between peristaltic waves. Further analysis of the descending inputs onto this circuit will help understand the higher control of this selective modulation.

neuroscience↗

bioRxiv2019

RIP1 kinase mediates angiogenesis by modulating macrophages in experimental neovascularization

Inflammation plays an important role in pathologic angiogenesis. Receptor-interacting protein 1 (RIP1) is highly expressed in inflammatory cells and is known to play an important role in the regulation of apoptosis, necroptosis, and inflammation, however its role in angiogenesis remains elusive. Here, we show that RIP1 is abundantly expressed in infiltrating macrophages during angiogenesis, and genetic or pharmacological inhibition of RIP1 kinase activity using kinase-inactive RIP1K45A/K45A mice or necrostatin-1 attenuates angiogenesis in laser-induced choroidal neovascularization (CNV), Matrigel plug angiogenesis, and alkali injury-induced corneal neovascularization in mice. The inhibitory effect on angiogenesis was mediated by caspase activation through a kinase-independent function of RIP1 and RIP3, and simultaneous caspase inhibition with RIP1 kinase inhibition abrogated the effects of RIP1 kinase inhibition on angiogenesis in vivo. Mechanistically, infiltrating macrophages are the key target for RIP1 kinase inhibition to attenuate pathological angiogenesis, and we observed that the inhibition of RIP1 kinase activity is associated with caspase activation in infiltrating macrophages and decreased expression of pro-angiogenic M2-like markers while M1 marker expressions were sustained. Similarly, in vitro, catalytic inhibition of RIP1 down-regulated M2 marker expressions in IL-4-activated bone marrow-derived macrophages, which was blocked by simultaneous caspase inhibition. Taken together, these results suggest a novel, non-necrotic function of RIP1 kinase activity and suggest that RIP1-mediated modulation of macrophage activation may represent a therapeutic target for the control of angiogenesis-related diseases.\n\nSignificancePathological angiogenesis has been implicated in diverse pathologies. Infiltrating macrophages, especially those activated to M2-like phenotype are critically important to support angiogenesis. Whereas the role of RIP1 kinase in the regulation of apoptosis, necroptosis, and inflammation have been well established, its role in angiogenesis remains elusive despite being abundantly expressed in angiogenesis-related infiltrating macrophages. This study demonstrated for the first time that RIP1 kinase inhibition attenuates angiogenesis in multiple mouse models of pathological angiogenesis in vivo. Mechanistically, the inhibitory effect on angiogenesis depends on RIP kinase inhibition-mediated caspase activation in infiltrating macrophages that suppresses M2-like polarization, thereby attenuating pathological angiogenesis.

molecular biology↗