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Background/Aim: Glioblastoma is the most common and aggressive malignant brain tumor in adults, and glioblastoma stem cells (GSCs) contribute to treatment resistance and recurrence. Inhibition of Stat5b in GSCs suppresses cell proliferation and induces apoptosis. Herein, we investigated the mechanisms of growth inhibition by Stat5b knockdown (KD) in GSCs. Materials and Methods: GSCs were established from a murine glioblastoma model in which shRNA-p53 and EGFR/Ras mutants were induced in vivo using a Sleeping Beauty transposon system. Microarray analyses were performed on Stat5b-KD GSCs to identify genes that are differentially expressed downstream of Stat5b. RT-qPCR and western blot analyses were used to determine Myb levels in GSCs. Myb-overexpressing GSCs were induced by electroporation. Proliferation and apoptosis were evaluated by a trypan blue dye exclusion test and annexin-V staining, respectively. Results: MYB, which is involved in the Wnt pathway, was identified as a novel gene whose expression was down-regulated by Stat5b-KD in GSCs. Both MYB mRNA and protein levels were down-regulated by Stat5b-KD. Overexpression of Myb rescued cell proliferation that was suppressed by Stat5b-KD. Furthermore, Stat5b-KD-induced apoptosis in GSCs was significantly inhibited by Myb overexpression. Conclusion: Down-regulation of Myb mediates Stat5b-KD-induced inhibition of proliferation and induction of apoptosis in GSCs. This may represent a promising novel therapeutic strategy against glioblastoma.

Adolescent idiopathic scoliosis (AIS) is a serious health problem affecting 3% of live births all over the world. Many loci associated with AIS have been identified by previous genome wide association studies, but their biological implication remains mostly unclear. In this study, we evaluated the AIS-associated variants in the 7p22.3 locus by combining in silico, in vitro, and in vivo analyses. rs78148157 was located in an enhancer of UNCX, a homeobox gene and its risk allele upregulated the UNCX expression. A transcription factor, early growth response 1 (EGR1), transactivated the rs78148157-located enhancer and showed a higher binding affinity for the risk allele of rs78148157. Furthermore, zebrafish larvae with UNCX messenger RNA (mRNA) injection developed body curvature and defective neurogenesis in a dose-dependent manner. rs78148157 confers the genetic susceptibility to AIS by enhancing the EGR1-regulated UNCX expression. © 2022 American Society for Bone and Mineral Research (ASBMR).

Animals make decisions under the principle of reward value maximization and surprise minimization. It is still unclear how these principles are represented in the brain and are reflected in behavior. We addressed this question using a closed-loop virtual reality system to train adult zebrafish for active avoidance. Analysis of the neural activity of the dorsal pallium during training revealed neural ensembles assigning rules to the colors of the surrounding walls. Additionally, one third of fish generated another ensemble that becomes activated only when the real perceived scenery shows discrepancy from the predicted favorable scenery. The fish with the latter ensemble escape more efficiently than the fish with the former ensembles alone, even though both fish have successfully learned to escape, consistent with the hypothesis that the latter ensemble guides zebrafish to take action to minimize this prediction error. Our results suggest that zebrafish can use both principles of goal-directed behavior, but with different behavioral consequences depending on the repertoire of the adopted principles., Using a closed-loop virtual reality system for fish, the authors show that zebrafish are capable of assigning rules to the scenery they see, and of generating a state prediction error by comparing reality with a prediction derived from an internal model.

Background: The term “addiction” encompasses both substance dependence and behavioral addiction and is associated with major societal problems. Measures to combat addiction are currently insufficient in Japan, and further research on addiction is necessary. Methods: Science Council of Japan (SCJ) has three subcommittees – the Addiction Subcommittee, Brain and Mind Subcommittee, and Neuroscience Subcommittee among others. Those three subcommittees are dealing directly or indirectly with addiction problems in Japan. Thus, all authors of this review, members of those subcommittees, collectively recommended what research activities are required in Japan for continuing effort in overcoming addiction problems in Japan. Results: We proposed the following measures. Proposal 1: Understand diversity in addiction and promote related research and education; Proposal 2: Promote personalized measures for patients with addiction disorders; Proposal 3: Foster addiction research personnel; Proposal 4: Develop new guidelines for the rehabilitation of patients with drug dependence; Proposal 5: Establish an institute specializing in addiction research and comprehensively handling information collection, research, countermeasures, treatment, and public relation related to addiction. Conclusion: The opinions of the review are based on the recommendations that were published in 2020 in Japanese by the Addiction Subcommittee, Brain and Mind Subcommittee, and Neuroscience Subcommittee of the SCJ. The authors here are sharing colleagues of Taiwanese Society of Psychiatry with these proposed research activities required to overcome addiction problems in Japan.

Levy walks, random walks where the frequency of occurrence of a linear step length follows a power-law distribution, are found in the migratory behavior of organisms at various levels, from bacteria and T cells to humans. However, it has been pointed out that in human migratory behavior, the step length series may have temporal correlation (i.e., it is not random walk) and that there is some relationship between this time dependency and the fact that the frequency distribution of step length follows the power-law distribution. Furthermore, some large marine organisms have been found to switch between Levy and Brownian walks, wherein the frequency of occurrence of the step length is characterized by an exponential distribution (EP), depending on the difficulty of prey acquisition. However, as of now it has not been clarified how the aforementioned three phenomena arise: the positive correlation created in the step length series, the relation between the positive correlation of the step length series and the form of an individual’s step length distribution, and the switching between Levy and Brownian behavior depending on the abundance of prey. The purpose of this study is to simulate foraging behavior by three Bayesian decision-making agents: an agent simultaneously performing both knowledge learning and knowledge-based inference, an agent performing only learning, an agent performing only inference, and to analyze how the aforementioned three phenomena arise. The simulation results show that only the agent with both learning and inference has a mechanism that simultaneously causes all the phenomena. This suggests that simultaneous learning on prey distribution and inference based on the knowledge gained in exploratory behavior under incomplete information may be the key to the emergence of Levy walk-like patterns found in humans and marine organisms.

Anal canal neuroendocrine carcinoma (NEC) with pagetoid spread (PS) is a rare disease, and its treatment strategy remains unclear. The prognosis of anal canal NEC with PS is poor. Resection margin status is very important for anorectal carcinoma because it affects survival. When accompanied by PS, the defect of the resulting perineal wound following radical surgical intervention may be necessarily enlarged to ensure the appropriate margin status. This case report discusses the treatment of a patient with advanced anal canal NEC with PS, inguinal lymph node metastasis and sphincter infiltration in which total pelvic exenteration with plastic surgery was successfully performed. The plastic surgery incorporated a gracilis muscle flap that was useful for the reconstruction of the enlarged perineal defect.

The North Pacific Loggerhead sea turtle (Caretta caretta) undergoes one of the greatest of all animal migrations, nesting exclusively in Japan and re-emerging several years later along important foraging grounds in the eastern North Pacific. Yet the mechanisms that connect these disparate habitats during what is known as the “lost years” have remained poorly understood. Here, we develop a new hypothesis regarding a possible physical mechanism for habitat connectivity – an intermittent “thermal corridor” – using remotely sensed oceanography and 6 juvenile loggerhead sea turtles that formed part of a 15 year tracking dataset of 231 individuals (1997–2013). While 97% of individuals remained in the Central North Pacific, these 6 turtles (about 3%), continued an eastward trajectory during periods associated with anomalously warm ocean conditions. These few individuals provided a unique opportunity to examine previously unknown recruitment pathways. To support this hypothesis, we employed an independently derived data set using novel stable isotope analyses of bone growth layers and assessed annual recruitment over the same time period (n = 33, 1997–2012). We suggest evidence of a thermal corridor that may allow for pulsed recruitment of loggerheads to the North American coast as a function of ocean conditions. Our findings offer, for the first time, the opportunity to explore the development of a dynamic ocean corridor for this protected species, illuminating a longstanding mystery in sea turtle ecology.

The onset of circulation in a developing embryo requires intact blood vessels to prevent hemorrhage. The development of endothelial cells, and their subsequent recruitment of perivascular mural cells are important processes to establish and maintain vascular integrity. These processes are genetically controlled during development, and mutations that affect endothelial cell specification, pattern formation, or maturation through the addition of mural cells can result in early developmental hemorrhage. We created a strong loss of function allele of the zebrafish GDP-mannose 4,6 dehydratase (gmds) gene that is required for the de novo synthesis of GDP-fucose, and homozygous embryos display cerebral hemorrhages. Our data demonstrate that gmds mutants have early defects in vascular patterning with ectopic branches observed at time of hemorrhage. Subsequently, defects in the number of mural cells that line the vasculature are observed. Moreover, activation of Notch signaling rescued hemorrhage phenotypes in gmds mutants, highlighting a potential downstream pathway that requires protein fucosylation for vascular integrity. Finally, supplementation with fucose can rescue hemorrhage frequency in gmds mutants, demonstrating that synthesis of GDP-fucose via an alternative (salvage) pathway may provide an avenue toward therapeutic correction of phenotypes observed due to defects in de novo GDP-fucose synthesis. Together, these data are consistent with a novel role for the de novo and salvage protein fucosylation pathways in regulating vascular integrity through a Notch dependent mechanism.

The habenula is among the evolutionarily most conserved parts of the brain and has been known for its role in the control of behavior to cope with aversive stimuli. Recent studies in zebrafish have revealed the novel roles of the two parallel neural pathways from the dorsal habenula to its target, the interpeduncular nucleus, in the control of behavioral choice whether to behave dominantly or submissively in the social conflict. They are modifiable depending on the internal state of the fish such as hunger and play another important role in orientation of attention whether to direct it internally to oneself or externally to others. These studies, therefore, are revealing a novel role for the habenula as the integrated switchboard for concertedly controlling behavior either as a winner with self-centered (idiothetic) attention or a loser with others-oriented (allothetic) attention.

How animals behave using suitable information to adapt to the environment is not well known. We address this issue by devising an automated system to let zebrafish exploit either internal (choice of left or right turn) or external (choice of cue color) navigation information to achieve operant behavior by reward reinforcement learning. The results of behavioral task with repeated rule shift indicate that zebrafish can learn operant behavior using both internal-directional and external-cued information. The learning time is reduced as rule shifts are repeated, revealing the capacity of zebrafish to adaptively retrieve the suitable rule memory after training. Zebrafish with an impairment in the neural pathway from the lateral subregion of the dorsal habenula to the interpeduncular nucleus, known to be potentiated in the winners of social conflicts, show specific defects in the application of the internal-directional rule, suggesting the dual roles of this pathway.

Ras related (R-Ras), a small GTPase, is involved in the maintenance of apico-basal polarity in neuroepithelial cells of the zebrafish hindbrain, axonal collapse in cultured murine hippocampal neurons, and maturation of blood vessels in adult mice. However, the role of R-Ras in neural tube formation remains unknown. Using antisense morpholino oligonucleotides (AMOs), we found that in the spinal cord of zebrafish embryos, the lumen was formed bilaterally in rras morphants, whereas it was formed at the midline in control embryos. As AMO can cause off-target effects, we generated rras mutant zebrafish lines using CRISPR/Cas9 technology. Although these rras mutant embryos did not have a bilateral lumen in the spinal cord, the following findings suggest that the phenotype is unlikely due to an off-target effect of rras AMO: 1) The rras morphant phenotype was rescued by an injection of AMO-resistant rras mRNA, and 2) a bilaterally segregated spinal cord was not observed in rras mutant embryos injected with rras AMO. The results suggest that the function of other ras family genes may be redundant in rras mutants. Previous research reported a bilaterally formed lumen in the spinal cord of zebrafish embryos with a mutation in a planar cell polarity (PCP) gene, van gogh-like 2 (vangl2). In the present study, in cultured cells, R-Ras was co-immunoprecipitated with Vangl2 but not with another PCP regulator, Pricke1. Interestingly, the interaction between R-Ras and Vangl2 was stronger in guanine-nucleotide free point mutants of R-Ras than in wild-type or constitutively active (GTP-bound) forms of R-Ras. R-Ras may regulate neural tube formation in cooperation with Vangl2 in the developing zebrafish spinal cord.

Optical measurement of membrane potentials enables fast, direct and simultaneous detection of membrane potentials from a population of neurons, providing a desirable approach for functional analysis of neuronal circuits. Here, we applied recently developed genetically encoded voltage indicators, ASAP1 (Accelerated Sensor of Action Potentials 1) and QuasAr2 (Quality superior to Arch 2), to zebrafish, an ideal model system for studying neurogenesis. To achieve this, we established transgenic lines which express the voltage sensors, and showed that ASAP1 is expressed in zebrafish neurons. To examine whether neuronal activity could be detected by ASAP1, we performed whole-cerebellum imaging, showing that depolarization was detected widely in the cerebellum and optic tectum upon electrical stimulation. Spontaneous activity in the spinal cord was also detected by ASAP1 imaging at single-cell resolution as well as at the neuronal population level. These responses mostly disappeared following treatment with tetrodotoxin, indicating that ASAP1 enabled optical measurement of neuronal activity in the zebrafish brain. Combining this method with other approaches, such as optogenetics and behavioural analysis may facilitate a deeper understanding of the functional organization of brain circuitry and its development.

Social subordination, which causes severe stress in animals, can affect animal's behaviors, homeostasis, and mental health. In rodents, experiences of repeated social defeats, but not a single defeat, induce a depression-like state. However, it is unclear whether such experiences similarly affect behaviors of other model animals than rodents. Here, we established a behavioral paradigm for repeated social defeats with zebrafish, an emerging model for behavioral neuroscience and pharmacological analysis. We put fish into repeated social subordination for 6 consecutive days. Using behaviors during fighting as indicators, we observed that experiencing repeated social defeats led to a reduction in fight frequency and duration. The continuously-defeated zebrafish failed to win even against the transgenic fish with an impaired winning-associated neural pathway. These results suggest that repeated social defeats led to demotivation to fight and to win against opponents. Moreover, they showed strong activity in the ventral habenula, an evolutionary homolog of the mammalian lateral habenula. However, unlike the mice model, the continuously-defeated zebrafish showed no change in anxiety level and sociability. Our established behavioral paradigm will be a new tool to investigate neural mechanisms underlying social defeats.

SummaryHuman predicts future. To ask if fish also has this capacity, we established the virtual reality training system with live imaging of the telencephalic neurons of adult zebrafish in the active avoidance and found that, at the onset of the trial, learned fish conceives two future conditions as the favorable status on its way to the safe goal, i.e. one with the backwardly moving landscape and the other with the color of the safe goal. And the two different neural ensembles monitor the discrepancy between these predictions and the perceived real external status. Once fish reaches the goal, another ensemble is set to work to monitor whether fish keeps staying in the safe goal. The manipulation to artificially enhance these prediction errors elevated the activities of these ensembles and induced fish to behave to correct errors, revealing that fish sets behavioral strategy to actively realize these predictions.

As the central pacemaker in mammals, the circadian clock in the suprachiasmatic nucleus (SCN) of the hypothalamus is a heterogeneous structure consisting of multiple types of GABAergic neurons with distinct chemical identities [1, 2]. Although individual cells have a cellular clock driven by autoregulatory transcriptional/translational feedback loops of clock genes, interneuronal communicationamong SCN clock neurons is likely essential for the SCN to generate a highly robust, coherent circadian rhythm [1]. However, neuronal mechanisms that determine circadian period length remain unclear. The SCN is composed of two subdivisions:a ventral core region containing vasoactive intestinal peptide (VIP)-producing neurons and a dorsal shell region characterized by arginine vasopressin (AVP)-producing neurons. Here we examined whether AVP neurons act as pacemaker cellsthat regulate the circadian period of behavior rhythm in mice. The deletion of casein kinase 1 delta (CK1δ) specific to AVP neurons, which was expected to lengthen the period of cellular clocks [3–6], lengthened the free-running period of circadian behavior as well. Conversely, the overexpression of CK1δ specific to SCN AVPneurons shortened the free-running period. PER2::LUC imaging in slices confirmed that cellularcircadian periods of the SCN shell were lengthened in mice without CK1δ in AVP neurons. Thus, AVP neurons may be an essential component of circadian pacemaker cells in the SCN. Remarkably, the alteration of the shell-core phase relationship in the SCN of these mice did not impair the generation per se of circadian behavior rhythm, thereby underscoring the robustness of the SCN network. © 2016 Elsevier Ltd, Embargo Period 12 months

When animals encounter conflict they initiate and escalate aggression to establish and maintain a social hierarchy. The neural mechanisms by which animals resolve fighting behaviors to determine such social hierarchies remain unknown. We identified two subregions of the dorsal habenula (dHb) in zebrafish that antagonistically regulate the outcome of conflict. The losing experience reduced neural transmission in the lateral subregion of dHb (dHbL)-dorsal/intermediate interpeduncular nucleus (d/iIPN) circuit. Silencing of the dHbL or medial subregion of dHb (dHbM) caused a stronger predisposition to lose or win a fight, respectively. These results demonstrate that the dHbL and dHbM comprise a dual control system for conflict resolution of social aggression.

Flow of cerebrospinal fluid (CSF) may contribute to spine morphogenesis, as mutations affecting both cilia motility and CSF flow lead to scoliosis1. However, the mechanisms underlying detection of the CSF flow in the central canal of the spinal cord remain elusive. Here we used full-field optical coherence tomography (FF-OCT) and bead tracking to demonstrate that CSF flows bidirectionally along the antero-posterior axis in the central canal of zebrafish embryos. In the zebrafish mutantcfap298tm304, previously known askurly, reduction of cilia motility slows transport down the length of central canal. To investigate downstream mechanisms that could transduce CSF flow, we performed calcium imaging in sensory neurons contacting the CSF (CSF-cNs) and found that disruption in cilia motility impaired the activity of CSF-cNs. CSF-cNs across species express the transient receptor potential channel PKD2L1, also known as TRPP3, which contributes to CSF-cN chemosensory properties. Using calcium imaging and whole-cell patch clamp recordings, we found that the loss of the Pkd2l1 channel inpkd2l1mutant embryos also abolished CSF-cN activity. Whole-cell recordings further demonstrated that opening of a single channel is sufficient to trigger action potentials in wild type CSF-cNs. Recording from isolated cellsin vitro,we showed that CSF-cNs are mechanosensory cells that respond to pressure in a Pkd2l1-dependent manner. Interestingly, adultpkd2l1mutant zebrafish develop an exaggerated spine curvature, reminiscent of kyphosis in humans. Our study indicates that CSF-cNs are mechanosensory cells whose spontaneous activity reflects CSF flowin vivo. Furthermore, Pkd2l1 in CSF-cNs contributes to the maintenance of the natural curvature of the spine.

Wearable technologies for functional whole brain imaging in freely moving animals would advance our understanding of cognitive processing and adaptive behavior. Fluorescence imaging can visualize the activity of individual neurons in real time, but conventional microscopes have limited sample coverage in both the width and depth of view. Here we developed a novel head-mounted laser camera (HLC) with macro and deep-focus lenses that enable fluorescence imaging at cellular resolution for comprehensive imaging in mice expressing a layer- and cell type-specific calcium probe. We visualized orientation selectivity in individual excitatory neurons across the whole visual cortex of one hemisphere, and cell assembly expressing the premotor activity that precedes voluntary movement across the motor cortex of both hemispheres. Including options for multiplex and wireless interfaces, our wearable, wide- and deep-imaging HLC technology could enable simple and economical mapping of neuronal populations underlying cognition and behavior.

Conservation of the genetic resources of endangered animals is crucial for future generations. The loggerhead sea turtle (Caretta caretta) is a critically endangered species, because of human hunting, hybridisation with other sea turtle species, and infectious diseases. In the present study, we established primary fibroblast cell lines from the loggerhead sea turtle, and showed its species specific chromosome number is 2n = 56, which is identical to that of the hawksbill and olive ridley sea turtles. We first showed that intensive hybridization among multiple sea turtle species caused due to the identical chromosome number, which allows existence of stable hybridization among the multiple sea turtle species. Expressions of human-derived mutant Cyclin-dependent kinase 4 (CDK4) and Cyclin D dramatically extended the cell culture period, when it was compared with the cell culture period of wild type cells. The recombinant fibroblast cell lines maintained the normal chromosome condition and morphology, indicating that, at the G1/S phase, the machinery to control the cellular proliferation is evolutionally conserved among various vertebrates. To our knowledge, this study is the first to demonstrate the functional conservation to overcome the negative feedback system to limit the turn over of the cell cycle between mammalian and reptiles. Our cell culture method will enable the sharing of cells from critically endangered animals as research materials.

International audience; Liver zonation, the spatial separation of different metabolic pathways along the liver sinusoids, is fundamental for proper functioning of this organ, and its disruption can lead to the development of metabolic disorders such as hyperammonemia. Metabolic zonation involves the induction of β-catenin signaling around the central veins, but how this patterned activity is established and maintained is unclear. Here, we show that the signaling molecule Rspondin3 is specifically expressed within the endothelial compartment of the central vein. Conditional deletion of Rspo3 in mice disrupts activation of central fate, demonstrating its crucial role in determining and maintaining β-catenin-dependent zonation. Moreover, ectopic expression of Rspo1, a close family member of Rspo3, induces the expression of pericentral markers, demonstrating Rspondins to be sufficient to imprint a more central fate. Thus, Rspo3 is a key angiocrine factor that controls metabolic zonation of liver hepatocytes.

Three satellite-tagged male loggerhead turtles (Caretta caretta) were released from the coastal waters of Satsuma Peninsula, Kyusyu, southwestern Japan (lat 31°42′N, long 130°18′E), and their movements were tracked for up to 449 d. Total distance traveled by the turtles ranged from 1540 to 5519 km. The turtles remained mainly along the coast and islands of the East China Sea and the Sea of Japan, except for spending a brief period of time (1–30 d) in the open ocean. The long-distance movement followed a seasonal pattern, evidently triggered by fluctuations in sea surface temperature.

Adult zebrafish are gaining attention in behavioral neuroscience. By combining video tracking and computer-controlled visual cue presentations on a liquid crystal display screen under the tank, we have developed a new method by which zebrafish can be trained to avoid one arm of a Y-shaped tank by presenting a specific color on the floor paired with an electric shock. Within two hours, zebrafish learn to choose the correct arm at an efficiency of 89.0%. In addition, we also developed a graphical user interface to modify the paradigm assessment parameters such as shape of the tank and time schedules.

Neuronal-activity-regulated pentraxin (NARP/NPTX2/NP2) is a secreted synaptic protein that regulates the trafficking of glutamate receptors and mediates learning, memory, and drug addiction. The role of NPTX2 in regulating structural synaptic plasticity and behavior in a developing vertebrate is indefinite. We characterized the expression of nptx2a in larvae and adult zebrafish and established a transcription activator-like effector nuclease (TALEN)-mediated nptx2a mutant (nptx2a(-/-)) to study the role of Nptx2a in regulating structural synaptic plasticity and behavior. Similar to mammals, the zebrafish nptx2a was expressed in excitatory neurons in the brain and spinal cord. Its expression was induced in response to a mechanosensory stimulus but did not change during day and night. Behavioral assays showed that loss of Nptx2a results in reduced locomotor response to light-to-dark transition states and to a sound stimulus. Live imaging of synapses using the transgenic nptx2a:GAL4VP16 zebrafish and a fluorescent presynaptic synaptophysin (SYP) marker revealed reduced synaptic density in the axons of the spinal motor neurons and the anterodorsal lateral-line ganglion (gAD), which regulate locomotor activity and locomotor response to mechanosensory stimuli, respectively. These results suggest that Nptx2a affects locomotor response to external stimuli by mediating structural synaptic plasticity in excitatory neuronal circuits.

The LIM-homeodomain transcription factor Islet2a establishes neuronal identity in the developing nervous system. Our previous study showed that Islet2a function is crucial for extending peripheral axons of sensory neurons in zebrafish embryo. Overexpressing a dominant-negative form of Islet2a significantly reduced peripheral axon extension in zebrafish sensory neurons, implicating Islet2a in the gene regulation required for neurite formation or proper axon growth in developing sensory neurons. Based on this, we conducted systematic screening to isolate genes regulated by Islet2a and affecting the development of axon growth in embryonic zebrafish sensory neurons. The 26 genes selected included some encoding factors involved in neuronal differentiation, axon growth, cellular signaling, and structural integrity of neurons, as well as genes whose functions are not fully determined. We chose four representative candidates as possible Islet2a downstream functional targets (simplet, tppp, tusc5 and tmem59l) and analyzed their respective mRNA expressions in dominant-negative Islet2a-expressing embryos. They are not reported the involvement of axonal extension or their functions in neural cells. Finally, knockdown of these genes suggested their direct actual involvement in the extension of peripheral axons in sensory neurons.

Local caspase activation at axonal branch points restricts arbor growth and synaptogenesis by interacting with Slit1a-Robo2 signaling in the central nervous system., In addition to being critical for apoptosis, components of the apoptotic pathway, such as caspases, are involved in other physiological processes in many types of cells, including neurons. However, very little is known about their role in dynamic, nonphysically destructive processes, such as axonal arborization and synaptogenesis. We show that caspases were locally active in vivo at the branch points of young, dynamic retinal ganglion cell axonal arbors but not in the cell body or in stable mature arbors. Caspase activation, dependent on Caspase-3, Caspase-9, and p38 mitogen-activated protein kinase (MAPK), rapidly increased at branch points corresponding with branch tip addition. Time-lapse imaging revealed that knockdown of Caspase-3 and Caspase-9 led to more stable arbors and presynaptic sites. Genetic analysis showed that Caspase-3, Caspase-9, and p38 MAPK interacted with Slit1a-Robo2 signaling, suggesting that localized activation of caspases lie downstream of a ligand receptor system, acting as key promoters of axonal branch tip and synaptic dynamics to restrict arbor growth in vivo in the central nervous system.

Intracellular Ca2+ imaging has widely been used to visualize intracellular signals, but the application in an intact animal is still limited due to difficulty of the indicator loading. In addition, the motion of the living animal produces artifacts. To investigate Ca2+ signaling at early embryonic stage, we established transgenic zebrafish line expressing a genetically encoded Ca2+ indicator, cameleon YC2.60, driven by a constitutively active promoter, hspa8. Although the embryo dynamically changes its morphology, the motion artifact could be canceled out by taking the advantage of YC2.60 as a ratiometric indicator. The transgenic zebrafish was used to visualize the propagation of cytosolic Ca2+ during the early embryonic stage upon fertilization and along cleavage furrow, and the rise in Ca2+ in the myocytes contracting spontaneously in the embryo. We also established a transgenic zebrafish line expressing YC2.60 targeted to the mitochondria. The rise in mitochondrial Ca2+ was rather sustained (≈2 min), which is consistent with the requirement of ATP refilling since the mitochondrial Ca2+ upregulates rate-limiting enzymes of Krebs cycle. This is in contrast with the transient rise in the cytosol Ca2+ that directly evokes the muscle contraction. These transgenic zebrafish lines are expected to serve as useful tools further Ca2+ imaging in vivo.

Multiple paternity within the same clutch has been detected in all sea turtle species. However, no study to date has addressed the likelihood of sperm storage across years in any sea turtle species in the wild because of the logistical difficulties associated with investigating the same individual females across breeding seasons. Here we provide paternity data from captive loggerhead turtles (Caretta caretta) during 2–4 successive breeding seasons and behavioral information to estimate sperm storage duration in this species. Data from interseasonal comparisons for individual females showed that paternity was identical between two successive breeding seasons. However, females were observed to copulate with males, which were sire of their hatchlings of the previous breeding season, just prior to the nesting period of the next breeding season. Therefore, it is appropriate to regard the consistency in paternity across two successive breeding seasons as a result of re-mating with a sire from the previous season. Conversely, paternity was entirely different from that in the previous season if copulatory behavior occurred just prior to the next season with a male that was not a sire of the female's hatchlings from the previous season. Furthermore, a female that had laid fertile eggs in the previous breeding season but was not observed to successfully copulate with any male during the next breeding season laid no fertile eggs during that next season. Taking these data into consideration, it appears that sperm storage across breeding seasons did not occur in this study of captive Caretta.

To adapt to their environment, animals subconsciously calculate how motor commands can be efficiently translated into the actual movements. Kawashima et al. discovered that serotonergic neurons in the dorsal raphe nucleus regulate the transient memory of such efficacy; thus, successive behaviors do not require repeated cumbersome readjustment of efficacy.

The custom-homebuilding company, Cosmic Garden Co. Ltd., located in Okayama City, Japan was established in 1997 and uses specific natural ore powder (SNOP) in wall materials and surveys customers in order to improve allergic symptoms.To investigate the biological effects of SNOP, patients with a pollen allergy were recruited to stay in a room surrounded by cloth containing SNOP (CCSNOP), and their symptoms and various biological parameters were compared with those of individuals staying in a room surrounded by control non-woven cloth (NWC). Each stay lasted 60 min. Before and immediately after the stay, a questionnaire regarding allergic symptoms, as well as POMS (Profile of Mood Status) and blood sampling, was performed. Post-stay minus pre-stay values were calculated and compared between CCSNOP and NWC groups.Results indicated that some symptoms, such as nasal obstruction and lacrimation, improved, and POMS evaluation showed that patients were calmer following a stay in CCSNOP. Relative eosinophils, non-specific Ig E, epidermal growth factor, monocyte chemotactic protein-1, and tumor necrosis factor-α increased following a stay in CCSNOP.This ore powder improved allergic symptoms, and long-term monitoring involving 1 to 2 months may be necessary to fully explore the biological and physical effects of SNOP on allergic patients.

The loggerhead turtle (Caretta caretta) is listed as an endangered species in the International Union for Conservation of Nature Red List, and this is critical for the maintenance of future genetic diversity. For the conservation of this species, it is important to understand the relationships between sexual selection and gene flow in the evolution of biodiversity. It is, however, virtually impossible to study sexual selection in such an oceanic species in the field. We investigated the relationships between mate preference and genetic relatedness of reproductively active loggerhead turtles (n = 7) kept in a tank at an aquarium using 4 different estimators of pairwise genetic relatedness (r) based on the genotypes at 23 microsatellite loci. Although relationships between total number of courtship behavior and r were not significant in the 4 estimators, there were significant and consistent inverse relationships between cumulative duration of mountings and r in all of the estimators. In addition...

The mammalian habenula is involved in regulating the activities of serotonergic and dopaminergic neurons. It consists of the medial and lateral habenulae, with each subregion having distinct neural connectivity. Despite the functional significance, manipulating neural activity in a subset of habenular pathways remains difficult because of the poor availability of molecular markers that delineate the subnuclear structures. Thus, we examined the molecular nature of neurons in the habenular subnuclei by analyzing the gene expressions of neurotransmitter markers. The results showed that different subregions of the medial habenula (MHb) use different combinations of neurotransmitter systems and could be categorized as either exclusively glutamatergic (superior part of MHb), both substance P-ergic and glutamatergic (dorsal region of central part of MHb), or both cholinergic and glutamatergic (inferior part, ventral region of central part, and lateral part of MHb). The superior part of the MHb strongly expressed interleukin-18 and was innervated by noradrenergic fibers. In contrast, the inferior part, ventral region of the central part, and lateral part of the MHb were peculiar in that acetylcholine and glutamate were cotransmitted from the axonal terminals. In contrast, neurons in the lateral habenula (LHb) were almost uniformly glutamatergic. Finally, the expressions of Htr2c and Drd2 seemed complementary in the medial LHb division, whereas they coincided in the lateral division, suggesting that the medial and lateral divisions of LHb show strong heterogeneity with respect to monoamine receptor expression. These analyses clarify molecular differences between subnuclei in the mammalian habenula that support their respective functional implications.

After coming back to Japan to work in the Department of Physics at the University of Tokyo, Yoshiki Hotta spent a year or so on searching for behavioral mutants of goldfish. Although this endeavor did not succeed, he remained an adamant supporter of the development of zebrafish research in Japan. Here we review how his support helped zebrafish neurogenetics in Japan gain a unique position in the world research community.

The habenula is a part of an evolutionarily highly conserved conduction pathway within the limbic system that connects telencephalic nuclei to the brain stem nuclei such as interpeduncular nucleus(IPN), the ventral tegmental area (VTA), and the raphe.In mammals, the medial habenula receives inputs from the septohippocampal system, and relaying such information to the IPN. In contrast, the lateral habenula receives inputs from the ventral pallidum, a part of the basal ganglia. The physical adjunction of these two habenular nuclei suggests that the habenula may act as an intersection of the neural circuits for controlling emotion and behavior. We have recently elucidated that zebrafish has the equivalent structure as the mammalian habenula. The transgenic zebrafish, in which the neural signal transmission from the lateral subnucleus of the dorsal habenula to the dorsal IPN was selectively impaired, showed extremely enhanced levels of freezing response to presentation of the conditioned aversive stimulus. Our observation supports that the habenula may act as the multimodal switching board for controlling emotional behaviors and/or memory inexperience dependent manners.

We investigated the effects of the order of sequential matings in captive female loggerhead turtles (Caretta caretta) on the paternity of their successive clutches. Paternity analysis revealed that only 3 of the 7 successive clutches were multiply sired, although all egg-laying females were observed to copulate with multiple males prior to egg-laying. In multiply sired, successive clutches of particular females, the relative paternal contributions of different males did not vary, although some potentially successful matings were observed during internesting intervals. Prior to nesting periods, males showed mating in response to the female reproductive cycle in which the cumulative durations of mountings observed by highly sensitive cameras peaked at 21–40 days before any individual female laid her first clutch. A regression line between cumulative duration of mountings and relative parental contributions for 21–40 days before laying the first clutch fit a predictive equation for sperm competition...

The assembly of progenitor cells is a crucial step for organ formation during vertebrate development. Kupffer’s vesicle (KV) is a key organ required for the left-right asymmetric body plan in zebrafish, and is generated from a cluster of approximately 20 dorsal forerunner cells (DFCs). Although several genes are known to be involved in KV formation, how DFC clustering is regulated and how cluster formation then contributes to KV formation remain unclear. Here we show that positive feedback regulation of FGF signaling by Canopy1 (Cnpy1) controls DFC clustering without affecting DFC specification and DFC number. Cnpy1 positively regulates FGF signals within DFCs, which in turn promotes Cadherin1-mediated cell adhesion between adjacent DFCs to sustain cell cluster formation. When this FGF positive feedback loop is disrupted, the DFC cluster fails to form, eventually leading to KV malformation and defects in the establishment of laterality. Our results therefore uncover both a previously unidentified role of FGF signaling during vertebrate organogenesis and a regulatory mechanism underlying cell cluster formation, which is an indispensable step for formation of a functional KV and establishment of the left-right asymmetric body plan.

Summary Left-right asymmetries are most likely a universal feature of bilaterian nervous systems and may serve to increase neural capacity by specializing equivalent structures on left and right sides for distinct roles [1]. However, little is known about how asymmetries are encoded within vertebrate neural circuits and how lateralization influences processing of information in the brain. Consequently, it remains unclear the extent to which lateralization of the nervous system is important for normal cognitive and other brain functions and whether defects in lateralization contribute to neurological deficits [2]. Here we show that sensory responses to light and odor are lateralized in larval zebrafish habenulae and that loss of brain asymmetry leads to concomitant loss of responsiveness to either visual or olfactory stimuli. We find that in wild-type zebrafish, most habenular neurons responding to light are present on the left, whereas neurons responding to odor are more frequent on the right. Manipulations that reverse the direction of brain asymmetry reverse the functional properties of habenular neurons, whereas manipulations that generate either double-left- or double-right-sided brains lead to loss of habenular responsiveness to either odor or light, respectively. Our results indicate that loss of brain lateralization has significant consequences upon sensory processing and circuit function., Graphical Abstract, Highlights • Habenular neuron responses to light and odor stimuli are lateralized • Lateralized habenular light responses depend upon the eyes • Loss of brain asymmetry leads to a loss of either light or odor responses, Dreosti et al. show that sensory responses to light and odor are lateralized in the larval zebrafish habenula and that loss of brain asymmetry leads to a loss of responses to visual or olfactory stimuli, suggesting that brain lateralization may play a significant role in sensory processing and circuit function.

We isolated a novel zebrafish mutant, lullaby (llb), and showed that the llb locus encodes the zebrafish orthologue of isl1. Rohon-Beard (RB) primary sensory neurons are multipolar neurons that extend their central axons longitudinally within the spinal cord and also extend their peripheral axons under the skin. In llb embryos, the outgrowth of the peripheral axons of RB neurons was selectively impaired, which correlated with down-regulation of the expression of dihydropyrimidinase-like 3 (dpysl3, also known as collapsin response mediator protein 4, crmp4). Antisense morpholino oligonucleotide (AMO)-mediated knockdown of dpysl3 inhibited the outgrowth of the peripheral axons of RB neurons, and semaphorin 3d (sema3d) AMO enhanced this effect. These data indicate that Dpysl3 is cooperating with Sema3d in the peripheral axon outgrowth, and Isl1 is required for the selective outgrowth of the peripheral axons of RB neurons by maintaining the expression of dpysl3.

In the adult teleost brain, proliferating cells are observed in a broad area, while these cells have a restricted distribution in adult mammalian brains. In the adult teleost optic tectum, most of the proliferating cells are distributed in the caudal margin of the periventricular gray zone (PGZ). We found that the PGZ is largely divided into 3 regions: 1 mitotic region and 2 post-mitotic regions—the superficial and deep layers. These regions are distinguished by the differential expression of several marker genes: pcna , sox2 , msi1 , elavl3 , gfap , fabp7a , and s100β . Using transgenic zebrafish Tg ( gfap :GFP), we found that the deep layer cells specifically express gfap :GFP and have a radial glial morphology. We noted that bromodeoxyuridine (BrdU)-positive cells in the mitotic region did not exhibit glial properties, but maintained neuroepithelial characteristics. Pulse chase experiments with BrdU-positive cells revealed the presence of self-renewing stem cells within the mitotic region. BrdU-positive cells differentiate into glutamatergic or GABAergic neurons and oligodendrocytes in the superficial layer and into radial glial cells in the deep layer. These results demonstrate that the proliferating cells in the PGZ contribute to neuronal and glial lineages to maintain the structure of the optic tectum in adult zebrafish.

The zebrafish is the simplest model vertebrate amenable to genetics, and genome information and methods of embryo manipulation have been accumulated worldwide. The numbers of mutant and transgenic zebrafish strains are rapidly increasing, and these strains will play important roles in the basic biology research and as model systems of the human diseases in the future. Although researchers who had established zebrafish strains, were distributing the fish on a discretionary basis, a well-established system for distributing the strains did not exit in Japan prior to 2003. Due to these circumstances, a system to collect, preserve, and provide zebrafish strains was established as part of the National BioResource Project useful model vertebrates in Japan and to the world.

By exploiting the cell-cycle-dependent proteolysis of two ubiquitination oscillators, human Cdt1 and geminin, which are the direct substrates of SCF Skp2 and APC Cdh1 complexes, respectively, Fucci technique labels mammalian cell nuclei in G 1 and S/G 2 /M phases with different colors. Transgenic mice expressing these G 1 and S/G 2 /M markers offer a powerful means to investigate the coordination of the cell cycle with morphogenetic processes. We attempted to introduce these markers into zebrafish embryos to take advantage of their favorable optical properties. However, although the fundamental mechanisms for cell-cycle control appear to be well conserved among species, the G 1 marker based on the SCF Skp2 -mediated degradation of human Cdt1 did not work in fish cells, probably because the marker was not ubiquitinated properly by a fish E3 ligase complex. We describe here the generation of a Fucci derivative using zebrafish homologs of Cdt1 and geminin, which provides sweeping views of cell proliferation in whole fish embryos. Remarkably, we discovered two anterior-to-posterior waves of cell-cycle transitions, G 1 /S and M/G 1 , in the differentiating notochord. Our study demonstrates the effectiveness of using the Cul4 Ddb1 -mediated Cdt1 degradation pathway common to all metazoans for the development of a G 1 marker that works in the nonmammalian animal model.

In the vertebrate olfactory system, odor information is represented as a topographic map in the olfactory bulb (OB). However, it remains unknown how this odor map is transferred from the OB to higher olfactory centers. Using genetic labeling techniques in zebrafish, we found that the OB output neurons, mitral cells (MCs), are heterogeneous with respect to transgene expression profiles and spatial distributions. Tracing MC axons at single-cell resolution revealed that (1) individual MCs send axons to multiple target regions in the forebrain; (2) MCs innervating the same glomerulus do not necessarily display the same axon trajectory; (3) MCs innervating distinct glomerular clusters tend to project axons to different, but partly overlapping, target regions; (4) MCs innervating the medial glomerular cluster directly and asymmetrically send axons to the right habenula. We propose that the topographic odor map in the OB is not maintained intact, but reorganized in higher olfactory centers. Moreover, our finding of asymmetric bulbo-habenular projection renders the olfactory system an attractive model for the studies of brain asymmetry and lateralized behaviors.

The amygdala is located in the caudal part of the ventral telencephalon. It is composed of many subdivisions and is involved in the control of emotion. It is important to know the mechanisms of amygdalar development in order to analyze the pathogenesis of emotional disorders, but they are still not adequately understood. In the present study the migration, differentiation, and distribution of amygdalar neurons in the mouse embryo were investigated by means of in utero electroporation. Ventricular zone cells in restricted regions, that is, the caudal ganglionic eminence (CGE), the ventral pallium, the lateral pallium, and the diencephalon, were labeled with an expression vector of the enhanced green fluorescent protein (EGFP) gene. Labeling at embryonic day (E)10 revealed that the central nucleus originates from the neuroepithelium in the ganglionic eminence and the labeling at E11 and E12 revealed that the basolateral complex originates from the neuroepithelium of the ventral and lateral pallia. The introduction of the EGFP gene into the neuroepithelium of the third ventricle at E11 showed that the medial nucleus originates, at least in part, from the neuroepithelium of the diencephalon and migrates over the diencephalo-telencephalic boundary. The radial glial arrangement corresponded well with the initial migration of amygdalar neurons, and the radial processes later formed the boundary demarcating the basolateral complex. These findings indicate that the neurons originating from the temporally and spatially restricted neuroepithelium in both the telencephalon and diencephalon migrate and differentiate to form the mosaic of amygdalar subdivisions.

Planar cell polarity (PCP) in epithelial cells is essential for the organization of tissues and their functions. The conserved non-canonical Wnt/PCP pathway regulates this process in both Drosophila and vertebrates. However, recent studies have revealed that a similar set of genes, which may not be related to PCP, regulates oriented cell movement during development. In the present review, recent findings on neural migration in zebrafish hindbrain and axonal guidance in mouse forebrain and spinal cord are discussed. Future analyses on defects in vertebrate PCP mutants will provide novel insights into the conserved and diverse roles of non-canonical Wnt/PCP pathway genes in vertebrate brain development.