Treatment Failure and Long-Term Prescription Risk for Guideline-Recommended Hypnotics in Japan.

Importance: Although insomnia guidelines recommend the use of several individual hypnotics, the most useful hypnotic for treating insomnia in a clinical setting remains unclear. Objective: To determine which guideline-recommended hypnotics have lower risks of monotherapy failure and which hypnotics have a higher risk of long-term prescription for insomnia treatment. Design, Setting, and Participants: This retrospective observational cohort study used data from the Japan Medical Data Center Claims Database from April 1, 2005, to March 31, 2021. Participants included adults whose first prescribed pharmaceutical treatment for insomnia was guideline-recommended hypnotic monotherapy. Data were analyzed from December 24, 2022, to September 26, 2023. Exposures: Suvorexant, ramelteon, eszopiclone, zolpidem, and triazolam monotherapy. Main Outcomes and Measures: The primary outcome was monotherapy failure, defined as a change in hypnotic or having an additional hypnotic prescribed for insomnia within 6 months of the first prescription of a guideline-recommended hypnotic monotherapy. The secondary outcome was monotherapy discontinuation, defined as no prescription of any hypnotic for 2 consecutive months within 6 months after prescribing a guideline-recommended hypnotic in patients for whom monotherapy did not fail. Monotherapy failure and discontinuation were compared using Cox proportional hazards and logistic regression models, respectively. Results: The study included 239 568 adults (median age, 45 [IQR, 34-55] years; 50.2% women) whose first prescription for insomnia was guideline-recommended hypnotic monotherapy. During the 6-month follow-up period, 24 778 patients (10.3%) experienced failure of monotherapy with a guideline-recommended hypnotic. In comparison with eszopiclone, there were more cases of monotherapy failure for ramelteon (adjusted hazard ratio [AHR], 1.23 [95% CI], 1.17-1.30; P < .001), fewer cases for zolpidem (AHR, 0.84 [95% CI, 0.81-0.87]; P < .001) and triazolam (AHR, 0.82 [95% CI, 0.78-0.87]; P < .001), and no significant difference between suvorexant and eszopiclone. Among those without monotherapy failure, monotherapy was discontinued in 84.6% of patients, with more discontinuations for ramelteon (adjusted odds ratio [AOR], 1.31 [95% CI, 1.24-1.40]; P < .001) and suvorexant (AOR, 1.20 [95% CI, 1.15-1.26]; P < .001) than for eszopiclone and no significant difference between zolpidem or triazolam and eszopiclone. Conclusions and Relevance: Due to uncontrolled confounding factors in this cohort study, no conclusions regarding the pharmacologic properties of guideline-recommended hypnotics can be drawn based on these results. Further studies accounting for confounding factors, including diagnoses of chronic vs acute insomnia disorder, insomnia and psychiatric symptom severity, and physician attitudes toward hypnotic prescription, are needed.

Impact of aripiprazole discontinuation in remitted major depressive disorder: a randomized placebo-controlled trial.

RATIONALE: The efficacy and safety of antidepressant augmentation therapy with aripiprazole (AATA) has been established; however, the ongoing effects of continuing aripiprazole after remission remain unclear because no studies have examined this issue. OBJECTIVES: We aimed to explore the effect of AATA discontinuation on the major depressive disorder (MDD) recurrence risk in patients with remitted MDD after AATA. METHODS: This 24-week, multicenter, placebo-controlled, double-blind, randomized trial evaluated recurrence risk in patients with MDD who achieved remission with AATA. Differences in MDD recurrence, as defined by the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, between the two groups were compared using survival analysis. The differences in depressive symptom severity and social functioning between the two groups were compared using a mixed model with repeated measures. Extrapyramidal symptoms and akathisia were also assessed. RESULTS: Twenty-three participants were randomized and treated. Two patients in each group experienced recurrence during the study. Kaplan-Meier analysis with Log-rank comparison showed no difference in recurrence between groups (p = 0.642). No significant difference in interactions between group and period was observed in the 17-item Hamilton depression rating scale (p = 0.492) or the Social and Occupational Functioning Assessment Scale (p = 0.638). No patients developed extrapyramidal symptoms or akathisia. CONCLUSIONS: Definitive conclusions could not be drawn owing to the small sample size. This study represents a starting point for investigating the safety of aripiprazole discontinuation on recurrence in patients with MDD who have achieved remission with AATA. Future studies with appropriate sample sizes calculated based on this study are needed.

Exploratory Validation of Sleep-Tracking Devices in Patients with Psychiatric Disorders.

Purpose: Sleep-tracking devices have performed well in recent studies that evaluated their use in healthy adults by comparing them with the gold standard sleep assessment technique, polysomnography (PSG). These devices have not been validated for use in patients with psychiatric disorders. Therefore, we tested the performance of three sleep-tracking devices against PSG in patients with psychiatric disorders. Patients and methods: In total, 52 patients (32 women; 48.1 ± 17.2 years, mean ± SD; 18 patients diagnosed with schizophrenia, 19 with depressive disorder, 3 with bipolar disorder, and 12 with sleep disorder cases) were tested in a sleep laboratory with PSG, along with portable electroencephalography (EEG) device (Sleepgraph), actigraphy (MTN-220/221) and consumer sleep-tracking device (Fitbit Sense). Results: Epoch-by-epoch sensitivity (for sleep) and specificity (for wake), respectively, were as follows: Sleepgraph (0.95, 0.76), Fitbit Sense (0.95, 0.45) and MTN-220/221 (0.93, 0.40). Portable EEG (Sleepgraph) had the best sleep stage-tracking performance. Sleep-wake summary metrics demonstrated lower performance on poor sleep (ice, shorter total sleep time, lower sleep efficiency, longer sleep latency, longer wake after sleep onset). Conclusion: Devices demonstrated similar sleep-wake detecting performance as compared with previous studies that evaluated sleep in healthy adults. Consumer sleep device may exhibit poor sleep stage-tracking performance in patients with psychiatric disorders due to factors that affect the sleep determination algorithm, such as changes in autonomic nervous system activity. However, Sleepgraph, a portable EEG device, demonstrated higher performance in mental disorders than the Fitbit Sense and actigraphy.

Facile Expansion of the Variety of Orthogonal Ligand/Aptamer Pairs for Artificial Riboswitches.

An RNA aptamer that induces suitable conformational changes upon binding to a user-defined ligand allows us to artificially construct a riboswitch, a ligand-dependent and cis-acting gene regulatory RNA. Although such an aptamer can be obtained through in vitro selection, it is still challenging to rationally expand the variety of orthogonal ligand/aptamer (ligand/riboswitch) pairs. To achieve this in a facile, selection-free way, we herein focused on a specific type of ligand, 6-nt nanosized DNA (nDNA) and its aptamer that was previously selected to construct a eukaryotic artificial riboswitch. Specifically, we merely mutated one or more possible Watson-Crick base pairs in the nDNA/aptamer (nDNA/riboswitch) interactions into another base pair or pairs. Using two sets that each had 16 comprehensive mutations, we obtained three groups of several orthogonal nDNA/riboswitch pairs. These pairs could be used to create complex gene circuits, including multiple simultaneous and/or multistep cascading regulations in synthetic biology.

Effects of Japanese policies and novel hypnotics on long-term prescriptions of hypnotics.

AIM: The current study aimed to examine the effect of Japanese policies for appropriate hypnotics use and novel hypnotics (e.g. melatonin receptor agonist and orexin receptor antagonist [ORA]) on long-term prescriptions of hypnotics. METHODS: This retrospective study was conducted using a large-scale health insurance claims database. Among subscribers prescribed hypnotics at least once between April 2005 and March 2021, those prescribed hypnotics for the first time after being included in the database in three periods (period 1: April 2012-March 2013; period 2: April 2016-March 2017; and period 3: April 2018-March 2019) were eligible. These were set considering the timing of the 2014 and 2018 medical fee revisions (2014 for polypharmacy of three or more hypnotics, 2018 for long-term prescription of benzodiazepine receptor agonists for >12 months). The duration of consecutive prescriptions of hypnotics over 12 months was evaluated. Factors associated with short-term prescriptions of hypnotics were also investigated. RESULTS: In total, 186 535 participants were newly prescribed hypnotics. The mean duration of prescriptions was 2.9 months, and 9.3% of participants were prescribed hypnotics for 12 months. Prescription periods were not associated with short-term prescriptions of hypnotics. ORA use was associated with short-term prescriptions of hypnotics (adjusted hazard ratio, 1.077 [95% confidence interval, 1.035-1.120]; P < 0.001), but melatonin receptor agonist use was not. CONCLUSION: Japanese policies had no statistically significant effect on long-term prescriptions of hypnotics. Although this study suggests initiating ORA for insomniacs as a candidate strategy to prevent long-term prescriptions of hypnotics, further research is necessary to draw conclusions.

Relationship between clozapine exposure and the onset of appendicitis in schizophrenia patients: a retrospective cohort study.

OBJECTIVE: Clozapine may cause serious side effects despite benefits in patients with schizophrenia. Thus, an accurate understanding of the side-effect profile of clozapine is extremely important in the management of its administration to patients with schizophrenia. Our aim was to validate the relationship between clozapine exposure and appendicitis onset in patients with schizophrenia. METHODS: In this study, we retrospectively compared the incidence and cumulative incidence of appendicitis in patients with schizophrenia with and without a history of clozapine exposure. Among the patients with schizophrenia who visited our hospital between June 2009 and August 2021, we extracted those with a history of clozapine treatment. Patients with a history of taking clozapine were defined as the clozapine exposure group, while the others were defined as the clozapine non-exposure group. Patients with a history of appendectomy before their initial visit to our hospital or with a history of clozapine use at other hospitals were excluded. RESULTS: There were 65 patients in the clozapine exposure group and 400 patients in the clozapine non-exposure group who met the inclusion criteria. The exposure group exhibited a remarkably higher incidence of appendicitis during the observation period than the non-exposure group (863 cases vs. 124 cases per 100,000 person-years). In particular, if limited to the period of clozapine exposure, the incidence of appendicitis is extremely high, at 2,086 cases per 100,000 person-years. Moreover, multivariable analysis showed that clozapine exposure was an independent factor contributing to the onset of appendicitis. CONCLUSIONS: Clozapine exposure is associated with appendicitis onset in patients with schizophrenia.

Relationship among psychotic features, benzodiazepine receptor agonists, and rehospitalization in patients with electroconvulsive therapy-responsive major depressive disorder: A retrospective 2-year observational study.

AIM: It is controversial whether psychotic features are a risk factor for relapse in patients with electroconvulsive therapy-responsive major depressive disorder. A recent study reported that benzodiazepine receptor agonists reduce relapse of psychotic depression. As long-term use of these agonists may induce dependence, further research is required. We examined whether psychotic features are associated with rehospitalization in electroconvulsive therapy-responsive major depressive disorder patients. We also investigated whether taking benzodiazepine receptor agonists at the end of electro-convulsive therapy was associated with rehospitalization among patients with psychotic depression. METHODS: This study included 47 hospitalized patients (22 with psychotic depression, 25 with non-psychotic depression) who had responded to electroconvulsive therapy. Rehospitalization for major depressive episodes within two years from the last session was investigated. RESULTS: Twenty-three subjects (49%) were rehospitalized during the two-year follow-up. Kaplan-Meier analysis revealed no difference in rehospitalization between patients with psychotic and non-psychotic depression (Log-rank P = 0.87). Among the 22 responders to electroconvulsive therapy with psychotic depression, there was no difference in benzodiazepine receptor agonist use at the end of electroconvulsive therapy between the rehospitalization and non-rehospitalization groups. CONCLUSION: Our exploratory study found no difference in the benzodiazepine receptor agonists use at the end of electroconvulsive therapy between rehospitalization and non-rehospitalization groups in patients with electroconvulsive therapy-responsive psychotic depression. Thus, the relapse-preventing effect of these agonists in psychotic depression should be investigated in future randomized controlled trials. Further research is also needed to determine whether psychotic features are associated with rehospitalization in these patients.

Associations Between the 2011 Great East Japan Earthquake and Tsunami and the Sleep and Mental Health of Japanese People: A 3-Wave Repeated Survey.

PURPOSE: Large-scale natural disasters have an enormous physical and mental impact, immediately after they occur, on people living near the central disaster areas. It is known that, in the early stages, a seismic disaster triggers high rates of symptoms for insomnia, depression, and anxiety. However, little information is available about their medium- to long-term clinical outcomes. In this study, we conducted a repeated cross-sectional nationwide questionnaire survey to clarify changes in the prevalence of insomnia and its background factors after the Great East Japan Earthquake, a huge earthquake with a moment magnitude of 9.0 that occurred on March 11, 2011. METHODS: We conducted a repeated cross-sectional survey in November 2009 (pre-earthquake, 1224 participants), July 2011 (4 months post-earthquake, 1259 participants), and August 2012 (18 months post-earthquake, 1289 participants) using stratified random sampling from 157 Japanese sites. RESULTS: Compared to 2009, the prevalence of insomnia statistically increased nationwide immediately post-disaster (11.7% vs 21.2%; p < 0.001) but significantly decreased in 2012 compared to immediately after the earthquake (10.6% vs 21.2%; p < 0.001). In 2011, insomnia was most frequent in the central disaster area. Multivariable logistic regression models demonstrated the association between the following factors and increased risk of insomnia: being a woman (odds ratio [OR] 1.48, 95% confidence interval [CI]: 1.00-2.19), being employed in 2009 (OR 1.74, 95% CI: 1.15-2.62), and being of younger age group (20-64 years) in 2011 (OR 1.64, 95% CI: 1.12-2.42) and 2012 (OR 2.50 95% CI: 1.47-4.23). Post-earthquake, the prevalence of insomnia symptoms in men increased, while the gender difference decreased and was no longer statistically significant. Additionally, insomnia was associated with psychological distress (scores ≥5 on the Kessler Psychological Distress Scale) in 2011 and 2012. CONCLUSION: This study demonstrated that the prevalence of insomnia was significantly higher after the earthquake. Moreover, individuals with insomnia were more likely to experience psychological distress after the earthquake that continued until 2012.

Severity of Depressive Symptoms is Associated with Venous Thromboembolism in Hospitalized Patients with a Major Depressive Episode.

PURPOSE: A major depressive episode is a risk factor for venous thromboembolism (VTE) in psychiatric inpatients. However, it is unclear whether the severity of depressive symptoms or duration of the current depressive episode is associated with VTE. Further, the VTE prevalence among hospitalized patients with a major depressive episode receiving electroconvulsive therapy is unknown. This retrospective study examined factors associated with VTE among hospitalized patients with a major depressive episode and estimated the prevalence of VTE in such patients who underwent electroconvulsive therapy. PATIENTS AND METHODS: Patients with a major depressive episode hospitalized in the Department of Neuropsychiatry at Akita University Hospital between January 2018 and December 2020 were included. Data from the first week of hospitalization were extracted from medical records. VTE was diagnosed based on the findings of computed tomography. To evaluate whether the severity of depressive symptoms or duration of the current depressive episode was associated with VTE, logistic regression analysis was conducted after adjusting for covariates with known VTE risk factors (antidepressants, antipsychotics, and physical comorbidities). RESULTS: We analyzed 133 patients; of these, 14 were diagnosed with asymptomatic VTE. The severity of depressive symptoms (odds ratio: 1.220, 95% confidence interval: 1.081-1.377, p = 0.001) was significantly associated with VTE. The prevalence of VTE among those receiving electroconvulsive therapy was 35% (7/20). CONCLUSION: The prevalence of VTE was 35% among patients receiving in-hospital electroconvulsive therapy for a major depressive episode. VTE should be considered for hospitalized patients with severe depressive symptoms and patients receiving in-hospital electroconvulsive therapy for a major depressive episode.

The Usefulness of the Combination of D-Dimer and Soluble Fibrin Monomer Complex for Diagnosis of Venous Thromboembolism in Psychiatric Practice: A Prospective Study.

PURPOSE: D-dimer has the advantage of excluding venous thromboembolism (VTE) due to its high sensitivity but is disadvantageous for diagnosing VTE due to its low specificity. A method to increase the usefulness of D-dimer in the diagnosis of VTE is warranted. This study aimed to investigate the usefulness of the combination of D-dimer and soluble fibrin monomer complex (SFMC), which has been suggested as a new candidate marker for VTE, in VTE diagnosis. PATIENTS AND METHODS: This prospective study in 109 subjects was performed at a psychiatric department between August 1, 2017 and December 31, 2019. Subjects' levels of D-dimer and SFMC were measured simultaneously. Plasma levels of D-dimer and SFMC were measured using NANOPIA® D-dimer and NANOPIA® SF. Subjects with positive D-dimer (≥1.0 µg/mL) results underwent contrast computed tomography for confirmation of VTE within 12 hours of D-dimer measurement. A receiver operating characteristic curve analysis was performed to examine the usefulness of SFMC for the diagnosis of VTE. RESULTS: Only 109 of the 783 subjects without symptoms suggestive of VTE participated in the study. Out of 41 subjects with positive D-dimer results, 17 subjects were diagnosed with VTE. A receiver operating characteristic curve analysis was performed to determine cutoff values. The area under the curves was 0.848 for SFMC (p<0.001, 95% CI 0.722 to 0.974), and the optimal cutoff value was 10.0 µg/mL (sensitivity 58.8%, specificity 100%, positive predictive value 100%, negative predictive value 77.4%). CONCLUSION: SFMC was useful for diagnosing VTE in the psychiatric patients with positive D-dimer results.

In Vitro Selection of RNA Aptamers Binding to Nanosized DNA for Constructing Artificial Riboswitches.

We here designed an in vitro selection scheme for obtaining an aptamer with which to rationally construct an artificial riboswitch as its component part. In fact, a nanosized DNA-binding aptamer obtained through this scheme allowed us to easily and successfully create eukaryotic riboswitches that upregulate internal ribosome entry site-mediated translation in response to the ligand (nanosized DNA) in wheat germ extract, a eukaryotic cell-free expression system. The induction ratio of the best riboswitch ligand-dose-dependently increased to 21 at 300 µM ligand. This switching efficiency is much higher than that of the same type of riboswitch with a widely used theophylline-binding aptamer, which was in vitro selected without considering its utility for constructing riboswitches. The selection scheme described here would facilitate obtaining various ligand/aptamer pairs suitable for constructing artificial riboswitches, which could serve as elements of synthetic gene circuits in synthetic biology.

Involvement of l-afadin, but not s-afadin, in the formation of puncta adherentia junctions of hippocampal synapses.

A hippocampal mossy fiber synapse has a complex structure in which presynaptic boutons attach to the dendritic trunk by puncta adherentia junctions (PAJs) and wrap multiply-branched spines, forming synaptic junctions. It was previously shown that afadin regulates the formation of the PAJs cooperatively with nectin-1, nectin-3, and N-cadherin. Afadin is a nectin-binding protein with two splice variants, l-afadin and s-afadin: l-afadin has an actin filament-binding domain, whereas s-afadin lacks it. It remains unknown which variant is involved in the formation of the PAJs or how afadin regulates it. We showed here that re-expression of l-afadin, but not s-afadin, in the afadin-deficient cultured hippocampal neurons in which the PAJ-like structure was disrupted, restored this structure as estimated by the accumulation of N-cadherin and αΝ-catenin. The l-afadin mutant, in which the actin filament-binding domain was deleted, or the l-afadin mutant, in which the αΝ-catenin-binding domain was deleted, did not restore the PAJ-like structure. These results indicate that l-afadin, but not s-afadin, regulates the formation of the hippocampal synapse PAJ-like structure through the binding to actin filaments and αN-catenin. We further found here that l-afadin bound αN-catenin, but not γ-catenin, whereas s-afadin bound γ-catenin, but hardly αN-catenin. These results suggest that the inability of s-afadin to form the hippocampal synapse PAJ-like structure is due to its inability to efficiently bind αN-catenin.

Localization of nectin-2α at the boundary between the adjacent somata of the clustered cholinergic neurons and its regulatory role in the subcellular localization of the voltage-gated A-type K+ channel Kv4.2 in the medial habenula.

The medial habenula (MHb), implicated in stress, depression, memory, and nicotine withdrawal syndromes, receives septal inputs and sends efferents to the interpeduncular nucleus. We previously showed that the immunoglobulin-like cell adhesion molecules (CAMs) nectin-2α and nectin-2δ are expressed in astrocytes in the brain, but their expression in neurons remains unknown. We showed here by immunofluorescence microscopy that nectin-2α, but not nectin-2δ, was prominently expressed in the cholinergic neurons in the developing and adult MHbs and localized at the boundary between the adjacent somata of the clustered cholinergic neurons where the voltage-gated A-type K+ channel Kv4.2 was localized. Analysis by immunoelectron microscopy on this boundary revealed that Kv4.2 was localized at the membrane specializations (MSs) with plasma membrane darkening in an asymmetrical manner, whereas nectin-2α was localized on the apposed plasma membranes mostly at the outside of these MSs, but occasionally localized at their edges and insides. Nectin-2α at this boundary was not colocalized with the nectin-2α-binding protein afadin, other CAMs, or their interacting peripheral membrane proteins, suggesting that nectin-2α forms a cell adhesion apparatus different from the Kv4.2-associated MSs. Genetic ablation of nectin-2 delayed the localization of Kv4.2 at the boundary between the adjacent somata of the clustered cholinergic neurons in the developing MHb. These results revealed the unique localization of nectin-2α and its regulatory role in the localization of Kv4.2 at the MSs in the MHb.

NGL-3-induced presynaptic differentiation of hippocampal neurons in an afadin-dependent, nectin-1-independent manner.

A hippocampal mossy fiber synapse, which is implicated in learning and memory, has a complex structure. We have previously shown using afadin-deficient mice that afadin plays multiple roles in the structural and functional differentiations of this synapse. We investigated here using a co-culture system with cultured hippocampal neurons and non-neuronal COS-7 cells expressing synaptogenic cell adhesion molecules (CAMs) whether afadin is involved in the presynaptic differentiation of hippocampal synapses. Postsynaptic CAMs NGL-3 (alias, a Lrrc4b gene product) and neuroligin induced presynaptic differentiation by trans-interacting with their respective presynaptic binding CAMs LAR (alias, a Ptprf gene product) and neurexin. This activity of NGL-3, but not neuroligin, was dependent on afadin, but not the afadin-binding presynaptic CAM nectin-1. The afadin-binding postsynaptic CAM nectin-3 did not induce presynaptic differentiation. Immunofluorescence and immunoelectron microscopy analyses showed that afadin was localized mainly at puncta adherentia junctions, but partly at synaptic junctions, of the mossy fiber synapse. ß-Catenin and γ-catenin known to bind to LAR were co-immunoprecipitated with afadin from the lysate of mouse brain. These results suggest that afadin is involved in the NGL-3-LAR system-induced presynaptic differentiation of hippocampal neurons cooperatively with ß-catenin and γ-catenin in a nectin-1-independent manner.

Multiple roles of afadin in the ultrastructural morphogenesis of mouse hippocampal mossy fiber synapses.

A hippocampal mossy fiber synapse, which is implicated in learning and memory, has a complex structure in which mossy fiber boutons attach to the dendritic shaft by puncta adherentia junctions (PAJs) and wrap around a multiply-branched spine, forming synaptic junctions. Here, we electron microscopically analyzed the ultrastructure of this synapse in afadin-deficient mice. Transmission electron microscopy analysis revealed that typical PAJs with prominent symmetrical plasma membrane darkening undercoated with the thick filamentous cytoskeleton were observed in the control synapse, whereas in the afadin-deficient synapse, atypical PAJs with the symmetrical plasma membrane darkening, which was much less in thickness and darkness than those of the control typical PAJs, were observed. Immunoelectron microscopy analysis revealed that nectin-1, nectin-3, and N-cadherin were localized at the control typical PAJs, whereas nectin-1 and nectin-3 were localized at the afadin-deficient atypical PAJs to extents lower than those in the control synapse and N-cadherin was localized at their nonjunctional flanking regions. These results indicate that the atypical PAJs are formed by nectin-1 and nectin-3 independently of afadin and N-cadherin and that the typical PAJs are formed by afadin and N-cadherin cooperatively with nectin-1 and nectin-3. Serial block face-scanning electron microscopy analysis revealed that the complexity of postsynaptic spines and mossy fiber boutons, the number of spine heads, the area of postsynaptic densities, and the density of synaptic vesicles docked to active zones were decreased in the afadin-deficient synapse. These results indicate that afadin plays multiple roles in the complex ultrastructural morphogenesis of hippocampal mossy fiber synapses.

Localization of nectin-2δ at perivascular astrocytic endfoot processes and degeneration of astrocytes and neurons in nectin-2 knockout mouse brain.

Nectins are Ca2+-independent immunoglobulin-like cell-cell adhesion molecules. In the nervous system, among four members (nectin-1, -2, -3, and -4), nectin-1 and -3 are asymmetrically localized at puncta adherentia junctions formed between the mossy fiber terminals and the dendrites of CA3 pyramidal neurons in the mouse hippocampus and heterophilic trans-interactions between nectin-1 and nectin-3 are involved in the selective interaction of axons and dendrites of cultured neurons. By contrast, nectin-2, which has two splicing variants, nectin-2α and -2δ, has not been well characterized in the brain. We showed here that nectin-2α was expressed in both cultured mouse neurons and astrocytes whereas nectin-2δ was selectively expressed in the astrocytes. Nectin-2δ was localized at the adhesion sites between adjacent cultured astrocytes, but in the brain it was localized on the plasma membranes of astrocytic perivascular endfoot processes facing the basement membrane of blood vessels. Genetic ablation of nectin-2 caused degeneration of astrocytic perivascular endfoot processes and neurons in the cerebral cortex. These results uncovered for the first time the localization and critical functions of nectin-2 in the brain.

Dynamic Change of Polarity in Primary Cultured Spheroids of Human Colorectal Adenocarcinoma and Its Role in Metastasis.

Intestinal epithelial cells possess apical-basal polarity, which governs the exchange of nutrients and waste. Perturbation of cell polarity appears to be a general feature of cancers, although most colorectal cancers are differentiated adenocarcinomas, in which polarity is maintained to some extent. Little is known about the role of dysregulated polarity in cancer. The cancer tissue-originated spheroid method was applied to the preparation and culture of spheroids. Spheroids were cultured in suspension or in type I collagen gel. Polarity was assessed by IHC of apical markers and electron microscopy. Two types of polarity status in spheroids were observed: apical-in, with apical membrane located at cavities inside the spheroids in type I collagen gel; and apical-out, with apical membrane located at the outermost layer of spheroids in suspension. These polarities were highly interchangeable. Inhibitors of Src and dynamin attenuated the polarity switch. In patients, clusters of cancer cells that invaded vessels had both apical-in and apical-out morphologic features, whereas primary and metastatic tumors had apical-in features. In a mouse liver metastasis model, apical-out spheroids injected into the portal vein became apical-in spheroids in the liver within a few days. Inhibitors of Src and dynamin significantly decreased liver metastasis. Polarity switching was observed in spheroids and human cancer. The polarity switch was critical in an experimental liver metastasis model.

Nectin-1 spots regulate the branching of olfactory mitral cell dendrites.

Olfactory mitral cells extend lateral secondary dendrites that contact the lateral secondary and apical primary dendrites of other mitral cells in the external plexiform layer (EPL) of the olfactory bulb. The lateral dendrites further contact granule cell dendrites, forming dendrodendritic reciprocal synapses in the EPL. These dendritic structures are critical for odor information processing, but it remains unknown how they are formed. We recently showed that the immunoglobulin-like cell adhesion molecule nectin-1 constitutes a novel adhesion apparatus at the contacts between mitral cell lateral dendrites, between mitral cell lateral and apical dendrites, and between mitral cell lateral dendrites and granule cell dendritic spine necks in the deep sub-lamina of the EPL of the developing mouse olfactory bulb and named them nectin-1 spots. We investigated here the role of the nectin-1 spots in the formation of dendritic structures in the EPL of the mouse olfactory bulb. We showed that in cultured nectin-1-knockout mitral cells, the number of branching points of mitral cell dendrites was reduced compared to that in the control cells. In the deep sub-lamina of the EPL in the nectin-1-knockout olfactory bulb, the number of branching points of mitral cell lateral dendrites and the number of dendrodendritic reciprocal synapses were reduced compared to those in the control olfactory bulb. These results indicate that the nectin-1 spots regulate the branching of mitral cell dendrites in the deep sub-lamina of the EPL and suggest that the nectin-1 spots are required for odor information processing in the olfactory bulb.

Nectin-1 spots as a novel adhesion apparatus that tethers mitral cell lateral dendrites in a dendritic meshwork structure of the developing mouse olfactory bulb.

Mitral cells project lateral dendrites that contact the lateral and primary dendrites of other mitral cells and granule cell dendrites in the external plexiform layer (EPL) of the olfactory bulb. These dendritic structures are critical for odor information processing, but it remains unknown how they are formed. In immunofluorescence microscopy, the immunofluorescence signal for the cell adhesion molecule nectin-1 was concentrated on mitral cell lateral dendrites in the EPL of the developing mouse olfactory bulb. In electron microscopy, the immunogold particles for nectin-1 were symmetrically localized on the plasma membranes at the contacts between mitral cell lateral dendrites, which showed bilateral darkening without dense cytoskeletal undercoats characteristic of puncta adherentia junctions. We named the contacts where the immunogold particles for nectin-1 were symmetrically accumulated "nectin-1 spots." The nectin-1 spots were 0.21 µm in length on average and the distance between the plasma membranes was 20.8 nm on average. In 3D reconstruction of serial sections, clusters of the nectin-1 spots formed a disc-like structure. In the mitral cell lateral dendrites of nectin-1-knockout mice, the immunogold particles for nectin-1 were undetectable and the plasma membrane darkening was electron-microscopically normalized, but the plasma membranes were partly separated from each other. The nectin-1 spots were further identified between mitral cell lateral and primary dendrites and between mitral cell lateral dendrites and granule cell dendritic spine necks. These results indicate that the nectin-1 spots constitute a novel adhesion apparatus that tethers mitral cell dendrites in a dendritic meshwork structure of the developing mouse olfactory bulb.