Comorbid functional dyspepsia reflects IL-33-mediated airway neuronal dysfunction in asthma.

BACKGROUND: Neuronal dysfunction is implicated in the pathophysiology of asthma and functional dyspepsia (FD). However, the relationship between these diseases remains unclear. OBJECTIVE: This study aimed to clarify the clinical implications of comorbid FD in asthma and to explore the unified pathway between asthma and FD by focusing on airway neuronal dysfunction. METHODS: Clinical indices and biomarkers, including capsaicin cough sensitivity (C-CS), were compared between patients with asthma with and without FD. C-CS was determined on the basis of capsaicin concentration that induced at least 2 coughs (C2) or 5 coughs (C5). Additionally, the associations of airway inflammation with airway innervation and gastrointestinal motility were evaluated in mouse models of type 2 airway inflammation. RESULTS: Patients with asthma with FD had worse asthma control and cough severity and lower C2 and C5 thresholds than those without FD. The severity of FD symptoms was negatively correlated with C2 and C5 thresholds. FD and poor asthma control were predictors of heightened C-CS (defined as C5 ≤ 2.44 µmol) in asthma. A mouse model of papain-induced airway inflammation developed airway hyperinnervation and gastrointestinal dysmotility, and both pathologies were ameliorated by an anti-IL-33 antibody. Moreover, papain-induced gastrointestinal dysmotility was mitigated by silencing the airway sensory neurons using QX-314, a sodium channel blocker. Furthermore, sputum IL-33 levels were significantly elevated in patients with asthma with FD or heightened C-CS compared to their counterparts. CONCLUSION: FD is significantly associated with airway neuronal dysfunction in asthma. IL-33-mediated airway neuronal dysfunction may contribute to the interaction between asthma and FD.

A gain-of-function mutation in the acid-sensing ion channel 2a induces marked cerebellar maldevelopment in rats.

Specific amino acid substitutions in degenerin mechano-gated channels (DEGs) of C. elegans convert these channels into constitutively active mutants that induce the degeneration of neurons where DEGs are expressed. Acid-sensing ion channel-2a (ASIC2a), a proton-gated cation channel predominantly expressed in central neurons, is a mammalian ortholog of DEGs, and it can remain unclosed to be cytotoxic once the same mutations as the DEG mutants are introduced into its gene. Here we show that heterozygous transgenic (Tg) rats expressing ASIC2a-G430F (ASIC2aG430F), the most active form of the gain-of-function mutants, under the control of the intrinsic ASIC2a promoter exhibited marked cerebellar maldevelopment with mild whole-brain atrophy. The Tg rats were small and developed an early-onset ataxic gait, as evidenced by rotarod and footprint tests. The overall gross-anatomy of the Tg brain was normal just after birth, but a reduction in brain volume, especially cerebellar volume, gradually emerged with age. Histological examination of the adult Tg brain revealed that the cell-densities of cerebellar Purkinje and granule cells were markedly reduced, while the cytoarchitecture of other brain regions was not significantly altered. RT-PCR and immunoblot analyses demonstrated that ASIC2aG430F transcripts and proteins were already present in various regions of the neonatal Tg brain before the deforming cerebellum became apparent. These results suggest that, according to the spatiotemporal pattern of the wild-type (WT) ASIC2a gene expression, the ASIC2aG430F channel induced lethal degeneration in Tg brain neurons expressing both ASIC2aG430F and ASIC2a channels.

Dynamic Changes in Ultrastructure of the Primary Cilium in Migrating Neuroblasts in the Postnatal Brain.

New neurons, referred to as neuroblasts, are continuously generated in the ventricular-subventricular zone of the brain throughout an animal's life. These neuroblasts are characterized by their unique potential for proliferation, formation of chain-like cell aggregates, and long-distance and high-speed migration through the rostral migratory stream (RMS) toward the olfactory bulb (OB), where they decelerate and differentiate into mature interneurons. The dynamic changes of ultrastructural features in postnatal-born neuroblasts during migration are not yet fully understood. Here we report the presence of a primary cilium, and its ultrastructural morphology and spatiotemporal dynamics, in migrating neuroblasts in the postnatal RMS and OB. The primary cilium was observed in migrating neuroblasts in the postnatal RMS and OB in male and female mice and zebrafish, and a male rhesus monkey. Inhibition of intraflagellar transport molecules in migrating neuroblasts impaired their ciliogenesis and rostral migration toward the OB. Serial section transmission electron microscopy revealed that each migrating neuroblast possesses either a pair of centrioles or a basal body with an immature or mature primary cilium. Using immunohistochemistry, live imaging, and serial block-face scanning electron microscopy, we demonstrate that the localization and orientation of the primary cilium are altered depending on the mitotic state, saltatory migration, and deceleration of neuroblasts. Together, our results highlight a close mutual relationship between spatiotemporal regulation of the primary cilium and efficient chain migration of neuroblasts in the postnatal brain.SIGNIFICANCE STATEMENT Immature neurons (neuroblasts) generated in the postnatal brain have a mitotic potential and migrate in chain-like cell aggregates toward the olfactory bulb. Here we report that migrating neuroblasts possess a tiny cellular protrusion called a primary cilium. Immunohistochemical studies with zebrafish, mouse, and monkey brains suggest that the presence of the primary cilium in migrating neuroblasts is evolutionarily conserved. Ciliogenesis in migrating neuroblasts in the rostral migratory stream is suppressed during mitosis and promoted after cell cycle exit. Moreover, live imaging and 3D electron microscopy revealed that ciliary localization and orientation change during saltatory movement of neuroblasts. Our results reveal highly organized dynamics in maturation and positioning of the primary cilium during neuroblast migration that underlie saltatory movement of postnatal-born neuroblasts.

Vascular endothelial growth factor-A is involved in intramuscular carrageenan-induced cutaneous mechanical hyperalgesia through the vascular endothelial growth factor-A receptor 1 and transient receptor potential vanilloid 1 pathways.

OBJECTIVES: Vascular endothelial growth factor-A (VEGF-A) plays a leading role in angiogenesis and pain hypersensitivity in cancer and chronic pain. It is not only induced by ischemic conditions but is also highly correlated with proalgesic cytokines, both of which are prominent in inflammatory muscle pain. However, the molecular basis of the involvement of VEGF-A in muscle pain remains unknown. METHODS: In the present study, we performed behavioral and pharmacological analyses to determine the possible involvement of VEGF-A in the development of inflammatory muscle pain and the associated signal transduction pathway. RESULTS: Unilateral intramuscular injection of carrageenan, a classical model of inflammatory muscle pain, increased VEGF-A gene expression in the tissues surrounding the injection site. Intramuscular administration of recombinant VEGF-A165 on the same side induced cutaneous mechanical hyperalgesia during the acute and subacute phases. The application of a specific VEGFR1 antibody on the same side significantly reduced the mechanical hyperalgesia induced by carrageenan or VEGF-A165 injection, whereas both a VEGFR2-neutralizing antibody and a VEGFR2 antagonist showed limited effects. Local preinjection of capsazepine, a transient receptor potential vanilloid 1 (TRPV1) antagonist, also inhibited VEGF-A165-induced hyperalgesia. Finally, intramuscular VEGF-A165-induced mechanical hyperalgesia was not found in TRPV1 knockout mice during the subacute phase. CONCLUSIONS: These findings suggest that inflammatory stimuli increase interstitial VEGF-A165, which in turn induces cutaneous mechanical pain via the VEGFR1-mediated TRPV1 nociceptive pathway during inflammatory muscle pain. VEGFR1 could be a novel therapeutic target for inflammation-induced muscle pain.

Additive Effects of L-Ornithine on Preferences to Basic Taste Solutions in Mice.

In addition to the taste receptors corresponding to the six basic taste qualities-sweet, salty, sour, bitter, umami, and fatty-another type of taste receptor, calcium-sensing receptor (CaSR), is found in taste-bud cells. CaSR is called the 'kokumi' receptor because its agonists increase sweet, salty and umami tastes to induce 'koku', a Japanese word meaning the enhancement of flavor characters such as thickness, mouthfulness, and continuity. Koku is an important factor for enhancing food palatability. However, it is not well known whether other kokumi-receptors and substances exist. Here, we show that ornithine (L-ornithine but not D-ornithine) at low concentrations that do not elicit a taste of its own, enhances preferences to sweet, salty, umami, and fat taste solutions in mice. Increased preference to monosodium glutamate (MSG) was the most dominant effect. Antagonists of G-protein-coupled receptor family C group 6 subtype A (GPRC6A) abolished the additive effect of ornithine on MSG solutions. The additive effects of ornithine on taste stimuli are thought to occur in the oral cavity, and are not considered post-oral events because ornithine's effects were confirmed in a brief-exposure test. Moreover, the additive effects of ornithine and the action of the antagonist were verified in electrophysiological taste nerve responses. Immunohistochemical analysis implied that GPRC6A was expressed in subsets of type II and type III taste cells of mouse circumvallate papillae. These results are in good agreement with those reported for taste modulation involving CaSR and its agonists. The present study suggests that ornithine is a kokumi substance and GPRC6A is a newly identified kokumi receptor.

In vitro Time-lapse Imaging of Primary Cilium in Migrating Neuroblasts.

Neuronal migration is a critical step for the development of neuronal circuits in the brain. Immature new neurons (neuroblasts) generated in the postnatal ventricular-subventricular zone (V-SVZ) show a remarkable potential to migrate for a long distance at a high speed in the postnatal mammalian brain, and are thus a powerful model to analyze the molecular and cellular mechanisms of neuronal migration. Here we describe a methodology for in vitro time-lapse imaging of the primary cilium and its related structures in migrating V-SVZ-derived neuroblasts using confocal or superresolution laser-scanning microscopy. The V-SVZ tissues are dissected from postnatal day 0-1 (P0-1) mouse brains and dissociated into single cells by trypsinization and gentle pipetting. These cells are then transduced with a plasmid(s) encoding a gene(s) of interest, aggregated by centrifugation, and cultured for 2 days in Matrigel. Time-lapse images of migratory behaviors of cultured neuroblasts and their ciliary structures, including the ciliary membrane and basal body, are acquired by confocal or superresolution laser-scanning microscopy. This method provides information about the spatiotemporal dynamics of neuroblasts' morphology and ciliary structures, and is widely applicable to various types of migrating neuronal and nonneuronal cells in various species.

Two mouse models carrying truncating mutations in Magel2 show distinct phenotypes.

Schaaf-Yang syndrome (SYS) is a neurodevelopmental disorder caused by truncating variants in the paternal allele of MAGEL2, located in the Prader-Willi critical region, 15q11-q13. Although the phenotypes of SYS overlap those of Prader-Willi syndrome (PWS), including neonatal hypotonia, feeding problems, and developmental delay/intellectual disability, SYS patients show autism spectrum disorder and joint contractures, which are atypical phenotypes for PWS. Therefore, we hypothesized that the truncated Magel2 protein could potentially produce gain-of-function toxic effects. To test the hypothesis, we generated two engineered mouse models; one, an overexpression model that expressed the N-terminal region of Magel2 that was FLAG tagged with a strong ubiquitous promoter, and another, a genome-edited model that carried a truncating variant in Magel2 generated using the CRISPR/Cas9 system. In the overexpression model, all transgenic mice died in the fetal or neonatal period indicating embryonic or neonatal lethality of the transgene. Therefore, overexpression of the truncated Magel2 could show toxic effects. In the genome-edited model, we generated a mouse model carrying a frameshift variant (c.1690_1924del; p(Glu564Serfs*130)) in Magel2. Model mice carrying the frameshift variant in the paternal or maternal allele of Magel2 were termed Magel2P:fs and Magel2M:fs, respectively. The imprinted expression and spatial distribution of truncating Magel2 transcripts in the brain were maintained. Although neonatal Magel2P:fs mice were lighter than wildtype littermates, Magel2P:fs males and females weighed the same as their wildtype littermates by eight and four weeks of age, respectively. Collectively, the overexpression mouse model may recapitulate fetal or neonatal death, which are the severest phenotypes for SYS. In contrast, the genome-edited mouse model maintains genomic imprinting and distribution of truncated Magel2 transcripts in the brain, but only partially recapitulates SYS phenotypes. Therefore, our results imply that simple gain-of-function toxic effects may not explain the patho-mechanism of SYS, but rather suggest a range of effects due to Magel2 variants as in human SYS patients.

Tumor necrosis factor receptor-associated protein 1 regulates cell adhesion and synaptic morphology via modulation of N-cadherin expression.

An increase in serum tumor necrosis factor-alpha (TNF-alpha) levels is closely related to the pathogenesis of major depression. However, the underlying molecular mechanism between this increase and impairment of brain function remains elusive. To better understand TNF-alpha/TNF receptor 1 signaling in the brain, we analyzed the brain distribution and function of tumor necrosis factor receptor-associated protein 1 (TRAP1). Here we show that TRAP1 is broadly expressed in neurons in the mouse brain, including regions that are implicated in the pathogenesis of major depression. We demonstrate that small interfering RNA-mediated knockdown of TRAP1 in a neuronal cell line decreases tyrosine phosphorylation of STAT3, followed by a reduction of the transcription factor E2F1, resulting in a down-regulation of N-cadherin, and affects the adhesive properties of the cells. In addition, in cultured hippocampal neurons, reduced expression of N-cadherin by TRAP1 knockdown influences the morphology of dendritic spines. We also report a significant association between several single nucleotide polymorphisms in the TRAP1 gene and major depression. Our findings indicate that TRAP1 mediates TNF-alpha/TNF receptor 1 signaling to modulate N-cadherin expression and to regulate cell adhesion and synaptic morphology, which may contribute to the pathogenesis of major depression.

Dysbindin engages in c-Jun N-terminal kinase activity and cytoskeletal organization.

A number of reports have provided genetic evidence for an association between the DTNBP1 gene (coding dysbindin) and schizophrenia. In addition, sandy mice, which harbor a deletion in the DTNBP1 gene and lack dysbindin, display behavioral abnormalities suggestive of an association with schizophrenia. However, the mechanism by which the loss of dysbindin induces schizophrenia-like behaviors remains unclear. Here, we report that small interfering RNA-mediated knockdown of dysbindin resulted in the aberrant organization of actin cytoskeleton in SH-SY5Y cells. Furthermore, we show that morphological abnormalities of the actin cytoskeleton were similarly observed in growth cones of cultured hippocampal neurons derived from sandy mice. Moreover, we report a significant correlation between dysbindin expression level and the phosphorylation level of c-Jun N-terminal kinase (JNK), which is implicated in the regulation of cytoskeletal organization. These findings suggest that dysbindin plays a key role in coordinating JNK signaling and actin cytoskeleton required for neural development.

Association studies and gene expression analyses of the DISC1-interacting molecules, pericentrin 2 (PCNT2) and DISC1-binding zinc finger protein (DBZ), with schizophrenia and with bipolar disorder.

Disrupted-in-Schizophrenia 1 (DISC1) and its molecular cascade have been implicated in the pathophysiology of major psychoses. Previously, we identified pericentrin 2 (PCNT2) and DISC1-binding zinc finger protein (DBZ) as binding partners of DISC1; further, we observed elevated expression of PCNT2 in the postmortem brains and in the lymphocytes of bipolar disorder patients, compared to controls. Here, we examined the association of PCNT2 with schizophrenia in a case-control study of Japanese cohorts. We also examined the association of DBZ with schizophrenia and with bipolar disorder, and compared the mRNA levels of DBZ in the postmortem brains of schizophrenia, bipolar and control samples. DNA from 180 schizophrenia patients 201 controls were used for the association study of PCNT2 and DBZ with schizophrenia. Association of DBZ with bipolar disorder was examined in DNA from 238 bipolar patients and 240 age- and gender-matched controls. We observed significant allelic and genotypic associations of the PCNT2 SNPs, rs2249057, rs2268524, and rs2073380 (Ser/Arg) with schizophrenia; the association of rs2249057 (P = 0.002) withstand multiple testing correction. Several two SNP- and three SNP-haplotypes showed significant associations; the associations of haplotypes involving rs2249057 withstand multiple testing correction. No associations were observed for DBZ with schizophrenia or with bipolar disorder; further, there was no significant difference between the DBZ mRNA levels of control, schizophrenia and bipolar postmortem brains. We suggest a possible role of PCNT2 in the pathogenesis of schizophrenia. Abnormalities of PCNT2, the centrosomal protein essential for microtubule organization, may be suggested to lead to neurodevelopmental abnormalities.

DISC1-kendrin interaction is involved in centrosomal microtubule network formation.

Disrupted-In-Schizophrenia 1 (DISC1) was identified as a novel gene disrupted by a (1;11)(q42.1;q14.3) translocation segregating with schizophrenia, bipolar disorder and other major mental illnesses in a Scottish family. We previously identified 446-533 amino acids of DISC1 as the kendrin-binding region by means of a directed yeast two-hybrid interaction assay and showed that the DISC1-kendrin interaction is indispensable for the centrosomal localization of DISC1. In this study, to confirm the DISC1-kendrin interaction, we examined the interaction between deletion mutants of DISC1 and kendrin. Then, we demonstrated that the carboxy-terminus of DISC1 is indispensable for the interaction with kendrin. Furthermore, the immunocytochemistry revealed that the carboxy-terminus of DISC1 is also required for the centrosomal targeting of DISC1. Overexpression of the DISC1-binding region of kendrin or the DISC1 deletion mutant lacking the kendrin-binding region impairs the microtubule organization. These findings suggest that the DISC1-kendrin interaction plays a key role in the microtubule dynamics.

Behavioral abnormalities and dopamine reductions in sdy mutant mice with a deletion in Dtnbp1, a susceptibility gene for schizophrenia.

Genetic susceptibility plays an important role in the pathogenesis of schizophrenia. Genetic evidence for an association between the dysbindin-1 gene (DTNBP1: dystrobrevin binding protein 1) and schizophrenia has been repeatedly reported in various populations worldwide. Thus, we performed behavioral analyses on homozygous sandy (sdy) mice, which lack dysbindin-1 owing to a deletion in the Dtnbp1 gene. Our results showed that sdy mice were less active and spent less time in the center of an open field apparatus. Consistent with the latter observation, sdy mice also displayed evidence of heightened anxiety-like response and deficits in social interaction. Compared to wild-type mice, sdy mice displayed lower levels of dopamine, but not glutamate, in the cerebral cortex, hippocampus, and hypothalamus. These findings indicate that sdy mice display a number of behavioral abnormalities associated with schizophrenia and suggest that these abnormalities may be mediated by reductions in forebrain dopamine transmission.

Basal cells express functional TRPV4 channels in the mouse nasal epithelium.

Basal cells in the nasal epithelium (olfactory and airway epithelia) are stem/progenitor cells that are capable of dividing, renewing and differentiating into specialized cells. These stem cells can sense their biophysical microenvironment, but the underlying mechanism of this process remains unknown. Here, we demonstrate the prominent expression of the transient receptor potential vanilloid type 4 (TRPV4) channel, a Ca2+-permeable channel that is known to act as a sensor for hypo-osmotic and mechanical stresses, in the basal cells of the mouse nasal epithelium. TRPV4 mRNA was expressed in the basal portions of the prenatal mouse nasal epithelium, and this expression continued into adult mice. The TRPV4 protein was also detected in the basal layers of the nasal epithelium in wild-type but not in TRPV4-knockout (TRPV4-KO) mice. The TRPV4-positive immunoreactions largely overlapped with those of keratin 14 (K14), a marker of basal cells, in the airway epithelium, and they partially overlapped with those of K14 in the olfactory epithelium. Ca2+ imaging analysis revealed that hypo-osmotic stimulation and 4α-phorbol 12,13 didecanoate (4α-PDD), both of which are TRPV4 agonists, caused an increase in the cytosolic Ca2+ concentration in a subset of primary epithelial cells cultured from the upper parts of the nasal epithelium of the wild-type mice. This response was barely noticeable in cells from similar parts of the epithelium in TRPV4-KO mice. Finally, there was no significant difference in BrdU-labeled proliferation between the olfactory epithelia of wild-type and TRPV4-KO mice under normal conditions. Thus, TRPV4 channels are functionally expressed in basal cells throughout the nasal epithelium and may act as sensors for the development and injury-induced regeneration of basal stem cells.

The role of TRPV1 channels in carrageenan-induced mechanical hyperalgesia in mice.

Peripheral inflammation leads to ipsilateral and contralateral mechanical hyperalgesia. The transient receptor potential channel vanilloid type 1 (TRPV1), a nonselective cation channel expressed in mammalian primary sensory neurons and the spinal cord, may be involved in peripheral inflammation, but there is no consensus on the role of this channel in inflammation-induced mechanical hyperalgesia. Here, we examined the role of TRPV1 channels in carrageenan-induced mechanical hyperalgesia using wild-type and TRPV1-knockout (KO) mice and compared the results with those obtained in mice peripherally administered capsazepine, a TRPV1 antagonist, or capsaicin, a TRPV1 agonist. In the TRPV1-KO mice, ipsilateral mechanical hyperalgesia was significantly reduced during the acute phase (10-60 min), and the contralateral mechanical hyperalgesia nearly disappeared during both the acute and subacute phases. Blocking peripheral TRPV1 using capsazepine before carrageenan administration resulted in similar effects as those observed in the TRPV1-KO mice, except that it was less effective against contralateral mechanical hyperalgesia during the subacute phase. In contrast, capsaicin remarkably decreased ipsilateral and contralateral mechanical hyperalgesia throughout both phases, but this analgesic effect was not observed in the TRPV1-KO mice. Thus, TRPV1 channels could be involved in the development of both ipsilateral and contralateral mechanical hyperalgesia after inflammation. Peripheral TRPV1 could participate in acute hyperalgesia, whereas central TRPV1 may participate in subacute secondary hyperalgesia. Capsaicin potentially acts on both primary and secondary hyperalgesia in a TRPV1-dependent manner.

Expression and Regulation of Cav3.2 T-Type Calcium Channels during Inflammatory Hyperalgesia in Mouse Dorsal Root Ganglion Neurons.

The Cav3.2 isoform of the T-type calcium channel is expressed in primary sensory neurons of the dorsal root ganglion (DRG), and these channels contribute to nociceptive and neuropathic pain in rats. However, there are conflicting reports on the roles of these channels in pain processing in rats and mice. In addition, the function of T-type channels in persistent inflammatory hyperalgesia is poorly understood. We performed behavioral and comprehensive histochemical analyses to characterize Cav3.2-expressing DRG neurons and examined the regulation of T-type channels in DRGs from C57BL/6 mice with carrageenan-induced inflammatory hyperalgesia. We show that approximately 20% of mouse DRG neurons express Cav3.2 mRNA and protein. The size of the majority of Cav3.2-positive DRG neurons (69 ± 8%) ranged from 300 to 700 µm2 in cross-sectional area and 20 to 30 µm in estimated diameter. These channels co-localized with either neurofilament-H (NF-H) or peripherin. The peripherin-positive cells also overlapped with neurons that were positive for isolectin B4 (IB4) and calcitonin gene-related peptide (CGRP) but were distinct from transient receptor potential vanilloid 1 (TRPV1)-positive neurons during normal mouse states. In mice with carrageenan-induced inflammatory hyperalgesia, Cav3.2 channels, but not Cav3.1 or Cav3.3 channels, were upregulated in ipsilateral DRG neurons during the sub-acute phase. The increased Cav3.2 expression partially resulted from an increased number of Cav3.2-immunoreactive neurons; this increase in number was particularly significant for TRPV1-positive neurons. Finally, preceding and periodic intraplantar treatment with the T-type calcium channel blockers mibefradil and NNC 55-0396 markedly reduced and reversed mechanical hyperalgesia during the acute and sub-acute phases, respectively, in mice. These data suggest that Cav3.2 T-type channels participate in the development of inflammatory hyperalgesia, and this channel might play an even greater role in the sub-acute phase of inflammatory pain due to increased co-localization with TRPV1 receptors compared with that in the normal state.

Lack of dopaminergic inputs elongates the primary cilia of striatal neurons.

In the rodent brain, certain G protein-coupled receptors and adenylyl cyclase type 3 are known to localize to the neuronal primary cilium, a primitive sensory organelle protruding singly from almost all neurons. A recent chemical screening study demonstrated that many compounds targeting dopamine receptors regulate the assembly of Chlamydomonas reinhardtii flagella, structures which are analogous to vertebrate cilia. Here we investigated the effects of dopaminergic inputs loss on the architecture of neuronal primary cilia in the rodent striatum, a brain region that receives major dopaminergic projections from the midbrain. We first analyzed the lengths of neuronal cilia in the dorsolateral striatum of hemi-parkinsonian rats with unilateral lesions of the nigrostriatal dopamine pathway. In these rats, the striatal neuronal cilia were significantly longer on the lesioned side than on the non-lesioned side. In mice, the repeated injection of reserpine, a dopamine-depleting agent, elongated neuronal cilia in the striatum. The combined administration of agonists for dopamine receptor type 2 (D2) with reserpine attenuated the elongation of striatal neuronal cilia. Repeated treatment with an antagonist of D2, but not of dopamine receptor type 1 (D1), elongated the striatal neuronal cilia. In addition, D2-null mice displayed longer neuronal cilia in the striatum compared to wild-type controls. Reserpine treatment elongated the striatal neuronal cilia in D1-null mice but not in D2-null mice. Repeated treatment with a D2 agonist suppressed the elongation of striatal neuronal cilia on the lesioned side of hemi-parkinsonian rats. These results suggest that the elongation of striatal neuronal cilia following the lack of dopaminergic inputs is attributable to the absence of dopaminergic transmission via D2 receptors. Our results provide the first evidence that the length of neuronal cilia can be modified by the lack of a neurotransmitter's input.

DISC1 (disrupted-in-schizophrenia-1) regulates differentiation of oligodendrocytes.

Disrupted-in-schizophrenia 1 (DISC1) is a gene disrupted by a translocation, t(1;11) (q42.1;q14.3), that segregates with major psychiatric disorders, including schizophrenia, recurrent major depression and bipolar affective disorder, in a Scottish family. Here we report that mammalian DISC1 endogenously expressed in oligodendroglial lineage cells negatively regulates differentiation of oligodendrocyte precursor cells into oligodendrocytes. DISC1 expression was detected in oligodendrocytes of the mouse corpus callosum at P14 and P70. DISC1 mRNA was expressed in primary cultured rat cortical oligodendrocyte precursor cells and decreased when oligodendrocyte precursor cells were induced to differentiate by PDGF deprivation. Immunocytochemical analysis showed that overexpressed DISC1 was localized in the cell bodies and processes of oligodendrocyte precursor cells and oligodendrocytes. We show that expression of the myelin related markers, CNPase and MBP, as well as the number of cells with a matured oligodendrocyte morphology, were decreased following full length DISC1 overexpression. Conversely, both expression of CNPase and the number of oligodendrocytes with a mature morphology were increased following knockdown of endogenous DISC1 by RNA interference. Overexpression of a truncated form of DISC1 also resulted in an increase in expression of myelin related proteins and the number of mature oligodendrocytes, potentially acting via a dominant negative mechanism. We also identified involvement of Sox10 and Nkx2.2 in the DISC1 regulatory pathway of oligodendrocyte differentiation, both well-known transcription factors involved in the regulation of myelin genes.

DBZ (DISC1-binding zinc finger protein)-deficient mice display abnormalities in basket cells in the somatosensory cortices.

Disrupted-in-schizophrenia 1 (DISC1)-binding zinc finger protein (DBZ) is a DISC1-interacting molecule and the interaction between DBZ and DISC1 is involved in neurite outgrowth in vitro. DBZ is highly expressed in brain, especially in the cortex. However, the physiological roles of DBZ in vivo have not been clarified. Here, we show that development of basket cells, a morphologically defined class of parvalbumin (PV)-containing interneurons, is disturbed in DBZ knockout (KO) mice. DBZ mRNA was highly expressed in the ventral area of the subventricular zone of the medial ganglionic eminence, where PV-containing cortical interneurons were generated, at embryonic 14.5 days (E14.5). Although the expression level for PV and the number of PV-containing interneurons were not altered in the cortices of DBZ KO mice, basket cells were less branched and had shorter processes in the somatosensory cortices of DBZ KO mice compared with those in the cortices of WT mice. Furthermore, in the somatosensory cortices of DBZ KO mice, the level of mRNAs for the gamma-aminobutyric acid-synthesizing enzymes GAD67 was decreased. These findings show that DBZ is involved in the morphogenesis of basket cells.

A role for primary cilia in glutamatergic synaptic integration of adult-born neurons.

The sequential synaptic integration of adult-born neurons has been widely examined in rodents, but the mechanisms regulating the integration remain largely unknown. The primary cilium, a microtubule-based signaling center, is essential for vertebrate development, including the development of the CNS. We examined the assembly and function of the primary cilium in the synaptic integration of adult-born mouse hippocampal neurons. Primary cilia were absent in young adult-born neurons, but assembled precisely at the stage when newborn neurons approach their final destination, further extend dendrites and form synapses with entorhinal cortical projections. Conditional deletion of cilia from adult-born neurons induced severe defects in dendritic refinement and synapse formation. Deletion of primary cilia led to enhanced Wnt and ß-catenin signaling, which may account for these developmental defects. Taken together, our findings identify the assembly of primary cilia as a critical regulatory event in the dendritic refinement and synaptic integration of adult-born neurons.

Increased stathmin1 expression in the dentate gyrus of mice causes abnormal axonal arborizations.

Pituitary adenylate cyclase-activating polypeptide (PACAP) is involved in multiple brain functions. To clarify the cause of abnormal behavior in PACAP deficient-mice, we attempted the identification of genes whose expression was altered in the dentate gyrus of PACAP-deficient mice using the differential display method. Expression of stathmin1 was up-regulated in the dentate gyrus at both the mRNA and protein levels. PACAP stimulation inhibited stathmin1 expression in PC12 cells, while increased stathmin1expression in neurons of the subgranular zone and in primary cultured hippocampal neurons induced abnormal arborization of axons. We also investigated the pathways involved in PACAP deficiency. Ascl1 binds to E10 box of the stathmin1 promoter and increases stathmin1 expression. Inhibitory bHLH proteins (Hes1 and Id3) were rapidly up-regulated by PACAP stimulation, and Hes1 could suppress Ascl1 expression and Id3 could inhibit Ascl1 signaling. We also detected an increase of stathmin1 expression in the brains of schizophrenic patients. These results suggest that up-regulation of stathmin1 in the dentate gyrus, secondary to PACAP deficiency, may create abnormal neuronal circuits that cause abnormal behavior.