SYMPTOM SEVERITY IN SCHIZOPHRENIA PATIENTS WITH NPAS3, DYSBINDIN-1 AND/OR TRIOBP PROTEIN PATHOLOGY IN THEIR BLOOD SERUM: A PANSS-BASED FOLLOW UP STUDY.

BACKGROUND: It has been proposed that aggregation of specific proteins in the brain may be a pathological element in schizophrenia and other chronic disorders. Multiple such aggregating proteins have now been implicated through post mortem investigation, including NPAS3 (Neuronal PAS domain protein 3), dysbindin-1 (encoded by the DTNBP1, Dystrobrevin Binding Protein 1, gene) and TRIOBP (Trio-Binding Protein, multiple isoforms). While the presence of protein aggregates in the brain is interesting in terms of understanding pathology, it is impractical as a biomarker. These proteins were therefore investigated recently in blood serum of schizophrenia patients and controls, showing patients to have higher levels of NPAS3 in their serum generally. TRIOBP-1 and dysbindin-1 were also found in an insoluble state, implying aggregation, but did not clearly corresponding to disease state. SUBJECT AND METHODS: We revisit 47 of the originally recruited 50 patients with schizophrenia, all of whom are Croatian and aged between 18 and 72. We assessed their symptom specificity and severity using PANSS (the Positive and Negative Symptoms Scale), comparing those with NPAS3, insoluble dysbindin-1 and/or insoluble TRIOBP-1 in their blood serum to those lacking any such protein dysregulation. RESULTS: The frequency of each individual potential protein pathology among these patients was too low for meaningful statistical analysis, however the 11 patients that displayed one or more of these pathologies (NPAS3, dysbindin-1, TRIOBP-1 and/or TRIOBP-5/6) showed a subtle but significant increase in total PANSS scores compared to the 36 patients displaying none of the pathologies (p = 0.031), seemingly driven principally by increased scores on the general psychopathology scale. CONCLUSION: While the numbers of patients involved do not allow firm conclusions to be drawn at this time, this provides the first indication that disturbed proteostasis in blood serum, of proteins that aggregate in the brains of schizophrenia patients, may correlate with the severity of schizophrenia symptoms.

Hermansky-Pudlak syndrome with early onset inflammatory bowel disease due to loss of dysbindin expression.

Hermansky-Pudlak syndrome (HPS) is a heterogeneous group of autosomal recessive genetic disorders characterized by oculocutaneous albinism, bleeding diathesis, and variable presentation of immune deficiency and dysregulation. The pathogenesis of HPS involves mutations in genes responsible for biogenesis and trafficking of lysosome-related organelles, essential for the function of melanosomes, platelet granules, and immune cell granules. Eleven genes coding for proteins in the BLOC-1, BLOC-2, BLOC-3 and AP-3 complexes have been implicated in the pathogenesis of HPS. To date, the rare subtype HPS-7 associated with bi-allelic mutations in DTNBP1 (dysbindin) has only been reported in 9 patients. We report a novel DTNBP1 splicing mutation in a 15-month-old patient with HPS-7 phenotype and severe inflammatory bowel disease (IBD). This patient's leukocytes have undetectable dysbindin protein. We also identify dysregulated expression of several genes involved in activation of the adaptive immune response. This case underscores the emerging immunological consequences of dysbindin deficiency and suggests that DTNBP1 mutations may underlie some rare cases of very early onset IBD.

Dopaminergic signalling and behavioural alterations by Comt-Dtnbp1 genetic interaction and their clinical relevance.

BACKGROUND AND PURPOSE: Cognitive and motor functions are modulated by dopaminergic signalling, which is shaped by several genetic factors. The biological effects of single genetic variants might differ depending on epistatic interactions that can be functionally multi-directional and non-linear. EXPERIMENTAL APPROACH: We performed behavioural and neurochemical assessments in genetically modified mice and behavioural assessments and genetic screening in human patients with 22q11.2 deletion syndrome (22q11.2DS). KEY RESULTS: Here, we confirm a genetic interaction between the Comt (catechol-O-methyltransferase, human orthologue: COMT) and Dtnbp1 (dystrobrevin binding protein 1, alias dysbindin, human orthologue: DTNBP1) genes that modulate cortical and striatal dopaminergic signalling in a manner not predictable by the effects of each single gene. In mice, Comt-by-Dtnbp1 concomitant reduction leads to a hypoactive mesocortical and a hyperactive mesostriatal dopamine pathway, associated with specific cognitive abnormalities. Like mice, in subjects with the 22q11.2DS (characterized by COMT hemideletion and dopamine alterations), COMT-by-DTNBP1 concomitant reduction was associated with analogous cognitive disturbances. We then developed an easy and inexpensive colourimetric kit for the genetic screening of common COMT and DTNBP1 functional genetic variants for clinical application. CONCLUSIONS AND IMPLICATIONS: These findings illustrate an epistatic interaction of two dopamine-related genes and their functional effects, supporting the need to address genetic interaction mechanisms at the base of complex behavioural traits.

The Role of Dopamine D3 Receptors, Dysbindin, and Their Functional Interaction in the Expression of Key Genes for Neuroplasticity and Neuroinflammation in the Mouse Brain.

Cognitive impairment in schizophrenia remains a clinically and pharmacologically unsolved challenge. Clinical and preclinical studies have revealed that the concomitant reduction in dysbindin (DYS) and dopamine receptor D3 functionality improves cognitive functions. However, the molecular machinery underlying this epistatic interaction has not yet been fully elucidated. The glutamate NMDA receptors and the neurotrophin BDNF, with their established role in promoting neuroplasticity, may be involved in the complex network regulated by the D3/DYS interaction. Furthermore, as inflammation is involved in the etiopathogenesis of several psychiatric diseases, including schizophrenia, the D3/DYS interaction may affect the expression levels of pro-inflammatory cytokines. Thus, by employing mutant mice bearing selective heterozygosis for D3 and/or DYS, we provide new insights into the functional interactions (single and synergic) between these schizophrenia susceptibility genes and the expression levels of key genes for neuroplasticity and neuroinflammation in three key brain areas for schizophrenia: the prefrontal cortex, striatum, and hippocampus. In the hippocampus, the epistatic interaction between D3 and DYS reversed to the wild-type level the downregulated mRNA levels of GRIN1 and GRIN2A were observed in DYS +/- and D3 +/- mice. In all the areas investigated, double mutant mice had higher BDNF levels compared to their single heterozygote counterparts, whereas D3 hypofunction resulted in higher pro-inflammatory cytokines. These results may help to clarify the genetic mechanisms and functional interactions involved in the etiology and development of schizophrenia.

Vaccinia-related kinase 2 variants differentially affect breast cancer growth by regulating kinase activity.

Genetic information is transcribed from genomic DNA to mRNA, which is then translated into three-dimensional proteins. mRNAs can undergo various post-transcriptional modifications, including RNA editing that alters mRNA sequences, ultimately affecting protein function. In this study, RNA editing was identified at the 499th base (c.499) of human vaccinia-related kinase 2 (VRK2). This RNA editing changes the amino acid in the catalytic domain of VRK2 from isoleucine (with adenine base) to valine (with guanine base). Isoleucine-containing VRK2 has higher kinase activity than the valine-containing VRK2, which leads to an increase in tumor cell proliferation. Earlier we reported that VRK2 directly interacts with dystrobrevin-binding protein (dysbindin) and results in reducing its stability. Herein, we demonstrate that isoleucine-containing VRK2 decreases the level of dysbindin than valine-containing VRK2. Dysbindin interacts with cyclin D and thereby regulates its expression and function. The reduction in the level of dysbindin by isoleucine-containing VRK2 further enhances the cyclin D expression, resulting in increased tumor growth and reduction in survival rates. It has also been observed that in patient samples, VRK2 level was elevated in breast cancer tissue compared to normal breast tissue. Additionally, the isoleucine form of VRK2 exhibited a greater increase in breast cancer tissue. Therefore, it is concluded that VRK2, especially dependent on the 167th variant amino acid, can be one of the indexes of tumor progression and proliferation.

Exposure to Circadian Disruption During Adolescence Interacts With a Genetic Risk Factor to Modify Schizophrenia-relevant Behaviors in a Sex-dependent Manner.

DTNBP1 is a gene associated with schizophrenia. Postmortem studies found a reduced expression of DTNBP1 in regions associated with schizophrenia in patients' brains. Sandy (Sdy) mice have a loss-of-function mutation in Dtnbp1 gene, resulting in behavioral deficits and brain changes similar to those seen in patients with schizophrenia. We previously showed that exposing adult Sdy mice to circadian disruption led to an exacerbation of schizophrenia-relevant behaviors. Here we asked whether the interaction between this genetic risk factor and circadian disruption occurs during adolescence, a period when environmental insults can promote schizophrenia symptoms, and whether sex affects this interaction. Starting at postnatal day 21, wild-type (WT) and Sdy males and females were housed for 4 weeks either in a 12 h light:12 h dark (LD 12:12) cycle or under chronic jetlag (CJL). Then, after 2 weeks in LD 12:12, behavioral assessments were conducted, including elevated plus maze (EPM), novel object recognition (NOR), social interaction, and prepulse inhibition (PPI) of acoustic startle. NOR and social novelty tests showed that, surprisingly, CJL during adolescence had opposite effects on WT and Sdy males, that is, behavioral deficits in WT males while rescuing preexisting deficits in Sdy mice. CJL led to decreased sociability in WT and Sdy mice while decreasing PPI only in females. Sdy mice showed decreased anxiety-like behavior compared with wild-type (WT), which was further accentuated by CJL in males. Thus, circadian disruption during adolescence, on its own or in association with Dtnbp1 mutation, can influence cognition, sociability, sensorimotor gating, and anxiety-like behaviors in a sex-dependent manner.

α-Dystrobrevin knockout mice have increased motivation for appetitive reward and altered brain cannabinoid receptor 1 expression.

α-Dystrobrevin (α-DB) is a major component of the dystrophin-associated protein complex (DAPC). Knockout (KO) of α-DB in the brain is associated with astrocytic abnormalities and loss of neuronal GABA receptor clustering. Mutations in DAPC proteins are associated with altered dopamine signaling and cognitive and psychiatric disorders, including schizophrenia. This study tested the hypothesis that motivation and associated underlying biological pathways are altered in the absence of α-DB expression. Male wildtype and α-DB KO mice were tested for measures of motivation, executive function and extinction in the rodent touchscreen apparatus. Subsequently, brain tissues were evaluated for mRNA and/or protein levels of dysbindin-1, dopamine transporter and receptor 1 and 2, mu opioid receptor 1 (mOR1) and cannabinoid receptor 1 (CB1). α-DB KO mice had significantly increased motivation for the appetitive reward, while measures of executive function and extinction were unaffected. No differences were observed between wildtype and KO animals on mRNA levels of dysbindin-1 or any of the dopamine markers. mRNA levels of mOR1were significantly decreased in the caudate-putamen and nucleus accumbens of α-DB KO compared to WT animals, but protein levels were unaltered. However, CB1 protein levels were significantly increased in the prefrontal cortex and decreased in the nucleus accumbens of α-DB KO mice. Triple-labelling immunohistochemistry confirmed that changes in CB1 were not specific to astrocytes. These results highlight a novel role for α-DB in the regulation of appetitive motivation that may have implications for other behaviours that involve the dopaminergic and endocannabinoid systems.

Dysbindin-1A modulation of astrocytic dopamine and basal ganglia dependent behaviors relevant to schizophrenia.

The mechanisms underlying the dichotomic cortical/basal ganglia dopaminergic abnormalities in schizophrenia are unclear. Astrocytes are important non-neuronal modulators of brain circuits, but their role in dopaminergic system remains poorly explored. Microarray analyses, immunohistochemistry, and two-photon laser scanning microscopy revealed that Dys1 hypofunction increases the reactivity of astrocytes, which express only the Dys1A isoform. Notably, behavioral and electrochemical assessments in mice selectively lacking the Dys1A isoform unraveled a more prominent impact of Dys1A in behavioral and dopaminergic/D2 alterations related to basal ganglia, but not cortical functioning. Ex vivo electron microscopy and protein expression analyses indicated that selective Dys1A disruption might alter intracellular trafficking in astrocytes, but not in neurons. In agreement, Dys1A disruption only in astrocytes resulted in decreased motivation and sensorimotor gating deficits, increased astrocytic dopamine D2 receptors and decreased dopaminergic tone within basal ganglia. These processes might have clinical relevance because the caudate, but not the cortex, of patients with schizophrenia shows a reduction of the Dys1A isoform. Therefore, we started to show a hitherto unknown role for the Dys1A isoform in astrocytic-related modulation of basal ganglia behavioral and dopaminergic phenotypes, with relevance to schizophrenia.

The E3 ligase Thin controls homeostatic plasticity through neurotransmitter release repression.

Synaptic proteins and synaptic transmission are under homeostatic control, but the relationship between these two processes remains enigmatic. Here, we systematically investigated the role of E3 ubiquitin ligases, key regulators of protein degradation-mediated proteostasis, in presynaptic homeostatic plasticity (PHP). An electrophysiology-based genetic screen of 157 E3 ligase-encoding genes at the Drosophila neuromuscular junction identified thin, an ortholog of human tripartite motif-containing 32 (TRIM32), a gene implicated in several neurological disorders, including autism spectrum disorder and schizophrenia. We demonstrate that thin functions presynaptically during rapid and sustained PHP. Presynaptic thin negatively regulates neurotransmitter release under baseline conditions by limiting the number of release-ready vesicles, largely independent of gross morphological defects. We provide genetic evidence that thin controls release through dysbindin, a schizophrenia-susceptibility gene required for PHP. Thin and Dysbindin localize in proximity within presynaptic boutons, and Thin degrades Dysbindin in vitro. Thus, the E3 ligase Thin links protein degradation-dependent proteostasis of Dysbindin to homeostatic regulation of neurotransmitter release.

Backbone and side chain resonance assignment of the intrinsically disordered human DBNDD1 protein.

The dysbindin domain-containing protein 1 (DBNDD1) is a conserved protein among higher eukaryotes whose structure and function are poorly investigated so far. Here, we present the backbone and side chain nuclear magnetic resonance assignments for the human DBNDD1 protein. Our chemical-shift based secondary structure analysis reveals the human DBNDD1 as an intrinsically disordered protein.

Protein Kinase B/Akt1 Phosphorylates Dysbindin-1A at Serine 10 to Regulate Neuronal Development.

Schizophrenia is a neurodevelopmental disorder with dendrite and dendritic spine dysfunction. Dysbindin-1, a protein decreased in the brains of schizophrenia patients, is involved in the development of dendrites and spines. However, it is still unclear how the role of dysbindin-1 in neuronal development is regulated. Here, we showed protein kinase B/Akt1, a serine/threonine kinase implicated in schizophrenia, phosphorylated dysbindin-1A at serine 10 (S10). S10 phosphorylation of dysbindin-1A was increased during postnatal neuronal and synapse development stage, and was enriched in postsynaptic densities (PSDs). Furthermore, overexpressing wild type or S10 phospho-mimic mutant (S10D), but not S10 phospho-dead mutant (S10A) of dysbindin-1A rescued the dendrite and spine deficits in dysbindin-1A knockdown neurons. These results indicate S10 phosphorylation of dysbindin-1A by Akt1 is essential for neuronal development, providing a potential regulation mechanism for dysbindin-1A in neuronal development.

Long-lasting rescue of schizophrenia-relevant cognitive impairments via risperidone-loaded microPlates.

Schizophrenia is a disorder characterized by cognitive impairment and psychotic symptoms that fluctuate over time and can only be mitigated with the chronic administration of antipsychotics. Here, we propose biodegradable microPlates made of PLGA for the sustained release of risperidone over several weeks. Two microPlate configurations - short: 20 × 20 × 10 µm; tall: 20 × 20 × 20 µm - are engineered and compared to conventional ~ 10 µm PLGA microspheres in terms of risperidone loading and release. Tall microPlates realize the slowest release documenting a 35% risperidone delivery at 100 days with a residual rate of 30 ng/ml. Short microPlates and microspheres present similar release profiles with over 50% of the loaded risperidone delivered within the first 40 days. Then, the therapeutic efficacy of one single intraperitoneal injection of risperidone microPlates is compared to the daily administration of free risperidone in heterozygous knockout mice for dysbindin-1, a clinically relevant mouse model of cognitive and psychiatric liability. In temporal order object recognition tasks, mice treated with risperidone microPlates outperform those receiving free risperidone up to 2, 4, 8, and 12 weeks of observation. This suggests that the sustained release of antipsychotics from one-time microPlate deposition can rescue cognitive impairment in dysbindin mice for up to several weeks. Overall, these results demonstrate that risperidone-loaded microPlates are a promising platform for improving cognitive symptoms associated to schizophrenia. Moreover, the long-term efficacy with one single administration could be of clinical relevance in terms of patient's compliance and adherence to the treatment regimen. Single injection of long-acting risperidone-loaded µPL ameliorates the dysbindin-induced deficit in a clinically relevant mouse model of cognitive and psychiatric liability for up to 12 weeks.

Objective to identify and verify the regulatory mechanism of DTNBP1 as a prognostic marker for hepatocellular carcinoma.

Although the overall survival of hepatocellular carcinoma (HCC) patients has been significantly improved, prognostic clinical evaluation remains a substantial problem owing to the heterogeneity and complexity of tumor. A reliable and accurate predictive biomarker may assist physicians in better monitoring of patient treatment outcomes and follow the overall survival of patients. Accumulating evidence has revealed that DTNBP1 plays functional roles in cancer prognosis. Therefore, the expression and function of DTNBP1in HCC was systematically investigated in our study. The expression and prognostic value of DTNBP1 were investigated using the data from Cancer Genome Atlas (TCGA) database, Gene Expression Omnibus (GEO) cohorts and clinical samples. A series of cellular function assays were performed to elucidate the effect of DTNBP1 on cellular proliferation, apoptosis and metastasis. Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathway enrichment and Protein-protein interaction (PPI) network construction were performed to screen the genes with highest interaction scores with DTNBP1. Finally, the underlying mechanism was also analyzed using Gene Set Enrichment Analysis (GSEA) and confirmed using RT-qPCR and western blotting. DTNBP1 was upregulated in many types of cancers, especially in HCC. The DTNBP1 expression levels is associated with clinicopathologic variables and patient survival status. The differential expression of DTNBP1 could be used to determine the risk stratification of patients with HCC. DTNBP1 deficiency inhibited cell proliferation and metastasis, but promoted cell apoptosis. Mechanistically, DTNBP1 regulated the cell cycle progression through affecting the expression of cell cycle-related genes such as CDC25A, CCNE1, CDK2, CDC20, CDC25B, CCNB1, and CDK1. DTNBP1, which regulates the cell cycle progression, may be used as a prognostic marker for HCC.

Cortical copper transporter expression in schizophrenia: interactions of risk gene dysbindin-1.

Schizophrenia susceptibility factor dysbindin-1 is associated with cognitive processes. Downregulated dysbindin-1 expression is associated with lower expression of copper transporters ATP7A and CTR1, required for copper transport to the central nervous system. We measured dysbindin-1 isoforms-1A and -1BC, CTR1, and ATP7A via Western blots of the postmortem dorsolateral prefrontal cortex (DLPFC) of schizophrenia subjects (n = 28) and matched controls (n = 14). In addition, we subdivided the schizophrenia group by treatment status and comorbidity of alcohol use disorder (AUD) and assessed the relationships between proteins. Schizophrenia subjects exhibited similar protein levels to that of controls, with no effect of antipsychotic treatment. We observed a shift towards more dysbindin-1A expression in schizophrenia, as revealed by the ratio of dysbindin-1 isoforms. Dysbindin-1A expression was negatively correlated with ATP7A in schizophrenia, with no correlation present in controls. AUD subjects exhibited less dysbindin-1BC and CTR1 than those without AUD. Our results, taken together with previous data, suggest that alterations in dysbindin-1 and copper transporters are brain-region specific. For example, protein levels of ATP7A, dysbindin 1BC, and CTR1 are lower in the substantia nigra in schizophrenia subjects. AUD in the DLPFC was associated with lower protein levels of dysbindin-1 and CTR1. Changes in dysbindin-1 isoform ratio and relationships appear to be prevalent in the disease, potentially impacting symptomology.

Dysbindin-1 regulates mitochondrial fission and gamma oscillations.

Mitochondria are cellular ATP generators. They are dynamic structures undergoing fission and fusion. While much is known about the mitochondrial fission machinery, the mechanism of initiating fission and the significance of fission to neurophysiology are largely unclear. Gamma oscillations are synchronized neural activities that impose a great energy challenge to synapses. The cellular mechanism of fueling gamma oscillations has yet to be defined. Here, we show that dysbindin-1, a protein decreased in the brain of individuals with schizophrenia, is required for neural activity-induced fission by promoting Drp1 oligomerization. This process is engaged by gamma-frequency activities and in turn, supports gamma oscillations. Gamma oscillations and novel object recognition are impaired in dysbindin-1 null mice. These defects can be ameliorated by increasing mitochondrial fission. These findings identify a molecular mechanism for activity-induced mitochondrial fission, a role of mitochondrial fission in gamma oscillations, and mitochondrial fission as a potential target for improving cognitive functions.

Schizophrenia-associated dysbindin modulates axonal mitochondrial movement in cooperation with p150glued.

Mitochondrial movement in neurons is finely regulated to meet the local demand for energy and calcium buffering. Elaborate transport machinery including motor complexes is required to deliver and localize mitochondria to appropriate positions. Defects in mitochondrial transport are associated with various neurological disorders without a detailed mechanistic information. In this study, we present evidence that dystrobrevin-binding protein 1 (dysbindin), a schizophrenia-associated factor, plays a critical role in axonal mitochondrial movement. We observed that mitochondrial movement was impaired in dysbindin knockout mouse neurons. Reduced mitochondrial motility caused by dysbindin deficiency decreased the density of mitochondria in the distal part of axons. Moreover, the transport and distribution of mitochondria were regulated by the association between dysbindin and p150glued. Furthermore, altered mitochondrial distribution in axons led to disrupted calcium dynamics, showing abnormal calcium influx in presynaptic terminals. These data collectively suggest that dysbindin forms a functional complex with p150glued that regulates axonal mitochondrial transport, thereby affecting presynaptic calcium homeostasis.

Markers of copper transport in the cingulum bundle in schizophrenia.

Imaging and postmortem studies indicate that schizophrenia subjects exhibit abnormal connectivity in several white matter tracts, including the cingulum bundle. Copper chelators given to experimental animals damage myelin and myelin-producing oligodendrocytes, and the substantia nigra of schizophrenia subjects shows lower levels of copper, copper transporters, and copper-utilizing enzymes. This study aimed to elucidate the potential role of copper homeostasis in white matter pathology in schizophrenia. Protein levels of the copper transporters ATP7A and CTR1, and dysbindin-1, an upstream modulator of copper metabolism and schizophrenia susceptibility factor, were measured using Western blot analyses of the postmortem cingulum bundle of schizophrenia subjects (n=16) and matched controls (n=13). Additionally, the patient group was subdivided by treatment status: off- (n=8) or on-medication (n=8). Relationships between proteins from the current study were correlated among themselves and markers of axonal integrity previously measured in the same cohort. Schizophrenia subjects exhibited similar protein levels to controls, with no effect of antipsychotic treatment. The dysbindin-1A/1BC relationship was positive in controls and schizophrenia subjects; however, antipsychotic treatment appeared to reverse this relationship in a statistically different manner from that of controls and unmedicated subjects. The relationships between dysbindin-1A/neurofilament heavy and ATP7A/α-tubulin were positively correlated in the schizophrenia group that was significantly different from the lack of correlation in controls. Copper transporters and dysbindin-1 appear to be more significantly affected in the grey matter of schizophrenia subjects. However, the relationships among proteins in white matter may be more substantial and dependent on treatment status.

Abnormalities in the copper transporter CTR1 in postmortem hippocampus in schizophrenia: A subregion and laminar analysis.

Dysbindin-1 modulates copper transport, which is crucial for cellular homeostasis. Several brain regions implicated in schizophrenia exhibit decreased levels of dysbindin-1, which may affect copper homeostasis therein. Our recent study showed decreased levels of dysbindin-1, the copper transporter-1 (CTR1) and copper in the substantia nigra in schizophrenia, providing the first evidence of disrupted copper transport in schizophrenia. In the present study, we hypothesized that there would be lower levels of dysbindin-1 and CTR1 in the hippocampus in schizophrenia versus a comparison group. Using semi-quantitative immunohistochemistry for dysbindin1 and CTR1, we measured the optical density in a layer specific fashion in the hippocampus and entorhinal cortex in ten subjects with schizophrenia and ten comparison subjects. Both regions were richly immunolabeled for CTR1 and dysbindin1 in both groups. In the superficial layers of the entorhinal cortex, CTR1 immunolabeled neuropil and cells showed lower optical density values in patients versus the comparison group. In the molecular layer of the dentate gyrus, patients had higher optical density values of CTR1 versus the comparison group. The density and distribution of dysbindin-1 immunolabeling was similar between groups. These laminar specific alterations of CTR1 in schizophrenia suggest abnormal copper transport in those locations.

The epistatic interaction between the dopamine D3 receptor and dysbindin-1 modulates higher-order cognitive functions in mice and humans.

The dopamine D2 and D3 receptors are implicated in schizophrenia and its pharmacological treatments. These receptors undergo intracellular trafficking processes that are modulated by dysbindin-1 (Dys). Indeed, Dys variants alter cognitive responses to antipsychotic drugs through D2-mediated mechanisms. However, the mechanism by which Dys might selectively interfere with the D3 receptor subtype is unknown. Here, we revealed an interaction between functional genetic variants altering Dys and D3. Specifically, both in patients with schizophrenia and in genetically modified mice, concomitant reduction in D3 and Dys functionality was associated with improved executive and working memory abilities. This D3/Dys interaction produced a D2/D3 imbalance favoring increased D2 signaling in the prefrontal cortex (PFC) but not in the striatum. No epistatic effects on the clinical positive and negative syndrome scale (PANSS) scores were evident, while only marginal effects on sensorimotor gating, locomotor functions, and social behavior were observed in mice. This genetic interaction between D3 and Dys suggests the D2/D3 imbalance in the PFC as a target for patient stratification and procognitive treatments in schizophrenia.

Schizophrenia-associated gene dysbindin-1 and tardive dyskinesia.

Tardive dyskinesia (TD) is a potentially irreversible movement disorder observed following long-term antipsychotic exposure. Its cause is unknown; however, a genetic component has been supported by studies of affected families. Dysbindin-1, encoded by the dystrobrevin-binding protein 1 DTNBP1 gene, has been associated with schizophrenia and is potentially involved in dopamine neurotransmission through its regulation of dopamine release and dopamine D2 receptor recycling, making it a candidate for investigation in TD. We investigated common variants across the DTNBP1 gene in our schizophrenia/patients with schizoaffective disorder of European ancestry. We found a number of DTNBP1 three-marker haplotypes to be associated with TD occurrence and TD severity (p < 0.05). These preliminary findings, if replicated in larger independent samples, would suggest that drugs targeting dysbindin-1 may be an option in the prevention and treatment of TD.