Koko Ishizuka

Dominant-negative DISC1 transgenic mice display schizophrenia-associated phenotypes detected by measures translatable to humans

Here, we report generation and characterization of Disrupted-In-Schizophrenia-1 (DISC1) genetically engineered mice as a potential model for major mental illnesses, such as schizophrenia. DISC1 is a promising genetic risk factor for major mental illnesses. In this transgenic model, a dominant-negative form of DISC1 (DN-DISC1) is expressed under the αCaMKII promoter. In vivo MRI of the DN-DISC1 mice detected enlarged lateral ventricles particularly on the left side, suggesting a link to the asymmetrical change in anatomy found in brains of patients with schizophrenia. Furthermore, selective reduction in the immunoreactivity of parvalbumin in the cortex, a marker for an interneuron deficit that may underlie cortical asynchrony, is observed in the DN-DISC1 mice. These results suggest that these transgenic mice may be used as a model for schizophrenia. DN-DISC1 mice also display several behavioral abnormalities, including hyperactivity, disturbance in sensorimotor gating and olfactory-associated behavior, and an anhedonia/depression-like deficit.

A Review of Disrupted-in-Schizophrenia-1 (disc1): Neurodevelopment, Cognition, and Mental Conditions

Disrupted-In-Schizophrenia-1 (DISC1) is a promising candidate gene for schizophrenia (SZ) and bipolar disorder (BP), but its basic biology remains to be elucidated. Accumulating genetic evidence supports that DISC1 is associated with some aspects of cognitive functions relevant to SZ and BP. Here, we provide a summary of the current updates in biological studies of DISC1. Disrupted-In-Schizophrenia-1, preferentially expressed in the forebrain, has multiple isoforms with potential posttranslational modifications. Disrupted-In-Schizophrenia-1 protein occurs in multiple subcellular compartments, which include the centrosome, microtubule fractions, postsynaptic densities, actin cytoskeletal fractions, the mitochondria, and the nucleus. Recent studies have clarified that DISC1 mediates at least centrosome-dynein cascade and cyclic adenosine monophosphate (cAMP) signaling. Furthermore, both cytogenetic and cell biological studies consistently suggest that an overall loss of DISC1 function (either haploinsufficiency or dominant-negative, or both) may be associated with SZ and BP. On the basis of these findings, production of DISC1 genetically engineered mice is proposed as a promising animal model for SZ and BP. Several groups are currently generating DISC1 mice and starting to characterize them. In this review, the advantages and disadvantages of each animal model are discussed.

DISC1-dependent switch from progenitor proliferation to migration in the developing cortex

Regulatory mechanisms governing the sequence from progenitor cell proliferation to neuronal migration during corticogenesis are poorly understood. Here we report that phosphorylation of DISC1, a major susceptibility factor for several mental disorders, acts as a molecular switch from maintaining proliferation of mitotic progenitor cells to activating migration of postmitotic neurons in mice. Unphosphorylated DISC1 regulates canonical Wnt signalling via an interaction with GSK3β, whereas specific phosphorylation at serine 710 (S710) triggers the recruitment of Bardet–Biedl syndrome (BBS) proteins to the centrosome. In support of this model, loss of BBS1 leads to defects in migration, but not proliferation, whereas DISC1 knockdown leads to deficits in both. A phospho-dead mutant can only rescue proliferation, whereas a phospho-mimic mutant rescues exclusively migration defects. These data highlight a dual role for DISC1 in corticogenesis and indicate that phosphorylation of this protein at S710 activates a key developmental switch.

Recruitment of PCM1 to the Centrosome by the Cooperative Action of DISC1 and BBS4 A Candidate for Psychiatric Illnesses

CONTEXT A role for the centrosome has been suggested in the pathology of major mental illnesses, especially schizophrenia (SZ). OBJECTIVES To show that pericentriolar material 1 protein (PCM1) forms a complex at the centrosome with disrupted-in-schizophrenia 1 (DISC1) and Bardet-Biedl syndrome 4 protein (BBS4), which provides a crucial pathway for cortical development associated with the pathology of SZ. To identify mutations in the PCM1 gene in an SZ population. DESIGN Interaction of DISC1, PCM1, and BBS proteins was assessed by immunofluorescent staining and coimmunoprecipitation. Effects of PCM1, DISC1, and BBS on centrosomal functions and corticogenesis in vivo were tested by RNA interference. The PCM1 gene was examined by sequencing 39 exons and flanking splice sites. SETTING Probands and controls were from the collection of one of us (A.E.P.). PATIENTS Thirty-two probands with SZ from families that had excess allele sharing among affected individuals at 8p22 and 219 white controls. MAIN OUTCOME MEASURES Protein interaction and recruitment at the centrosome in cells; neuronal migration in the cerebral cortex; and variant discovery in PCM1 in patients with SZ. RESULTS PCM1 forms a complex with DISC1 and BBS4 through discrete binding domains in each protein. DISC1 and BBS4 are required for targeting PCM1 and other cargo proteins, such as ninein, to the centrosome in a synergistic manner. In the developing cerebral cortex, suppression of PCM1 leads to neuronal migration defects, which are phenocopied by the suppression of either DISC1 or BBS4 and are exacerbated by the concomitant suppression of both. Furthermore, a nonsense mutation that segregates with SZ spectrum psychosis was found in 1 family. CONCLUSIONS Our data further support for the role of centrosomal proteins in cortical development and suggest that perturbation of centrosomal function contributes to the development of mental diseases, including SZ.

Elucidating the relationship between DISC1, NDEL1 and NDE1 and the risk for schizophrenia: Evidence of epistasis and competitive binding

DISC1 influences susceptibility to psychiatric disease and related phenotypes. Intact functions of DISC1 and its binding partners, NDEL1 and NDE1, are critical to neurodevelopmental processes aberrant in schizophrenia (SZ). Despite evidence of an NDEL1–DISC1 protein interaction, there have been no investigations of the NDEL1 gene or the relationship between NDEL1 and DISC1 in SZ. We genotyped six NDEL1 single-nucleotide polymorphisms (SNPs) in 275 Caucasian SZ patients and 200 controls and tested for association and interaction between the functional SNP Ser704Cys in DISC1 and NDEL1. We also evaluated the relationship between NDE1 and DISC1 genotype and SZ. Finally, in a series of in vitro assays, we determined the binding profiles of NDEL1 and NDE1, in relation to DISC1 Ser704Cys. We observed a single haplotype block within NDEL1; the majority of variation was captured by NDEL1 rs1391768. We observed a significant interaction between rs1391768 and DISC1 Ser704Cys, with the effect of NDEL1 on SZ evident only against the background of DISC1 Ser704 homozygosity. Secondary analyses revealed no direct relationship between NDE1 genotype and SZ; however, there was an opposite pattern of risk for NDE1 genotype when conditioned on DISC1 Ser704Cys, with NDE1 rs3784859 imparting a significant effect but only in the context of a Cys-carrying background. In addition, we report opposing binding patterns of NDEL1 and NDE1 to Ser704 versus Cys704, at the same DISC1 binding domain. These data suggest that NDEL1 significantly influences risk for SZ via an interaction with DISC1. We propose a model where NDEL1 and NDE1 compete for binding with DISC1.

The psychiatric disease risk factors DISC1 and TNIK interact to regulate synapse composition and function

Disrupted in schizophrenia 1 (DISC1), a genetic risk factor for multiple serious psychiatric diseases including schizophrenia, bipolar disorder and autism, is a key regulator of multiple neuronal functions linked to both normal development and disease processes. As these diseases are thought to share a common deficit in synaptic function and architecture, we have analyzed the role of DISC1 using an approach that focuses on understanding the protein–protein interactions of DISC1 specifically at synapses. We identify the Traf2 and Nck-interacting kinase (TNIK), an emerging risk factor itself for disease, as a key synaptic partner for DISC1, and provide evidence that the DISC1–TNIK interaction regulates synaptic composition and activity by stabilizing the levels of key postsynaptic density proteins. Understanding the novel DISC1–TNIK interaction is likely to provide insights into the etiology and underlying synaptic deficits found in major psychiatric diseases.

Disrupted-in-Schizophrenia-1 expression is regulated by β-site amyloid precursor protein cleaving enzyme-1-neuregulin cascade

Neuregulin-1 (NRG1) and Disrupted-in-Schizophrenia-1 (DISC1) are promising susceptibility factors for schizophrenia. Both are multifunctional proteins with roles in a variety of neurodevelopmental processes, including progenitor cell proliferation, migration, and differentiation. Here, we provide evidence linking these factors together in a single pathway, which is mediated by ErbB receptors and PI3K/Akt. We show that signaling by NRG1 and NRG2, but not NRG3, increase expression of an isoform of DISC1 in vitro. Receptors ErbB2 and ErbB3, but not ErbB4, are responsible for transducing this effect, and PI3K/Akt signaling is also required. In NRG1 knockout mice, this DISC1 isoform is selectively reduced during neurodevelopment. Furthermore, a similar decrease in DISC1 expression is seen in β-site amyloid precursor protein cleaving enzyme–1 (BACE1) knockout mice, in which NRG1/Akt signaling is reportedly impaired. In contrast to neuronal DISC1 that was reported and characterized, expression of DISC1 in other types of cells in the brain has not been addressed. Here we demonstrate that DISC1, like NRG and ErbB proteins, is expressed in neurons, astrocytes, oligodendrocytes, microglia, and radial progenitors. These findings may connect NRG1, ErbBs, Akt, and DISC1 in a common pathway, which may regulate neurodevelopment and contribute to susceptibility to schizophrenia.

Nuclear DISC1 regulates CRE-mediated gene transcription and sleep homeostasis in the fruit fly

Disrupted-in-schizophrenia-1 (DISC1) is one of major susceptibility factors for a wide range of mental illnesses, including schizophrenia, bipolar disorder, major depression and autism spectrum conditions. DISC1 is located in several subcellular domains, such as the centrosome and the nucleus, and interacts with various proteins, including NudE-like (NUDEL/NDEL1) and activating transcription factor 4 (ATF4)/CREB2. Nevertheless, a role for DISC1 in vivo remains to be elucidated. Therefore, we have generated a Drosophila model for examining normal functions of DISC1 in living organisms. DISC1 transgenic flies with preferential accumulation of exogenous human DISC1 in the nucleus display disturbance in sleep homeostasis, which has been reportedly associated with CREB signaling/CRE-mediated gene transcription. Thus, in mammalian cells, we characterized nuclear DISC1, and identified a subset of nuclear DISC1 that colocalizes with the promyelocytic leukemia (PML) bodies, a nuclear compartment for gene transcription. Furthermore, we identified three functional cis-elements that regulate the nuclear localization of DISC1. We also report that DISC1 interacts with ATF4/CREB2 and a corepressor N-CoR, modulating CRE-mediated gene transcription.

Differential Expression of Disrupted-in-Schizophrenia (DISC1) in Bipolar Disorder

BACKGROUND The disruption of the disrupted-in-schizophrenia (DISC1) gene segregates with major mental illnesses in a Scottish family. Association of DISC1 with schizophrenia has been reported in several ethnic groups, and now recently with mood disorder. METHODS A family-based association study of DISC1 and bipolar disorder (BP) in 57 bipolar pedigrees was conducted. Then, we examined possible association of bipolar disorder with DISC1 mRNA expression in human lymphoblasts. We also studied the correlation of several clinical features with the levels of DISC1 mRNA expression. RESULTS Haplotype analysis identified one haplotype (HP1) that was overtransmitted to the BP phenotype (p = .01) and a second haplotype that was undertransmitted (HP2). There was a gender influence in the transmission distortion, with overtransmission of HP1 to affected females (p = .004). A significant decrease in DISC1 mRNA expression was observed in lymphoblasts from affected HP1 group compared to those from unaffected subjects with the HP2 (p = .006). Further, a higher number of manic symptoms correlated with lower levels of DISC1 expression (p = .008). CONCLUSIONS These results suggest that decreased mRNA levels of DISC1 expression, associating with the risk haplotype, may be implicated in the pathophysiology of bipolar disorder.

Evidence that many of the DISC1 isoforms in C57BL/6J mice are also expressed in 129S6/SvEv mice

Evidence that many of the DISC1 isoforms in C57BL/6J mice are also expressed in 129S6/SvEv mice