Schizophrenia is a genetically complex disorder with an unknown pathophysiology. Several genes implicated in glutamate metabolism have been associated with the disorder. Recent studies of polymorphisms in the dystrobrevin-binding protein 1 gene (DTNBP1; dysbindin) and D-amino-acid-oxidase (DAO) gene, both involved in glutamate receptor function, reported associations with negative symptoms and with anxiety and depression, respectively, when measured with the Positive and Negative Syndrome Scale (PANSS).
In the present study, the suggested association between dysbindin and DAO single nucleotide polymorphisms (SNPs) and PANSS scores was analyzed in 155 Norwegian schizophrenia patients.
There was a significant association between the dysbindin SNP rs3213207 and severity of both negative symptoms and total symptom load, as well as between the DAO SNP rs2070587 and total symptom score and severity of anxiety and depression.
The present association of dysbindin SNPs with negative symptoms and DAO SNPs with anxiety and depression is a replication of earlier findings and strengthens the hypothesis of a genetic association. It further indicates involvement of glutamate abnormalities in schizophrenia pathophysiology, as suggested by previous studies, and suggests that polymorphisms may be associated with subgroups of clinical characteristics in schizophrenia.
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"–). An increasing number of studies report that several of these DTNBP1 risk variants are associated with severity of the positive symptoms (e.g., delusions and hallucinations) and especially the negative symptoms (e.g., flattened affect and social withdrawal) of schizophrenia –. Such genetic variants are also associated with severity of cognitive deficits in this disorder ,–. "
[Show abstract][Hide abstract] ABSTRACT: An increasing number of studies report associations between variation in DTNBP1, a top candidate gene in schizophrenia, and both the clinical symptoms of the disorder and its cognitive deficits. DTNBP1 encodes dysbindin-1, reduced levels of which have been found in synaptic fields of schizophrenia cases. This study determined whether such synaptic reductions are isoform-specific.
Using Western blotting of tissue fractions, we first determined the synaptic localization of the three major dysbindin-1 isoforms (A, B, and C). All three were concentrated in synaptosomes of multiple brain areas, including auditory association cortices in the posterior half of the superior temporal gyrus (pSTG) and the hippocampal formation (HF). Tests on the subsynaptic tissue fractions revealed that each isoform is predominantly, if not exclusively, associated with synaptic vesicles (dysbindin-1B) or with postsynaptic densities (dysbindin-1A and -1C). Using Western blotting on pSTG (n = 15) and HF (n = 15) synaptosomal fractions from schizophrenia cases and their matched controls, we discovered that synaptic dysbindin-1 is reduced in an isoform-specific manner in schizophrenia without changes in levels of synaptophysin or PSD-95. In pSTG, about 92% of the schizophrenia cases displayed synaptic dysbindin-1A reductions averaging 48% (p = 0.0007) without alterations in other dysbindin-1 isoforms. In the HF, by contrast, schizophrenia cases displayed normal levels of synaptic dysbindin-1A, but 67% showed synaptic reductions in dysbindin-1B averaging 33% (p = 0.0256), while 80% showed synaptic reductions in dysbindin-1C averaging 35% (p = 0.0171).
Given the distinctive subsynaptic localization of dysbindin-1A, -1B, and -1C across brain regions, the observed pSTG reductions in dysbindin-1A are postsynaptic and may promote dendritic spine loss with consequent disruption of auditory information processing, while the noted HF reductions in dysbindin-1B and -1C are both presynaptic and postsynaptic and could promote deficits in spatial working memory.
"Sanacora et al., 2008). Furthermore, considering reports of dysbindin gene variation to be associated with a wide continuum of mental disorders such as schizophrenia (e.g., Straub et al., 2002; Schwab et al., 2003; van den Oord et al., 2003), schizophrenia with anxiety/depression symptoms (Wirgenes et al., 2009), bipolar disorder with or without psychotic features (Raybould et al., 2005; Pae et al., 2007b), major depression (Kim et al., 2008; but: Wray et al., 2008; Zill et al., 2004), Table 4 Association of DTNBP1 gene haplotypes with psychotic depression. "
[Show abstract][Hide abstract] ABSTRACT: Previous studies yielded evidence for dysbindin (DTNBP1) to impact the pathogenesis of schizophrenia on the one hand and affective disorders such as bipolar or major depressive disorder (MDD) on the other. Thus, in the present study we investigated whether DTNBP1 variation was associated with psychotic depression as a severe clinical manifestation of MDD possibly constituting an overlapping phenotype between affective disorders and schizophrenia. A sample of 243 Caucasian inpatients with MDD (SCID-I) was genotyped for 12 SNPs spanning 92% of the DTNBP1 gene region. Differences in DTNBP1 genotype distributions across diagnostic subgroups of psychotic (N = 131) vs. non-psychotic depression were estimated by Pearson Chi(2) test and logistic regression analyses adjusted for age, gender, Beck Depression Inventory (BDI) and the Global Assessment of Functioning Scale (GAF). Overall, patients with psychotic depression presented with higher BDI and lower GAF scores expressing a higher severity of the illness as compared to depressed patients without psychotic features. Four DTNBP1 SNPs, particularly rs1997679 and rs9370822, and the corresponding haplotypes, respectively, were found to be significantly associated with the risk of psychotic depression in an allele-dose fashion. In summary, the present results provide preliminary support for dysbindin (DTNBP1) gene variation, particularly SNPs rs1997679 and rs9370822, to be associated with the clinical phenotype of psychotic depression suggesting a possible neurobiological mechanism for an intermediate trait on the continuum between affective disorders and schizophrenia.
Full-text · Article · Oct 2010 · Journal of Psychiatric Research
"It has been shown to affect personality traits [47,48], intelligence [49-53], attention capacity , verbal fluency [37,52] and several memory domains [52-55] in both healthy subjects and patients with schizophrenia. In particular, negative symptoms in schizophrenia have been shown to be associated with several SNP of the DTNBP1 gene [56,57]. "
[Show abstract][Hide abstract] ABSTRACT: Attention deficits belong to the main cognitive symptoms of schizophrenia and come along with altered neural activity in previously described cerebral networks. Given the high heritability of schizophrenia the question arises if impaired function of these networks is modulated by susceptibility genes and detectable in healthy risk allele carriers.
The present event-related fMRI study investigated the effect of the single nucleotide polymorphism (SNP) rs1018381 of the DTNBP1 (dystrobrevin-binding protein 1) gene on brain activity in 80 subjects while performing the attention network test (ANT). In this reaction time task three domains of attention are probed simultaneously: alerting, orienting and executive control of attention.
Risk allele carriers showed impaired performance in the executive control condition associated with reduced neural activity in the left superior frontal gyrus [Brodmann area (BA) 9]. Risk allele carriers did not show alterations in the alerting and orienting networks.
BA 9 is a key region of schizophrenia pathology and belongs to a network that has been shown previously to be involved in impaired executive control mechanisms in schizophrenia. Our results identified the impact of DTNBP1 on the development of a specific attention deficit via modulation of a left prefrontal network.