Molecular Cloning of a Brain-specific, Developmentally Regulated Neuregulin 1 (NRG1) Isoform and Identification of a Functional Promoter Variant Associated with Schizophrenia

Department of Psychiatry, University of Oxford, Oxford, England, United Kingdom
Journal of Biological Chemistry (Impact Factor: 4.57). 09/2007; 282(33):24343-51. DOI: 10.1074/jbc.M702953200
Source: PubMed


Neuregulin 1 (NRG1) is essential for the development and function of multiple organ systems, and its dysregulation has been linked to diseases such as cancer and schizophrenia. Recently, altered expression of a novel isoform (type IV) in the brain has been associated with schizophrenia-related genetic variants, especially rs6994992 (SNP8NRG243177). Here we have isolated and characterized full-length NRG1 type IV cDNAs from the adult and fetal human brain and identified novel splice variants of NRG1. Full-length type IV spans 1.8 kb and encodes a putative protein of 590 amino acids with a predicted molecular mass of approximately 66 kDa. The transcript consists of 11 exons with an Ig-like domain, an epidermal growth factor-like (EGF) domain, a beta-stalk, a transmembrane domain, and a cytoplasmic "a-tail," placing it in the beta1a NRG1 subclass. NRG1 type IV was not detected in any tissues except brain and a putative type IV NRG1 protein of 66 kDa was similarly brain-specific. Type IV transcripts are more abundantly expressed in the fetal brain, where, in addition to the full-length structure, two novel type IV variants were identified. In vitro luciferase-reporter assays demonstrate that the 5' promoter region upstream of type IV is functional, with differential activity associated with genetic variation at rs6994992, and that promoter competition may impact on type IV expression. Our data suggest that type IV is a unique brain-specific NRG1 that is differentially expressed and processed during early development, is translated, and its expression regulated by a schizophrenia risk-associated functional promoter or single nucleotide polymorphism (SNP).

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    • "Genetic variation in NRG1 was associated to an increased risk for developing schizophrenia [6]. Among the several markers in this gene, the single-nucleotide polymorphism (SNP) rs6994992 (SNP8NRG243177) in the promoter region is particularly interesting because of its effect on the expression levels of type-IV NRG1 in human post-mortem brain samples and in luciferase in vitro assays [7,8]. Other genetic variants related to NRG1 have been associated to schizophrenia, such as the non-synonymous (Arg/Gln) SNP rs3924999 [9]. "
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    ABSTRACT: Background Neuregulins are a family of signalling proteins that orchestrate a broad range of cellular responses. Four genes encoding Neuregulins 1–4 have been identified so far in vertebrates. Among them, Neuregulin 1 and Neuregulin 3 have been reported to contribute to an increased risk for developing schizophrenia. We hypothesized that three specific variants of these genes (rs6994992 and rs3924999 for Neuregulin 1 and rs10748842 for Neuregulin 3) that have been related to this illness may modify information processing capacity in the cortex, which would be reflected in electrophysiological parameters (P3b amplitude or gamma noise power) and/or cognitive performance. Methods We obtained DNA from 31 patients with schizophrenia and 23 healthy controls and analyzed NRG1 rs6994992, NRG1 rs3924999 and NRG3 rs10748842 promoter polymorphisms by allelic discrimination with real-time polymerase chain reaction (PCR). We compared cognitive outcome, P300 amplitude parameters and an electroencephalographic measure of noise power in the gamma band between the groups dichotomized according to genotype. Results Contrary to our hypothesis, we could not detect any significant influence of variation in Neuregulin 1/Neuregulin 3 polymorphisms on cognitive performance or electrophysiological parameters of patients with schizophrenia. Conclusions Despite our findings, we cannot discard that other genetic variants and, more likely, interactions between those variants and with genetic variation related to different pathways may still influence cerebral processing in schizophrenia.
    Full-text · Article · Jun 2014 · Annals of General Psychiatry
    • "rs6994992/SNP8NRG243177 and rs35753505/ SNP8NRG221533 located in the promoter region were first identified as the core at-risk haplotype (HAP ICE ) in schizophrenic families of Iceland (Stefansson et al., 2002). rs6994992 is known to be a functional polymorphism associated with type IV isoform messenger RNA expression and modification of NRG1 signaling (Law et al., 2006; Tan et al., 2007; Shamir and Buonanno, 2010). Thus, both of the SNPs might affect cognitive ability through the regulation of NRG1 expression. "
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    ABSTRACT: The neuregulin 1 (NRG1) gene has been investigated as a candidate susceptibility gene for schizophrenia. A number of studies have also explored the genetic effect of NRG1 on cognitive deficits related to schizophrenia, and thus far generated inconsistent results. The current study aimed to determine whether genetic variations in NRG1 are associated with cognitive domains in schizophrenic patients and healthy individuals. Comprehensive neuropsychological tests composed of six cognitive domains were administered to 135 clinically stable patients with schizophrenia and 119 healthy individuals. On the basis of previous reports of positive association, a total of four single nucleotide polymorphisms were analyzed. In testing the genotype effect on cognitive domains, we used repeated-measure analysis for six cognitive domain scores of each individual as repeated measurements. An association of P-value less than 0.05 with at least one cognitive domain in patients and/or healthy individuals was observed for all of the single nucleotide polymorphisms. After applying the correction for multiple testing, the association remained statistically significant between rs6994992 and general cognitive ability (g) in the patient group and between rs2439272 and the 'working memory' domain in the group of healthy participants. This study suggests the involvement of NRG1 in the susceptibility for developing cognitive deficits in schizophrenic patients. For some cognitive domains, its genetic effect was also significant in generating interindividual variability within the normal functional range.
    No preview · Article · Apr 2014 · Schizophrenia Research
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    • "Several studies have focused on the signaling protein NRG1 and its receptor ERRB4. A variety of NRG1 isoforms (estimated n =30) are produced by alternative splicing (Tan et al., 2007; Liu et al., 2011). They are expressed in varying proportions at relatively high levels in a variety of peripheral tissues as well as the brain. "
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    ABSTRACT: Background: Neuregulin-1 (NRG1) gene polymorphisms have been proposed as risk factors for several common disorders. Associations with cognitive variation have also been tested. With regard to schizophrenia (SZ) risk, studies of Caucasian ancestry samples indicate associations more consistently than East Asian samples, suggesting heterogeneity. To exploit the differences in linkage disequilibrium (LD) structure across ethnic groups, we conducted a SZ case-control study (that included cognitive evaluations) in a sample from the north Indian population. Methods: NRG1 variants (n=35 SNPs, three microsatellite markers) were initially analyzed among cases (DSM IV criteria, n=1007) and controls (n=1019, drawn from two groups) who were drawn from the same geographical region in North India. Nominally significant associations with SZ were next analyzed in relation to neurocognitive measures estimated with a computerized neurocognitive battery in a subset of the sample (n=116 cases, n=170 controls). Results: Three variants and one microsatellite showed allelic association with SZ (rs35753505, rs4733263, rs6994992, and microsatellite 420M9-1395, p≤0.05 uncorrected for multiple comparisons). A six marker haplotype 221121 (rs35753505-rs6994992-rs1354336-rs10093107-rs3924999-rs11780123) showed (p=0.0004) association after Bonferroni corrections. Regression analyses with the neurocognitive measures showed nominal (uncorrected) associations with emotion processing and attention at rs35753505 and rs6994992, respectively. Conclusions: Suggestive associations with SZ and SZ-related neurocognitive measures were detected with two SNPs from the NRG1 promoter region in a north Indian cohort. The functional role of the alleles merits further investigation.
    Full-text · Article · Jan 2013 · Schizophrenia Research
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