Structure, organization, and chromosomal mapping of the human neurogranin gene (NRGN)

The diagnostic and prognostic value of serum neurogranin in acute ischemic stroke

OBJECTIVES

Stroke is a frequently encountered life-threatening medical condition in emergency departments (EDs). Despite all worldwide efforts, a reliable circulating biomarker has not been identified yet. This study investigates the diagnostic and prognostic value of neurogranin (Ng) in acute ischemic stroke (AIS).

METHODS

This prospective case-control study was conducted on ED patients with AIS and healthy volunteers. We collected the basic demographics, measured serum Ng levels of the patients vs. controls, and followed up the patient group for 6-month by phone or clinical notes to assess the functional outcomes.

RESULTS

Data analysis was completed with 142 subjects (86 patients vs. 55 controls). The groups did not differ in terms of age and gender. The median serum Ng level of the patient group was significantly higher compared to the control group [160.00 (75.93) vs. 121.26 (90.35) ng/mL and p ˂ 0.001, respectively]. Serum Ng level of 25 patients admitted to the ED within the first 6 hours from the onset of AIS was 177.93 (24.03) ng/mL, while serum Ng level of 61 patients admitted to the ED within 6-24 hours was 131.84 (76.44) ng/mL. AUROC results were 0.717 vs. 0.868 vs. 0.874 for stroke patients admitted during the first 24 hours, 6 hours, and 4.5 hours after the onset, respectively. Lesion volume, NIHSS, and modified Rankin Scale scores (mRS) at admission showed no significant correlation with Ng levels as well as 6-month mortality and 6-month mRS.

CONCLUSIONS

Timely AIS diagnosis is still a challenge for emergency departments due to the dependency on imaging. Serum Ng can be a promising diagnostic biomarker for AIS patients admitted in the first 24 hours. Even it outperformed in the first 4.5 and 6-hour time windows. However, it did not show a significant prognostic value.

Neurogranin in Alzheimer's disease and ageing: A human post-mortem study

Neurogranin (Ng), a post-synaptic protein involved in memory formation, has been investigated as a biomarker in the cerebrospinal fluid (CSF) in Alzheimer's disease (AD) and ageing. CSF Ng levels are elevated in AD relative to healthy controls and correlate with cognition; however, few studies have focused on Ng abundance in the brain. Synapse loss in the brain correlates closely with cognitive decline in AD making synaptic biomarkers potentially important for tracking disease progression, but the links between synaptic protein changes in CSF and brain remain incompletely understood. In the current study, Ng abundance was examined in post-mortem human brain tissue across AD, healthy ageing (HA), and mid-life (ML) cohorts. Ng levels were quantified in three brain regions associated with cognitive change found during ageing and neurodegenerative diseases, namely the middle temporal gyrus, primary visual cortex and the posterior hippocampus using immunohistochemistry. To support immunohistochemical analysis, total homogenate and biochemically enriched synaptic fractions from available temporal gyrus tissues were examined by immunoblot. Finally, we examined whether Ng is associated with lifetime cognitive ageing. Ng levels were significantly reduced in AD relative to HA and ML cases across all regions. Additionally Ng was significantly reduced in HA in comparison to ML in the primary visual cortex. Immunoblotting confirms reduced Ng levels in AD cases supporting immunohistochemical results. Interestingly, there was also a significant reduction of synapse-associated Ng in our group who had lifetime cognitive decline in comparison to the group with lifetime cognitive resilience indicating loss of neurogranin in remaining synapses during ageing is associated with cognitive decline. Our findings indicate that increases in CSF Ng reflect loss of brain neurogranin and support the use of CSF Ng as a biomarker of AD and potentially of cognitive decline in healthy ageing.

Neurogranin-like immunoreactivity in the zebrafish brain during development

Neurogranin (Nrgn) is a neural protein that is enriched in the cerebral cortex and is involved in synaptic plasticity via its interaction with calmodulin. Recently we reported its expression in the brain of the adult zebrafish (Alba-González et al. J Comp Neurol 530:1569–1587, 2022). In this study we analyze the development of Nrgn-like immunoreactivity (Nrgn-like-ir) in the brain and sensory structures of zebrafish embryos and larvae, using whole mounts and sections. First Nrgn-like positive neurons appeared by 2 day post-fertilization (dpf) in restricted areas of the brain, mostly in the pallium, epiphysis and hindbrain. Nrgn-like populations increased noticeably by 3 dpf, reaching an adult-like pattern in 6 dpf. Most Nrgn-like positive neurons were observed in the olfactory organ, retina (most ganglion cells, some amacrine and bipolar cells), pallium, lateral hypothalamus, thalamus, optic tectum, torus semicircularis, octavolateralis area, and viscerosensory column. Immunoreactivity was also observed in axonal tracts originating in Nrgn-like neuronal populations, namely, the projection of Nrgn-like immunopositive primary olfactory fibers to olfactory glomeruli, that of Nrgn-like positive pallial cells to the hypothalamus, the Nrgn-like-ir optic nerve to the pretectum and optic tectum, the Nrgn-like immunolabeled lateral hypothalamus to the contralateral region via the horizontal commissure, the octavolateralis area to the midbrain via the lateral lemniscus, and the viscerosensory column to the dorsal isthmus via the secondary gustatory tract. The late expression of Nrgn in zebrafish neurons is probably related to functional maturation of higher brain centers, as reported in the mammalian telencephalon. The analysis of Nrgn expression in the zebrafish brain suggests that it may be a useful marker for specific neuronal circuitries.

All-trans Retinoic Acid has Limited Therapeutic Effects on Cognition and Hippocampal Protein Expression After Controlled Cortical Impact

Traumatic brain injury (TBI) is known to impair synaptic function, and subsequently contribute to observed cognitive deficits. Retinoic Acid (RA) signaling modulates expression of synaptic plasticity proteins and is involved in hippocampal learning and memory. All trans-retinoic acid (ATRA), a metabolite of Vitamin A, has been identified as a potential pharmacotherapeutic for other neurological disorders due to this role. This study conducted an ATRA dose response to determine its therapeutic effects on cognitive behaviors and expression of hippocampal markers of synaptic plasticity and RA signaling proteins after experimental TBI. Under isoflurane anesthesia, adult male Sprague Dawley rats received either controlled cortical impact (CCI, 2.5 mm deformation, 4 m/s) or control surgery. Animals received daily intraperitoneal injection of 0.5, 1, 5, or 10 mg/kg of ATRA or vehicle for 2 weeks. Animals underwent motor and spatial learning and memory testing. Hippocampal expression of synaptic plasticity proteins neurogranin (Ng), and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor GluA1 sub-unit, as well as RA signaling proteins STRA6, ADLH1a1, CYP26A1 and CYP26B1 were evaluated by western blot at 2-weeks post-injury. ATRA treatment significantly recovered Ng synaptic protein expression, while having no effect on motor performance, spatial learning, and memory, and GluA1 expression after TBI. RA signaling protein expression is unchanged 2 weeks after TBI. Overall, ATRA administration after TBI showed limited therapeutic benefits compared to the vehicle.

Neurogranin: A Potential Biomarker of Neurological and Mental Diseases

Neurogranin (Ng) is a small protein usually expressed in granule-like structures in pyramidal cells of the hippocampus and cortex. However, its clinical value is not fully clear so far. Currently, Ng is proved to be involved in synaptic plasticity, synaptic regeneration, and long-term potentiation mediated by the calcium- and calmodulin-signaling pathways. Due to both the synaptic integrity and function as the growing concerns in the pathogenesis of a wide variety of neurological and mental diseases, a series of researches published focused on the associations between Ng and these kinds of diseases in the past decade. Therefore, in this review, we highlight several diseases, which include, but are not limited to, Alzheimer’s disease, Parkinson disease, Creutzfeldt–Jakob disease, neuro-HIV, neurosyphilis, schizophrenia, depression, traumatic brain injury, and acute ischemic stroke, and summarize the associations between cerebrospinal fluid or blood-derived Ng with these diseases. We propose that Ng is a potential and promising biomarker to improve the diagnosis, prognosis, and severity evaluation of these diseases in the future.

Association between NRGN gene polymorphism and resting-state hippocampal functional connectivity in schizophrenia

BACKGROUND

Based on genome-wide association studies, a single-nucleotide polymorphism in the NRGN gene (rs12807809) is considered associated with schizophrenia (SZ). Moreover, hippocampal dysfunction is associated with rs12807809. In addition, converging evidence suggests that hippocampal dysfunction is involved in SZ pathophysiology. However, the association among rs12807809, hippocampal dysfunction and SZ pathophysiology is unknown. Therefore, this study investigated the association between rs12807809 and hippocampal functional connectivity at rest in SZ.

METHODS

In total, 158 participants were studied, including a C-carrier group carrying the non-risk C allele (29 SZ patients and 46 healthy controls) and a TT homozygous group carrying the risk T allele (30 SZ patients and 53 healthy controls). All participants were scanned using resting-state functional magnetic resonance imaging. Hippocampal functional connectivity was computed and compared among the 4 groups.

RESULTS

Significant main effects of diagnosis were observed in the functional connectivity between the hippocampus and bilateral fusiform gyrus, bilateral lingual gyrus, left inferior temporal gyrus, left caudate nucleus, bilateral thalamus and bilateral anterior cingulate gyri. In contrast, no significant main effect of genotype was found. In addition, a significant genotype by diagnosis interaction in the functional connectivity between the hippocampus and left anterior cingulate gyrus, as well as bilateral middle cingulate gyri, was observed, with TT homozygotes with SZ showing less functional connectivity than C-carriers with SZ and healthy control TT homozygotes.

CONCLUSIONS

These findings are the first to suggest an association between rs12807809 and abnormal Papez circuit function in patients with SZ. This study also implicates NRGN variation and abnormal Papez circuit function in SZ pathophysiology.

Mass spectrometry imaging shows major derangements in neurogranin and in purine metabolism in the triple-knockout 3×Tg Alzheimer mouse model

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI) can simultaneously measure hundreds of biomolecules directly from tissue. Using different sample preparation strategies, proteins and metabolites have been profiled to study the molecular changes in a 3×Tg mouse model of Alzheimer's disease. In comparison with wild-type (WT) control mice MALDI-MSI revealed Alzheimer's disease-specific protein profiles, highlighting dramatic reductions of a protein with m/z 7560, which was assigned to neurogranin and validated by immunohistochemistry. The analysis also revealed substantial metabolite changes, especially in metabolites related to the purine metabolic pathway, with a shift towards an increase in hypoxanthine/xanthine/uric acid in the 3×Tg AD mice accompanied by a decrease in AMP and adenine. Interestingly these changes were also associated with a decrease in ascorbic acid, consistent with oxidative stress. Furthermore, the metabolite N-arachidonyl taurine was increased in the diseased mouse brain sections, being highly abundant in the hippocampus. Overall, we describe an interesting shift towards pro-inflammatory molecules (uric acid) in the purinergic pathway associated with a decrease in anti-oxidant level (ascorbic acid). Together, these observations fit well with the increased oxidative stress and neuroinflammation commonly observed in AD. This article is part of a Special Issue entitled: MALDI Imaging, edited by Dr. Corinna Henkel and Prof. Peter Hoffmann.

Serum neurogranin measurement as a biomarker of acute traumatic brain injury

OBJECTIVES

Neurogranin (NRGN) is a small neuronal protein that plays an important role in synaptic signaling by regulating calmodulin (CaM) availability. In this study, we developed an ELISA to measure NRGN quantitatively in serum samples from a cohort of acute traumatic brain injury (TBI) patients and a non-TBI control cohort, and explored the potential value of NRGN as a circulating biomarker for TBI.

DESIGN AND METHODS

Recombinant His-NRGN protein was used to develop mouse monoclonal capture and rabbit polyclonal detection antibodies, and they were used to develop a sandwich ELISA. After validation, we used this ELISA to measure serum samples from a cohort of typical adult acute TBI patients (N=76 TBI cases) and non-TBI control patients (N=150 controls).

RESULTS

The NRGN ELISA lower limit of detection was 0.055ng/mL, lower limit of quantification was 0.2ng/mL, and interassay CVs were ≤10.7%. The average recovery was 99.9% (range from 97.2-102%). Serum NRGN concentrations in TBI cases were significantly higher than in controls (median values were 0.18ng/mL vs. 0.02ng/mL, p<0.0001), but did not discriminate TBI cases with intracranial hemorrhage (p=0.09).

CONCLUSIONS

We have developed a highly sensitive and reproducible ELISA for measuring circulating NRGN in blood samples. Serum NRGN concentrations in acute TBI patients were significantly higher than in controls, indicating that NRGN could have utility as a circulating biomarker for acute TBI. This report provides evidence to support larger and controlled TBI clinical studies for NRGN validation and prediction of outcomes.

Effects of the neurogranin variant rs12807809 on thalamocortical morphology in schizophrenia

Although the genome wide supported psychosis susceptibility neurogranin (NRGN) gene is expressed in human brains, it is unclear how it impacts brain morphology in schizophrenia. We investigated the influence of NRGN rs12807809 on cortical thickness, subcortical volumes and shapes in patients with schizophrenia. One hundred and fifty six subjects (91 patients with schizophrenia and 65 healthy controls) underwent structural MRI scans and their blood samples were genotyped. A brain mapping algorithm, large deformation diffeomorphic metric mapping, was used to perform group analysis of subcortical shapes and cortical thickness. Patients with risk TT genotype were associated with widespread cortical thinning involving frontal, parietal and temporal cortices compared with controls with TT genotype. No volumetric difference in subcortical structures (hippocampus, thalamus, amygdala, basal ganglia) was observed between risk TT genotype in patients and controls. However, patients with risk TT genotype were associated with thalamic shape abnormalities involving regions related to pulvinar and medial dorsal nuclei. Our results revealed the influence of the NRGN gene on thalamocortical morphology in schizophrenia involving widespread cortical thinning and thalamic shape abnormalities. These findings help to clarify underlying NRGN mediated pathophysiological mechanisms involving cortical-subcortical brain networks in schizophrenia.

Influence of the NRGN gene on intellectual ability in schizophrenia

Genome-wide association studies have reported an association between schizophrenia and rs12807809 of the neurogranin (NRGN) gene. We have recently found that an rs12807809-rs12278912 haplotype of the gene is associated with schizophrenia in a Japanese population and that the NRGN expression of the high-risk TG haplotype is lower than that of the protective TA haplotype in immortalized lymphoblasts. In this study, we investigated the influences of neurogranin genotypes (rs12807809 and rs12278912), haplotypes and diplotypes and genetic variant-diagnosis interactions on intellectual ability in 414 Japanese patients with schizophrenia and healthy subjects. We detected possible effects of the genome-wide screen-supported rs12807809, haplotypes, diplotypes and their genetic variant-diagnosis interactions on intellectual abilities at the threshold level of P<0.05. After applying Bonferroni correction for 13 genotype measures and setting P-values for significance (P<0.0039; 0.05/13), three effects remained significant: the rs12807809-rs12278912 diplotype-diagnosis interactions on performance intelligence quotient (CG/CG: P=3.9 × 10(-13); TA/TA: P=1.1 × 10(-7)) and TA/TA diplotype on performance intelligence quotient in patients with schizophrenia (P=8.2 × 10(-8)) remained significant. The intellectual abilities of the high-risk TG/TG diplotype of the neurogranin gene were lower compared to those with the non-risk TA/TA diplotype. Our findings suggest that the genetic risk variant in the neurogranin gene may be related to reduced intellectual ability.

The effect of neurogranin on neural correlates of episodic memory encoding and retrieval

Neurogranin (NRGN) is the main postsynaptic protein regulating the availability of calmodulin-Ca(2+) in neurons. NRGN is expressed exclusively in the brain, particularly in dendritic spines and has been implicated in spatial learning and hippocampal plasticity. Genetic variation in rs12807809 in the NRGN gene has recently been confirmed to be associated with schizophrenia in a meta-analysis of genome-wide association studies: the T-allele was found to be genome-wide significantly associated with schizophrenia. Cognitive tests and personality questionnaires were administered in a large sample of healthy subjects. Brain activation was measured with functional magnetic resonance imaging (fMRI) during an episodic memory encoding and retrieval task in a subsample. All subjects were genotyped for NRGN rs12807809. There was no effect of genotype on personality or cognitive measures in the large sample. Homozygote carriers of the T-allele showed better performance in the retrieval task during fMRI. After controlling for memory performance, differential brain activation was evident in the anterior cingulate cortex for the encoding and posterior cingulate regions during retrieval. We could demonstrate that rs12807809 of NRGN is associated with differential neural functioning in the anterior and posterior cingulate. These areas are involved in episodic memory processes and have been implicated in the pathophysiology of schizophrenia in structural and functional imaging as well as postmortem studies.

The effect of the neurogranin schizophrenia risk variant rs12807809 on brain structure and function

A single nucleotide polymorphism rs12807809 located upstream of the neurogranin (NRGN) gene has been identified as a risk variant for schizophrenia in recent genome-wide association studies. To date, there has been little investigation of the endophenotypic consequences of this variant, and our own investigations have suggested that the effects of this gene are not apparent at the level of cognitive function in patients or controls. Because the impact of risk variants may be more apparent at the level of brain, the aim of this investigation was to delineate whether NRGN genotype predicted variability in brain structure and/or function. Healthy individuals participated in structural (N = 140) and/or functional (N = 36) magnetic resonance imaging (s/fMRI). Voxel-based morphometry was used to compare gray and white matter volumes between carriers of the non-risk C allele (i.e., CC/CT) and those who were homozygous for the risk T allele. Functional imaging data were acquired during the performance of a spatial working memory task, and were also analyzed with respect to the difference between C carriers and T homozygotes. There was no effect of the NRGN variant rs12807809 on behavioral performance or brain structure. However, there was a main effect of genotype on brain activity during performance of the working memory task, such that while C carriers exhibited a load-independent decrease in left superior frontal gyrus/BA10, TT individuals failed to show a similar decrease in activity. The failure to disengage this ventromedial prefrontal region, despite preserved performance, may be indicative of a reduction in processing efficiency in healthy TT carriers. Although it remains to be established whether this holds true in larger samples and in patient cohorts, if valid, this suggests a potential mechanism by which NRGN variability might contribute to schizophrenia risk.

Functional genetic variation at the NRGN gene and schizophrenia: evidence from a gene-based case-control study and gene expression analysis

Genome-wide association and follow-up studies have reported an association between schizophrenia and rs12807809 of the NRGN gene on chromosome 11q24.2. We investigated the association of five linkage disequilibrium-tagging SNPs and haplotypes that cover the NRGN gene with schizophrenia in a Japanese sample of 2,019 schizophrenia patients and 2,574 controls to determine whether rs12807809 is the most strongly associated variant for schizophrenia in the vicinity of the NRGN gene. We found that the rs12807809-rs12278912 haplotype of the NRGN gene was associated with schizophrenia (global P = 0.0042). The frequencies of the TG and TA haplotypes of rs12807809-rs12278912 in patients were higher (OR = 1.14, P = 0.0019) and lower (OR = 0.85, P = 0.0053), respectively, than in the controls. We did not detect any evidence of association of schizophrenia with any SNPs; however, two nominal associations of rs12278912 (OR = 1.10, P = 0.057) and rs2075713 (OR = 1.10, P = 0.057) were observed. Furthermore, we detected an association between the rs12807809-rs12278912 haplotype and NRGN expression in immortalized lymphoblasts derived from 45 HapMap JPT subjects (z = 2.69, P = 0.007) and confirmed the association in immortalized lymphoblasts derived from 42 patients with schizophrenia and 44 healthy controls (z = 3.09, P = 0.002). The expression of the high-risk TG haplotype was significantly lower than the protective TA haplotype. The expression was lower in patients with schizophrenia than in controls; however, this difference was not statistically significant. This study provides further evidence of the association of the NRGN gene with schizophrenia, and our results suggest that there is a link between the TG haplotype of rs12807809-rs12278912, decreased expression of NRGN and risk of developing schizophrenia.

Genetic and functional analysis of the gene encoding neurogranin in schizophrenia

OBJECTIVES

Schizophrenia is a highly heritable disorder, but many aspects of its etiology and pathophysiology remain poorly understood. Recently, a SNP rs12807809 located upstream of the neurogranin (NRGN) gene achieved genome-wide significance in this disorder.

METHODS

In order to find the causal variants of NRGN gene in schizophrenia, we searched for genetic variants in the promoter region and all the exons (including both UTR ends and rs12807809) using direct sequencing in a sample of patients with schizophrenia (n=346) and non-psychotic controls (n=345), both being Han Chinese from Taiwan, and conducted an association and functional study.

RESULTS

We identified 7 common polymorphisms in the NRGN gene. SNP and haplotype-based analyses displayed no associations with schizophrenia. Additionally, we identified 5 rare variants in 6 out of 346 patients, including 3 rare variants located at the promoter region (g.-620A>G, g.-578C>G, and g.-344G>A) and 2 rare variants located at 5' UTR (c.-74C>G, and c.-41G>A). No rare variants were found in the control subjects. The results of the reporter gene assay demonstrated that the regulatory activity of construct containing g.-620G, g.-578G, g.-344A, c.-74G, and c.-41A was significantly lower as compared to the wild type construct (P<0.01 for g.-578G; P<0.001 for the other constructs). In silico analysis also demonstrated their influences on the regulatory function of NRGN gene.

CONCLUSIONS

Our study lends support to the hypothesis of multiple rare mutations in schizophrenia, and provides genetic clues that indicate the involvement of NRGN in this disorder.

Impact of the genome wide supported NRGN gene on anterior cingulate morphology in schizophrenia

Background

The rs12807809 single-nucleotide polymorphism in NRGN is a genetic risk variant with genome-wide significance for schizophrenia. The frequency of the T allele of rs12807809 is higher in individuals with schizophrenia than in those without the disorder. Reduced immunoreactivity of NRGN, which is expressed exclusively in the brain, has been observed in Brodmann areas (BA) 9 and 32 of the prefrontal cortex in postmortem brains from patients with schizophrenia compared with those in controls.

Methods

Genotype effects of rs12807809 were investigated on gray matter (GM) and white matter (WM) volumes using magnetic resonance imaging (MRI) with a voxel-based morphometry (VBM) technique in a sample of 99 Japanese patients with schizophrenia and 263 healthy controls.

Results

Although significant genotype-diagnosis interaction either on GM or WM volume was not observed, there was a trend of genotype-diagnosis interaction on GM volume in the left anterior cingulate cortex (ACC). Thus, the effects of NRGN genotype on GM volume of patients with schizophrenia and healthy controls were separately investigated. In patients with schizophrenia, carriers of the risk T allele had a smaller GM volume in the left ACC (BA32) than did carriers of the non-risk C allele. Significant genotype effect on other regions of the GM or WM was not observed for either the patients or controls.

Conclusions

Our findings suggest that the genome-wide associated genetic risk variant in the NRGN gene may be related to a small GM volume in the ACC in the left hemisphere in patients with schizophrenia.

A serial analysis of gene expression profile of the Alzheimer's disease Tg2576 mouse model

Serial analysis of gene expression (SAGE), a technique that allows for the simultaneous detection of expression levels of the entire genome without a priori knowledge of gene sequences, was used to examine the transcriptional expression pattern of the Tg2576 mouse model of Alzheimer's disease (AD). Pairwise comparison between the Tg2576 and nontransgenic SAGE libraries identified a number of differentially expressed genes in the Tg2576 SAGE library, some of which were not previously revealed by the microarray studies. Real-time PCR was used to validate a panel of genes selected from the SAGE analysis in the Tg2576 mouse brain, as well as the hippocampus and temporal cortex of sporadic AD and normal age-matched controls. NADH dehydrogenase (ubiquinone) 1 alpha subcomplex 5 (NDUFA5) and FXYD domain-containing ion transport regulator 6 (FXYD6) were found to be significantly decreased in the Tg2576 mouse brain and AD hippocampus. PTEN-induced putative kinase 1 (PINK1), phosphatidylethanolamine binding protein (PEBP), crystalline mu (CRYM), and neurogranin (NRGN) were significantly decreased in AD tissues. The gene ontologies represented in the Tg2576 data were statistically analyzed and demonstrated a significant under-representation of genes involved with G-protein-coupled receptor signaling and odorant binding, while genes significantly over-represented were focused on cellular communication and cellular physiological processes. The novel approach of profiling the Tg2576 mouse brain using SAGE has identified different genes that could subsequently be examined for their potential as peripheral diagnostic and prognostic markers for Alzheimer's disease.

Activation of the brain-specific neurogranin gene in murine T-cell lymphomas by proviral insertional mutagenesis

Neurogranin (Nrgn) is a highly expressed brain-specific protein, which sequesters calmodulin at low Ca(2+)-levels. We report here on retroviral activation of the Nrgn gene in tumors induced by the T-cell lymphomagenic SL3-3 murine leukemia virus. We have performed a systematic expression analysis of Nrgn in various mouse tissues and SL3-3 induced T-cell tumors. This demonstrated that insertional activation of Nrgn increased RNA and protein expression levels to that observed in brain. Furthermore, elevated Nrgn expression was also observed in some T-cell tumors with no detected provirus integrations into this genomic region. The presented data demonstrate that Nrgn can be produced at high levels outside the brain, and suggest a novel oncogenic role in T-cell lymphomas in mice.

Multiple expressed MHC class II loci in salmonids; details of one non-classical region in Atlantic salmon (Salmo salar)

Background

In teleosts, the Major Histocompatibility Complex (MHC) class I and class II molecules reside on different linkage groups as opposed to tetrapods and shark, where the class I and class II genes reside in one genomic region. Several teleost MHC class I regions have been sequenced and show varying number of class I genes. Salmonids have one major expressed MHC class I locus (UBA) in addition to varying numbers of non-classical genes. Two other more distant lineages are also identifyed denoted L and ZE. For class II, only one major expressed class II alpha (DAA) and beta (DAB) gene has been identified in salmonids so far.

Results

We sequenced a genomic region of 211 kb encompassing divergent MHC class II alpha (Sasa-DBA) and beta (Sasa-DBB) genes in addition to NRGN, TIPRL, TBCEL and TECTA. The region was not linked to the classical class II genes and had some synteny to genomic regions from other teleosts. Two additional divergent and expressed class II sequences denoted DCA and DDA were also identified in both salmon and trout. Expression patterns and lack of polymorphism make these genes non-classical class II analogues. Sasa-DBB, Sasa-DCA and Sasa-DDA had highest expression levels in liver, hindgut and spleen respectively, suggestive of distinctive functions in these tissues. Phylogenetic studies revealed more yet undescribed divergent expressed MHC class II molecules also in other teleosts.

Conclusion

We have characterised one genomic region containing expressed non-classical MHC class II genes in addition to four other genes not involved in immune function. Salmonids contain at least two expressed MHC class II beta genes and four expressed MHC class II alpha genes with properties suggestive of new functions for MHC class II in vertebrates. Collectively, our data suggest that the class II is worthy of more elaborate studies also in other teleost species.

Association of the gene encoding neurogranin with schizophrenia in males

The neurogranin (NRGN) gene produces a postsynaptic brain-specific protein that regulates calmodulin-Ca(2+) availability in neurons. Acting downstream of the NMDA receptor and upstream of calcineurin and other proteins implicated in schizophrenia, NRGN is a good candidate for association studies in schizophrenia. NRGN expression is regulated during development and is modulated by thyroid hormones and retinoids, molecules essential for the proper development of the central nervous system. Given the genetic complexity of schizophrenia and the potential genetic heterogeneity in different populations, we studied a possible association of NRGN with schizophrenia in 73 Azorean proband-parent triads and in two independent case-control samples from the Portuguese-mainland (244 schizophrenic and 210 controls) and Brazil (69 schizophrenic and 85 mentally healthy individuals). Genotype distribution showed association of the rs7113041 SNP with schizophrenia in males of Portuguese origin, which was confirmed by the analysis of the proband-parent triads. This evidence, implicating NRGN in schizophrenia, introduces another player into the glutamatergic hypothesis of schizophrenia.

Involvement of the GC-rich sequence and specific proteins (Sp1/Sp3) in the basal transcription activity of neurogranin gene

Neurogranin (Ng), a neuronal protein implicated in learning and memory, contains a TATA-less promoter. Analysis of 5'-deletion mutations and site-directed mutations of the mouse Ng promoter revealed that a 258bp 5'-flanking sequence (+3 to +260) conferred the basal transcription activity, and that the GC-rich sequence (+22 to +33) served as an important determinant of the promoter activity. Transient transfection of the Sp1 expression plasmid transactivated the reporter activity in neuroblastoma N2A cells while knocking down of endogenous Sp1 expression resulted in a 2.5-fold reduction of the reporter activity in HEK 293 cells. Exogenous expression of Sp3 in HEK 293 cells, however, repressed the reporter activity by 50%. Nevertheless, by gel shift assays, Sp1 and Sp3 were not found to be responsible for the protein-DNA complexes formed by the GC-rich sequence. Moreover, a nuclear factor from the mouse brain tissues was discovered to bind to multiple AT-rich regions in Ng promoter.

Environmental perchlorate: why it matters

The only known mechanism of toxicity for perchlorate is interference with iodide uptake at the sodium-iodide symporter (NIS). The NIS translocates iodide across basolateral membranes to the thyroid gland so it can be used to form thyroid hormones (TH). NIS is also expressed in the mammary gland during lactation, so that iodide can be transferred from a mother to her child. Without adequate iodide, an infant cannot produce sufficient TH to meet its developmental needs. Effects expected from perchlorate are those that would be seen in conditions of hypothyroidism or hypothyroxinemia. The probability of a permanent adverse effect is greatest during early life, as successful neurodevelopment is TH-dependent. Study of perchlorate risk is complicated by a number of factors including thyroid status of the mother during gestation, thyroid status of the fetus, maternal and infant iodine intake, and exposure of each to other TH-disrupting chemicals. Perhaps the greatest standing issue, and the issue most relevant to the field of analytical chemistry, is the simple fact that human exposure has not been quantified. This review will summarize perchlorate's potential to adversely affect neurodevelopment. Whether current environmental exposures to perchlorate contribute to neuro-impairment is unknown. Risks posed by perchlorate must be considered in conjunction with iodine intake.

RC3/neurogranin is expressed in pyramidal neurons of motor and somatosensory cortex in normal and denervated monkeys

RC3/neurogranin is a neuron-specific calpacitin located in the cytoplasm and, especially, in dendrites and dendritic spines of cortical neurons, involved in many aspects of excitatory transmission and long-term potentiation. We investigated RC3 expression in pyramidal cortical neurons and interneurons of the motor and somatosensory cortex of normal Macaca fascicularis by means of double immunofluorescence and with techniques that combine immunohistochemistry and radioactive in situ hybridization. We show that RC3 is expressed in virtually all pyramidal neurons and spiny stellate neurons of neocortical areas 4, 3b, 1, 2, 5, 7, and SII, but not in the majority of cortical interneurons. RC3 protein and mRNA are tightly colocalized with the alpha subunit of CaM kinase II and the 200-kD, nonphosphorylated neurofilament, whereas they are absent from cells expressing the 27-kD, vitamin D-dependent calbindin and parvalbumin. In order to investigate possible activity-dependent regulation of the expression of RC3, we compared these results with those obtained from monkeys subjected to chronic peripheral cutaneous denervation of the first finger. We found that the pattern of distribution of RC3 in motor and somatosensory cortices after nerve cut did not differ from normal.

Transcript profiling of human platelets using microarray and serial analysis of gene expression

Human platelets are anucleate blood cells that retain cytoplasmic mRNA and maintain functionally intact protein translational capabilities. We have adapted complementary techniques of microarray and serial analysis of gene expression (SAGE) for genetic profiling of highly purified human blood platelets. Microarray analysis using the Affymetrix HG-U95Av2 approximately 12 600-probe set maximally identified the expression of 2147 (range, 13%-17%) platelet-expressed transcripts, with approximately 22% collectively involved in metabolism and receptor/signaling, and an overrepresentation of genes with unassigned function (32%). In contrast, a modified SAGE protocol using the Type IIS restriction enzyme MmeI (generating 21-base pair [bp] or 22-bp tags) demonstrated that 89% of tags represented mitochondrial (mt) transcripts (enriched in 16S and 12S ribosomal RNAs), presumably related to persistent mt-transcription in the absence of nuclear-derived transcripts. The frequency of non-mt SAGE tags paralleled average difference values (relative expression) for the most "abundant" transcripts as determined by microarray analysis, establishing the concordance of both techniques for platelet profiling. Quantitative reverse transcription-polymerase chain reaction (PCR) confirmed the highest frequency of mt-derived transcripts, along with the mRNAs for neurogranin (NGN, a protein kinase C substrate) and the complement lysis inhibitor clusterin among the top 5 most abundant transcripts. For confirmatory characterization, immunoblots and flow cytometric analyses were performed, establishing abundant cell-surface expression of clusterin and intracellular expression of NGN. These observations demonstrate a strong correlation between high transcript abundance and protein expression, and they establish the validity of transcript analysis as a tool for identifying novel platelet proteins that may regulate normal and pathologic platelet (and/or megakaryocyte) functions.

Molecular analysis of the GCF gene identifies revisions to the cDNA and amino acid sequences(1)

GC factor (GCF) was reported as a transcriptional regulator that binds to a specific GC-rich sequence in the epidermal growth factor receptor (EGFR) gene promoter and represses its expression. In this paper, we present the data on three revisions of the cDNA sequence that lead to significant changes of the amino acid sequences of the published GCF. Firstly, 5'-rapid amplification of cDNA end (5'-RACE) analysis revealed that the 308 nucleotides of 5'-end of the previously published GCF cDNA does not exist at the 5'-end of the RACE product. Simultaneously, the correct 5'-end cDNA sequence of 31 nucleotides was identified. Secondly, the 'T' at the position 787 of the published GCF cDNA was not observed. Finally, a new sequence of 114 nucleotides was identified between the positions 851 and 852 of the published cDNA sequence. The revisions result in a GCF cDNA of 2661 nucleotides that encodes a protein of 781 amino acids, replacing the highly basic region of the amino-terminus of the published GCF with a new sequence of 147 amino acids. In this era of massive gene cloning and sequencing, this study is a warning to the biological research of recent years.

The human RC3 gene homolog, NRGN contains a thyroid hormone-responsive element located in the first intron

NRGN is the human homolog of the neuron-specific rat RC3/neurogranin gene. This gene encodes a postsynaptic 78-amino acid protein kinase substrate that binds calmodulin in the absence of calcium, and that has been implicated in dendritic spine formation and synaptic plasticity. In the rat brain RC3 is under thyroid hormone control in specific neuronal subsets in both developing and adult animals. To evaluate whether the human gene is also a target of thyroid hormone we have searched for T3-responsive elements in NRGN cloned genomic fragments spanning the whole gene. Labeled DNA fragments were incubated with T3 receptors (T3R) and 9-cis-retinoic acid receptors and immunoprecipitated using an anti T3R antibody. A receptor-binding site was localized in the first intron, 3000 bp downstream from the origin of transcription. Footprinting analysis revealed the sequence GGATTAAATGAGGTAA, closely related to the consensus T3-responsive element of the direct repeat (DR4) type. This sequence binds the T3R-9-cis-retinoic acid receptors heterodimers, but not T3R monomers or homodimers, and is able to confer regulation by T3R and T3 when fused upstream of the NRGN or thymidine kinase promoters. The data reported in this work suggest that NRGN is a direct target of thyroid hormone in human brain, and that control of expression of this gene could underlay many of the consequences ofhypothyroidism on mental states during development as well as in adult subjects.

RC3/neurogranin, a postsynaptic calpacitin for setting the response threshold to calcium influxes

In this review, we attempt to cover the descriptive, biochemical and molecular biological work that has contributed to our current knowledge about RC3/neurogranin function and its role in dendritic spine development, long-term potentiation, long-term depression, learning, and memory. Based on the data reviewed here, we propose that RC3, GAP-43, and the small cerebellum-enriched peptide, PEP-19, belong to a protein family that we have named the calpacitins. Membership in this family is based on sequence homology and, we believe, a common biochemical function. We propose a model wherein RC3 and GAP-43 regulate calmodulin availability in dendritic spines and axons, respectively, and calmodulin regulates their ability to amplify the mobilization of Ca2+ in response to metabotropic glutamate receptor stimulation. PEP-19 may serve a similar function in the cerebellum, although biochemical characterization of this molecule has lagged behind that of RC3 and GAP-43. We suggest that these molecules release CaM rapidly in response to large influxes of Ca2+ and slowly in response to small increases. This nonlinear response is analogous to the behavior of a capacitor, hence the name calpacitin. Since CaM regulates the ability of RC3 to amplify the effects of metabotropic glutamate receptor agonists, this activity must, necessarily, exhibit nonlinear kinetics as well. The capacitance of the system is regulated by phosphorylation by protein kinase C, which abrogates interactions between calmodulin and RC3 or GAP-43. We further propose that the ratio of phosphorylated to unphosphorylated RC3 determines the sliding LTP/LTD threshold in concept with Ca2+/ calmodulin-dependent kinase II. Finally, we suggest that the close association between RC3 and a subset of mitochondria serves to couple energy production with the synthetic events that accompany dendritic spine development and remodeling.