Altered hippocampal gene expression and structure in transgenic mice overexpressing neuregulin 1 (Nrg1) type I.

Transgenic mice overexpressing the type I isoform of neuregulin 1 (Nrg1; NRG1) have alterations in hippocampal gamma oscillations and an age-emergent deficit in hippocampus-dependent spatial working memory. Here, we examined the molecular and morphological correlates of these findings. Microarrays showed over 100 hippocampal transcripts differentially expressed in Nrg1tg-type I mice, with enrichment of genes related to neuromodulation and, in older mice, of genes involved in inflammation and immunity. Nrg1tg-type I mice had an enlarged hippocampus with a widened dentate gyrus. The results show that Nrg1 type I impacts on hippocampal gene expression and structure in a multifaceted and partly age-related way, complementing the evidence implicating Nrg1 signaling in aspects of hippocampal function. The findings are also relevant to the possible role of NRG1 signaling in the pathophysiology of schizophrenia or other disorders affecting this brain region.

Metabotropic glutamate receptor 3 (mGlu3; mGluR3; GRM3) in schizophrenia: Antibody characterisation and a semi-quantitative western blot study.

BACKGROUND: Metabotropic glutamate receptor 3 (mGlu3, mGluR3), encoded by GRM3, is a risk gene for schizophrenia and a therapeutic target. It is unclear whether expression of the receptor is altered in the disorder or related to GRM3 risk genotype. Antibodies used to date to assess mGlu3 in schizophrenia have not been well validated. OBJECTIVE: To characterise six commercially available anti-mGlu3 antibodies for use in human brain, and then conduct a semi-quantitative study of mGlu3 immunoreactivity in schizophrenia. METHODS: Antibodies tested using Grm3-/- and Grm2-/-/3-/- mice and transfected HEK293T/17 cells. Western blotting on membrane protein isolated from superior temporal cortex of 70 patients with schizophrenia and 87 healthy comparison subjects, genotyped for GRM3 SNP rs10234440. RESULTS: One (out of six) anti-mGlu3 antibodies was fully validated, a C-terminal antibody which detected monomeric (~100kDa) and dimeric (~200kDa) mGlu3. A second, N-terminal, antibody detected the 200kDa band but also produced non-specific bands. Using the C-terminal antibody for western blotting in human brain, mGlu3 immunoreactivity was found to decline with age, and was affected by pH and post mortem interval. There were no differences in monomeric or dimeric mGlu3 immunoreactivity in schizophrenia or in relation to GRM3 genotype. The antibody was not suitable for immunohistochemistry. INTERPRETATION: These data highlight the value of knockout mouse tissue for antibody validation, and the need for careful antibody characterisation. The schizophrenia data show that involvement of GRM3 in the disorder and its genetic risk architecture is not reflected in total membrane mGlu3 immunoreactivity in superior temporal cortex.

Expression of ZNF804A in human brain and alterations in schizophrenia, bipolar disorder, and major depressive disorder: a novel transcript fetally regulated by the psychosis risk variant rs1344706.

IMPORTANCE: The single-nucleotide polymorphism rs1344706 in the zinc finger protein 804A gene (ZNF804A) shows genome-wide association with schizophrenia and bipolar disorder. Little is known regarding the expression of ZNF804A and the functionality of rs1344706. OBJECTIVES: To characterize ZNF804A expression in human brain and to investigate how it changes across the life span and how it is affected by rs1344706, schizophrenia, bipolar disorder, and major depressive disorder. DESIGN, SETTING, AND PARTICIPANTS: Molecular and immunochemical methods were used to study ZNF804A messenger RNA (mRNA) and ZNF804A protein, respectively. ZNF804A transcripts were investigated using next-generation sequencing and polymerase chain reaction-based methods, and ZNF804A protein was investigated using Western blots and immunohistochemistry. Samples of dorsolateral prefrontal cortex and inferior parietal lobe tissue were interrogated from 697 participants between 14 weeks' gestational age and age 85 years, including patients with schizophrenia, bipolar disorder, or major depressive disorder. MAIN OUTCOMES AND MEASURES: Quantitative measurements of ZNF804A mRNA and immunoreactivity, and the effect of diagnosis and rs1344706 genotype. RESULTS: ZNF804A was expressed across the life span, with highest expression prenatally. An abundant and developmentally regulated truncated ZNF804A transcript was identified, missing exons 1 and 2 (ZNF804AE3E4) and predicted to encode a protein lacking the zinc finger domain. rs1344706 influenced expression of ZNF804AE3E4 mRNA in fetal brain (P = .02). In contrast, full-length ZNF804A showed no association with genotype (P > .05). ZNF804AE3E4 mRNA expression was decreased in patients with schizophrenia (P = .006) and increased in those with major depressive disorder (P < .001), and there was a genotype-by-diagnosis interaction in bipolar disorder (P = .002). ZNF804A immunoreactivity was detected in fetal and adult human cerebral cortex. It was localized primarily to pyramidal neurons, with cytoplasmic as well as dendritic and nuclear staining. No differences in ZNF804A-immunoreactive neurons were seen in schizophrenia or related to rs1344706 (P > .05). CONCLUSIONS AND RELEVANCE: rs1344706 influences the expression of ZNF804AE3E4, a novel splice variant. The effect is limited to fetal brain and to this isoform. It may be part of the mechanism by which allelic variation in ZNF804A affects risk of psychosis. ZNF804A is translated in human brain, where its functions may extend beyond its predicted role as a transcription factor.

Anomalies of asymmetry of pyramidal cell density and structure in dorsolateral prefrontal cortex in schizophrenia.

BACKGROUND: Studies suggest that neuronal density in left dorsolateral prefrontal cortex is increased in schizophrenia. AIMS: To replicate these findings and extend them to both hemispheres. METHOD: Neuronal density, size and shape were estimated in the prefrontal cortex (Brodmann area 9) of the left and right hemispheres of brains taken post-mortem from 10 people with schizophrenia and 10 without mental illness (6 men, 4 women in both groups). RESULTS: Overall neuronal density (individually corrected for shrinkage) did not differ between the groups. In the control brains, density was generally greater in the left than the right hemisphere, the reverse was seen in the schizophrenia brains; this loss or reversal of asymmetry was most significant in cortical layer 3. Pyramidal neurons in this cell layer were significantly larger on the left and more spherical in shape than on the right side in control brains, but size and shape did not differ between the two sides in schizophrenia. Non-pyramidal and glial cell densities were unchanged. CONCLUSIONS: We failed to find an increase in neuronal density, but found evidence at a cellular level of loss or reversal of asymmetry, consistent with the hypothesis of a primary change in the relative development of areas of heteromodal association cortex in the two hemispheres.

Low medial and lateral right pulvinar volumes in schizophrenia: a postmortem study.

OBJECTIVE: In this study, the volume and neuronal number of the pulvinar thalamic nucleus in schizophrenia patients were measured. METHOD: The authors examined medial and lateral pulvinar nuclei bilaterally in 27 patients with schizophrenia and 28 normal comparison subjects. RESULTS: In the comparison subjects, the medial pulvinar was larger on the right. The right but not left pulvinar nuclei were smaller in the schizophrenia patients than in the comparison subjects. The number of neurons showed similar trends. CONCLUSIONS: These findings confirm low pulvinar volume in schizophrenia and show that it affects both medial and lateral nuclei. The lateralized findings may reflect pulvinar connections with asymmetrical neocortical regions and their asymmetrical involvement in schizophrenia.

Asymmetry of the uncinate fasciculus: a post-mortem study of normal subjects and patients with schizophrenia.

The uncinate fasciculus interconnects the anterior temporal and inferior frontal lobes. The temporal lobes show a number of anatomical asymmetries, some of which are altered in schizophrenia. This study was performed to assess the size and symmetry of the uncinate fasciculus in normal subjects and in patients with the disorder. The area, fibre density and total fibre number of left and right uncinate fasciculi were estimated using stereological methods in 21 control subjects and 17 schizophrenics. The uncinate fasciculus was found to be asymmetrical in both sexes, being 27% larger and containing 33% more fibres in the right than the left hemisphere. Of the 25 brains from which both hemispheres were available, the size asymmetry was seen in 20 subjects and the greater number of fibres in 21 subjects. There was no significant effect of schizophrenia upon the uncinate fasiculus, nor interactions of diagnosis with side or sex. We conclude that the uncinate fasciculus is larger in the right hemisphere, perhaps indicating greater right-sided fronto-temporal connectivity. The unchanged size of the fasciculus in schizophrenia contrasts with commissural tracts, which are affected in this brain series in a sex-specific manner.

Estimated neuronal populations and volumes of the hippocampus and its subfields in schizophrenia.

OBJECTIVE: It has been suggested that the primary focus of the pathological process in schizophrenia is on the limbic system, and there have been several postmortem reports of changes in the histological structure or volume of the hippocampus, as well as a larger number of MRI reports of volume reductions. There are conflicting findings, however, with both techniques. METHOD: The authors conducted a study of the gross and subfield structure and cellular composition of the hippocampus in postmortem brains from 30 patients with DSM-IV-diagnosed schizophrenia (13 women, 17 men) and 29 comparison subjects with no psychopathology (14 women, 15 men). Stereological sampling procedures were applied to 25-microm-thick coronal paraffin sections taken at 5-mm intervals throughout the formalin-fixed hippocampus. Subfields were defined as the dentate fascia, the hilus (CA4), an amalgamation of the CA2 and CA3 subfields, the CA1 subfield, and the subiculum. Volumes, cell densities, and cell numbers of the subfields were assessed microscopically, and the volume of the hippocampus was estimated from both photographs and histological slides of the coronal slices. RESULTS: As assessed from histologically stained slides, the volumes of the hippocampus and its subfields did not differ between patients and comparison subjects. Left-sided reduction in hippocampal volumes estimated from photographs, which may have included parahippocampal tissue, was not confirmed on histological examination. No significant differences were observed between patients and comparison subjects in the cellular composition of the hippocampus. CONCLUSIONS: These findings do not support a primary alteration of the hippocampus in schizophrenia.