Thalamic and caudate volumes in monozygotic twins discordantfor schizophrenia

A novel risk variant block across introns 36-45 of CACNA1C for schizophrenia: a cohort-wise replication and cerebral region-wide validation study

OBJECTIVES

Numerous genome-wide association studies have identified CACNA1C as one of the top risk genes for schizophrenia. As a necessary post-genome-wide association study (GWAS) follow-up, here, we focused on this risk gene, carefully investigated its novel risk variants for schizophrenia, and explored their potential functions.

METHODS

We analyzed four independent samples (including three European and one African-American) comprising 5648 cases and 6936 healthy subjects to identify replicable single nucleotide polymorphism-schizophrenia associations. The potential regulatory effects of schizophrenia-risk alleles on CACNA1C mRNA expression in 16 brain regions (n = 348), gray matter volumes (GMVs) of five subcortical structures (n = 34 431), and surface areas and thickness of 34 cortical regions (n = 36 936) were also examined.

RESULTS

A novel 17-variant block across introns 36-45 of CACNA1C was significantly associated with schizophrenia in the same effect direction across at least two independent samples (1.8 × 10-4 ≤ P ≤ 0.049). Most risk variants within this block showed significant associations with CACNA1C mRNA expression (1.6 × 10-3 ≤ P ≤ 0.050), GMVs of subcortical structures (0.016 ≤ P ≤ 0.048), cortical surface areas (0.010 ≤ P ≤ 0.050), and thickness (0.004 ≤ P ≤ 0.050) in multiple brain regions.

CONCLUSION

We have identified a novel and functional risk variant block at CACNA1C for schizophrenia, providing further evidence for the important role of this gene in the pathogenesis of schizophrenia.

A significant, functional and replicable risk KTN1 variant block for schizophrenia

Cortical and subcortical structural alteration has been extensively reported in schizophrenia, including the unusual expansion of gray matter volumes (GMVs) of basal ganglia (BG), especially putamen. Previous genome-wide association studies pinpointed kinectin 1 gene (KTN1) as the most significant gene regulating the GMV of putamen. In this study, the role of KTN1 variants in risk and pathogenesis of schizophrenia was explored. A dense set of SNPs (n = 849) covering entire KTN1 was analyzed in three independent European- or African-American samples (n = 6704) and one mixed European and Asian Psychiatric Genomics Consortium sample (n = 56,418 cases vs. 78,818 controls), to identify replicable SNP-schizophrenia associations. The regulatory effects of schizophrenia-associated variants on the KTN1 mRNA expression in 16 cortical or subcortical regions in two European cohorts (n = 138 and 210, respectively), the total intracranial volume (ICV) in 46 European cohorts (n = 18,713), the GMVs of seven subcortical structures in 50 European cohorts (n = 38,258), and the surface areas (SA) and thickness (TH) of whole cortex and 34 cortical regions in 50 European cohorts (n = 33,992) and eight non-European cohorts (n = 2944) were carefully explored. We found that across entire KTN1, only 26 SNPs within the same block (r2 > 0.85) were associated with schizophrenia across ≥ 2 independent samples (7.5 × 10-5 ≤ p ≤ 0.048). The schizophrenia-risk alleles, which increased significantly risk for schizophrenia in Europeans (q < 0.05), were all minor alleles (f < 0.5), consistently increased (1) the KTN1 mRNA expression in 12 brain regions significantly (5.9 × 10-12 ≤ p ≤ 0.050; q < 0.05), (2) the ICV significantly (6.1 × 10-4 ≤ p ≤ 0.008; q < 0.05), (3) the SA of whole (9.6 × 10-3 ≤ p ≤ 0.047) and two regional cortices potentially (2.5 × 10-3 ≤ p ≤ 0.042; q > 0.05), and (4) the TH of eight regional cortices potentially (0.006 ≤ p ≤ 0.050; q > 0.05), and consistently decreased (1) the BG GMVs significantly (1.8 × 10-19 ≤ p ≤ 0.050; q < 0.05), especially putamen GMV (1.8 × 10-19 ≤ p ≤ 1.0 × 10-4; q < 0.05, (2) the SA of four regional cortices potentially (0.010 ≤ p ≤ 0.048), and (3) the TH of four regional cortices potentially (0.015 ≤ p ≤ 0.049) in Europeans. We concluded that we identified a significant, functional, and robust risk variant block covering entire KTN1 that might play a critical role in the risk and pathogenesis of schizophrenia.

Brain features of nearly drug-naïve female monozygotic twins with first-episode schizophrenia and the classification accuracy of brain feature patterns: A pilot study

BACKGROUND

Data on differences in brain features between monozygotic (MZ) twins with and without schizophrenia are scarce.

METHODS

We compared brain features of female MZ twins with and without first-episode schizophrenia and healthy controls (n = 20 each). Voxel-based morphometry and tract-based spatial statistics were used to analyze differences in brain structure. Whole-brain effective connectivity (EC) and functional connectivity (FC) networks were constructed using resting-state functional magnetic resonance imaging (rs-fMRI) data.

RESULTS

Female twins with schizophrenia exhibited abnormal gray matter volume (GMV) in the basal ganglia and prefrontal and parietal cortices, impairments in the arcuate fasciculus, and significant disruptions (primarily decreases) in nine EC networks. They exhibited rs-EC alterations involving the limbic areas and subcortex. Combined rs-EC and rs-FC data distinguished twins with first-episode schizophrenia with high accuracy. Combined consideration of structural and functional features enabled the distinction of female MZ twins with schizophrenia from those without schizophrenia and healthy controls with 100% accuracy.

CONCLUSIONS

Female MZ twins with schizophrenia exhibited increased GMV, white matter impairment, and disruptions in EC and FC networks. The combination of rs-EC + rs-FC data could distinguish female twins with schizophrenia from twins without schizophrenia and healthy controls with 97.4% accuracy, and the addition of structural brain features yielded a 100% accuracy rate. These findings may provide pivotal insight for further study of the mechanisms underlying schizophrenia.

Twin studies of brain structure and cognition in schizophrenia

Twin studies in schizophrenia have been crucial in establishing estimates for the heritability and thus providing evidence for a genetic component in this disorder. Recent years have seen the application of the twin study paradigm to both putative intermediate phenotypes and biomarkers of disease as well as a diversification of its use in schizophrenia research. This review addressed studies of brain structure (T1 morphometry) and cognition in schizophrenia using twin study designs. We review major findings such as the overlap of genetic variance between schizophrenia and cognition as a model for the emergence of psychopathology. The use of novel hybrid models integrating molecular genetic risk markers, as well as the use of twin studies in epigenetics might prove to significantly enhance schizophrenia research in the post-GWAS era.

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.

Optimizing hippocampal segmentation in infants utilizing MRI post-acquisition processing

This study aims to determine the most reliable method for infant hippocampal segmentation by comparing magnetic resonance (MR) imaging post-acquisition processing techniques: contrast to noise ratio (CNR) enhancement, or reformatting to standard orientation. MR scans were performed with a 1.5 T GE scanner to obtain dual echo T2 and proton density (PD) images at term equivalent (38-42 weeks' gestational age). 15 hippocampi were manually traced four times on ten infant images by 2 independent raters on the original T2 image, as well as images processed by: a) combining T2 and PD images (T2-PD) to enhance CNR; then b) reformatting T2-PD images perpendicular to the long axis of the left hippocampus. CNRs and intraclass correlation coefficients (ICC) were calculated. T2-PD images had 17% higher CNR (15.2) than T2 images (12.6). Original T2 volumes' ICC was 0.87 for rater 1 and 0.84 for rater 2, whereas T2-PD images' ICC was 0.95 for rater 1 and 0.87 for rater 2. Reliability of hippocampal segmentation on T2-PD images was not improved by reformatting images (rater 1 ICC = 0.88, rater 2 ICC = 0.66). Post-acquisition processing can improve CNR and hence reliability of hippocampal segmentation in neonate MR scans when tissue contrast is poor. These findings may be applied to enhance boundary definition in infant segmentation for various brain structures or in any volumetric study where image contrast is sub-optimal, enabling hippocampal structure-function relationships to be explored.

Putative structural neuroimaging endophenotypes in schizophrenia: a comprehensive review of the current evidence

The genetic contribution to schizophrenia etiopathogenesis is underscored by the fact that the best predictor of developing schizophrenia is having an affected first-degree relative, which increases lifetime risk by tenfold, as well as the observation that when both parents are affected, the risk of schizophrenia increases to approximately 50%, compared with 1% in the general population. The search to elucidate the complex genetic architecture of schizophrenia has employed various approaches, including twin and family studies to examine co-aggregation of brain abnormalities, studies on genetic linkage and studies using genome-wide association to identify genetic variations associated with schizophrenia. ‘Endophenotypes’, or ‘intermediate phenotypes’, are potentially narrower constructs of genetic risk. Hypothetically, they are intermediate in the pathway between genetic variation and clinical phenotypes and can supposedly be implemented to assist in the identification of genetic diathesis for schizophrenia and, possibly, in redefining clinical phenomenology.

Updated meta-analyses reveal thalamus volume reduction in patients with first-episode and chronic schizophrenia

OBJECTIVES

Although several structural MRI studies report significant thalamus volume reduction in patients with schizophrenia, many other studies do not. Therefore, the present meta-analyses aimed to clarify whether a reduction in thalamic volume characterizes patients diagnosed with schizophrenia by considering first-episode and chronic phases of the illness and right and left thalamus separately.

METHODS

Using Pubmed databases, we made a detailed literature search for structural MRI studies on patients with schizophrenia that reported physical volumetric measures of the right and left thalamus. Thirteen structural MRI studies were considered eligible for meta-analysis of the entire sample of patients and of the healthy control subjects. Individual meta-analyses were also performed on 6 studies of first-episode patients only and on 7 studies of chronic patients only. These were followed by additional meta-analyses to investigate the role of the factors "illness phase" and "side" on thalamic volume reduction.

RESULTS

Overall, the patient group showed a significant bilateral thalamus volume reduction compared to healthy control subjects. This was found in both first-episode and chronic patients. Furthermore, left thalamus was smaller than right in both patients and healthy control subjects.

CONCLUSIONS

When only studies that used physical volumetric measures were considered, the present meta-analyses confirmed that thalamic volume reduction characterizes patients with schizophrenia, both at the first-episode and chronic phases of the illness.

Is gray matter volume an intermediate phenotype for schizophrenia? A voxel-based morphometry study of patients with schizophrenia and their healthy siblings

BACKGROUND

Shared neuropathological characteristics of patients with schizophrenia and their siblings might represent intermediate phenotypes that could be used to investigate genetic susceptibility to the illness. We sought to discover previously unidentified gray matter volume differences in patients with schizophrenia and their siblings with optimized voxel-based morphometry.

METHODS

We studied 169 patients with schizophrenia, 213 of their unaffected siblings, and 212 healthy volunteers from the Clinical Brain Disorders Branch/National Institute of Mental Health Genetic Study of Schizophrenia with magnetic resonance imaging.

RESULTS

Patients with schizophrenia had significant regional gray matter decreases in the frontal, temporal, and parietal cortices compared with healthy volunteers. Their unaffected siblings tended to share gray matter decreases in the medial frontal, superior temporal, and insular cortices, but these decreases were not significant after correction for multiple comparisons, even when we looked at a subgroup of siblings with a past history of mood disorder. As an exploratory analysis, we estimated heritability with regions of interest from the VBM analysis as well as from the hippocampus. Hippocampal volume was significantly correlated within sibling-pairs.

CONCLUSIONS

Our findings confirm and extend previous voxel-based morphometry analyses in ill subjects with schizophrenia. Furthermore, these data argue that although siblings might share some regional gray matter decreases with their affected siblings, the pattern of regional differences might be a weak intermediate phenotype for schizophrenia.

Brain neuroplasticity in healthy, hyperactive and psychotic children: insights from neuroimaging

Noninvasive brain imaging permits longitudinal studies of anatomic brain development in healthy and psychiatrically ill children. The time course for gray matter maturation varies by region and parallels earlier histological studies, indicating dynamic patterns of overproduction and regression. Developmental trajectories vary in relation to gender, intelligence, and overall functioning. Twin studies show high heritability for brain volumes, which varies with region and with age. Diagnostically specific, illness-related changes as well as outcome-associated plastic response are observed as illustrated for two pediatric populations, childhood-onset schizophrenia and attention-deficit/hyperactivity disorder, conditions which may be, in part, disorders of brain plasticity.

Evidence of altered prefrontal–thalamic circuitry in schizophrenia: An optimized diffusion MRI study

MRI diffusion tensor imaging (DTI), optimized for measuring the trace of the diffusion tensor, was used to investigate microstructural changes in the brains of 12 individuals with schizophrenia compared with 12 matched control subjects. To control for the effects of anatomic variation between subject groups, all participants' diffusion images were nonlinearly registered to standard anatomical space. Significant statistical differences in mean diffusivity (MD) measures between the two groups were determined on a pixel-by-pixel basis, using Gaussian random field theory. We found significantly elevated MD measures within temporal, parietal and prefrontal cortical regions in the schizophrenia group (P > 0.001), especially within the medial frontal gyrus and anterior cingulate. The dorsal medial and anterior nucleus of the thalamus, including the caudate, also exhibited significantly increased MD in the schizophrenia group (P > 0.001). This study has shown for the first time that MD measures offer an alternative strategy for investigating altered prefrontal-thalamic circuitry in schizophrenia.

Testing models of thalamic dysfunction in schizophrenia using neuroimaging

Neural models of schizophrenia have implicated the thalamus in deficits of early sensory processing and multimodal integration. We have reviewed the existing neuroimaging literature for evidence in support of models that propose abnormalities of thalamic relay nuclei, the mediodorsal thalamic nucleus, and large-scale cortico-thalamic networks. Thalamic volume reduction was found in some but not all studies. Studies of the early stages of schizophrenia suggest that thalamic volume reduction is present early in the course of the illness. Functional imaging studies have revealed task related abnormalities in several cortical and subcortical areas including the thalamus, suggesting a disruption of distributed thalamocortical networks. Chemical imaging studies have provided evidence for a loss of thalamic neuronal integrity in schizophrenia. There is, at present, inadequate data to support the hypothesis that schizophrenia is associated with abnormalities of sensory relay or association nuclei. There is evidence for a perturbation of cortico-thalamic networks, but further research is needed to elucidate the underlying mechanisms at the cellular and systems levels. The challenges ahead include better delineation of thalamic structure and function in vivo, the combination of genetic and imaging techniques to elucidate the genetic contributions to a thalamic phenotype of schizophrenia, and longitudinal studies of thalamic structure and function.

N-acetylaspartate reductions in the mediodorsal and anterior thalamus in men with schizophrenia verified by tissue volume corrected proton MRSI

OBJECTIVE

Deficits in the mediodorsal and anterior nuclei of the thalamus may contribute to the psychopathological symptoms of schizophrenia. These thalamic nuclei have been found to be abnormal in schizophrenia and have close connections with other brain structures implicated in the disorder. We therefore examined schizophrenia-related alterations in brain metabolite levels specifically in the mediodorsal and anterior thalamic subregions.

METHOD

We used in vivo proton magnetic resonance spectroscopic imaging ((1)H MRSI) to measure N-acetylaspartate (NAA), choline-containing compounds (Cho), and creatine+phosphocreatine (Cr) in the mediodorsal and anterior thalamus in 22 male patients with schizophrenia and 22 male controls. Magnetic resonance imaging (MRI) tissue segmentation and thalamic volume mask techniques were performed to distinguish the thalamus, extrathalamic gray and white matter, and CSF within the spectroscopic voxels.

RESULTS

Compared to healthy subjects, patients with schizophrenia had significantly lower NAA in the mediodorsal and anterior thalamus bilaterally. No significant differences in Cho or Cr levels were seen. NAA was significantly higher in the left thalamus relative to the right in both groups. We found a strong negative correlation between left thalamic NAA and duration of illness, even after partialling out the effect of age. Tissue segmentation and thalamic volume mask techniques detected no group or lateralized differences in tissue type or CSF percentages, demonstrating that the metabolite reductions were not an artifact of spectroscopic voxel heterogeneity.

CONCLUSIONS

These findings suggest diminished function and/or structure in the mediodorsal and anterior thalamus in male patients with schizophrenia and support earlier research demonstrating schizophrenia-related abnormalities in the thalamus and its circuitry.

Correlations between MRI-assessed volumes of the thalamus and cortical Brodmann's areas in schizophrenia

BACKGROUND

We compared the thalamic-cortical volumetric correlational patterns in patients with schizophrenia and normal comparison subjects, and evaluated their relations to outcome.

METHODS

High-resolution MR images were acquired in patients with schizophrenia (n=106) and normal comparison subjects (n=42). Patients were divided into good-outcome (n=52) and poor-outcome (Kraepelinian, n=54) subtypes based on their ability for self-care. Correlations between the relative gray and white matter volumes of the individual cortical Brodmann's areas and five dorsoventral levels of the thalamus were assessed.

RESULTS

Compared to normal subjects, schizophrenia patients lacked significant thalamic gray matter volume correlations with the prefrontal and medial temporal cortical regions in the right hemisphere, and with frontal, cingulate, posterior parietal and occipital regions in the left hemisphere, while normal white matter volume cortical-thalamic correlations along the cingulate gyrus and in the temporal lobe were not found in schizophrenia patients in both hemispheres. In contrast to both normal comparison subjects and good-outcome group, schizophrenia patients with poor outcomes showed significant bilateral gray matter volume correlations between the dorsal thalamus and ventral prefrontal cortex, while the group differences in the white matter volume correlations were mostly restricted to the cingulate arch.

CONCLUSIONS

Whereas patients with schizophrenia exhibit deficiencies in cortical-thalamic correlational patterns, poor outcome is associated with abnormal interregional correlations not observed in either normal subjects or patients with good outcomes. This latter finding may be explained by a core neurodevelopmental disturbance that results in aberrant cortical-thalamic connectivity in poor-outcome schizophrenia.

A manual and automated MRI study of anterior cingulate and orbito-frontal cortices, and caudate nucleus in obsessive-compulsive disorder: comparison with healthy controls and patients with schizophrenia

Functional imaging and neuropsychological data suggest that interconnected brain structures including the orbito-frontal cortex (OFC), anterior cingulate cortex (ACC) and caudate nucleus (CN) are involved in the pathophysiology of obsessive-compulsive disorder (OCD), but structural imaging studies investigating these regions have yielded inconclusive results. This may be due to inconsistencies in the identification of anatomical boundaries and methodologies utilised (i.e. automated vs. manual tracing). This magnetic resonance imaging study used manual tracing to measure volumes of selected brain regions (OFC, ACC and CN) in OCD patients and compared them with samples of healthy (HC) and psychiatric (schizophrenia; SCZ) controls (n=18 in each group). Concurrently, automated voxel-based analysis was also used to detect subtle differences in cerebral grey and white matter. For the OCD vs. HC comparison, there were no significant volumetric differences detected using the manual or the automated method (although the latter revealed a deficit in the subcortical white matter of the right temporal region). A direct comparison of the two patient groups showed no significant differences using the manual method. However, a moderate effect size was detected for OFC grey matter (reduced in SCZ), which was supported by findings of reduced OFC volume in the automated analysis. Automated analyses also showed reduced volumes in the dorsal (white matter) and ventral ACC (grey and white matter), as well as the left posterior cingulate (grey and white matter) in SCZ. The findings suggest that in contrast to findings in SCZ, there are very few (if any) gross structural anomalies in OCD.

Thalamus size and outcome in schizophrenia

The size of the thalamus was assessed in 106 patients with schizophrenia and 42 normal controls using high-resolution magnetic resonance imaging. The thalamus was traced at five axial levels proportionately spaced from dorsal to ventral directions. Patients with schizophrenia had significantly smaller thalamic areas at more ventral levels. Thalamic size was positively associated with frontal lobe and temporal lobe size. The effects were most marked in the patients with poorer clinical outcome (i.e., "Kraepelinian" patients). These findings are consistent with post-mortem and MRI measurement suggesting reduction in volume of the pulvinar, which occupies a large proportion of the ventral thalamus and which has prominent connections to the temporal lobe.

Thalamic dysfunction in schizophrenia: neurochemical, neuropathological, and in vivo imaging abnormalities

While abnormalities of the prefrontal cortex and temporal lobe structures have typically been associated with the pathophysiology of schizophrenia, recent findings implicate thalamic dysfunction in this illness as well. The thalamus plays a critical role in processing and integrating sensory information relevant to emotional and cognitive functions. Neuropathological and in vivo imaging studies in schizophrenia have identified several structural and metabolic abnormalities in the thalamus, which may contribute to a deficit in sensory processing and be related to psychotic symptomatology. In addition to these postmortem and in vivo imaging studies indicating structural and metabolic changes in the thalamus in schizophrenia, more recent studies have examined the neurochemical substrates that accompany these changes. Much of this work to date has focused on glutamatergic abnormalities in the thalamus, in part because it is a predominant neurotransmitter used in the thalamus, and because glutamatergic dysfunction has been hypothesized to be involved in schizophrenia. Several studies, however, have also examined markers of gamma-aminobutyric acid (GABA) and dopaminergic neurotransmission in the thalamus in schizophrenia. We review these neurochemical findings, as well as the growing body of postmortem and in vivo imaging evidence that supports the hypothesis of thalamic dysfunction in schizophrenia.

Serial MRI in multiple sclerosis: a prospective pilot study of lesion load, whole brain volume and thalamic atrophy

Using serial magnetic resonance imaging (MRI), we investigated the relationship between diffuse cerebral atrophy, T1 and T2 lesion volumes, mean thalamic volumes and clinical progression in patients with established multiple sclerosis (MS). Eleven patients were included in this prospective serial study. Cerebral volumes, T1 hypointense lesion volumes, and T2 hyperintense lesion volumes at baseline and at up to 3 years follow-up were assessed on MRI brain scans. As a putative measure of cerebral atrophy mean thalamic volumes were also obtained. The outcome measures were the MRI parameters and disability on Kurtzke's expanded disability status scale (EDSS). Of the 11 patients 6 worsened clinically as measured by an increase of 0.5 or more on the EDSS. Cerebral atrophy occurred in 91% of patients and was independent of changes in lesion volumes and was not associated with disease progression as determined by the EDSS.