Altered cognitive development in the siblings of individuals with schizophrenia

Influence of TMX2-CTNND1 polymorphism on cortical thickness in schizophrenia patients and unaffected siblings: an exploratory study based on target region sequencing

OBJECTIVE

The advancement of neuroimaging and genetic research has revealed the presence of morphological abnormalities and numerous risk genes, along with their associations. We aimed to estimate magnetic resonance imaging-derived cortical thickness across multiple brain regions.

METHODS

The cortical thickness of 129 schizophrenia patients, 42 of their unaffected siblings, and 112 healthy controls was measured and the candidate genes were sequenced. Comparisons were made of cortical thickness (including 68 regions of the Desikan-Killiany Atlas) and genetic variants (in 108 risk genes for schizophrenia) among the three groups, and correlation analyses were performed regarding cortical thickness, clinical symptoms, cognitive tests (such as the N-back task and the logical memory test), and genetic variants.

RESULTS

Schizophrenia patients had significantly thinner bilateral frontal, temporal, and parietal gyri than healthy controls and unaffected siblings. Association analyses in target genes showed that four single nucleotide variants (SNVs) were significantly associated with schizophrenia, including thioredoxin-related transmembrane protein 2-catenin, cadherin-associated protein, delta 1 (SNV20673) (positive false discovery rate [PFDR] = 0.008) and centromere protein M (rs35542507, rs41277477, rs73165153) (PFDR = 0.030). Additionally, cortical thickness in the right pars triangularis was lower in carriers of the SNV20673 variant than in non-carriers (PFDR = 0.048). Finally, a positive correlation was found between right pars triangularis cortical thickness and logical memory in schizophrenia patients (r = 0.199, p = 0.032).

CONCLUSIONS

This study identified regional morphological abnormalities in schizophrenia, including the right homologue of Broca's area, which was associated with a risk variant that affected delta-1 catenin and logical memory. These findings suggest a potential association between candidate gene loci, cortical thickness, and schizophrenia.

Clustering of cognitive subtypes in schizophrenia patients and their siblings: relationship with regional brain volumes

Schizophrenia patients (SZH) often show impaired cognition and reduced brain structural volumes; these deficits are also detectable in healthy relatives of SZH. However, there is considerable heterogeneity: a sizable percentage of SZH are relatively cognitively intact; clustering strategies have proved useful for categorising into cognitive subgroups. We used a clustering strategy to investigate relationships between subgroup assignment and brain volumes, in 102 SZH (N = 102) and 32 siblings of SZH (SZH-SIB), alongside 92 controls (CON) and 48 of their siblings. SZH had poorer performance in all cognitive domains, and smaller brain volumes within prefrontal and temporal regions compared to controls. We identified three distinct cognitive clusters (‘neuropsychologically normal’, ‘intermediate’, ‘cognitively impaired’) based on age- and gender-adjusted cognitive domain scores. The majority of SZH (60.8%) were assigned to the cognitively impaired cluster, while the majority of SZH-SIB (65.6%) were placed in the intermediate cluster. Greater right middle temporal volume distinguished the normal cluster from the more impaired clusters. Importantly, the observed brain volume differences between SZH and controls disappeared after adjustment for cluster assignment. This suggests an intimate link between cognitive performance levels and regional brain volume differences in SZH. This highlights the importance of accounting for heterogeneity in cognitive performance within SZH populations when attempting to characterise the brain structural abnormalities associated with the disease.

A network analysis and empirical validation of executive deficits in patients with psychosis and their healthy siblings

BACKGROUND

Psychopathological symptoms and cognitive impairment are core features of patients with psychotic disorders. Executive dysfunctions are commonly observed and typically assessed using tests like the Wisconsin Card Sorting Test (WCST). However, the structure of executive deficits remains unclear, and the underlying processes may be different. This study aimed to explore and compare the network structure of WCST measures in patients with psychosis and their unaffected siblings and to empirically validate the resulting network structure of the patients.

METHODS

The subjects were 298 patients with a DSM 5 diagnosis of a psychotic disorder and 89 of their healthy siblings. The dimensionality and network structure of the WCST were examined by means of exploratory graph analysis (EGA) and network centrality parameters.

RESULTS

The WCST network structure comprised 4 dimensions: perseveration (PER), inefficient sorting (IS), failure to maintain set (FMS) and learning (LNG). The patient and sibling groups showed a similar network structure, which was reliably estimated. PER and IS showed common and strong associations with antecedent, concurrent and outcome validators. The LNG dimension was also moderately associated with these validators, but FMS did not show significant associations.

CONCLUSIONS

Four cognitive processes underlying WCST performance were identified by the network analysis. PER, IS and LNG were associated with and shared common antecedent, concurrent and outcome validators, while FMS was not associated with external validators. These four underlying dysfunctions might help disentangle the neurofunctional basis of executive deficits in psychosis.

Adolescent trajectories of fine motor and coordination skills and risk for schizophrenia

Premorbid motor dysfunction is one of the earliest of developmental antecedents identified among individuals who develop schizophrenia in adulthood. However, among individuals with schizophrenia, premorbid motor dysfunction is not apparent at all stages of childhood development and may reduce with increasing age. Currently, little is known about the trajectories of motor development during adolescence among youth at-risk for the disorder. One hundred and one participants were assessed repeatedly, at approximately 24-month intervals (time 1, aged 9-12 years; time 2, 11-14 years; and time 3, 13-16 years), on the Purdue Pegboard assessment, comprising four subtests: Dominant Hand (DH), Non-Dominant Hand (NDH), Both Hands (BH), and Assembly. Fine motor and coordination skills development between ages 9-16 years was compared between youth characterised by a triad of developmental antecedents of schizophrenia (ASz, N = 32); youth with at least one affected relative with schizophrenia/schizoaffective disorder (FHx; N = 26); and typically developing youth without antecedents or family history (TD, N = 43). Longitudinal mixed models for repeated measures indicated significant motor skills improvements with age in TD youth on the Assembly subtest only. Relative to TD youth, we found evidence for developmental deficits (i.e., dysfunction that emerged early and remained stable) among ASz youth on DH and BH subtests, and among FHx youth on the Assembly subtest. ASz youth were characterised by a developmental delay on the Assembly subtest (i.e., initial performance decrement in middle childhood that caught up with peers' performance during adolescence). These divergences from normative motor development may reflect differences in structural and functional neural correlates.

Differential expression of synaptic markers regulated during neurodevelopment in a rat model of schizophrenia-like behavior

Schizophrenia is considered a neurodevelopmental disorder. Recent reports relate synaptic alterations with disease etiology. The inbred Roman High- (RHA-I) and Low- (RLA-I) Avoidance rat strains are a congenital neurobehavioral model, with the RHA-I displaying schizophrenia-related behaviors and serotonin 2A (5-HT2A) and metabotropic glutamate 2 (mGlu2) receptor alterations in the prefrontal cortex (PFC). We performed a comprehensive characterization of the RHA-I/RLA-I rats by real-time qPCR and Western blotting for 5-HT1A, 5-HT2A, mGlu2, dopamine 1 and dopamine 2 receptors (DRD1 and DRD2), AMPA receptor subunits Gria1, Gria2 and NMDA receptor subunits Grin1, Grin2a and Grin2b, as well as pre- and post-synaptic components in PFC and hippocampus (HIP). Besides corroborating decreased mGlu2 (Grm2) expression, we found increased mRNA levels for Snap25, Synaptophysin (Syp), Homer1 and Neuregulin-1 (Nrg1) in the PFC of the RHA-I and decreased expression of Vamp1, and Snapin in the HIP. We also showed alterations in Vamp1, Grin2b, Syp, Snap25 and Nrg1 at protein levels. mRNA levels of Brain Derived Neurotrophic Factor (BDNF) were increased in the PFC of the RHA-I rats, with no differences in the HIP, while BDNF protein levels were decreased in PFC and increased in HIP. To investigate the temporal dynamics of these synaptic markers during neurodevelopment, we made use of the open source BrainCloud™ dataset, and found that SYP, GRIN2B, NRG1, HOMER1, DRD1 and BDNF expression is upregulated in PFC during childhood and adolescence, suggesting a more immature neurobiological endophenotype in the RHA-I strain.

Trajectories of cognitive development during adolescence among youth at-risk for schizophrenia

BACKGROUND

Among adults with schizophrenia, evidence suggests that premorbid deficits in different cognitive domains follow distinct developmental courses during childhood and adolescence. The aim of this study was to delineate trajectories of adolescent cognitive functions prospectively among different groups of youth at-risk for schizophrenia, relative to their typically developing (TD) peers.

METHOD

Using linear mixed models adjusted for sex, ethnicity, parental occupation and practice effects, cognitive development between ages 9 and 16 years was compared for youth characterised by a triad of well-replicated developmental antecedents of schizophrenia (ASz; N = 32) and youth with a least one affected relative with schizophrenia or schizoaffective disorder (FHx; N = 29), relative to TD youth (N = 45). Participants completed measures of IQ, scholastic achievement, memory and executive function at three time-points, separated by approximately 24-month intervals.

RESULTS

Compared to TD youth, both ASz and FHx youth displayed stable developmental deficits in verbal working memory and inhibition/switching executive functions. ASz youth additionally presented with stable deficits in measures of vocabulary (IQ), word reading, numerical operations, and category fluency executive function, and a slower rate of growth (developmental lag) on spelling from 9 to 16 years than TD peers. Conversely, faster rates of growth relative to TD peers (developmental delay) were observed on visual and verbal memory, and on category fluency executive function (ASz youth only) and on matrix reasoning (IQ) and word reading (FHx youth only).

CONCLUSIONS

These differential patterns of deviation from normative adolescent cognitive development among at-risk youth imply potential for cognitive rehabilitation targeting of specific cognitive deficits at different developmental phases.

Differences in 5-HT2A and mGlu2 Receptor Expression Levels and Repressive Epigenetic Modifications at the 5-HT2A Promoter Region in the Roman Low- (RLA-I) and High- (RHA-I) Avoidance Rat Strains

The serotonin 2A (5-HT_2A) and metabotropic glutamate 2 (mGlu2) receptors regulate each other and are associated with schizophrenia. The Roman high- (RHA-I) and the Roman low- (RLA-I) avoidance rat strains present well-differentiated behavioral profiles, with the RHA-I strain emerging as a putative genetic rat model of schizophrenia-related features. The RHA-I strain shows increased 5-HT_2A and decreased mGlu2 receptor binding levels in prefrontal cortex (PFC). Here, we looked for differences in gene expression and transcriptional regulation of these receptors. The striatum (STR) was included in the analysis. 5-HT_2A, 5-HT_1A, and mGlu2 mRNA and [³H]ketanserin binding levels were measured in brain homogenates. As expected, 5-HT_2A binding was significantly increased in PFC in the RHA-I rats, while no difference in binding was observed in STR. Surprisingly, 5-HT_2A gene expression was unchanged in PFC but significantly decreased in STR. mGlu2 receptor gene expression was significantly decreased in both PFC and STR. No differences were observed for the 5-HT_1A receptor. Chromatin immunoprecipitation assay revealed increased trimethylation of histone 3 at lysine 27 (H3K27me3) at the promoter region of the HTR2A gene in the STR. We further looked at the Akt/GSK3 signaling pathway, a downstream point of convergence of the serotonin and glutamate system, and found increased phosphorylation levels of GSK3β at tyrosine 216 and increased β-catenin levels in the PFC of the RHA-I rats. These results reveal region-specific regulation of the 5-HT_2A receptor in the RHA-I rats probably due to absence of mGlu2 receptor that may result in differential regulation of downstream pathways.

Collection of developmental history in the evaluation of schizophrenia spectrum disorders

BACKGROUND

Schizophrenia is a heterogeneous disorder that is characterized by varying levels of hallucinations, delusions, negative symptoms, and disorganized features. The presence and severity of neurodevelopmental precursors and premorbid psychopathology also vary among individuals. To fully understand individual patients and to sort out phenotypic heterogeneity for genetic research studies, instruments designed to collect developmental history relevant to schizophrenia may be helpful.

OBJECTIVE

The goal was to describe a pair of self-report and parent-report instruments developed for the purpose of collecting the developmental history of patients with known or suspected schizophrenia spectrum disorders.

METHOD

Two developmental history instruments were designed for use in studies of brain morphology and cognition in schizophrenia probands and their unaffected siblings. The instruments focus mainly on motor abnormalities and other features that have been described as schizophrenia precursors.

RESULTS

The Motor Skills History Form is a brief self-report form that asks about patients' childhood and adolescent motor abilities as well as their current motor functioning. The Developmental & Motor History Form is a more detailed parent-rated form that covers aspects of patients' early (infant/preschool) development; their childhood and adolescent motor abilities; any childhood behaviors that may be related to later psychosis risk; and their history of any neurological, emotional, or cognitive disorders diagnosed during childhood or adolescence. The instruments can be used either for interviews or as self-administered questionnaires. The parent-rated form has been used for research and for the clinical assessment of children and adolescents with complex neurodevelopmental presentations with or without strong evidence of schizophrenia risk.

CONCLUSIONS

The collection of developmental history information is important when evaluating individuals with schizophrenia and related disorders. The Motor Skills History Form and the Developmental & Motor History Form can be used to collect this information for clinical evaluation or research purposes.

Neonatal ventral hippocampus lesion changes nuclear restricted protein/brain (NRP/B) expression in hippocampus, cortex and striatum in developmental periods of rats

Schizophrenia is conceptualized as a neurodevelopmental disorder in which developmental alterations in immature brain systems are not clear. Rats with neonatal ventral hippocampal lesions (NVHL) can exhibit schizophrenia-like behaviors, and these rats have been widely used to study the developmental mechanisms of schizophrenia. The nuclear restricted protein/brain (NRP/B) is a nuclear matrix protein that is critical for the normal development of the neuronal system. This study assessed the effect of NVHL induced by the administration of ibotenic acid on the protein expression of NRP/B in the hippocampus, cortex and striatum in pre- and post-pubertal rats. The expressions of NeuN in various developmental periods were assessed accordingly. Sprague-Dawley rat pups were administered ibotenic acid at postnatal day (PD) 7. Western blotting and an immunofluorescence staining analysis showed that the expression of NRP/B was significantly decreased in the hippocampus, cortex and striatum of the NVHL rats at PD14, 28 and 42. The expressions of NeuN were decreased accordingly. In vitro experiment showed the NRP/B knockdown can decrease the Tuj1 expression in cultured cortical neurons. The data suggest that NVHL induces a change in NRP/B expression that affects neurons in the developmental period.