Schizophrenia-risk variant rs6994992 in the neuregulin-1 gene on brain developmental trajectories in typically developing children

New clues for the role of cerebellum in schizophrenia and the associated cognitive impairment

Schizophrenia (SZ) is a complex neuropsychiatric disorder associated with severe cognitive dysfunction. Although research has mainly focused on forebrain abnormalities, emerging results support the involvement of the cerebellum in SZ physiopathology, particularly in Cognitive Impairment Associated with SZ (CIAS). Besides its role in motor learning and control, the cerebellum is implicated in cognition and emotion. Recent research suggests that structural and functional changes in the cerebellum are linked to deficits in various cognitive domains including attention, working memory, and decision-making. Moreover, cerebellar dysfunction is related to altered cerebellar circuit activities and connectivity with brain regions associated with cognitive processing. This review delves into the role of the cerebellum in CIAS. We initially consider the major forebrain alterations in CIAS, addressing impairments in neurotransmitter systems, synaptic plasticity, and connectivity. We then focus on recent findings showing that several mechanisms are also altered in the cerebellum and that cerebellar communication with the forebrain is impaired. This evidence implicates the cerebellum as a key component of circuits underpinning CIAS physiopathology. Further studies addressing cerebellar involvement in SZ and CIAS are warranted and might open new perspectives toward understanding the physiopathology and effective treatment of these disorders.

Disruptions in white matter microstructure associated with impaired visual associative memory in schizophrenia-spectrum illness

Episodic memory ability relies on hippocampal-prefrontal connectivity. However, few studies have examined relationships between memory performance and white matter (WM) microstructure in hippocampal-prefrontal pathways in schizophrenia-spectrum disorder (SSDs). Here, we investigated these relationships in individuals with first-episode psychosis (FEP) and chronic schizophrenia-spectrum disorders (SSDs) using tractography analysis designed to interrogate the microstructure of WM tracts in the hippocampal-prefrontal pathway. Measures of WM microstructure (fractional anisotropy [FA], radial diffusivity [RD], and axial diffusivity [AD]) were obtained for 47 individuals with chronic SSDs, 28 FEP individuals, 52 older healthy controls, and 27 younger healthy controls. Tractography analysis was performed between the hippocampus and three targets involved in hippocampal-prefrontal connectivity (thalamus, amygdala, nucleus accumbens). Measures of WM microstructure were then examined in relation to episodic memory performance separately across each group. Both those with FEP and chronic SSDs demonstrated impaired episodic memory performance. However, abnormal WM microstructure was only observed in individuals with chronic SSDs. Abnormal WM microstructure in the hippocampal-thalamic pathway in the right hemisphere was associated with poorer memory performance in individuals with chronic SSDs. These findings suggest that disruptions in WM microstructure in the hippocampal-prefrontal pathway may contribute to memory impairments in individuals with chronic SSDs but not FEP.

Identification of Neuregulin 1 as Predictor Outcome in Intracranial Astrocytoma

BACKGROUND: Astrocytoma is the most common primary brain tumor. The combination of adhesion molecules, proteases, and cytokines that regulate their expression likely underlies tumor progression. The cytokine of neuregulin 1 (NRG1) has a role in progression and invasion of tumor cells by activating signal after binding its receptor. AIM: To identification NRG1 expression with characteristic of intracranial astrocytoma patient is the purpose of this study. METHODS: This study uses analytic method with retrospective study. It analyzed the association between NRG1 expressions in astrocytoma patients. The study included 32 samples which were admitted to Haji Adam Malik Hospital Medan from September 2016 to August 2018. RESULTS: There was no significant association between NRG1 expression with age (p = 0.853) and gender (p = 0.565) of astrocytoma patients, while there was a significant association between NRG1 expression with cell proliferation (p = 0.00), WHO grading of astrocytoma (p = 0.00), and outcomes (p = 0.023). According to this study, the most common results are strong NRG1 expression has many cells proliferation in 10 (31.1%) patients, strong NRG1 expression with Grade IV astrocytoma found in 7 (21.9%) patients, and moderate NRG1 expression in live patient found in 7 (21.9%) patient. CONCLUSION: There is significant association between NRG1 expression and cell proliferation, WHO grading of astrocytoma, and outcomes.

Association between schizophrenia risk allele dosage of rs6994992 and whole-brain structural and functional characteristics

The rs6994992 polymorphism has been reported as a candidate variant associated with schizophrenia (SZ). Neuroimaging studies have revealed that SZ is associated with widespread structural and functional alterations in brain. However, whether the allele dosage of rs6994992 is associated with brain structural or functional features is unclear. We aimed to investigate the association between the risk allele dosage of rs6994992 and whole-brain structural and functional characteristics and to further explore the relationship between these characteristics and cognition. Magnetic resonance images and the rs6994992 genotype were obtained from 53 healthy participants. A general linear model was used to determine the effects of risk allele dosage of rs6994992 on brain characteristics. Spearman correlation analysis was employed to calculate the correlation between altered brain characteristics and cognitive scores. Our results demonstrated that regions with significant differences in structural characteristics between groups with different dosages of rs6994992 were mainly located in the frontal and temporal lobes, hippocampus and angular gyrus. Moreover, significant regions of functional connectivity (FC) partly overlapped with the structural results. Measurements in those significant regions and FCs were correlated with the cognition scales. This association can inform our understanding of the mechanisms through which rs6994992 variants increase the risk for SZ.

Lifetime surgical exposure, episodic memory, and forniceal microstructure in older adults

Introduction: Aging is associated with heterogeneous cognitive trajectories. There is considerable interest in identifying risk factors for pathological aging, with recent studies demonstrating a link between surgical procedures and proximal cognitive decline; however, the role of lifetime exposure to surgical procedures and cognitive function has been relatively unexplored. This pilot study aimed to evaluate the association between total lifetime surgical procedures and memory function in older adults. Methods: A cohort of 62 older adults underwent a neuropsychological evaluation and health history assessment. Self-reported lifetime surgical history was categorized as "cardiac" or "non-cardiac." General linear models were fit with demographics as nuisance covariates, and the total number of non-cardiac surgeries as our predictor of interest. Total scores on measures of episodic memory, language, working memory, fluency, and visuospatial function were separate outcome variables. In a secondary analysis, vascular risk factors were included as covariates. Diffusion tensor imaging was obtained for exploratory analyses of selected regions of interest. Results: The mean age of participants was 70, and 0-13 lifetime non-cardiac surgical procedures were reported. Higher numbers of lifetime non-cardiac surgical procedures were associated with worse verbal learning and memory (p = .04). The negative association between lifetime non-cardiac procedures and cognition was specific to memory. Exploratory analyses showed that higher number of lifetime non-cardiac procedures was related to lower FA in the fornix body (p = .02). Conclusions: These results of this pilot study suggest that greater lifetime exposure to surgery may be associated with worse verbal learning and memory in healthy older adults. These findings add to a growing body of literature suggesting that cumulative medical events may be risk factors for negative cognitive outcomes.

A functional neuregulin-1 gene variant and stressful life events: Effect on drug use in a longitudinal population-representative cohort study

BACKGROUND

The neuregulin 1 gene is a susceptibility gene for substance dependence. A functional polymorphism (SNP8NRG243177/rs6994992; C/T) in the promoter region of the brain-specific type IV neuregulin-1 gene ( NRG1) has been associated with psychiatric disorders (e.g. schizophrenia and bipolar disorder) that often present higher odds of smoking, alcohol and illicit drug use. This study assessed the association of the NRG1 genotype with drug use and possible interaction with stressful life events (SLEs).

METHODS

The database of the Estonian Children Personality Behaviour and Health Study (beginning in 1998) was used. Cohorts of children initially 9 years old ( n=583; followed up at 15 and 18 years) and 15 years old ( n=593; followed up at 18 and 25 years) provided self-reports on alcohol, tobacco and illicit substance use and SLEs. Psychiatric assessment based on DSM-IV was carried out on the older birth cohort at age 25 to assess the lifetime presence of substance use disorders. NRG1 rs6994992 was genotyped in all participants by TaqMan® Pre-Designed SNP Genotyping Assay on the Applied Biosystems ViiA™ 7 Real-Time PCR System. The minor (T) allele frequency was 0.37.

RESULTS

NRG1 rs6994992 C/C homozygotes, especially those who had experienced more SLEs, were more likely to develop alcohol use disorders by young adulthood, were generally more active consumers of tobacco products, and had more likely used illicit drugs. In T allele carriers, SLEs had a negligible effect on substance use.

CONCLUSIONS

In humans, NRG1 genotype is associated with substance use, and this relationship is moderated by adverse life events, with a gain-of-function allele being protective.

Dyslexia and language impairment associated genetic markers influence cortical thickness and white matter in typically developing children

Dyslexia and language impairment (LI) are complex traits with substantial genetic components. We recently completed an association scan of the DYX2 locus, where we observed associations of markers in DCDC2, KIAA0319, ACOT13, and FAM65B with reading-, language-, and IQ-related traits. Additionally, the effects of reading-associated DYX3 markers were recently characterized using structural neuroimaging techniques. Here, we assessed the neuroimaging implications of associated DYX2 and DYX3 markers, using cortical volume, cortical thickness, and fractional anisotropy. To accomplish this, we examined eight DYX2 and three DYX3 markers in 332 subjects in the Pediatrics Imaging Neurocognition Genetics study. Imaging-genetic associations were examined by multiple linear regression, testing for influence of genotype on neuroimaging. Markers in DYX2 genes KIAA0319 and FAM65B were associated with cortical thickness in the left orbitofrontal region and global fractional anisotropy, respectively. KIAA0319 and ACOT13 were suggestively associated with overall fractional anisotropy and left pars opercularis cortical thickness, respectively. DYX3 markers showed suggestive associations with cortical thickness and volume measures in temporal regions. Notably, we did not replicate association of DYX3 markers with hippocampal measures. In summary, we performed a neuroimaging follow-up of reading-, language-, and IQ-associated DYX2 and DYX3 markers. DYX2 associations with cortical thickness may reflect variations in their role in neuronal migration. Furthermore, our findings complement gene expression and imaging studies implicating DYX3 markers in temporal regions. These studies offer insight into where and how DYX2 and DYX3 risk variants may influence neuroimaging traits. Future studies should further connect the pathways to risk variants associated with neuroimaging/neurocognitive outcomes.

ERBB4 polymorphism and family history of psychiatric disorders on age-related cortical changes in healthy children

Genetic variations in ERBB4 were associated with increased susceptibility for schizophrenia (SCZ) and bipolar disorders (BPD). Structural imaging studies showed cortical abnormalities in adolescents and adults with SCZ or BPD. However, less is known about subclinical cortical changes or the influence of ERBB4 on cortical development. 971 healthy children (ages 3-20 years old; 462 girls and 509 boys) were genotyped for the ERBB4-rs7598440 variants, had structural MRI, and cognitive evaluation (NIH Toolbox ®). We investigated the effects of ERBB4 variants and family history of SCZ and/or BPD (FH) on cortical measures and cognitive performances across ages 3-20 years using a general additive model. Variations in ERBB4 and FH impact differentially the age-related cortical changes in regions often affected by SCZ and BPD. The ERBB4-TT-risk genotype children with no FH had subtle cortical changes across the age span, primarily located in the left temporal lobe and superior parietal cortex. In contrast, the TT-risk genotype children with FH had more pronounced age-related changes, mainly in the frontal lobes compared to the non-risk genotype children. Interactive effects of age, FH and ERBB4 variations were also found on episodic memory and working memory, which are often impaired in SCZ and BPD. Healthy children carrying the risk-genotype in ERBB4 and/or with FH had cortical measures resembling those reported in SCZ or BPD. These subclinical cortical variations may provide early indicators for increased risk of psychiatric disorders and improve our understanding of the effect of the NRG1-ERBB4 pathway on brain development.

Fornix as an imaging marker for episodic memory deficits in healthy aging and in various neurological disorders

The fornix is a part of the limbic system and constitutes the major efferent and afferent white matter tracts from the hippocampi. The underdevelopment of or injuries to the fornix are strongly associated with memory deficits. Its role in memory impairments was suggested long ago with cases of surgical forniceal transections. However, recent advances in brain imaging techniques, such as diffusion tensor imaging, have revealed that macrostructural and microstructural abnormalities of the fornix correlated highly with declarative and episodic memory performance. This structure appears to provide a robust and early imaging predictor for memory deficits not only in neurodegenerative and neuroinflammatory diseases, such as Alzheimer's disease and multiple sclerosis, but also in schizophrenia and psychiatric disorders, and during neurodevelopment and “typical” aging. The objective of the manuscript is to present a systematic review regarding published brain imaging research on the fornix, including the development of its tracts, its role in various neurological diseases, and its relationship to neurocognitive performance in human studies.