Genetic basis of schizophrenia: trinucleotide repeats. An update

Significant association of GRM7 and GRM8 genes with schizophrenia and major depressive disorder in the Han Chinese population

Metabotropic glutamate receptor type 7 (GRM7) and type 8 (GRM8) are involved in the neurotransmission of glutamate which is supposed to play an important role in the development of schizophrenia (SCZ) and major depressive disorders (MDD). We designed this study to investigate whether common DNA variants or their genetic interactions within GRM7 and GMR8 genes were associated with these disorders in the Han Chinese population. Fourteen SNPs in GRM7 and GRM8 were selected within a sample set comprising 1235 SCZ patients, 1045 MDD patients and 1235 normal controls. Significant association in SCZ case-control subjects was observed for rs2229902 (permutated Pallele=0.0005, OR=1.492 [95% CI=1.231-1.807]) and rs9870680 (permutated Pallele=0.0023, OR=1.262 [95% CI=1.116-1.426]) in GRM7 and rs2237781 (permutated Pallele=0.0027, OR=1.346 [95% CI=1.149-1.575]) in GRM8. Association analysis for MDD case-control subjects revealed positive results in rs779706 (permutated Pallele=0.0099, OR=1.237 [95% CI=1.093-1.399]) of GRM7 and in rs1361995 (permutated Pallele=0.0017, OR=1.488 [95% CI=1.215-1.823]) of GRM8. Moreover, a three-locus model, constituted by polymorphisms in GRM7 and GRM8 significantly correlated with MDD in the gene-gene interaction analysis. Meta-analysis and haplotype analysis further confirmed our significant results. We demonstrated the genetic association of GRM7 and GRM8 with SCZ and MDD in the Han Chinese population. We also found susceptibility interactive effects of these two genes with both psychiatric disorders, which might provide new insights into the etiology of them.

Genetic association of ACSM1 variation with schizophrenia and major depressive disorder in the Han Chinese population

Schizophrenia (SCZ) and major depressive disorder (MDD) are two of the most common and severe mental disorders, the etiologies of which are not yet clearly elucidated. The ACSM1 gene has been identified as a susceptibility gene for SCZ in two previous genome-wide association studies (GWAS). ACSM1 catalyzes the activation of fatty acids and plays an important role in the metabolic system. Some evidence has suggested that ACSM1 contributes to a genetic risk for MDD. The present study aimed to evaluate the common genetic risk of the ACSM1 gene in these two disorders in the Han Chinese population. In total, 1235 patients with SCZ, 1045 patients with MDD and 1235 control subjects of Chinese origin were recruited. Six single nuclear polymorphisms (SNPs) in ACSM1 were genotyped to test their associations with SCZ and MDD. SNP rs163234 was found to be significantly associated with both SCZ (permutated Pallele=1.700×10(-3), OR=1.350 [95% CI=1.152-1.581]) and MDD (permutated Pallele=4.800×10(-3), OR=1.329 [95% CI=1.127-1.567]). SNP rs433598 showed a strong association with SCZ (permutated Pallele=4.300×10(-3), OR=1.303 [95% CI=1.117-1.520]). Haplotype analysis of the blocks containing the two positive markers also revealed a significant association. This is the first study to assess the possible association of the ACSM1 gene with a genetic susceptibility for MDD. Our data are the first to suggest a positive association of the ACSM1 gene with a genetic susceptibility for SCZ and MDD in the Han Chinese population.

Functional −141C Ins/Del polymorphism in the dopamine D2 receptor gene promoter and schizophrenia in a Chinese Han population

Objective

The association between a putative functional promoter polymorphism, −141C insertion/deletion (Ins/Del), in the dopamine receptor D2 gene ( DRD2) and schizophrenia was investigated in a Chinese Han population.

Methods

The polymorphism was studied in unrelated schizophrenia patients and unrelated healthy controls. Linkage relationships were explored in core families of the schizophrenic patients using the transmission disequilibrium test. The Positive and Negative Syndrome Scale was used to evaluate the severity of the disorder.

Results

The Del allele was significantly less frequently found in patients (13/120; 11%) than in controls (18/100; 18%). In the 32 core families studied, 16 parents were Ins/Del heterozygotes. Parents transmitted the Ins and Del alleles to their children in 10 and six cases, respectively. Data from core families did not demonstrate linkage. Age, age at onset of schizophrenia and sex were not significantly different between carriers of the Ins and Del alleles. The group with the Ins allele had a significantly higher positive symptom score (75.3 ± 23.4 versus 53.9 ± 21.9) and excitement score (83.6 ± 16.8 versus 50.3 ± 24.6) than the Del group. Groups did not differ significantly in negative symptom and general psychopathology scores.

Conclusions

The DRD2 −141C Ins/Del polymorphism may affect susceptibility to schizophrenia in a Chinese Han population.

Transcriptional response to the neuroleptic-like compound Ampullosporin A in the rat ketamine model

Psychotic disorders affecting up to 1% of the human population represent pathological changes to the metabolic homeostasis of the brain. Increasing evidence in the literature suggests complex biochemical and/or transcriptional alterations accompanying schizophrenia-like phenomena. Sub-chronic treatment with sub-anaesthetic doses of ketamine induces schizophrenia-related psychotic alterations that can be used as an animal model in the study of this disorder. Ampullosporin A belongs to a specific group of pore-forming fungal peptides, peptaibols. We focused on the analysis of molecular events occurring in the brain of ketamine-pre-treated rats after administration of Ampullosporin A with neuroleptic-like activity. The complex experimental approach allowed us to correlate the use of low molecular weight substances with a transcriptome fingerprint in the prefrontal cortex. We found 63 genes to be up-regulated and 22 genes suppressed, with transthyretin, syndecan-1 and NeuroD1 showing the highest degree of up-regulation. Our results suggest the possibility that Ampullosporin A belongs to the group of neuroleptic-like compounds, inducing massive changes in neurotransmitter receptor composition, calcium signalling cascades and second messenger systems, and leading to the plastic reorganization of brain tissue, metabolic pathways and synapses.

Chaotic solar cycles modulate the incidence and severity of mental illness

This paper hypothesizes that the intensity of ultraviolet radiation (UVR) from the Sun predisposes humans to polygenic mutation fostering major mental illness (MMI) and other disorders of neurodevelopment. In addition, the variation in the intensity of this radiation acts to stress immune systems, possibly mediated by cytokines, resulting in variable clinical expressions of mental illness and autoimmune disorders. Organisms can adapt to chronic high-intensity UVR by producing melanin and by retaining various pigments. We found that 28% of 11-year solar cycles produce particularly severe solar flares during which UVR is 300% more intense and hence more damaging than normal. Out of a total of six severe cycles in the past 250 years, four have occurred in the past 55 years, possibly explaining the apparent increase in the incidence of MMI in recent decades. UVR is 10 times more mutagenic than ionizing radiation to nuclear DNA, and especially damaging to mitochondrial DNA. However, variable light as manifested by seasons stresses adaptability to UVR, possibly through an immune mechanism. We show that the region of the Earth having the most UVR, relative to the most variation in that light, is at 54 +/-10 degrees (N or S) latitude. Therefore, the most potential damage from sunlight occurs between the Equator and the Poles, not at the Equator itself. The human brain, our most important organ of adaptability, must be able to survive environmental variation, with successful matching to the environment resulting in adaptation. Unsuccessful adaptation to UVR (and possibly other types of radiation) results in mutation, which can produce neuro-chemical abnormalities manifested by MMI. We postulate that the combination of intensity and variation in UVR serves as a global modulator of MMI.

The Sun determines human longevity: teratogenic effects of chaotic solar radiation

An association between fertility and longevity has been known for many years, and considerable research has been focused on the mechanisms of ageing that ultimately determine longevity, which has remained essentially unchanged despite a near doubling of human life expectancy in the past 200 years. In this paper, the authors present evidence that the Sun determines the limits of longevity for the longest-living complex organisms. The Sun is a dynamical system and although solar cycles occur every 8-14 years (averaging approximately 11.1 years), the authors show that 28% of these cycles exhibit chaotic features and irregularly release up to 300% more ultraviolet radiation than usual. These chaotic solar cycles create an environment mutagenic to DNA that must be largely avoided in order to pass uncorrupted genes to the next generation. This requirement determines the limits of fertility, e.g., menarche and menopause in humans, and sets longevity to approximately 100 years.

Association study of CAG repeats in the KCNN3 gene in Israeli patients with major psychosis

OBJECTIVES

Several studies reported contradictory findings regarding the association of major psychosis with CAG repeats in the KCNN3 gene. We investigated the contribution of the CAG repeat at the KCNN3 gene, localized to chromosome 1q21.3, to the genetic susceptibility for schizophrenia, schizoaffective and bipolar disorders.

METHODS

Analysis of the number of CAG repeats and the differences in allele length were performed for Israeli Ashkenazi Jews, non-Ashkenazi Jews, and Arabs diagnosed with major psychosis (n=181) versus matched ethnic controls (n=207).

RESULTS

We found no significant difference in the number of CAG repeats between the entire sample of patients and controls. However, an analysis of the differences of allele length revealed a significantly greater number of patients with identical allele length (43.1%) when compared with normal controls (30.4%). Furthermore, an earlier age of non-paranoid schizophrenia onset was found associated with differences in allele sizes. There were no significant differences in the number of CAG repeats and the differences in allele length when subjects were grouped according to gender, ethnic origins of their parents, family history, and diagnostic groups.

CONCLUSIONS

Our results support the hypothesis that a contribution of the KCNN3 gene to genetic susceptibility to major psychosis and their phenotypic polymorphism may be related to the difference of allele length rather than to the number of CAG repeats.