Guang He

Common variants on 8p12 and 1q24.2 confer risk of schizophrenia

Schizophrenia is a severe mental disorder affecting ∼1% of the world population, with heritability of up to 80%. To identify new common genetic risk factors, we performed a genome-wide association study (GWAS) in the Han Chinese population. The discovery sample set consisted of 3,750 individuals with schizophrenia and 6,468 healthy controls (1,578 cases and 1,592 controls from northern Han Chinese, 1,238 cases and 2,856 controls from central Han Chinese, and 934 cases and 2,020 controls from the southern Han Chinese). We further analyzed the strongest association signals in an additional independent cohort of 4,383 cases and 4,539 controls from the Han Chinese population. Meta-analysis identified common SNPs that associated with schizophrenia with genome-wide significance on 8p12 (rs16887244, P = 1.27 × 10−10) and 1q24.2 (rs10489202, P = 9.50 × 10−9). Our findings provide new insights into the pathogenesis of schizophrenia.

Prenatal Malnutrition and Adult Schizophrenia: Further Evidence From the 1959-1961 Chinese Famine

OBJECTIVE Evidence from the 1944-1995 Dutch Hunger Winter and the 1959-1961 Chinese famines suggests that those conceived or in early gestation during famines, have a 2-fold increased risk of developing schizophrenia in adult life. We tested the hypothesis in a second Chinese population and also determined whether risk differed between urban and rural areas. METHOD The risk of schizophrenia was examined in Liuzhou prefecture of Guangxi autonomous region. Rates were compared among those conceived before, during, and after the famine years. Based on the decline in birth rates, we predicted that those born in 1960 and 1961 would have been exposed to the famine during conception or early gestation. All psychiatric case records in Liuzhou psychiatric hospital for the years 1971 through 2001 were examined and clinical/sociodemographic data extracted by psychiatrists blind to exposure status. Data on births and deaths in the famine years were also available, and cumulative mortality was estimated from later demographic surveys. Evidence of famine was verified, and results were adjusted for mortality. Relative risks (RRs) for schizophrenia were calculated for the region as a whole and for urban and rural areas separately. RESULTS Mortality-adjusted RR for schizophrenia was 1.5 (1960) and 2.05 (1961), respectively. However, the effect was exclusively from the rural areas RR = 1.68 (1960) and RR = 2.25 (1961). CONCLUSIONS We observe a 2-fold increased risk of schizophrenia among those conceived or in early gestation at the height of famine with risk related to severity of famine conditions.

A case-control study of the relationship between the metabotropic glutamate receptor 3 gene and schizophrenia in the Chinese population

Recent studies of the association between the metabotropic glutamate receptor 3 gene (GRM3) and schizophrenia have produced conflicting results, although GRM3 is a promising candidate gene. Fujii et al. found a single nuclear polymorphism (SNP) for within this gene, rs1468412 to have a positive association to schizophrenia in Japanese patients. To investigate this further, we genotyped 7 SNPs around GRM3 including rs1468412, in 752 Chinese patients with schizophrenia and 752 controls using Taqman technology. We did not detect any association between rs1468412 and schizophrenia, however we found differences in the allele frequency distribution of SNP rs2299225 (p=0.0297, odds ration [OR]=1.44, 95% confidence interval 1.05-1.99) between cases and controls. Moreover, the overall frequency of haplotypes constructed from three SNPs including rs2299225 showed significant differences between cases and controls (p=0.0017). Our results partially support the previous studies in other ethnic groups and indicate that the GRM3 gene may play an important role in the etiology of schizophrenia in the Han Chinese.

Association of DAAO with schizophrenia in the Chinese population.

Recently, the gene called DAAO was reported to be associated with schizophrenia in the French Canadian populations. Here, we report a result obtained in the study of our large collection of 547 schizophrenia cases and 536 controls in the Chinese population. Six single-nucleotide polymorphisms (SNPs) were genotyped at and around the DAAO locus, covering a 10-kb region entirely encompassing the complementary DNA sequences of DAAO. We found statistically significant differences in allele distributions on one marker: SNP rs3741775 (P = 0.0000001). In the haplotype analysis based on the information of linkage-disequilibrium block across this gene locus, we demonstrated a highly significant association between schizophrenia and a DAAO haplotype (P = 2.0173 x 10(-21)), which therefore provides an independent statistical support for association of the DAAO gene with schizophrenia and indicates that the DAAO gene may play a significant role in the etiology of schizophrenia in the Han Chinese.

Copy-number mutations on chromosome 17q24.2-q24.3 in congenital generalized hypertrichosis terminalis with or without gingival hyperplasia.

Congenital generalized hypertrichosis terminalis (CGHT) is a rare condition characterized by universal excessive growth of pigmented terminal hairs and often accompanied with gingival hyperplasia. In the present study, we describe three Han Chinese families with autosomal-dominant CGHT and a sporadic case with extreme CGHT and gingival hyperplasia. We first did a genome-wide linkage scan in a large four-generation family. Our parametric multipoint linkage analysis revealed a genetic locus for CGHT on chromosome 17q24.2-q24.3. Further two-point linkage and haplotyping with microsatellite markers from the same chromosome region confirmed the genetic mapping and showed in all the families a microdeletion within the critical region that was present in all affected individuals but not in unaffected family members. We then carried out copy-number analysis with the Affymetrix Genome-Wide Human SNP Array 6.0 and detected genomic microdeletions of different sizes and with different breakpoints in the three families. We validated these microdeletions by real-time quantitative PCR and confirmed their perfect cosegregation with the disease phenotype in the three families. In the sporadic case, however, we found a de novo microduplication. Two-color interphase FISH analysis demonstrated that the duplication was inverted. These copy-number variations (CNVs) shared a common genomic region in which CNV is not reported in the public database and was not detected in our 434 unrelated Han Chinese normal controls. Thus, pathogenic copy-number mutations on 17q24.2-q24.3 are responsible for CGHT with or without gingival hyperplasia. Our work identifies CGHT as a genomic disorder.

Positive association between synapsin II and schizophrenia

BACKGROUND Synapsin II encodes a neuron-specific phosphoprotein that selectively binds to small synaptic vesicles in the presynaptic nerve terminal. The expressions of messenger ribonucleic acid and protein of synapsin II have been reported to be significantly reduced in the brains of schizophrenia patients. The synapsin II gene is located on 3p25, a region that has been implicated to be associated with schizophrenia by genetic linkage. All these findings suggest synapsin II as a candidate gene for schizophrenia. METHODS In this work, we studied four markers (two single nucleotide polymorphisms (SNPs): rs308963 and rs795009; and two insertion/deletion polymorphisms: rs2307981 and rs2308169) covering 144.2 kilobase pairs (kb) with an average interval of 38 kb in synapsin II in a sample of 654 schizophrenic patients and 628 normal control subjects to explore the mechanism underlying schizophrenia. RESULTS We found significant differences in allele frequency distribution of SNP rs795009 (p =.000018, odds ratio 1.405, 95% confidence interval 1.202-1.641) between patients and control subjects. The T allele was significantly higher in patients than in control subjects. Moreover, the overall frequency of haplotype showed significant differences between patients and control subjects (p <.000001). CONCLUSIONS This study suggests a positive association between synapsin II and schizophrenia, implying that synapsin II is involved in the etiology of schizophrenia.

Family-based association study of synapsin II and schizophrenia.

Synapsin II has been proposed as a candidate gene for vulnerability to schizophrenia on the basis of its function and its location in a region of the genome implicated by linkage studies in families with schizophrenia. We recently reported positive association of synapsin II with schizophrenia in a case-control study (Chen et al. 2004). However, since case-control analyses can generate false-positive results in the presence of minor degrees of population stratification, we have performed a replication study in 366 additional Han Chinese probands and their parents by use of analyses of transmission/disequilibrium for three in/del markers and three single-nucleotide polymorphisms. Positive association was observed for rs2307981 (P =.02), rs2308169 (P =.005), rs308963 (P =.002), rs795009 (P =.02), and rs2307973 (P =.02). For transmission of six-marker haplotypes, the global P value was.0000016 (5 degrees of freedom), principally because of overtransmission of the most common haplotype, CAA/-/G/T/C/- (frequency 53.6%; chi (2) = 20.8; P =.0000051). This confirms our previous study and provides further support for the role of synapsin II variants in susceptibility to schizophrenia.

Systematic study of association of four GABAergic genes: Glutamic acid decarboxylase 1 gene, glutamic acid decarboxylase 2 gene, GABAB receptor 1 gene and GABAA receptor subunit β2 gene, with schizophrenia using a universal DNA microarray

Several studies have suggested the dysfunction of the GABAergic system as a risk factor in the pathogenesis of schizophrenia. In the present study, case-control association analysis was conducted in four GABAergic genes: two glutamic acid decarboxylase genes (GAD1 and GAD2), a GABA(A) receptor subunit beta2 gene (GABRB2) and a GABA(B) receptor 1 gene (GABBR1). Using a universal DNA microarray procedure we genotyped a total of 20 SNPs on the above four genes in a study involving 292 patients and 286 controls of Chinese descent. Statistically significant differences were observed in the allelic frequencies of the rs187269C/T polymorphism in the GABRB2 gene (P=0.0450, chi(2)=12.40, OR=1.65) and the -292A/C polymorphism in the GAD1 gene (P=0.0450, chi(2)=14.64 OR=1.77). In addition, using an electrophoretic mobility shift assay (EMSA), we discovered differences in the U251 nuclear protein binding to oligonucleotides representing the -292 SNP on the GAD1 gene, which suggests that the -292C allele has reduced transcription factor binding efficiency compared with the 292A allele. Using the multifactor-dimensionality reduction method (MDR), we found that the interactions among the rs187269C/T polymorphism in the GABRB2 gene, the -243A/G polymorphism in the GAD2 gene and the 27379C/T and 661C/T polymorphisms in the GAD1 gene revealed a significant association with schizophrenia (P<0.001). These findings suggest that the GABRB2 and GAD1 genes alone and the combined effects of the polymorphisms in the four GABAergic system genes may confer susceptibility to the development of schizophrenia in the Chinese population.

Possible association of the MAG locus with schizophrenia in a Chinese Han cohort of family trios

Neurotransmitter-based hypotheses have so far led to only moderate success in predicting new pathogenetic findings in etiology of schizophrenia. On the other hand, the more recent oligodendroglia hypotheses of this disorder have been supported by an increasing body of evidence. For example, the expression level of the myelin associated glycoprotein (MAG) gene has been shown to be significantly lower in schizophrenia patient groups compared to control groups. Such an effect might be a result of genetic variations of the MAG gene. In order to test this hypothesis, we genotyped four markers within the MAG locus in 413 trios sample of the Han Chinese using allele-specific PCR. None of the four markers revealed noticeable allelic significance. However, the four-marker and two-marker haplotypes covering components rs720309 and rs720308 were observed to be significantly associated with schizophrenia (P < 0.0001) in this study. In addition, we identified one common risk haplotype TA (rs720309-rs720308, present in 78.5% of the general population) that showed increased evidence of overtransmission from parents to affected offspring (P = 0.0001). The results demonstrated MAG might play a role in genetic susceptibility to schizophrenia. Furthermore, our finding of a possible association between the MAG locus and schizophrenia is in agreement with the hypotheses of oligodendrltic and myelination dysfunction.

BDNF gene is a genetic risk factor for schizophrenia and is related to the chlorpromazine-induced extrapyramidal syndrome in the Chinese population

Background Brain-derived neurotrophic factor (BDNF) belongs to a family of the neurotrophin, which plays important roles in the neurodevelopment of dopaminergic-related systems and interacts with meso-limbic dopaminergic systems involved in the therapeutic response to antipsychotics. Functional experiments have suggested that BDNF may be involved in the etiology of schizophrenia. Methods and results In this study, we genotyped two important functional polymorphisms in the BDNF gene using a sample of Han Chinese patients consisting of 340 schizophrenic patients and 343 healthy controls. We found a statistical difference in the 232-bp allele distribution of the BDNF gene (GT)n dinucleotide repeat polymorphism between the schizophrenic patients and controls. In early onset patients, the 234-bp allele had a risk role. For the chlorpromazine-induced extrapyramidal syndrome, the 230-bp allele and the 234-bp allele acted in opposite directions, that is, patients with the 230-bp allele of the (GT)n polymorphism exhibited a lower degree of induced extrapyramidal syndrome. Haplotype-based analysis also revealed a very important risk haplotype (P=0.0000226546). Conclusion These findings suggest that BDNF plays an important role in the susceptibility to schizophrenia and that the (GT)n repeat polymorphism of the BDNF gene may be an independent contributor to the chlorpromazine treatment-sensitive form of schizophrenia.