Lack of association between MPC2 variants and schizophrenia in a replication study of Han Chinese

Mitochondrial Pyruvate Carrier Function in Health and Disease across the Lifespan

As a nodal mediator of pyruvate metabolism, the mitochondrial pyruvate carrier (MPC) plays a pivotal role in many physiological and pathological processes across the human lifespan, from embryonic development to aging-associated neurodegeneration. Emerging research highlights the importance of the MPC in diverse conditions, such as immune cell activation, cancer cell stemness, and dopamine production in Parkinson’s disease models. Whether MPC function ameliorates or contributes to disease is highly specific to tissue and cell type. Cell- and tissue-specific differences in MPC content and activity suggest that MPC function is tightly regulated as a mechanism of metabolic, cellular, and organismal control. Accordingly, recent studies on cancer and diabetes have identified protein–protein interactions, post-translational processes, and transcriptional factors that modulate MPC function. This growing body of literature demonstrates that the MPC and other mitochondrial carriers comprise a versatile and dynamic network undergirding the metabolism of health and disease.

Genetic association and meta-analysis of a schizophrenia GWAS variant rs10489202 in East Asian populations

Previous genome-wide association studies (GWAS) suggest that rs10489202 in the intron of MPC2 (mitochondrial pyruvate carrier 2) is a risk locus for schizophrenia in Han Chinese populations. To validate this discovery, we conducted a replication analysis in an independent case-control sample of Han Chinese ancestry (437 cases and 2031 controls), followed by a meta-analytic investigation in multiple East Asian samples. In the replication analysis, rs10489202 showed marginal association with schizophrenia (two-tailed P = 0.071, OR = 1.192 for T allele); in the meta-analysis using a total of 14,340 cases and 20,349 controls from ten East Asian samples, rs10489202 was genome-wide significantly associated with schizophrenia (two-tailed P = 3.39 × 10^-10, OR = 1.161 for T allele, under the fixed-effect model). We then performed an explorative investigation of the association between this SNP and bipolar disorder, as well as a major depressive disorder, and the schizophrenia-predisposing allele was associated with an increased risk of major depressive disorder in East Asians (two-tailed P = 2.49 × 10^-2, OR = 1.103 for T allele). Furthermore, expression quantitative trait loci (eQTL) analysis in lymphoblastoid cell lines from East Asian donors (N = 85 subjects) revealed that rs10489202 was specifically and significantly associated with the expression of TIPRL gene (P = 5.67 × 10^-4). Taken together, our data add further support for the genetic involvement of this genomic locus in the susceptibility to schizophrenia in East Asian populations, and also provide preliminary evidence for the underlying molecular mechanisms.

Association of NKAPL, TSPAN18, and MPC2 gene variants with schizophrenia based on new data and a meta-analysis in Han Chinese

BACKGROUND

Schizophrenia (SZ) is suggested to be a complex polygenetic disorder with high heritability. Genome-wide association studies have found that the rs1635, rs11038167, and rs10489202 polymorphisms are associated with SZ in Han Chinese. However, results of validation studies are inconsistent. This study aimed to test the association between the NKAPL rs1635, TSPAN18 rs11038167, and MPC2 rs10489202 polymorphisms and SZ in a Chinese population.

METHODS

This study contained 700 unrelated SZ patients (300 Zhuang and 400 Han) and 700 gender- and age-matched controls (300 Zhuang and 400 Han). The polymorphisms in TSPAN18 (rs11038167), NKAPL (rs1635), and MPC2 (rs10489202) were genotyped using the Sequenom MassARRAY method. Statistical analyses were performed with PLINK program and SPSS l6.0 for Windows. STATA11.1 was used for meta-analysis.

RESULTS

No statistically significant difference was found in different allele and genotype frequencies of rs1635, rs11038167, and rs10489202 between SZ cases and controls of Zhuang and Han ethnicities and the total samples (all p>0.05). Further meta-analysis suggested that single-nucleotide polymorphism rs10489202 was significantly associated with SZ in a Han Chinese population (p OR=0.002).

CONCLUSIONS

Our case-control study failed to validate the significant association of NKAPL rs1635, TSPAN18 rs11038167, and MPC2 rs10489202 polymorphisms with SZ susceptibility in the southern Zhuang or Han Chinese population. However, meta-analysis showed a significant association between MPC2 variant rs10489202 and SZ susceptibility in Han Chinese.

Common variants on 17q25 and gene-gene interactions conferring risk of schizophrenia in Han Chinese population and regulating gene expressions in human brain

Recently, two genome-wide association studies (GWASs) of schizophrenia (SCZ) in Han Chinese identified several susceptibility loci. Replication efforts aiming to validate the GWAS findings were made and focused on the top hits. We conducted a more extensive follow-up study in an independent sample of 1471 cases and 1528 matched controls to verify 26 genetic variants by including nine top single-nucleotide polymorphisms (SNPs) that reached genome-wide significance and 17 promising SNPs nominated in the initial discovery phase. rs8073471 in an intron of tubulin-folding cofactor D (TBCD) obtained nominal significance (P<0.01) in single SNP analysis. Logistic regression identified significant interaction between rs3744165 (5'-untranslated region variant of exon 2 of zinc finger protein 750 (ZNF750), and in an intron of TBCD) and rs8073471 (Deviance test P-value=2.77 × 10(-34)). Both SNPs are located at 17q25, an interesting region that has been implicated in SCZ. By using the Genotype-Tissue Expression (GTEx) data set, we implemented an expression quantitative trait loci epistasis analysis to explore the association between the genotype combinations of the two SNPs and gene expression levels in 13 areas of human central nervous system. We observed that rs3744165 × rs8073471 interaction modulated the expression profile of TEAD3 (P=1.87 × 10(-8)), SH3TC2 (P=2.00 × 10(-8)), KCNK9 (P=5.20 × 10(-7)) and PPDPF (P=1.13 × 10(-6)) in postmortem cortex tissue; EFNA1 (P=7.26 × 10(-9)), RNU4ATAC (P=2.32 × 10(-8)) and NUPL2 (P=6.79 × 10(-8)) in cerebellum tissue. To the best of our knowledge, our study is the first one that links TBCD and ZNF750 mutations to SCZ susceptibility and to the transcript levels in human brain tissues. Further efforts are needed to understand the role of those variants in the pathogenesis of SCZ.

Replication of Han Chinese GWAS loci for schizophrenia via meta-analysis of four independent samples

Schizophrenia is a highly heritable psychiatric disorder with unclear aetiology. Recent genome-wide association studies (GWAS) in European populations have reported numerous susceptibility variants, while GWAS in East Asians also identified several risk loci but with fewer independent replications. Here we focus on nine single nucleotide polymorphisms (SNPs) which have shown genome-wide significant associations with schizophrenia in previous Han Chinese GWAS, and we tend to replicate the associations in four independent samples of East Asian origin including a total of 3977 cases and 5589 controls. The results showed that rs10489202 in MPC2 (BRP44) is significantly associated with schizophrenia in these East Asian replication samples (one-tailed P=5.75×10(-3), OR=1.12), and further meta-analysis after including previous GWAS data yielded a genome-wide significant association (two-tailed P=1.11×10(-10), OR=1.19), adding further support for the involvement of this locus in the genetic risk of schizophrenia, and future studies regarding the underlying molecular mechanisms of the risk association are necessary.

Lack of Association between the TSPAN18 Gene and Schizophrenia Based on New Data from Han Chinese and a Meta-Analysis

Tetraspanin-18 (TSPAN18) potentially plays a role in the calcium signaling that is associated with dopamine-induced cortical neuron apoptosis and is considered to be an important mechanism in the pathogenesis of schizophrenia (SCZ). Furthermore, a genome-wide association study (GWAS) identified TSPAN18 as a possible susceptibility gene for SCZ. To validate these findings and reveal the effects of different inheritance models, seven single nucleotide polymorphisms (SNPs) of the TSPAN18 gene were analyzed in 443 patients with SCZ and 628 controls of Han Chinese descent via the SNPscan method. Single SNP, genotype, and association analyses with different models (i.e., additive, dominant, and recessive models) were performed, and the published datasets (2062 cases and 2053 controls) were combined with our results to determine the inheritance effects of the SNPs on SCZ. We observed genotypes and allele distributions of TSPAN18 gene did not show any significant associations in the Han Chinese population based on our experimental and meta-analytical results. Our findings indicate that the TSPAN18 gene is unlikely to be a major susceptibility gene for schizophrenia in Han Chinese.

An exploratory study of the association between SORL1 polymorphisms and sporadic Alzheimer's disease in the Han Chinese population

In previous studies, we reported that the sortilin-related receptor, L (DLR class) A repeats containing (SORL1) gene single nucleotide polymorphisms (SNPs) are associated with the risk of sporadic Alzheimer's disease (SAD) in the Han Chinese population. To further explore the relationships between SORL1 genetic variants and SAD, we conducted a two-step study. Sequencing analysis in 50 case samples identified 14 SNPs within the promoter and untranslated region of the SORL1 gene. Subsequent genotyping analysis in 106 patients with SAD and 179 healthy controls detected a significant association between the "G" allele of SNP rs1133174 in the 3' untranslated region of the SORL1 gene and SAD risk (odds ratio =1.92, 95% confidence interval [95% CI] =1.28-2.90, adjusted P=0.028). In addition, "G" allele carriers of rs1133174 (GA + GG) have a 2.15-fold increased risk of SAD compared to noncarriers (AA) (adjusted P=0.042). However, no significant positive associations were observed in the other 13 SNPs within the SORL1 gene. These preliminary findings suggest that the SORL1 SNP rs1133174 may be a potential risk locus for SAD in the Han Chinese population.

TSNARE1 polymorphisms are associated with schizophrenia susceptibility in Han Chinese

t-SNARE domain containing 1 gene (TSNARE1) is located at human chromosome 8q24.3, and may play a crucial role in intracellular protein transport and synaptic transmission. Recently, a large-scale meta-analysis of genome-wide association study dataset identified that rs10098073 and rs4129585, two single nucleotide polymorphisms (SNPs) within TSNARE1, were closely associated with the risk of schizophrenia in Caucasians. However, this finding has not been validated in other populations or ethnic groups thus far. In the current study, we conducted a case-control study to confirm the association of these two SNPs with the schizophrenia risk in a Han Chinese population comprising 440 schizophrenia patients and 450 control subjects. According to the genotype data of Han Chinese from Beijing in 1,000 Genomes Project database, rs10098073 and rs4129585 were located in one haplotype block and were in almost complete linkage disequilibrium (D' = 1, r (2) ≥ 0.952). Therefore, only rs10098073 was selected for the subsequent analysis. We showed for the first time that the minor allele (A) of rs10098073 was associated with a reduced risk of schizophrenia (OR = 0.753; 95 % CI 0.613-0.924; P = 0.007). Furthermore, we found that the A allele of rs10098073 reduced the schizophrenia risk through a recessive manner (A/A vs. A/C + C/C, OR = 0.563; 95 % CI 0.357-0.89; P = 0.013, P Bonferroni corrected = 0.026) rather than a dominant manner (A/A + A/C vs. C/C, OR = 0.762; 95 % CI 0.586-0.992; P = 0.043, P Bonferroni corrected = 0.086). Taken together, these findings demonstrate a significant association between TSNARE1 polymorphisms and schizophrenia risk in a Han Chinese population, suggesting TSNARE1 may represent a susceptibility gene for this disease.

The SORL1 polymorphism rs985421 may confer the risk for amnestic mild cognitive impairment and Alzheimer's disease in the Han Chinese population

Although the pathogenetic mechanisms driving Alzheimer's disease (AD) are unclear, genetic variations may play an important role. Previous studies have identified that single nucleotide polymorphisms (SNPs) in the sortilin-related receptor, L (DLR class) A repeats containing (SORL1) gene are associated with AD or amnestic mild cognitive impairment (aMCI) patients. However, the association of SORL1 variants with AD or aMCI susceptibility in the Han Chinese population has not been adequately reported. Thus, we conducted a case-control study in 106 sporadic AD patients, 67 aMCI patients, and 179 healthy control Han Chinese subjects to determine whether SORL1 genetic variations alter the risk for AD or aMCI. Using the LDR-PCR method to genotype five polymorphisms in SORL1, we found significant associations (for AD: OR=1.968, 95% CI=1.273-3.042; for aMCI: OR=2.210, 95% CI=1.353-3.610) between the 'A' allele of the SORL1 SNP rs985421 and AD and aMCI, which may represent an ApoE ɛ4-independent risk factor for SAD. These findings suggest that the SORL1 SNP rs985421 may alter the risk for sporadic AD and aMCI in the Han Chinese population.