Xiaopan Wu

Targeted genomic sequencing identifies PRRT2 mutations as a cause of paroxysmal kinesigenic choreoathetosis

Background Paroxysmal kinesigenic choreoathetosis (PKC) is characterised by recurrent and brief attacks of involuntary movement, inherited as an autosomal dominant trait with incomplete penetrance. A PKC locus has been previously mapped to the pericentromeric region of chromosome 16 (16p11.2-q12.1), but the causative gene remains unidentified. Methods/results Deep sequencing of this 30 Mb region enriched with array capture in five affected individuals from four Chinese PKC families detected two heterozygous PRRT2 insertions (c.369dupG and c.649dupC), producing frameshifts and premature stop codons (p.S124VfsX10 and p.R217PfsX8, respectively) in two different families. Sanger sequencing confirmed these two mutations and revealed a missense PRRT2 mutation (c.859G→A, p.A287T) in one of the two remaining families. This study also sequenced PRRT2 in 29 sporadic cases affected with PKC and identified mutations in 10 cases, including six with the c.649dupC mutation. Most variants were truncating mutations, consistent with loss-of-function and haploinsufficiency. Conclusion The present study identifies PRRT2 as the gene mutated in a subset of PKC, and suggests that PKC is genetically heterogeneous.

Evaluation of susceptibility locus for response to interferon-α based therapy in chronic hepatitis B patients in Chinese.

In 2009, three independent genome-wide association studies reported that genetic variation in the interleukin 28B gene to be associated with the response to interferon-α/ribavirin therapy in hepatitis C virus genotype 1 infected patients. We carried out the present study to assess whether such polymorphisms also affect the therapy effect of another interferon-α responsive illness as chronic hepatitis B. Five hundred and twelve interferon-α treatment-naïve HBeAg seropositive chronic hepatitis B patients were enrolled in the present retrospective nested case-control study. All patients received PEG-IFN-α-2a based treatment and were examined for the therapy efficacy. SNP rs8099917 was genotyped using the MassArray system (Sequenom). Interestingly, the frequency of G allele of rs8099917 was significantly higher in response group than in non response group (8.3% vs. 3.9%, p=0.003, OR=0.44, 95%CI=0.25-0.79). The genotype distributions of this SNP also differed significantly between two groups (p=0.003). Our study suggested that the G allele of rs8099917 was associated with higher rate of response in HBeAg seropositive chronic hepatitis B patients treated with interferon α.

PRRT2 Mutant Leads to Dysfunction of Glutamate Signaling.

Paroxysmal kinesigenic choreoathetosis (PKC) is an inherited disease of the nervous system. We previously identified PRRT2 as the causative gene of PKC. However, as little is known about the function of PRRT2, elucidating its function will benefit not only PKC studies, but also many other related disorders. Here, we reveal higher levels of glutamate in the plasma of PKC patients and the culture medium of neurons following knock-out Prrt2 expression. Using double immunostaining assays we confirm Prrt2 is located at the glutamatergic neurons in accordance with its function. Our co-immunoprecipitation assays reveal mutant PRRT2 interferes with SNAP25 and GRIA1 interactions, respectively. Furthermore, using live-labeling techniques, we confirmed co-transfection with mutant PRRT2 caused an increase in GRIA1 distribution on the cell surface. Therefore, our results suggest that mutant PRRT2, probably through its weakened interaction with SNAP25, affects glutamate signaling and glutamate receptor activity, resulting in the increase of glutamate release and subsequent neuronal hyperexcitability.

Apolipoprotein M promoter polymorphisms alter promoter activity and confer the susceptibility to the development of type 1 diabetes.

OBJECTIVES Apolipoprotein M plays an important role in the formation of prebeta-HDL and cholesterol efflux to HDL. In the present study, we investigate the potential association between the ApoM promoter polymorphisms and type 1 diabetes. DESIGN AND METHODS The study was conducted in Peking Union Medical College, Beijing, China and Karolinska Institutet, Stockholm, Sweden. Two populations, including 493 Han Chinese subjects (177 T1D patients/316 controls) and 225 Swedish (124/101), are enrolled in the present study. Three single nucleotide polymorphisms (SNP) C-1065A, T-855C and T-778C in the promoter region of the ApoM gene are genotyped using a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) protocol. Promoter activity was measured by reporter gene assay. RESULTS SNP T-778C was strongly associated with T1D in both Han Chinese (p=0.002, OR=2.188, CI 95%=1.338-3.581) and Swedish (p=0.021, OR=2.865, CI 95%=1.128-7.278) populations. The luciferase activity of -778C promoter was 1.41 times as high as that of -778T promoter (9.90+/-1.92 vs. 7.04+/-0.76, p=0.001). CONCLUSIONS Allele C of SNP T-778C may increase promoter activity and confer the risk susceptibility to the development of T1D.

Replication of Genome Wide Association Studies on Hepatocellular Carcinoma Susceptibility Loci in a Chinese Population

Background Genome-wide association studies (GWAS) have identified three loci (rs17401966 in KIF1B, rs7574865 in STAT4, rs9275319 in HLA-DQ) as being associated with hepatitis B virus-related hepatocellular carcinoma (HBV-related HCC) in a Chinese population, two loci (rs2596542 in MICA, rs9275572 located between HLA-DQA and HLA-DQB) with hepatitis C virus-related HCC (HCV-related HCC) in a Japanese population. In the present study, we sought to determine whether these SNPs are predictive for HBV-related HCC development in other Chinese population as well. Method and Findings We genotyped 4 SNPs, rs2596542, rs9275572, rs17401966, rs7574865, in 506 HBV-related HCC patients and 772 chronic hepatitis B (CHB) patients in Han Chinese by TaqMan methods. Odds ratio(OR)and 95% confidence interval (CI) were calculated by logistic regression. In our case-control study, significant association between rs9275572 and HCC were observed (P = 0.02, OR = 0.73, 95% CI = 0.56–0.95). In the further haplotype analysis between rs2596542 at 6p21.33 and rs9275572 at 6p21.3, G-A showed a protective effect on HBV-related HCC occurrence (P<0.001, OR = 0.66, 95% CI = 0.52–0.84). Conclusion These findings provided convincing evidence that rs9275572 significantly associated with HBV-related HCC.

Association between the γ-aminobutyric acid type B receptor 1 and 2 gene polymorphisms and mesial temporal lobe epilepsy in a Han Chinese population

An abnormal gamma-aminobutyric acid B receptor composed of gamma-aminobutyric acid type B receptor 1 (GABBR1) and gamma-aminobutyric acid type B receptor 2 (GABBR2) can provoke seizures. This study was designed to assess the contribution of GABBR1 and GABBR2 in mesial temporal lobe epilepsy (MTLE). Two tag single-nucleotide polymorphisms (SNPs) of GABBR1 and four tag SNPs of GABBR2 were selected and genotyped in 318 MTLE patients and 315 non-epileptic individuals. The rs967932 A-allele of GABBR2 increased the risk of MTLE in an additive and a dominant genetic model, respectively (P=0.018, OR=1.305, 95% CI 1.048-1.624 and P=0.003, OR=1.667, 95% CI 1.186-2.343, respectively). rs1999501 and rs944688 of GABBR2, and rs29259 of GABBR1 were thought to be associated with MTLE; however, after a Bonferroni correction, these associations were not observed and only the rs967932 A-allele was found to increase the risk of MTLE in the dominant model (P=0.036). The frequency at which the haplotype G-C-A-C (rs3780428-rs1999501-rs967932-rs944688) occurred in MTLE patients was significantly higher compared to the controls (12.26% vs. 6.51%, P=0.0004) and patients carrying this haplotype exhibited an earlier onset of MTLE (P=0.028). No evidence of significant allelic, genotypic, or haplotypic associations were identified in the tag SNPs of the GABBR1 gene in patients with MTLE, and the polymorphism at G1465A was not observed in our samples. Our results provide the first evidence that common genetic variations in the GABBR2 gene contribute to the risk of MTLE. Moreover, the present results do not support the hypothesis that common variants of GABBR1 contribute substantially to the epileptogenic effect during MTLE in the Han Chinese.

Genetic variations in STAT4,C2,HLA-DRB1 and HLA-DQ associated with risk of hepatitis B virus-related liver cirrhosis.

Recent genome-wide associated studies (GWASs) have revealed several common loci associated with the risk of hepatitis B virus (HBV)- or hepatitis C virus (HCV)-related hepatocellular carcinoma (HCC). We selected 15 single nucleotide polymorphisms (SNPs) identified through GWASs on HBV- or HCV-related HCC, and genotyped them in two independent Chinese cohorts of chronic HBV carriers, including 712 LC cases and 2601 controls. The association of each SNP with the risk of HBV-related LC was assessed by meta-analysis of the two cohorts. Of the 12 SNPs reported in HBV-related HCC GWASs, five SNPs (rs7574865 in STAT4, rs9267673 near C2, rs2647073 and rs3997872 near HLA-DRB1 and rs9275319 near HLA-DQ), were found to be significantly associated with the risk of HBV-related LC (rs7574865: P = 1.79 × 10−2, OR = 1.17, 95% CI = 1.03–1.34; rs9267673: P = 4.91 × 10−4, OR = 1.37, 95% CI = 1.15–1.63; rs2647073: P = 3.53 × 10−5, OR = 1.63, 95% CI = 1.29–2.06; rs3997872: P = 4.22 × 10−4, OR = 1.86, 95% CI = 1.32–2.62; rs9275319: P = 1.30 × 10−2, OR = 1.32, 95% CI = 1.06–1.64). However, among the three SNPs associated with the risk of HCV-related HCC in previous GWASs, none of them showed significant association with the risk of HBV-related LC. Our results suggested that genetic variants associated with HBV-related hepatocarcinogenesis may already play an important role in the progression from CHB to LC.

Association between polymorphisms of the cytokine and cytokine receptor genes and immune response to hepatitis B vaccination in a Chinese Han population

The immune response to hepatitis B vaccination varies among individuals. It has been reported that polymorphisms in cytokine and cytokine receptor genes are associated with these individual differences. The aim of the current study was to investigate the association between polymorphisms of the Th1/Th2 cytokine and cytokine receptor genes and the response to hepatitis B vaccination in a Chinese Han population. A total of 10 single nucleotide polymorphisms distributed in 6 genes (TNFRSF1A, IL12A, IL12B, IFNG, IL4, and IL10) were genotyped in 214 high‐responders [hepatitis B surface antibody (anti‐HBs) ≥1,000 mIU/ml] and 107 low‐responders (anti‐HBs: 10–99 mIU/ml). The minor CTCTAA allele of rs17860508 in the IL12B gene was associated with a low response to hepatitis B vaccination (P = 0.039, odds ratio = 1.41, 95% confidence interval = 1.00–1.99). In addition, a significant gene–gene interaction was found: the frequency of the combined genotypes IL12A rs2243115 TT and IL12B rs17860508 CTCTAA/CTCTAA was significantly higher in the low‐response group than in the high‐response group (P = 0.008, odds ratio = 2.19, 95% confidence interval = 1.23–3.93). These findings suggest that polymorphisms in the IL12A and IL12B genes might play an important role jointly in determining the response to hepatitis B vaccination. J. Med. Virol. 84:26–33, 2011.

Genetic Variation and Association Analyses of the Nuclear Respiratory Factor 1 (NRF1) Gene in Chinese Patients with Type 2 Diabetes

OBJECTIVE—Nuclear respiratory factor 1 (NRF1) is a strong biological and positional candidate to contribute to type 2 diabetes susceptibility. This study aimed at evaluating associations between NRF1 genetic polymorphisms and development of type 2 diabetes. RESEARCH DESIGN AND METHODS—Using a variation screening approach, 6 novel and 10 known single nucleotide polymorphisms (SNPs) in the NRF1 gene were identified. Nine SNPs were then selected using pairwise tagging with an r2 cutoff of 0.8 and/or minor allele frequency of >5% and genotyped in 596 type 2 diabetic patients and 431 nondiabetic subjects, all of whom were Han Chinese. RESULTS—Two novel SNPs (−46127T>C and +98560A>G) were associated with type 2 diabetes (P = 0.018 and 0.036; for possession of minor allele, odds ratio [OR] 0.620 and 3.199, with dominant model and correction for multiple comparisons). In SNP rs1882094 (+141G>T), the nondiabetic control subjects carrying GG genotype had lower fasting plasma glucose levels than carriers with other genotypes (P = 0.0002). One common haplotype (H2) mainly composed of SNPs rs6969098 (−24833 A>G), rs1882094, and another novel variant (+97884G>A) was significantly associated with type 2 diabetes (P = 0.016, OR 0.706). Subjects with this haplotype had lower fasting triglyceride levels when compared with those with other haplotypes (P = 0.010). CONCLUSIONS—The present study shows an association of SNPs in the NRF1 gene with type 2 diabetes in a Han Chinese population. NRF1 genetic polymorphisms may be a suspectibility factor for type 2 diabetes by conferring abnormalities in triglyceride metabolism. Further studies should replicate this finding using larger and racially diverse populations.

Intron polymorphism in the KIAA0350 gene is reproducibly associated with susceptibility to type 1 diabetes (T1D) in the Han Chinese population

Objective  Three independent genome‐wide association studies in white populations have reported that single nucleotide polymorphisms (SNPs) in the KIAA0350 gene are associated with susceptibility to type 1 diabetes (T1D). The gene product of KIAA0350 is predicted to be a sugar binding C‐type lectin. In the present study, we investigated whether SNPs in this gene were associated with T1D in the Han Chinese population.