Yan Ruan

Positive Association of the Oxytocin Receptor Gene (OXTR) with Autism in the Chinese Han Population

BACKGROUND Previous research has suggested that the social impairments exhibited by individuals with autism are associated with changes in plasma oxytocin (OT) levels. The physiologic effects of oxytocin are mediated through its specific receptors (OTRs), and numerous studies have implicated OTRs in the regulation of social cognition and behavior. Animal models and linkage data from genome screens indicate that the oxytocin receptor gene (OXTR) is an excellent candidate for research concerning psychiatric disorders, particularly those involving social impairments, such as autism. METHODS We genotyped four single nucleotide polymorphisms (SNPs) located within the OXTR gene of 195 Chinese Han autism trios, using polymerase chain reaction-restriction fragment length polymorphism analysis. RESULTS The family-based association test (FBAT) revealed a significant genetic association between autism and two of the SNPs tested (rs2254298 A: Z = 2.287, p = .0222; rs53576 A: Z = 2.573, p = .0101). When haplotypes were constructed with two, three, and four markers, the haplotype-specific FBAT revealed that a number of haplotypes, particularly those involving rs53576, were significantly associated with autism. Furthermore, haplotypes constructed with all markers showed a significant excess transmission for the specific and global haplotype analyses (p = .0020 and .0289, respectively). CONCLUSIONS These data suggest an involvement of OXTR in the susceptibility to autism, and replication is important.

Family‐based association study between autism and glutamate receptor 6 gene in Chinese Han trios

The glutamate pathways are involved in diverse processes such as learning and memory, epilepsy, and they play important roles in neural plasticity, neural development, and neurodegeneration. It has been proposed that autism could be a hypoglutamatergic disorder. Recently, Jamain et al. [Mol Psychiatry 7:302–310] reported that the glutamate receptor 6 (GluR6 or GRIK2) is in linkage disequilibrium with autism. In the present study, the transmission disequilibrium test (TDT) and the haplotype transmission were performed to analyze the four SNPs (SNP1: rs995640; SNP2: rs2227281; SNP3: rs2227283; SNP4: rs2235076) of GluR6 in 174 Chinese Han parent‐offspring trios. The TDT demonstrated that the two SNPs (SNP2 and SNP3) showed preferential transmission (TDT P = 0.032). The global χ2 test for haplotype transmission also revealed an association between GluR6 and autism (χ2 = 10.78, df = 3, P = 0.013). Our results suggested that GluR6 is in linkage disequilibrium with autism.

Positive association of the Disrupted‐in‐Schizophrenia‐1 gene (DISC1) with schizophrenia in the Chinese han population

Disrupted‐in‐Schizophrenia‐1 (DISC1) is located on 1q42.1, one of the most promising susceptibility loci in schizophrenia linkage studies. A non‐synonymous genetic variation rs821616 (Ser704Cys) in DISC1, has recently been shown to be associated with schizophrenia in family‐based study [Callicott et al. (2005); Proc Natl Acad Sci USA 102: 8627–8632]. In order to further confirm this issue, we examined four single nucleotide polymorphisms (SNPs) in a chromosomal region spanning 42 kb of this gene, namely rs821616, rs821597, rs4658971, and rs843979, in Chinese sample of 313 schizophrenia patients and 317 healthy controls. Our results showed that two SNPs had strong associations with schizophrenia (rs821616: Allele A > T, χ2 = 7.8006, df = 1, P = 0.0052; Genotype, χ2 = 7.7935, df = 2, P = 0.0203; rs821597: Allele A > G, χ2 = 9.5404, df = 1, P = 0.0020; Genotype, χ2 = 12.2780, df = 2, P = 0.0022). When haplotypes were constructed with two, three, and four markers, a number of haplotype combinations, especially those including rs821616 and rs821597, were significantly associated with schizophrenia. Furthermore, there was a strong evidence for association in a four‐marker haplotype analysis (χ2 = 7.686, df = 4, P = 0.005581, corrected P = 0.006199). Although the case‐control and family‐based association studies both suggest that DISC1 gene may play a role in genetic susceptibility to schizophrenia, the risk haplotypic combinations have subtle differences in the two studies. Our findings provide further evidence for DISC1 as a predisposing gene involved in schizophrenia in the Chinese Han Population.

Tenuigenin treatment decreases secretion of the Alzheimer’s disease amyloid β-protein in cultured cells

Amyloid beta-protein (A beta) is a pivotal pathological factor in Alzheimers disease (AD). Tenuigenin, extracted from the Chinese herb Polygala tenuifolia, seems to ameliorate the reduction in cholinergic function on rat models induced by A beta. To examine this therapeutic effect, we tested whether Tenuigenin could inhibit secretion of A beta in neuroblastoma cells stably transfected with two amyloid precursor protein (APP) constructs: the APP695 cDNA (SH-SY5Y APP695) and the C-terminal 99 amino acid residues of APP plus the signal peptide (SH-SY5Y SPA4CT). Tenuigenin inhibited the secretion of A beta and the C-terminal 99 amino acids of APP (C99) in SH-SY5Y APP695 cells, but did not change the A beta and C99 levels in SH-SY5Y SPA4CT cells. Fluorescence Resonance Energy Transfer (FRET) assays showed that Tenuigenin inhibited the proteolytic activities of BACE1 (beta-secretase) on its substrate in vitro. In addition, Tenuigenin did not demonstrate any cytotoxic effects, nor did it affect APP mRNA expression, holoAPP synthesis or sAPP alpha secretion. Our data suggest that Tenuigenin can inhibit the secretion of A beta in SH-SY5Y APP 695 cells via BACE1 inhibition. Taken together, these results suggest that Tenuigenin may be worthy of future study as an anti-AD drug.

Association between the FOXP2 gene and autistic disorder in Chinese population

Several genomewide screens indicated that chromosome 7q was linked to autistic disorder. FOXP2, located on 7q31, is a putative transcription factor containing a polyglutamine tract and a forkhead DNA binding domain. It is one member of the forkhead family who are known to be key regulators of embryogenesis. A point mutation at a highly conserved residue within the forkhead domain co‐segregated with affected status in the KE family who was a unique three generation pedigree with a severe speech and language disorder and FOXP2 was directly disrupted by a translocation in an individual who had similar deficits as those of the KE family. Several studies have investigated the role of FOXP2 polymorphisms in autism and none of them found positive association. We performed a family‐based association study of three single nucleotide polymorphisms (SNPs) of FOXP2 in 181 Chinese Han trios using the analyses of transmission/disequilibrium test (TDT) and haplotype. We found a significant association between autistic disorder and one SNP, as well as with specific haplotypes formed by this SNP with two other SNPs we investigated. Our findings suggest that the FOXP2 gene may be involved in the pathogenesis of autism in Chinese population.

Association of the ENGRAILED 2 (EN2) gene with autism in Chinese Han population

Human ENGRAILED 2 (EN2) gene is localized to 7q36, an autism susceptibility locus. En2 knockout mice display hypoplasia of cerebellum and a decrease in the number of Purkinje cell, which are similar to those reported for individuals with autism. Furthermore, deficits in social behavior were detected in En2−/− mice. Two recent studies have demonstrated that two intronic SNPs (rs1861972, rs1861973) in the EN2 gene are significantly associated with autism. To investigate whether this finding could be replicated in Chinese Han population, we performed the association study between eight single nucleotide polymorphisms (SNPs) of the EN2 gene and autism in 210 Chinese Han trios, using the family‐based association test (FBAT). The present study demonstrated that a preferential transmission of the rs3824068 A‐allele to affected offspring (A > G: Z = 2.399, P = 0.0165). After the Bonferroni correction, this statistical significance of preferential transmission did not remain. However, when haplotypes were constructed with multiple markers, a number of haplotypes including three two‐marker haplotypes, nine three‐marker haplotypes, one four‐marker haplotype, and one six‐marker haplotype, all of which contain the major allele A of rs3824068, displayed significantly associated with autism. These results were still significant after using the permutation method to obtain empirical P values. Thus, our data provide evidence that the EN2 gene may be implicated in the predisposition to autism in the Chinese Han population.

Association study of the human FZD3 locus with schizophrenia

The FZD3 protein is a transmembrane receptor for secreted Wnt glycoproteins involved in the Wnt signal transduction cascades. The alteration of Wnt signal transduction cascades has been thought to be involved in producing the cytoarchitectural defects observed in schizophrenia. Because the human FZD3 gene is mapped to chromosome 8p21, which is a potential region containing a gene for schizophrenia, it may play a role in conferring susceptibility to the disease. This study was conducted with the detection of three single nucleotide polymorphisms (SNPs) located within the FZD3 locus by using the polymerase chain reaction-based restriction fragment length polymorphism (RFLP) analysis among 246 schizophrenic family trios of Chinese Han descent.The transmission disequilibrium test (TDT) demonstrated that the three SNPs all showed a preferential transmission with a p value ranging from.0003-.000007. The global chi-squared test for haplotype transmission also showed a strong association (chi(2) = 48.84, df = 7, p <.000001).The strong association between the FZD3 locus and schizophrenia suggests that the gene itself may play a role in underlying schizophrenia, although a nearby gene responsible for predisposing to the illness cannot be ruled out.

Positive association of the human frizzled 3 (FZD3) gene haplotype with schizophrenia in Chinese Han population

Frizzled 3 (FZD3) gene is located on chromosome 8p21, a region that has been implicated in schizophrenia in genetic linkage studies. The FZD3 is a transmembrane receptor required for Wnt signal transduction cascades that have been thought to be involved in producing the cytoarchitectural defects observed in schizophrenia. Previous work has showed a strong association between FZD3 locus and schizophrenia in family‐based study. To confirm this issue further, we investigated a genetic association between four single nucleotide polymorphisms (SNPs) located in the FZD3 gene and schizophrenia by case‐control study using polymerase chain reaction (PCR)‐based restriction fragment length polymorphism (RFLP) in the Chinese Han population. Our studies showed the SNPs rs2323019 and rs880481 have significant differences in both genotype and allele frequencies between control subjects and schizophrenic patients (rs2323019: Allele A > G, χ2 = 6.7277, df = 1, P = 0.0095; Genotype, χ2 = 10.6583, df = 2, P = 0.0049; rs880481: Allele A > G, χ2 = 10.3945, df = 1, P = 0.0013; Genotype, χ2 = 16.8049, df = 2, P = 0.0002). In addition, we constructed three‐locus haplotypes to test their association with schizophrenia. The globe chi‐squared test for haplotype analysis showed a significant association (χ2 = 66.38, df = 7, P < 0.000001). These results suggested that the FZD3 gene might be involved in the predisposition to schizophrenia.

Association of the neuropilin-2 (NRP2) gene polymorphisms with autism in Chinese Han population.

Autism is a pervasive neurodevelopmental disorder, with a significant role of genetic factors in its development. The neuropilin‐2 (NRP2) gene is localized to 2q34, an autism susceptibility locus. NRP2 has been demonstrated to both guide axons and to control neuronal migration in the central nervous system. It has been reported that NRP2 may be required in vivo for sorting migrating cortical and striatal interneurons to their correct destination. We examine the association between the NRP2 gene and autism using a cohort of 169 Chinese Han family trios. Four single nucleotide polymorphisms (SNPs) were genotyped by the polymerase chain reaction‐based restriction fragment length polymorphism (PCR‐RFLP) analyses. The transmission disequilibrium tests (TDT) of SNPs and haplotype association were carried out using the TDTPHASE program. We found significant genetic association between autism and two of the SNPs of the NRP2 gene (rs849578: P = 0.017, rs849563: P = 0.027), as well as specific haplotypes, especially those formed by rs849563. Furthermore, haplotypes constructed with all markers showed significant excess transmission in both global and individual haplotype analyses (P = 0.004 and 0.017, respectively). The polymorphisms in the NRP2 gene are associated with autism, implying that the NRP2 gene may render individuals to be predisposed to autism.

Association of DAOA polymorphisms with schizophrenia and clinical symptoms or therapeutic effects

The present study examined the correlation between variants in the d-amino acid oxidase activator (DAOA) locus and clinical symptoms and response to antipsychotics in schizophrenia. Case-control analysis and the family-based association test (FBAT) were performed to investigate whether four single nucleotide polymorphisms (SNPs) at DAOA gene are associated with schizophrenia. The association between the DAOA risk haplotype and clinical symptoms were examined by the positive and negative syndrome scale (PANSS) and the brief psychiatric rating scale (BPRS). Our findings showed that the SNP rs947267 was significantly associated with schizophrenia in both case control and familial trio samples (A>C, chi(2)=8.36, p=0.004; Z=2.335, p=0.019), as well as with specific haplotypes, in particular those formed by the A allele of rs947267. In addition, the risk haplotype AAG was significantly correlated with negative, depression and cognitive impairment factors of PANSS, even with the BPRS change scores after 6-week treatment of atypical antipsychotic drugs (p<0.05). These results support the hypothesis that variations in DAOA may play a role in schizophrenia and clinical characteristics.