Social isolation stress induces ATF-7 phosphorylation and impairs silencing of the 5-HT 5B receptor gene.

Many symptoms induced by isolation rearing of rodents may be relevant to neuropsychiatric disorders, including depression. However, identities of transcription factors that regulate gene expression in response to chronic social isolation stress remain elusive. The transcription factor ATF-7 is structurally related to ATF-2, which is activated by various stresses, including inflammatory cytokines. Here, we report that Atf-7-deficient mice exhibit abnormal behaviours and increased 5-HT receptor 5B (Htr5b) mRNA levels in the dorsal raphe nuclei. ATF-7 silences the transcription of Htr5B by directly binding to its 5'-regulatory region, and mediates histone H3-K9 trimethylation via interaction with the ESET histone methyltransferase. Isolation-reared wild-type (WT) mice exhibit abnormal behaviours that resemble those of Atf-7-deficient mice. Upon social isolation stress, ATF-7 in the dorsal raphe nucleus is phosphorylated via p38 and is released from the Htr5b promoter, leading to the upregulation of Htr5b. Thus, ATF-7 may have a critical role in gene expression induced by social isolation stress.

Identification of single-nucleotide polymorphisms in the human N-methyl-D-aspartate receptor subunit NR2D gene, GRIN2D, and association study with schizophrenia.

OBJECTIVES: The glutamatergic dysfunction is one of the main hypotheses for the pathophysiology of schizophrenia. N-methyl-D-aspartate receptors are of major interest because phencyclidine, a non-competitive antagonist of N-methyl-D-aspartate receptors, produces a schizophrenia-like psychosis. Therefore, the genes encoding N-methyl-D-aspartate receptor subunits are strong candidates for schizophrenia susceptibility genes. We focused on the N-methyl-D-aspartate receptor subunit NR2D gene in the case-control study of schizophrenia. METHODS: We screened for polymorphisms in exons, exon-intron boundaries and the 5' upstream region of GRIN2D by direct sequencing in 32 Japanese patients. Out of the total 13 single-nucleotide polymorphisms identified, we genotyped 200-201 Japanese patients and 219-221 controls for nine common single-nucleotide polymorphisms (minor allele frequency over 0.05). RESULTS: None of the nine single-nucleotide polymorphisms showed significant differences in genotype and allele frequencies between cases and controls. We observed significant associations of pairwise haplotypes in three combinations of four single-nucleotide polymorphisms, INT10SNP-EX13SNP2, EX13SNP2-EX13SNP3 and EX6SNP-EX13SNP2, with the disease even after the Bonferroni correction (P=1.094 x 10(-6), Pcorrected=2.297 x 10(-5), P=2.825 x 10(-6), Pcorrected=5.933 x 10(-5) and P=2.02 x 10(-4), Pcorrected=4.242 x 10(-3), respectively). The same results were also obtained using the false discovery rate (BL) method at the threshold P value, 2.908 x 10(-3). CONCLUSIONS: We conclude that the GRIN2D locus is a possible genomic region contributing to schizophrenia susceptibility in the Japanese population.

Positive associations of polymorphisms in the metabotropic glutamate receptor type 3 gene (GRM3) with schizophrenia.

OBJECTIVES: Glutamatergic dysfunction is one of the major hypotheses of schizophrenia pathophysiology. We have been conducting systematic studies on the association between glutamate receptors and schizophrenia. We focused on the metabotropic glutamate receptor type 3 gene (GRM3) as a candidate for schizophrenia susceptibility. METHODS: We genotyped Japanese schizophrenics (n=100) and controls (n=100) for six single nucleotide polymorphisms (SNPs) located in the GRM3 region at intervals of approximately 50 kb. Statistical differences in genotype, allele and haplotype frequencies between cases and controls were evaluated by the chi2 test and Fisher's exact probability test at a significance level of 0.05. Haplotype frequencies were estimated by the EM algorithm. RESULTS: A case-control association study identified a significant difference in allele frequency distribution of a SNP, rs1468412, between schizophrenics and controls (P=0.011). We also observed significant differences in haplotype frequencies estimated from SNP frequencies between schizophrenics and controls. The haplotype constructed from three SNPs, including rs1468412, showed a significant association with schizophrenia (P=8.30 x 10-4). CONCLUSIONS: Our data indicate that at least one susceptibility locus for schizophrenia is situated within or very close to the GRM3 region in the Japanese patients.

Sin1 binds to both ATF-2 and p38 and enhances ATF-2-dependent transcription in an SAPK signaling pathway.

Yeast Sin1 binds to the Sty1 kinase, a member of the stress-activated kinases (SAPKs), and is required for stress-induced phosphorylation and activation of the transcription factor Atf1, a homolog of the vertebrate-activating transcription factor-2 (ATF-2). Here we report that mammalian Sin1 plays an important role in the SAPK signaling pathway by binding to both ATF-2 and p38. In response to stress, ATF-2, a member of the ATF/cAMP response element-binding protein family, is phosphorylated by p38/Jun NH2-terminal protein kinase and activates the transcription of apoptosis-related genes. In contrast, in response to serum stimulation, ATF-2 is phosphorylated via the Ras effector pathway and leads to the induction of growth-related genes. We found that Sin1 binds directly to both ATF-2 and p38. Sin1 over-expression enhanced osmotic stress-induced phosphorylation of ATF-2 and ATF-2-mediated transcription, whereas knockdown of Sin1 expression by siRNA suppressed these responses. Moreover, a reduction in Sin1 expression suppressed osmotic stress-induced apoptosis and the expression of Gadd45beta, one of the ATF-2 target genes that is correlated with apoptosis. Decreased Sin1 expression, however, did not affect the serum stimulation-induced phosphorylation of ATF-2. Sin1 may contribute to ATF-2 signaling specificity by acting as a nuclear scaffold.

Positive association of the AMPA receptor subunit GluR4 gene (GRIA4) haplotype with schizophrenia: linkage disequilibrium mapping using SNPs evenly distributed across the gene region.

The glutamatergic dysfunction hypothesis suggests that genes involved in the glutamate neurotransmitter system are candidates for schizophrenia-susceptibility genes. We have been conducting systematic studies of the association between glutamate receptors and schizophrenia. We report on a positive association of some haplotypes of the AMPA receptor subunit GluR4 gene (GRIA4) with schizophrenia. We genotyped 100 Japanese schizophrenics and 100 controls for six single nucleotide polymorphism (SNP) markers distributed at intervals of about 50 kb in the GRIA4 region, and estimated the degree of linkage disequilibrium (LD) between the SNPs. We constructed haplotypes of the SNPs in LD using the EM algorithm to test their association with schizophrenia. Significant associations were detected for the combination of SNP4-5 (chi(2) = 12.54, df = 3, P = 0.0057, P = 0.029 with Bonferroni correction) and for the combination of SNP3-4-5 (chi(2) = 18.9, df = 7, P = 0.0085, P = 0.043 with Bonferroni correction). These results suggest that at least one susceptibility locus for schizophrenia is located within or very close to the GRIA4 region in Japanese.