A rare WNT1 missense variant overrepresented in ASD leads to increased Wnt signal pathway activation

Wnt signaling, which encompasses multiple biochemical pathways that regulate neural development downstream of extracellular Wnt glycoprotein ligands, has been suggested to contribute to major psychiatric disorders including autism spectrum disorders (ASD). We used next-generation sequencing and Sequenom genotyping technologies to resequence 10 Wnt signaling pathway genes in 198 ASD patients and 240 matched controls. Results for single-nucleotide polymorphisms (SNPs) of interest were confirmed in a second set of 91 ASD and 144 control samples. We found a significantly increased burden of extremely rare missense variants predicted to be deleterious by PolyPhen-2, distributed across seven genes in the ASD sample (3.5% in ASD vs 0.8% in controls; Fisher's exact test, odds ratio (OR)=4.37, P=0.04). We also found a missense variant in WNT1 (S88R) that was overrepresented in the ASD sample (8 A/T in 267 ASD (minor allele frequency (MAF)=1.69%) vs 1 A/T in 377 controls (MAF=0.13%), OR=13.0, Fisher's exact test, P=0.0048; OR=8.2 and P=0.053 after correction for population stratification). Functional analysis revealed that WNT1-S88R is more active than wild-type WNT1 in assays for the Wnt/β-catenin signaling pathway. Our findings of a higher burden in ASD of rare missense variants distributed across 7 of 10 Wnt signaling pathway genes tested, and of a functional variant at the WNT1 locus associated with ASD, support that dysfunction of this pathway contributes to ASD susceptibility. Given recent findings of common molecular mechanisms in ASD, schizophrenia and affective disorders, these loci merit scrutiny in other psychiatric conditions as well.

Novel loci for major depression identified by genome-wide association study of Sequenced Treatment Alternatives to Relieve Depression and meta-analysis of three studies

We report a genome-wide association study (GWAS) of major depressive disorder (MDD) in 1221 cases from the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) study and 1636 screened controls. No genome-wide evidence for association was detected. We also carried out a meta-analysis of three European-ancestry MDD GWAS data sets: STAR*D, Genetics of Recurrent Early-onset Depression and the publicly available Genetic Association Information Network-MDD data set. These data sets, totaling 3957 cases and 3428 controls, were genotyped using four different platforms (Affymetrix 6.0, 5.0 and 500 K, and Perlegen). For each of 2.4 million HapMap II single-nucleotide polymorphisms (SNPs), using genotyped data where available and imputed data otherwise, single-SNP association tests were carried out in each sample with correction for ancestry-informative principal components. The strongest evidence for association in the meta-analysis was observed for intronic SNPs in ATP6V1B2 (P=6.78 x 10⁻⁷), SP4 (P=7.68 x 10⁻⁷) and GRM7 (P=1.11 x 10⁻⁶). Additional exploratory analyses were carried out for a narrower phenotype (recurrent MDD with onset before age 31, N=2191 cases), and separately for males and females. Several of the best findings were supported primarily by evidence from narrow cases or from either males or females. On the basis of previous biological evidence, we consider GRM7 a strong MDD candidate gene. Larger samples will be required to determine whether any common SNPs are significantly associated with MDD.

Investigation of serotonin-related genes in antidepressant response

In this study, we sought out to test the hypothesis that genetic factors may influence antidepressant response to fluoxetine. The investigation focused on seven candidate genes in the serotonergic pathway involved in the synthesis, transport, recognition, and degradation of serotonin. Our clinical sample consisted of 96 subjects with unipolar major depression treated with fluoxetine with response variables assessed after a 12-week trial. Patient data were also collected to investigate the pattern of drug response. Using a high-throughput single-nucleotide polymorphism (SNP) genotyping platform and capillary electrophoresis, we genotyped patients at 110 SNPs and four repeat polymorphisms located in seven candidate genes (HTR1A, HTR2A, HTR2C, MAOA, SLC6A4, TPH1, and TPH2). Statistical tests performed included single-locus and haplotype association tests, and linkage disequilibrium (LD) estimation. Little evidence of population stratification was observed in the sample with 20 random SNPs using a genomic control procedure. Our most intriguing result involved three SNPs in the TPH1 gene and one SNP in the SLC6A4 gene, which show significant single-locus association when response to fluoxetine is compared to nonresponse (P=0.02-0.04). All odds ratios indicated an increased risk of not responding to fluoxetine. In the specific response vs nonspecific and nonresponse comparison, three SNPs in the TPH2 gene (P=0.02-0.04) were positively associated and one SNP in the HTR2A gene (P=0.02) was negatively associated. When comparing specific response to nonspecific response, we found significant negative associations in three SNPs in the HTR2A gene (P=0.001-0.03) and two SNPs in the MAOA gene (P=0.03-0.05). We observed variable, although strong LD, in each gene and unexpectedly low numbers of estimated haplotypes, formed from tagged SNPs. Significant haplotype associations were found in all but the HTR1A and HTR2C genes. Although these data should be interpreted cautiously due to the small sample size, these results implicate TPH1 and SLC6A4 in general response, and HTR2A, TPH2, and MAOA in the specificity of response to fluoxetine. Intriguingly, we observe that a number of the less frequent alleles of many of the SNP markers were associated with the nonresponse and nonspecific phenotypes.

Panic attack as a marker of core psychopathological processes

OBJECTIVE

The goal of this study is to test the hypothesis that panic attacks are a marker of core psychopathological processes across mental disorders and that there are distinct syndromal patterns of psychopathology associated with specific subtypes of panic attack that can be distinguished by age and associated fear at onset.

METHODS

Data were drawn from the National Comorbidity Survey, a community-based household sample (n = 8,098) representative of the United States adult population. Four panic subtypes were identified based on findings from clinical studies and on our hypothesis. Multivariate logistic regression models were used to identify sociodemographic characteristics, panic symptoms and mental disorder correlates of each subtype.

RESULTS

Results of multivariate logistic regression analyses identified distinct sociodemographic characteristics, panic symptoms, psychiatric comorbidity, suicidal behavior and use of services associated with early-onset and late-onset panic with and without fear/anticipatory anxiety at the first attack.

CONCLUSIONS

These findings provide support for the hypothesis that panic attacks are a marker of core underlying psychopathological processes and introduce new, preliminary evidence to support the possible existence of different panic subtypes in the general population. While these results need replication, these findings suggest that the specific type of comorbidity among those with panic attacks can be predicted to a large degree by the age and associated fear/anticipatory anxiety at the onset of the panic attacks.

The effect of sertraline on methadone plasma levels in methadone-maintenance patients

The authors examine methadone plasma levels in 31 depressed methadone-maintained opiate addicts enrolled in a 12-week placebo-controlled, double-blind study of sertraline. Between baseline and week 6, patients on sertraline showed a mean increase in methadone plasma level/dose (P/D) ratio of 26% (SD = 43%, range -32% to +118%), while patients on placebo showed a mean decrease of 16% (SD = 27%, range -62% to +50%). This difference was significant (p < 0.02). The sertraline and placebo groups did not differ in reported side effects or methadone dose adjustments. Between weeks 6 and 12, methadone P/D in the sertraline group decreased back towards baseline, and the treatment groups did not differ significantly at week 12. The results suggest sertraline may produce a modest increase in methadone serum levels over the first six weeks of treatment. Depression and anxiety disorders are common in methadone-maintained patients. Serotonin uptake inhibitors are attractive choices for treatment due to their low toxicity and low abuse potential, but these agents variously inhibit isoenzymes responsible for the metabolism of methadone. Clinicians treating depressed or anxious methadone patients with second-generation antidepressants should monitor for clinical signs of increased or decreased methadone levels and consider monitoring serum methadone levels.

No association or linkage between polymorphisms in the genes encoding cholecystokinin and the cholecystokinin B receptor and panic disorder

Growing animal data implicate cholecystokinin in the regulation of anxiety, while human clinical research confirms the role of cholecystokinin in the provocation of panic attacks. Antipanic medications suppress the ability of cholecystokinin to induce panic attacks, and may alter the expression of the cholecystokinin gene. Thus, there is increased interest in understanding the molecular genetic component of these observations. Recent association studies using persons with panic disorder described some association between polymorphisms in the genes encoding cholecystokinin and the cholecystokinin B-receptor and panic disorder. In this study, we used a family-based design, employing 596 individuals in 70 panic disorder pedigrees, as well as 77 haplotype relative risk 'triads'. Subjects were genotyped for two polymorphisms: the polymorphic microsatellite marker in the CCK-BR locus using PCR-based genotyping and at a single nucleotide polymorphism in the CCK promoter using a fluorescence polarization detection assay, and the data were analyzed for genetic association and linkage. Employing a variety of diagnostic and genetic models, linkage analysis produced no significant lod scores at either locus. Family-based tests of association, the haplotype-based haplotype relative risk statistic and the transmission disequilibrium test, were likewise non-significant. The results reported here provide little support for the role of these polymorphisms in panic disorder.

Investigation of dopamine receptor (DRD4) and dopamine transporter (DAT) polymorphisms for genetic linkage or association to panic disorder

Clinical and animal studies suggest a role for the neurotransmitter dopamine in anxiety states. In humans, one such condition is panic disorder, which is typified by recurrent panic attacks accompanied by anticipatory anxiety. Family, segregation, and twin studies imply a genetic component to the pathophysiology of panic disorder. In this study, we examined the genes for the D4 dopamine receptor (DRD4) and the dopamine transporter (DAT) using three common sequence polymorphisms. Two of these polymorphisms were in DRD4, a 12 base-pair insertion/deletion in exon 1 and a 48 base-pair repeat in exon 3, and the third was a 40 base-pair repeat in the 3' untranslated region of DAT. We employed a family-based design, using 622 individuals in 70 families, as well as 82 haplotype relative risk "trios". Subjects were genotyped at the polymorphic loci, and the data were analyzed for genetic association and linkage. There were no significant differences in allele frequencies or occurrence of genotypes within the triads for any of the three polymorphisms. No significant linkage between the DRD4 or DAT polymorphisms and panic disorder was observed in the multiplex families, using a variety of simulations for dominant and recessive models of inheritance. However, LOD scores of approximately 1.1 and 1.05 were observed for the DAT and DRD4 exon 1 loci, respectively. The results reported here provide little support for the role of these polymorphisms in panic disorder.

Lack of genetic linkage or association between a functional serotonin transporter polymorphism and panic disorder

Given the efficacy of medications that interact with the serotonin transporter (5-HTT) in the treatment of panic disorder, we have used a family-based design to test for genetic association and linkage between panic disorder and a functional polymorphism in the promoter of the gene for 5-HTT. In this study, 340 individuals in 45 families, as well as 74 haplotype relative risk 'trios' were genotyped at the polymorphic locus, which consists of a 44 base pair deletion/insertion. There were no significant differences in allele frequencies or occurrence of genotypes within the triads. No linkage between the 5-HTT polymorphism and panic disorder was observed in the multiplex families, using a variety of simulations for dominant and recessive models of inheritance. Recent reports suggest an association between the 5-HTT polymorphism and anxiety-related traits, as measured with personality assessment. The results reported here provide evidence that the genetic basis of panic disorder may be distinct from anxiety-related traits assessed by personality inventories in normal populations.

Treatment of depressed methadone maintenance patients with nefazodone. A case series

The authors presented four consecutive case studies in which depressed methadone-maintained patients previously treated with other drugs, such as sertraline, risperidone, and bupropion, and who did not respond and/or suffered various side effects, responded well to nefazodone.

Stimulation of in vitro myelin synthesis by microglia

Central nervous system myelin is elaborated by oligodendrocytes, which have been studied extensively in cell culture. Dissociated brain cultures allow in vitro analysis of events in myelinogenesis, including cell-cell interactions. Microglia, the primary phagocytic cell of the central nervous system, appear in developing fiber tracts prior to the onset of myelination in vivo. To gain insight into potential oligodendrocyte-microglial interactions during development, these cells were co-cultured and various parameters of myelin synthesis were measured. In co-culture, microglia stimulated the synthesis of sulfatide, a myelin-specific galactolipid, in oligodendrocytes, as well as the expression of the myelin-specific proteins myelin basic protein and proteolipid protein. Activity of the oligodendrocyte cytoplasm-specific enzyme 2',3'-cyclic nucleotide 3'-phosphohydrolase was not elevated, suggesting that the effects of microglia were not due to stimulation of oligodendrocyte proliferation. This was confirmed by the inability of microglia to induce significant DNA synthesis. Conditioned medium from cultured microglia provided a similar stimulatory activity, suggesting that the increase in myelin synthesis does not require contact between oligodendrocytes and microglia. These findings suggest a stimulatory role for microglia during myelinogenesis.