Serotonin transporter promoter methylation in peripheral cells and neural responses to negative stimuli : a study of adolescent monozygotic twins

Several studies have examined associations between peripheral DNA methylation patterns of the serotonin transporter gene (SLC6A4) promoter and symptoms of depression and anxiety. The SLC6A4 promoter methylation has also been associated with frontal-limbic brain responses to negative stimuli. However, it is unclear how much of this association is confounded by DNA sequence variations. We utilized a monozygotic-twin within-pair discordance design, to test whether DNA methylation at specific CpG sites in the SLC6A4 promoter of peripheral cells is associated with greater frontal-limbic brain responses to negative stimuli (sadness and fear), independently of DNA sequence effects. In total 48 pairs of healthy 15-year-old monozygotic twins from the Quebec Newborn Twin Study, followed regularly since birth, underwent functional magnetic resonance imaging while conducting an emotion-processing task. The SLC6A4 promoter methylation level was assessed in saliva samples using pyrosequencing. Relative to the co-twins with lower SLC6A4 promoter methylation levels, twins with higher peripheral SLC6A4 methylation levels showed greater orbitofrontal cortical (OFC) activity and left amygdala-anterior cingulate cortex (ACC) and left amygdala-right OFC connectivity in response to sadness as well as greater ACC-left amygdala and ACC-left insula connectivity in response to fearful stimuli. By utilising a monozygotic-twin design, we provided evidence that associations between peripheral SLC6A4 promoter methylation and frontal-limbic brain responses to negative stimuli are, in part, independent of DNA sequence variations. Although causality cannot be determined here, SLC6A4 promoter methylation may be one of the mechanisms underlying how environmental factors influence the serotonin system, potentially affecting emotional processing through frontal-limbic areas

Differential genetic effect of the norepinephrine transporter promoter polymorphisms on attention problems in clinical and non-clinical samples

Among the monoaminergic modulatory neurotransmitters, norepinephrine is involved in task orienting, hence noradrenergic genetic variants have been studied in connection to attentional processes. The role of this catecholamine system is also highlighted by the selective norepinephrine transporter blocking atomoxetine, which has proved to be effective in the pharmacological treatment of Attention Deficit Hyperactivity Disorder (ADHD). In the present genetic association study three single nucleotide polymorphisms (rs28386840, rs2242446, rs3785143 SNPs) were analyzed from the 5′ region of the norepinephrine transporter (NET, SLC6A2) gene, which have been linked to ADHD previously. Attention problems scores of the mother-rated Child Behavior Checklist (CBCL) were used in separate analyses of 88 preschoolers (59.1% male, 6 years of age) recruited from the general population and 120 child psychiatry patients with ADHD diagnosis (85.8% male, age: 9.8 ± 2.9). The NET SNPs showed associations with attention problems, but the direction was different in the two groups. Regarding the promoter variant rs28386840, which showed the most consistent association, the T-allele-carrier patients with ADHD had lower CBCL attention problems scores compared to patients with AA genotype (p = 0.023), whereas T-allele-carriers in the community sample had more attention problems (p = 0.042). Based on previous reports of lower NE levels in ADHD children and the inverted-U shape effect of NE on cognitive functions, we propose that rs28386840 (-3081) T-allele, which is associated with lower NET expression (and potentially higher synaptic NE level) would support attention processes among ADHD patients (similarly as atomoxetine increases NE levels), whereas it would hinder cortical functions in healthy children

Activity-regulated RNA editing in select neuronal subfields in hippocampus

RNA editing by adensosine deaminases is a widespread mechanism to alter genetic information in metazoa. In addition to modifications in non-coding regions, editing contributes to diversification of protein function, in analogy to alternative splicing. However, although splicing programs respond to external signals, facilitating fine tuning and homeostasis of cellular functions, a similar regulation has not been described for RNA editing. Here, we show that the AMPA receptor R/G editing site is dynamically regulated in the hippocampus in response to activity. These changes are bi-directional, reversible and correlate with levels of the editase Adar2. This regulation is observed in the CA1 hippocampal subfield but not in CA3 and is thus subfield/celltype-specific. Moreover, alternative splicing of the flip/flop cassette downstream of the R/G site is closely linked to the editing state, which is regulated by Ca(2+). Our data show that A-to-I RNA editing has the capacity to tune protein function in response to external stimuli

Assessing genetic polymorphisms using DNA extracted from cells present in saliva samples

<p>Abstract</p> <p>Background</p> <p>Technical advances following the Human Genome Project revealed that high-quality and -quantity DNA may be obtained from whole saliva samples. However, usability of previously collected samples and the effects of environmental conditions on the samples during collection have not been assessed in detail. In five studies we document the effects of sample volume, handling and storage conditions, type of collection device, and oral sampling location, on quantity, quality, and genetic assessment of DNA extracted from cells present in saliva.</p> <p>Methods</p> <p>Saliva samples were collected from ten adults in each study. Saliva volumes from .10-1.0 ml, different saliva collection devices, sampling locations in the mouth, room temperature storage, and multiple freeze-thaw cycles were tested. One representative single nucleotide polymorphism (SNP) in the catechol-<it>0</it>-methyltransferase gene (COMT rs4680) and one representative variable number of tandem repeats (VNTR) in the serotonin transporter gene (5-HTTLPR: serotonin transporter linked polymorphic region) were selected for genetic analyses.</p> <p>Results</p> <p>The smallest tested whole saliva volume of .10 ml yielded, on average, 1.43 ± .77 μg DNA and gave accurate genotype calls in both genetic analyses. The usage of collection devices reduced the amount of DNA extracted from the saliva filtrates compared to the whole saliva sample, as 54-92% of the DNA was retained on the device. An "adhered cell" extraction enabled recovery of this DNA and provided good quality and quantity DNA. The DNA from both the saliva filtrates and the adhered cell recovery provided accurate genotype calls. The effects of storage at room temperature (up to 5 days), repeated freeze-thaw cycles (up to 6 cycles), and oral sampling location on DNA extraction and on genetic analysis from saliva were negligible.</p> <p>Conclusions</p> <p>Whole saliva samples with volumes of at least .10 ml were sufficient to extract good quality and quantity DNA. Using 10 ng of DNA per genotyping reaction, the obtained samples can be used for more than one hundred candidate gene assays. When saliva is collected with an absorbent device, most of the nucleic acid content remains in the device, therefore it is advisable to collect the device separately for later genetic analyses.</p

Serotonin transporter polymorphism and borderline or antisocial traits among low-income young adults

Objectives The short allele of the serotonin transporter linked polymorphic region (5HTTLPR) has been associated with anxiety, major depressive disorder, and suicidality. The impulsive self- and other-damaging behaviors seen in borderline personality disorder (BPD) and antisocial personality disorder (APD) also have substantial comorbidity with depression but are associated with more severe environmental stressors. This study tested the hypothesis of an association between the short allele of the 5HTTLPR and borderline or antisocial traits in young adulthood. Methods The 5HTTLPR was genotyped among 96 young adults from low- to moderate-income families (62 without and 34 with BPD or APD features). Features of borderline and antisocial personality disorder were assessed with the Structured Clinical interview for Diagnosis (SCID)-Axis II. Results The number of short 5HTTLPR alleles was significantly related to incidence of BPD or APD traits, as well as to each set of traits independently. Male gender and quality of care in infancy were also associated with incidence of BPD and APD traits but did not account for the association with the short allele. Depressive disorders were not associated with the short allele in this sample. Conclusions Young adults of lower socioeconomic status who carry the short 5HTTLPR allele may be especially vulnerable to developing antisocial or borderline traits by young adulthood

Relationship of each of the Buss-Perry Aggression Questionnaire subscales with rs7322347 A allele carrier status.

<p>Mean scores of each the Buss-Perry Aggression Questionnaire subscales according to rs7322347 genotypes. Error bars represent standard errors of the mean.</p

Infant genotype may moderate sensitivity to maternal affective communications: Attachment disorganization, quality of care, and the DRD4 polymorphism

Disorganized attachment is an early predictor of the development of psychopathology in childhood and adolescence. Lyons-Ruth, Bronfman, and Parsons (1999) developed the AMBIANCE coding scheme to assess disrupted communication between mother and infant, and reported the link between maternal behavior and disorganized attachment. The Hungarian group found an association between a polymorphism of the DRD4 gene and disorganized attachment (Gervai et al., 2005; Lakatos et al., 2000, 2002). The present collaborative work investigated the interplay between genetic and caregiving contributions to disorganized attachment. Mother–infant dyads (138), from a Hungarian low-social-risk sample (96) and a US high-social-risk sample (42), were assessed for infant disorganized attachment behavior, for DRD4 gene polymorphisms, and for disrupted forms of maternal affective communication with the infant. In accord with literature reports, we found a robust main effect of maternal AMBIANCE scores on infant disorganization. However, this relation held only for the majority of infants who carried the short form of the DRD4 allele. Among carriers of the 7-repeat DRD4 allele, there was no relation between quality of maternal communication and infant disorganization. This interaction effect was independent of degree of social risk and maternal DRD4 genotype