Childhood behaviour problems show the greatest gap between DNA-based and twin heritability

For most complex traits, DNA-based heritability (‘SNP heritability’) is roughly half that of twin-based heritability. A previous report from the Twins Early Development Study suggested that this heritability gap is much greater for childhood behaviour problems than for other domains. If true, this finding is important because SNP heritability, not twin heritability, is the ceiling for genome-wide association studies. With twice the sample size as the previous report, we estimated SNP heritabilities (N up to 4653 unrelated individuals) and compared them with twin heritabilities from the same sample (N up to 4724 twin pairs) for diverse domains of childhood behaviour problems as rated by parents, teachers, and children themselves at ages 12 and 16. For 37 behaviour problem measures, the average twin heritability was 0.52, whereas the average SNP heritability was just 0.06. In contrast, results for cognitive and anthropometric traits were more typical (average twin and SNP heritabilities were 0.58 and 0.28, respectively). Future research should continue to investigate the reasons why SNP heritabilities for childhood behaviour problems are so low compared with twin estimates, and find ways to maximise SNP heritability for genome-wide association studies

The combined effect of paraoxonase promoter and coding region polymorphisms on the risk of arterial ischemic stroke among young adults

Background: Serum paraoxonase (PON1) is a high-density lipoprotein-associated esterase with antioxidant and antiatherogenic properties that has recently been implicated in the pathogenesis of cardiovascular disease. Interindividual variability in PON1 levels is determined by the Q192R and L55M coding region polymorphisms and by 2 recently described polyrnorphisms in the promoter of the PON1 gene, C(-107)T and G(-824)A. Objective: To determine the association of the PON1 promoter polymorphisms with arterial ischemic stroke (AIS) in the young. Design, Setting, and Patients: We studied 118 young patients (age, <45 years) with a first nonfatal AIS of undetermined etiology and 118 control subjects, matched simultaneously for age and sex. The PON1 C(-107)T polymorphism was determined by single-stranded conformational polymorphism analysis and the G(-824)A substitution by polymerase chain reaction and restriction enzyme digestion. Results: The presence of the low-expressor -107T allele was associated with an independent increase in overall risk of AIS (odds ratio [OR], 2.69; 95% confidence interval [Cl], 1.06-6.78; P=.04) by conditional multiple logistic regression analysis. Among individuals with the 192RR genotype, the presence of the -107T allele led to a higher but nonsignificant risk, yielding an OR of 4.15 (95% CI, 0.35-48.76; P=.15) when compared with noncarriers of the T allele and 17.01 (95% CI, 1.74-166.35; P=.02) when compared with noncarriers of either variant. No significant difference between groups was found regarding the G(-824)A polymorphism. Conclusion: These findings suggest that the PON1 -107T allele is independently associated with the risk of AIS, in addition to interacting with and potentiating the risk conferred by the Q192R polymorphism.61335135

Paraoxonase 192 Gln -> Arg polymorphism - An independent risk factor for nonfatal arterial ischemic stroke among young adults

Background and Purpose-The etiology of arterial ischemic stroke (AIS) in the young remains unknown in one third of patients. Serum paraoxonase (PON1) is an HDL-associated esterase that hydrolyzes products of lipid peroxidation and prevents the oxidation of LDL. Two common polymorphisms in the PON1 gene, the 192 Gln (Q) --> Arg (R) and 55 Leu (L) --> Met (M) substitutions, determine interindividual variation in PON1 activity. The association of these polymorphisms with the risk of AIS remains controversial. Methods-We analyzed 118 patients (64 women) with a first nonfatal AIS occurring <45 years of age and 118 1:1 age (+/- 2 years)- and sex-matched controls. The PON1 polymorphisms were determined by polymerase chain reaction amplification and restriction digestion. Results-The prevalence of the PON1 192RR genotype (P=0.006) and the frequency of the R allele (P=0.010) were significantly increased among young AIS patients compared with controls. After adjustment for conventional vascular and prothrombotic risk factors, the 192RR genotype remained independently associated with a 4-fold increase in the risk of AIS (odds ratio=4.1; 95% CI, 1.14 to 14.73). Subanalyses stratified by the presence of vascular risk factors and ethnicity did not significantly modify the effect of the PON1 192 polymorphism on AIS risk. No significant differences were found between patients and controls regarding the PON1 55 polymorphism. Conclusions-These findings suggest that the PON1 192RR genotype is independently associated with an increased risk of nonfatal AIS among young adults. Further studies are necessary to understand better the mechanistic implications of these observations in the development of AIS in the young.O TEXTO COMPLETO DESTE ARTIGO, ESTARÁ DISPONÍVEL À PARTIR DE FEVEREIRO DE 2015.3361459146

Promoter polymorphisms in the plasma glutathione peroxidase (GPx-3) gene: anovel risk factor for arterial ischemic stroke among young adults and children.

BACKGROUND AND PURPOSE: Plasma glutathione peroxidase (GPx-3)-deficiency increases extracellular oxidant stress, decreases bioavailable nitric oxide, and promotes platelet activation. The aim of this study is to identify polymorphisms in the GPx-3 gene, examine their relationship to arterial ischemic stroke (AIS) in a large series of children and young adults, and determine their functional molecular consequences. METHODS: We studied the GPx-3 gene promoter from 123 young adults with idiopathic AIS and 123 age- and gender-matched controls by single-stranded conformational polymorphism and sequencing analysis. A second, independent population with childhood stroke was used for a replication study. We identified 8 novel, strongly linked polymorphisms in the GPx-3 gene promoter that formed 2 main haplotypes (H1 and H2). The transcriptional activity of the 2 most prevalent haplotypes was studied with luciferase reporter gene constructs. RESULTS: The H2 haplotype was over-represented in both patient populations and associated with an independent increase in the risk of AIS in young adults (odds ratio=2.07, 95% CI=1.03 to 4.47; P=0.034) and children (odds ratio=2.13, 95% CI=1.23 to 4.90; P=0.027). In adults simultaneously exposed to vascular risk factors, the risk of AIS approximately doubled (odds ratio=5.18, 95% CI=1.82 to 15.03; P<0.001). Transcriptional activity of the H2 haplotype was lower than that of the H1 haplotype, especially after upregulation by hypoxia (normalized relative luminescence: 3.54+/-0.32 versus 2.47+/-0.26; P=0.0083). CONCLUSIONS: These findings indicate that a novel GPx-3 promoter haplotype is an independent risk factor for AIS in children and young adults. This haplotype reduces the gene's transcriptional activity, thereby compromising gene expression and plasma antioxidant and antithrombotic activities

Promoter polymorphisms peroxidase in the plasma glutathione (GPx-3) gene - A novel risk factor for arterial ischemic stroke among young adults and children

Background and Purpose-Plasma glutathione peroxidase (GPx-3)-deficiency increases extracellular oxidant stress, decreases bioavailable nitric oxide, and promotes platelet activation. The aim of this study is to identify polymorphisms in the GPx-3 gene, examine their relationship to arterial ischemic stroke (AIS) in a large series of children and young adults, and determine their functional molecular consequences. Methods-We studied the GPx-3 gene promoter from 123 young adults with idiopathic AIS and 123 age- and gender-matched controls by single-stranded conformational polymorphism and sequencing analysis. A second, independent population with childhood stroke was used for a replication study. We identified 8 novel, strongly linked polymorphisms in the GPx-3 gene promoter that formed 2 main haplotypes (H1 and H2). The transcriptional activity of the 2 most prevalent haplotypes was studied with luciferase reporter gene constructs. Results-The H2 haplotype was over-represented in both patient populations and associated with an independent increase in the risk of AIS in young adults (odds ratio=2.07, 95% CI= 1.03 to 4.47; P=0.034) and children (odds ratio=2.13. 95% CI=1.23 to 4.90; P=0.027). In adults' simultaneously exposed to vascular risk factors, the risk of AIS approximately doubled (odds ratio=5.18, 95% CI=1.82 to 15.03; P < 0.001). Transcriptional activity of the H2 haplotype was lower than that of the H1 haplotype, especially after upregulation by hypoxia (normalized relative luminescence: 3.54 +/- 0.32 versus 2.47 +/- 0.26; P=0.0083). Conclusion-These findings indicate that a novel GPx-3 promoter haplotype is an independent risk factor for AIS in children and young adults. This haplotype reduces the gene's transcriptional activity, thereby compromising gene expression and plasma antioxidant and antithrombotic activities.O TEXTO COMPLETO DESTE ARTIGO, ESTARÁ DISPONÍVEL À PARTIR DE FEVEREIRO DE 2015.381414

A pharmacogenetic 'restriction-of-function' approach reveals evidence for anxiolytic-like actions mediated by α5-containing GABAA receptors in mice

Benzodiazepines have been widely used for their anxiolytic actions. However, the contribution of GABAA receptor subtypes to anxiolysis is still controversial. Studies with mutant mice harboring diazepam-insensitive α-subunits α1, α2, α3, or α5 have revealed that α2-containing GABAA receptors (α2-GABAARs) are required for diazepam-induced anxiolysis, with no evidence for an involvement of any other α-subunit, whereas TP003, described as a selective modulator of α3-containing GABAA receptors, was shown to be anxiolytic. Here, we describe a novel, systematic approach to evaluate the role of positive allosteric modulation of each of the four diazepam-sensitive α-subtypes in anxiety-related behavioral paradigms. By combining H to R point mutations in three out of the four diazepam-sensitive α-subunits in mice with a 129X1/SvJ background, diazepam becomes a subtype-specific modulator of the remaining non-mutated α-subtype. Modulation of α5-GABAARs, but not of α2-GABAARs, increased the time in the light side of the light-dark box as well as open-arm exploration in the elevated plus maze. In contrast, modulation of α3-GABAARs decreased open-arm exploration, whereas modulation of α2-GABAARs increased time in the center in the open-field test. Modulation of any single α-subtype had no effect on stress-induced hyperthermia. Our results provide evidence that modulation of α5-GABAARs elicits anxiolytic-like actions, whereas our data do not provide evidence for an anxiolytic-like action of α3-GABAARs. Thus, α5-GABAARs may be suitable targets for novel anxiolytic drugs.Neuropsychopharmacology advance online publication, 11 May 2016; doi:10.1038/npp.2016.49