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Molecular genetics of the platelet serotonin system in first-degree relatives of patients with autism.

ABSTRACT: Elevated platelet serotonin (5-hydroxytryptamine, 5-HT) is found in a subset of children with autism and in some of their first-degree relatives. Indices of the platelet serotonin system, including whole blood 5-HT, 5-HT binding affinity for the serotonin transporter (K(m)), 5-HT uptake (V(max)), and lysergic acid diethylamide (LSD) receptor binding, were previously studied in 24 first-degree relatives of probands with autism, half of whom were selected for elevated whole blood 5-HT levels. All subjects were then genotyped for selected polymorphisms at the SLC6A4, HTR7, HTR2A, ITGB3, and TPH1 loci. Previous studies allowed an a priori prediction of SLC6A4 haplotypes that separated the subjects into three groups that showed significantly different 5-HT binding affinity (K(m), p=0.005) and 5-HT uptake rate (V(max), p=0.046). Genotypes at four individual polymorphisms in SLC6A4 were not associated with platelet 5-HT indices. Haplotypes at SLC6A4 and individual genotypes of polymorphisms at SLC6A4, HTR7, HTR2A, ITGB3, and TPH1 showed no significant association with whole blood 5-HT. Haplotype analysis of two polymorphisms in TPH1 revealed a nominally significant association with whole blood 5-HT (p=0.046). These initial studies of indices of the 5-HT system with several single-nucleotide polymorphisms at loci in this system generate hypotheses for testing in other samples.

SUBMITTER: Cross S

PROVIDER: S-EPMC2739682 | biostudies-literature | 2008 Jan

REPOSITORIES: biostudies-literature

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Molecular genetics of the platelet serotonin system in first-degree relatives of patients with autism.

Cross Sarah S Kim Soo-Jeong SJ Weiss Lauren A LA Delahanty Ryan J RJ Sutcliffe James S JS Leventhal Bennett L BL Cook Edwin H EH Veenstra-Vanderweele Jeremy J

Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology 20070404 2

Elevated platelet serotonin (5-hydroxytryptamine, 5-HT) is found in a subset of children with autism and in some of their first-degree relatives. Indices of the platelet serotonin system, including whole blood 5-HT, 5-HT binding affinity for the serotonin transporter (K(m)), 5-HT uptake (V(max)), and lysergic acid diethylamide (LSD) receptor binding, were previously studied in 24 first-degree relatives of probands with autism, half of whom were selected for elevated whole blood 5-HT levels. All ...[more]

PMID: 17406648

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Project description:ContextStudying sensorimotor and neurocognitive impairments in unaffected family members of individuals with autism may help identify familial pathophysiological mechanisms associated with the disorder.ObjectiveTo determine whether atypical sensorimotor or neurocognitive characteristics associated with autism are present in first-degree relatives of individuals with autism.DesignCase-control comparison of neurobehavioral functions.SettingUniversity medical center.ParticipantsFifty-seven first-degree relatives of individuals with autism and 40 age-, sex-, and IQ-matched healthy control participants (aged 8-54 years).Main outcome measuresOculomotor tests of sensorimotor responses (saccades and smooth pursuit); procedural learning and response inhibition; neuropsychological tests of motor, memory, and executive functions; and psychological measures of social behavior, communication skills, and obsessive-compulsive behaviors.ResultsOn eye movement testing, family members demonstrated saccadic hypometria, reduced steady-state pursuit gain, and a higher rate of voluntary response inhibition errors relative to controls. They also showed lateralized deficits in procedural learning and open-loop pursuit gain (initial 100 milliseconds of pursuit) and increased variability in the accuracy of large-amplitude saccades that were confined to rightward movements. In neuropsychological studies, only executive functions were impaired relative to those of controls. Family members reported more communication abnormalities and obsessive-compulsive behaviors than controls. Deficits across oculomotor, neuropsychological, and psychological domains were relatively independent from one another.ConclusionsFamily members of individuals with autism demonstrate oculomotor abnormalities implicating pontocerebellar and frontostriatal circuits and left-lateralized alterations of frontotemporal circuitry and striatum. The left-lateralized alterations have not been identified in other neuropsychiatric disorders and are of interest given atypical brain lateralization and language development associated with the disorder. Similar oculomotor deficits have been reported in individuals with autism, suggesting that they may be familial and useful for studies of neurophysiological and genetic mechanisms in autism.

Project description:Meehl conceptualized schizotypy as the phenotypic manifestations of a neural integrative defect resulting from a schizophrenia diathesis. The majority of schizotypy studies recruited subjects from the general population and revealed a multidimensional construct. This 2-phase investigation first examined the clustering of schizotypy in 194 unaffected relatives of schizophrenia patients using the Chapman Psychosis Proneness scales and then directly compared the cognitive profiles of negative schizotypal individuals and positive schizotypal individuals with schizophrenia patients and controls. In the first phase, cluster analysis categorized 194 unaffected relatives of schizophrenia patients into positive schizotypy (n = 33), negative schizotypy (n = 66), mixed schizotypy (n = 27), and low schizotypy (n = 64). Positive schizotypal participants showed more self-report pleasure experiences than negative schizotypal participants, replicating earlier cluster analytic findings. In the second phase, 27 negative schizotypal individuals, 18 positive schizotypal individuals, 19 schizophrenia patients, and 29 controls were recruited. Although the groups were matched in terms of age, gender, and IQ, they differed significantly in cognitive profiles. While schizophrenia patients exhibited the broadest cognitive impairments, negative schizotypal participants exhibited visual memory, working memory, and verbal fluency impairments, and positive schizotypal participants exhibited logical memory, visual memory, working memory, and theory-of-mind impairments. Among people with familial risk of schizophrenia, individuals exhibiting positive rather than negative schizotypal features resembled schizophrenia patients in cognitive profiles. Using the psychometric-familial method to identify schizotypy, our findings support the heterogeneity of schizotypy as well as the potential utility of the positive schizotypy dimension in genetically high-risk individuals to predict the risk of developing schizophrenia.

Project description:RationaleObsessive-compulsive disorder (OCD) is characterized by executive function impairment and by clinical responsivity to selective serotonin reuptake inhibitors (SSRIs). Executive planning deficits constitute a candidate endophenotype for OCD. It is not known whether this endophenotype is responsive to acute serotonin manipulation.ObjectiveThe study aimed to investigate the effects of acute SSRI administration on executive function in patients with OCD, first-degree relatives of patients with OCD, and healthy controls.MethodsA randomized double-blind cross-over study assessed the effects of single-dose escitalopram (20 mg) and placebo on executive planning in 24 patients with OCD, 13 clinically unaffected first-degree relatives of patients with OCD, and 28 healthy controls. Performance on a Tower of London task measuring executive planning was assessed 4 h after oral administration of the pharmacological challenge/placebo and compared across and within groups using a mixed model analysis of variance.ResultsOn the outcome measure of interest, i.e., the mean number of choices to obtain the correct solution, there was a marginally significant effect of group (F(2, 59) = 3.1; p = 0.052), with patients (least square (LS) mean 1.43; standard error [SE] 0.06; 95% confidence interval (CI), 1.31-1.55) and their relatives (LS mean 1.46; SE 0.08; 95% CI, 1.30-1.62) performing worse than matched healthy controls (LS mean 1.26; SE 0.05; 95% CI, 1.15-1.37) on placebo. There was a trend towards a significant group × treatment interaction (F(2, 58) = 2.8, p = 0.069), with post hoc tests showing (i) patients (p = 0.009; LS mean difference 0.23; SE 0.08) and relatives (p = 0.03; LS mean difference 0.22; SE 0.10) were more impaired compared to controls and (ii) escitalopram was associated with improved executive planning in patients with OCD (p = 0.013; LS mean difference 0.1; SE 0.04), but not other groups (both p > 0.1; controls: LS mean difference - 0.03; SE 0.04; relatives: LS mean difference 0.02; SE 0.05).ConclusionOur findings are consistent with a view that there is impaired executive planning in OCD and that this constitutes a behavioural endophenotype. In patients with OCD, but not in relatives, acute SSRI administration ameliorated this deficit. Further investigation is needed to understand common and differential involvement of neurochemical systems in patients with OCD and their relatives.

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Molecular genetics of the platelet serotonin system in first-degree relatives of patients with autism.

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Molecular genetics of the platelet serotonin system in first-degree relatives of patients with autism.

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