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Simulated nonlinear genetic and environmental dynamics of complex traits

Genetic studies of complex traits often show disparities in estimated heritability depending on the method used, whether by genomic associations or twin and family studies. We present a simulation of individual genomes with dynamic environmental conditions to consider how linear and nonlinear effects, gene-by-environment interactions, and gene-by-environment correlations may work together to govern the long-term development of complex traits and affect estimates of heritability from common methods. Our simulation studies demonstrate that the genetic effects estimated by genome wide association studies in unrelated individuals are inadequate to characterize gene-by-environment interaction, while including related individuals in genome-wide complex trait analysis (GCTA) allows gene-by-environment interactions to be recovered in the heritability. These theoretical findings provide an explanation for the "missing heritability" problem and bridge the conceptual gap between the most common findings of GCTA and twin studies. Future studies may use the simulation model to test hypotheses about phenotypic complexity either in an exploratory way or by replicating well-established observations of specific phenotypes.

What Do We Know About the Genetic Architecture of Psychopathology?

In the second half of the twentieth century, twin and family studies established beyond a reasonable doubt that all forms of psychopathology are substantially heritable and highly polygenic. These conclusions were simultaneously an important theoretical advance and a difficult methodological obstacle, as it became clear that heritability is universal and undifferentiated across forms of psychopathology, and the radical polygenicity of genetic effects limits the biological insight provided by genetically informed studies at the phenotypic level. The paradigm-shifting revolution brought on by the Human Genome Project has recapitulated the great methodological promise and the profound theoretical difficulties of the twin study era. We review these issues using the rubric of genetic architecture, which we define as a search for specific genetic insight that adds to the general conclusion that psychopathology is heritable and polygenic. Although significant problems remain, we see many promising avenues for progress.

Expected final online publication date for the Annual Review of Clinical Psychology, Volume 18 is May 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Gene Flow by Selective Emigration as a Possible Cause for Personality Differences between Small Islands and Mainland Populations

Whether personality differences exist between populations is a controversial question. Even though such differences can be measured, it is still not clear whether they are due to individual phenotypic responses to the environment or whether they have a genetic influence. In a population survey we compared the personality traits of inhabitants of an Italian archipelago (the three Egadi islands; N = 622) with those of the closest mainland population (Trapani area; N = 106) and we found that personality differences between small populations can be detected. Islanders scored significantly lower on the personality traits of openness to experience and extraversion and higher on conscientiousness. We suggest that these personality trait differences could be an adaptive response to a confined socio–environmental niche, genetically produced by a strong, non–random gene flow in the last 20–25 generations, rather than the flexible response of islanders to environmental variables. To test this hypothesis, we compared subsets of the islander population classified by ancestry, birthplace, immigration and emigration and found that differences in extraversion can be accounted for by gene flow, while openness to experience and conscientiousness can also be accounted for by some gene–environment interactions. We propose a Personality Gene Flow hypothesis suggesting that, in small isolated communities, whenever there is strong, non–random emigration, paired with weak and random immigration, we can expect rapid genetic personality change within the population. Copyright © 2010 John Wiley & Sons, Ltd.

The social nature of mitochondria: Implications for human health

Sociality has profound evolutionary roots and is observed from unicellular organisms to multicellular animals. In line with the view that social principles apply across levels of biological complexity, a growing body of data highlights the remarkable social nature of mitochondria - life-sustaining endosymbiotic organelles with their own genome that populate the cell cytoplasm. Here, we draw from organizing principles of behavior in social organisms to reveal that similar to individuals among social networks, mitochondria communicate with each other and with the cell nucleus, exhibit group formation and interdependence, synchronize their behaviors, and functionally specialize to accomplish specific functions within the organism. Mitochondria are social organelles. The extension of social principles across levels of biological complexity is a theoretical shift that emphasizes the role of communication and interdependence in cell biology, physiology, and neuroscience. With the help of emerging computational methods capable of capturing complex dynamic behavioral patterns, the implementation of social concepts in mitochondrial biology may facilitate cross-talk across disciplines towards increasingly holistic and accurate models of human health.

Effect of socioeconomic status on behavioral problems from preschool to early elementary school - A Japanese longitudinal study

Purpose

Social inequalities are widely accepted to have a deleterious effect on children’s mental health, and those with lower socioeconomic status generally experience more mental health issues. In this study, we examine the impact of socioeconomic situations of children’s families during their early childhood on the children’s social adaptation in Japanese elementary school.

Methods

The current investigation consisted of two sets of data relating to two separate years (with a one-year interval). The participants included preschoolers aged five years at Time 1 (the first year) and first graders aged six years at Time 2 (the second year); 1,712 met the inclusion criteria for both years. Parents of the participants completed a self-reported questionnaire regarding their SES (i.e., family economy and mother’s education) and their children’s mental health. Mental health was assessed using the Child Behavior Checklist/4–18, Parent Report.

Results

For each SES indicator, we found an inverse relationship across all the symptom dimensions. Specifically, bivariate analyses revealed that lower family income, maternal education level, and paternal education level predict all three domains of behavioral problems (i.e., internalized problems, externalized problems, and total behavioral problems). Further, multivariate analyses revealed that lower family income consistently predicts all domains of behavioral problems, lower maternal education level predicted externalized problems and total behavioral problems, and paternal education level did not predict any clinically significant behavioral problems.

Conclusion

In this sample, we found that, for children, family income and parental education when entering preschool were significant predictors of mental health problems after elementary school enrollment; in particular, low income and low maternal educational achievement predicted a high probability of the development of a psychiatric disorder. A greater understanding of the mechanisms of these associations could contribute to improvements in interventions aimed at preventing child maladjustment.

A longitudinal study of socioeconomic status, family processes, and child adjustment from preschool until early elementary school: the role of social competence

OBJECTIVE

Using a short-term longitudinal design, this study examined the concurrent and longitudinal relationships among familial socioeconomic status (SES; i.e., family income and maternal and paternal education levels), marital conflict (i.e., constructive and destructive marital conflict), parenting practices (i.e., positive and negative parenting practices), child social competence (i.e., social skills), and child behavioral adjustment (i.e., internalizing and externalizing problems) in a comprehensive model.

METHODS

The sample included a total of 1604 preschoolers aged 5 years at Time 1 and first graders aged 6 years at Time 2 (51.5% male). Parents completed a self-reported questionnaire regarding their SES, marital conflict, parenting practices, and their children's behavioral adjustment. Teachers also evaluated the children's social competence.

RESULTS

The path analysis results revealed that Time 1 family income and maternal and paternal education levels were respectively related to Time 1 social skills and Time 2 internalizing and externalizing problems, both directly and indirectly, through their influence on destructive and constructive marital conflict, as well as negative and positive parenting practices. Notably, after controlling for Time 1 behavioral problems as mediating mechanisms in the link between family factors (i.e., SES, marital conflict, and parenting practices) and behavioral adjustment, Time 1 social skills significantly and inversely influenced both the internalization and externalization of problems at Time 2.

CONCLUSIONS

The merit of examining SES, marital conflict, and parenting practices as multidimensional constructs is discussed in relation to an understanding of processes and pathways within families that affect child mental health functioning. The results suggest social competence, which is influenced by the multidimensional constructs of family factors, may prove protective in reducing the risk of child maladjustment, especially for children who are socioeconomically disadvantaged.

Molecular genetic approaches to understanding the comorbidity of psychiatric disorders

Epidemiologic studies demonstrating high rates of co-occurrence among psychiatric disorders at the population level have contributed to large literatures focused on identifying the causal mechanisms underlying the patterns of co-occurrence among these disorders. Such efforts have long represented a core focus of developmental psychopathologists and have more recently been supported by the Research Domain Criteria initiative developed by the NIMH, which provides a further framework for how the hypothesized mechanisms can be studied at different levels of analysis. The present overview focuses on molecular genetic approaches that are being used currently to study the etiology of psychiatric disorders, and how these approaches have been applied in efforts to understand the biological mechanisms that give rise to comorbid conditions. The present report begins with a review of molecular genetic approaches used to identify individual variants that confer risk for multiple disorders and the intervening biological mechanisms that contribute to their comorbidity. This is followed by a review of molecular genetic approaches that use genetic data in aggregate to examine these questions, and concludes with a discussion of how developmental psychopathologists are uniquely positioned to apply these methods in a way that will further our understanding of the causal factors that contribute to the development of comorbid conditions.

What Drives the Development of Social Inequality Over the Life Course? The German TwinLife Study

The German twin family study ‘TwinLife’ was designed to enhance our understanding of the development of social inequalities over the life course. The interdisciplinary project investigates mechanisms of social inequalities across the lifespan by taking into account psychological as well as social mechanisms, and their genetic origin as well as the interaction and covariation between these factors. Main characteristics of the study are: (1) a multidimensional perspective on social inequalities, (2) the assessment of developmental trajectories in childhood, adolescence, and young adulthood in a longitudinal design by using (3) a combination of a multi-cohort cross-sequential and an extended twin family design, while (4) capturing a large variation of behavioral and environmental factors in a representative sample of about 4,000 German twin families. In the present article, we first introduce the theoretical and empirical background of the TwinLife study, and second, describe the design, content, and implementation of TwinLife. Since the data will be made available as scientific use file, we also illustrate research possibilities provided by this project to the scientific community.

Counseling Psychology in the Era of Genetic Testing

The field of genetics and the process of testing for genetic disorders have advanced considerably over the past half century, ushering in significant improvements in certain areas of medical diagnosis and disease prediction. However, genetic discoveries are accompanied by many social, emotional, and psychological implications, and counseling psychologists may be uniquely equipped to help clients deal with these issues. The present overview is intended to raise awareness of the multidimensional issues inherent in situations where clients seek genetic testing to diagnose or predict various medical conditions. Initially, the author presents a framework to help counseling psychologists identify and organize information within a genetic-testing context, followed by suggestions for addressing the various psychological, social, and multicultural issues potentially affecting client decision making, mental health, and behavior. Finally, the author raises considerations for training, continuing education, and professional practice to foster continued discussion among counseling psychologists preparing for, or presently working in, research and applied settings involving clients with genetic concerns.

Behavioural genetics in the 21st century

Behavioural genetics will continue to flow into the mainstream of behavioural research as more behavioural scientists incorporate this approach in their research. Future research will go beyond simply asking whether and how much genetic factors influence behaviour to ask questions about development, about relations among traits, and about the interplay between nature and nurture. The identification of specific genes associated with behaviour will make it possible for behavioural scientists to ask more precise questions about how genotypes become phenotypes.

Understanding the Links Between Social Support and Physical Health: A Life-Span Perspective With Emphasis on the Separability of Perceived and Received Support

Social support has been reliably related to physical health outcomes. However, the conceptual basis of such links needs greater development. In this article, I argue for a life-span perspective on social support and health that takes into account distinct antecedent processes and mechanisms that are related to measures of support over time. Such a view highlights the need to distinguish measures of perceived and received support and its links to more specific diseases (e.g., chronic, acute) and stages of disease development (e.g., incidence). I discuss both the novel implications of these theoretical arguments for research on social support and physical health, as well as the potential intervention approaches that are apparent from this perspective.

[The role of genotype in the intergenerational transmission of experiences of childhood adversity]

The prevalence of childhood abuse and maltreatment is estimated to lie at about 15% in the overall German population. Previous research suggested that about one third of all individuals who had experienced childhood adversity subsequently maltreated their own children or responded insensitively to their children's needs. Empirical studies imply that interindividual differences in the responsiveness to childhood adversity can partially be explained by gene-environment interactions. This article discusses the potential interplay of genes and environment in the context of transmitting maltreating behavior and (in)sensitive parenting against the background of current challenges in genetic research. Selected studies on gene × environment interactions are presented and relevant gene polymorphisms are identified. Overall, previous studies reported interactions between polymorphisms of the serotonergic, dopaminergic, oxytocin-related, and arginine vasopressin-related systems and childhood experiences of care and abuse in the prediction of social behaviors during mother-child interactions. The results indicate a differential susceptibility toward both negative and positive environments which is dependent on genetic characteristics. Future research should thus investigate the effects of children's presumed risk gene variants toward negative as well as positive parenting. This could contribute to a deeper understanding of the underlying mechanisms of the intergenerational transmission of abusive and beneficial parenting behavior and help to avoid false stigmatizations.

A twin study of self-regulatory eating in early childhood: estimates of genetic and environmental influence, and measurement considerations

OBJECTIVE

Children differ greatly in their ability to self-regulate food intake for reasons that are poorly understood. This laboratory-based twin study tested the genetic and environmental contributions to self-regulatory eating and body fat in early childhood.

METHODS

A total of 69 4-7 year-old same-sex twin pairs, including 40 monozygotic and 29 dizygotic pairs, were studied. Self-regulatory eating was operationalized as the percentage compensation index (COMPX%), assessed by a 'preload' challenge in which lunch intake was measured following a low- (3 kcal) or high-calorie (159 kcal) drink. Body fat indexes also were measured. The familial association for COMPX% was estimated by an intraclass correlation, and biometric analyses estimated heritability.

RESULTS

Children ate more at lunch following the low- compared with high-energy preload (P<0.001), although variability in COMPX% was considerable. Compensation was significantly poorer among African American and Hispanic compared with European American children, and among girls compared with boys. There was a familial association for self-regulatory eating (ρ = 0.23, P = 0.03) but no significant genetic component. In all, 22% of the variance in COMPX% was due to shared environmental 'household' factors, with the remaining variance attributable to child-specific 'unique' or 'random' environments. Poorer self-regulatory eating was associated with greater percent body fat (r = -0.21, P = 0.04).

CONCLUSIONS

Self-regulatory eating was influenced by environmental factors, especially those differing among siblings. The absence of a significant genetic effect may reflect the age of the sample or could be artifactual due to measurement issues that need to be considered in future studies.

Association analysis of STX1A gene variants in common forms of migraine

OBJECTIVES

To examine the association of genetic variants in the syntaxin 1A gene (STX1A) with common forms of migraine, and perform a combined analysis of the data from the current study and previously published reports.

METHODS

We investigated the parent-to-offspring transmission of rs6951030, rs4363087 and rs2293489 in 191 family trios, each with a proband with childhood-onset migraine, and performed a case-control analysis between the probands and 223 unrelated controls. In addition, we performed a combined data analysis with an overall sample of 567 migraine patients and 720 unrelated controls and performed a migraine-specific gene-network analysis.

RESULTS

The transmission disequilibrium test revealed significant transmission distortion of rs4363087 in migraine overall (OR = 1.56, p = 0.006; p = 0.01 after correction for multiple testing) and migraine without aura (OR = 1.58, p = 0.01; corrected p = 0.04). Two-marker haplotype analysis revealed transmission distortion of A-G (rs6951030-rs4363087; OR = 1.47, p = 0.01) and A-C (rs4363087-rs2293489; OR = 0.66, p = 0.01). Combined analysis showed significant association of rs941298 with migraine overall (OR = 1.28, p = 0.004) and migraine without aura (OR = 1.3, p = 0.008). Network analysis identified 24 genes relating STX1A to other migraine candidate genes, including KCNK18 (TRESK channel) involved in the cytoplasmatic calcium signalling together with syntaxin 1A.

CONCLUSION

Our results provide support for the hypothesis that STX1A represents a susceptibility gene for migraine.

Individual differences in cognition, affect, and performance: behavioral, neuroimaging, and molecular genetic approaches

We describe the use of behavioral, neuroimaging, and genetic methods to examine individual differences in cognition and affect, guided by three criteria: (1) relevance to human performance in work and everyday settings; (2) interactions between working memory, decision-making, and affective processing; and (3) examination of individual differences. The results of behavioral, functional MRI (fMRI), event-related potential (ERP), and molecular genetic studies show that analyses at the group level often mask important findings associated with sub-groups of individuals. Dopaminergic/noradrenergic genes influencing prefrontal cortex activity contribute to inter-individual variation in working memory and decision behavior, including performance in complex simulations of military decision-making. The interactive influences of individual differences in anxiety, sensation seeking, and boredom susceptibility on evaluative decision-making can be systematically described using ERP and fMRI methods. We conclude that a multi-modal neuroergonomic approach to examining brain function (using both neuroimaging and molecular genetics) can be usefully applied to understanding individual differences in cognition and affect and has implications for human performance at work.

Profiling trait anxiety: transcriptome analysis reveals cathepsin B (Ctsb) as a novel candidate gene for emotionality in mice

Behavioral endophenotypes are determined by a multitude of counteracting but precisely balanced molecular and physiological mechanisms. In this study, we aim to identify potential novel molecular targets that contribute to the multigenic trait “anxiety”. We used microarrays to investigate the gene expression profiles of different brain regions within the limbic system of mice which were selectively bred for either high (HAB) or low (LAB) anxiety-related behavior, and also show signs of comorbid depression-like behavior.

We identified and confirmed sex-independent differences in the basal expression of 13 candidate genes, using tissue from the entire brain, including coronin 7 (Coro7), cathepsin B (Ctsb), muscleblind-like 1 (Mbnl1), metallothionein 1 (Mt1), solute carrier family 25 member 17 (Slc25a17), tribbles homolog 2 (Trib2), zinc finger protein 672 (Zfp672), syntaxin 3 (Stx3), ATP-binding cassette, sub-family A member 2 (Abca2), ectonucleotide pyrophosphatase/phosphodiesterase 5 (Enpp5), high mobility group nucleosomal binding domain 3 (Hmgn3) and pyruvate dehydrogenase beta (Pdhb). Additionally, we confirmed brain region-specific differences in the expression of synaptotagmin 4 (Syt4).

Our identification of about 90 polymorphisms in Ctsb suggested that this gene might play a critical role in shaping our mouse model's behavioral endophenotypes. Indeed, the assessment of anxiety-related and depression-like behaviors of Ctsb knock-out mice revealed an increase in depression-like behavior in females.

Altogether, our results suggest that Ctsb has significant effects on emotionality, irrespective of the tested mouse strain, making it a promising target for future pharmacotherapy.

Animal models of human anxiety disorders: reappraisal from a developmental psychopathology vantage point

We are witnessing a tremendous expansion of strategies and techniques that derive from basic and preclinical science to study the fine genetic, epigenetic, and proteomic regulation of behavior in the laboratory animal. In this endeavor, animal models of psychiatric illness are becoming the almost exclusive domain of basic researchers, with lesser involvement of clinician researchers in their conceptual design, and transfer into practice of new paradigms. From the side of human behavioral research, the growing interest in gene-environment interplay and the fostering of valid endophenotypes are among the few substantial innovations in the effort of linking common mental disorders to cutting-edge clinical research questions. We argue that it is time for cross-fertilization between these camps. In this article, we a) observe that the "translational divide" can-and should-be crossed by having investigators from both the basic and the clinical sides cowork on simpler, valid "endophenotypes" of neurodevelopmental relevance; b) emphasize the importance of unambiguous physiological readouts, more than behavioral equivalents of human symptoms/syndromes, for animal research; c) indicate and discuss how this could be fostered and implemented in a developmental framework of reference for some common anxiety disorders and ultimately lead to better animal models of human mental disorders.

No association between bipolar disorder risk polymorphisms in ANK3 and CACNA1C and common migraine

BACKGROUND

Migraine and bipolar disorder are characterized by a high level of co-morbidity, and a common familial-genetic basis has recently been hypothesized for the 2 disorders. Genome-wide association studies have reported strong evidence of association between the polymorphisms rs10994336[T] in the ANK3 gene and rs1006737[A] in the CACNA1C gene and risk of bipolar disorder.

OBJECTIVE

The aim of this study was to evaluate the hypothesis of a genetic linkage between migraine and bipolar disorder by investigating the familial transmission of the 2 bipolar disorder risk polymorphisms, in a sample of family trios with probands with childhood migraine, and unrelated controls.

METHODS

Our sample comprised 192 family trios, each with a proband with childhood migraine (137 migraine without aura, 44 migraine with aura) and 228 unrelated controls. The markers rs10994336 and rs1006737 were genotyped using a TaqMan single nucleotide polymorphism Genotyping Assay. The transmission disequilibrium test analysis for the family trios and the case-control analysis were performed using the program UNPHASED.

RESULTS

The allelic and genotypic transmission disequilibrium test analysis did not show any evidence of transmission distortion of the 2 markers in both migraine overall (rs10994336: OR = 1.61, P = .11; rs1006737: OR = 1.12, P = .49) and in the migraine without aura and migraine with aura subgroups. Likewise, the case-control analysis of alleles and genotypes frequencies did not show any evidence of association.

CONCLUSION

In the present study, we did not find evidence for association between the bipolar disorder risk polymorphisms rs10994336 in the ANK3 gene and rs1006737 in the CACNA1C gene in migraine. However, as these are variants that have a small effect on the risk of bipolar disorder (OR < 1.5), we cannot exclude a similar small effect on migraine susceptibility with the present sample size.

The HTR1A and HTR1B receptor genes influence stress-related information processing

The serotonergic system has been widely implicated in stress related psychiatric disorders such as depression and anxiety. We investigated the possible association between depression and anxiety scores and SNPs within the HTR1A and HTR1B genes in a population sample (n=1387). There was no direct SNP-phenotype association, but in interaction with recent stressful life events rs6295 G, rs878567 T alleles and rs6296 C alleles were associated with significantly higher symptom scores. A subset of control subjects (n=101) took part in a computerised face emotion processing task. Healthy rs6295 GG carriers did not show an affective bias to perceive more negative emotions but reacted more quickly to fearful faces. Thus we conclude that the serotonin-1A receptor conveys vulnerability to these psychiatric disorders by modulating threat-related information processing. Our results extend previous findings of an interaction between stressful life events and the serotonin transporter gene to two other genes in the serotonergic pathway and emphasise the possible role of increased threat-related information processing as an intermediate phenotype.

Neurogenetic effects on cognition in aging brains: a window of opportunity for intervention?

Knowledge of genetic influences on cognitive aging can constrain and guide interventions aimed at limiting age-related cognitive decline in older adults. Progress in understanding the neural basis of cognitive aging also requires a better understanding of the neurogenetics of cognition. This selective review article describes studies aimed at deriving specific neurogenetic information from three parallel and interrelated phenotype-based approaches: psychometric constructs, cognitive neuroscience-based processing measures, and brain imaging morphometric data. Developments in newer genetic analysis tools, including genome wide association, are also described. In particular, we focus on models for establishing genotype-phenotype associations within an explanatory framework linking molecular, brain, and cognitive levels of analysis. Such multiple-phenotype approaches indicate that individual variation in genes central to maintaining synaptic integrity, neurotransmitter function, and synaptic plasticity are important in affecting age-related changes in brain structure and cognition. Investigating phenotypes at multiple levels is recommended as a means to advance understanding of the neural impact of genetic variants relevant to cognitive aging. Further knowledge regarding the mechanisms of interaction between genetic and preventative procedures will in turn help in understanding the ameliorative effect of various experiential and lifestyle factors on age-related cognitive decline.

Inbred mouse strains differ in multiple hippocampal activity traits

A major challenge in neuroscience is to identify genes that influence specific behaviors and to understand the intermediary neuronal mechanisms. One approach is to identify so-called endophenotypes at different levels of neuronal organization from synapse to brain activity. An endophenotype is a quantitative trait that is closer to the gene action than behavior, and potentially a marker of neuronal mechanisms underlying behavior. Hippocampal activity and, in particular, hippocampal oscillations have been suggested to underlie various cognitive and motor functions. To identify quantitative traits that are potentially useful for identifying genes influencing hippocampal activity, we measured gamma oscillations and spontaneous activity in acute hippocampal slices from eight inbred mouse strains under three experimental conditions. We estimated the heritability of more than 200 quantitative traits derived from this activity. We observed significant differences between the different mouse strains, particularly in the amplitude of the activity and the correlation between activities in different hippocampal subregions. Interestingly, these traits had a low genetic correlation between the three experimental conditions, which suggests that different genetic components influence the activity in different conditions. Our findings show that several traits of hippocampal gamma oscillations and spontaneous activity are heritable and could thus be potentially useful in gene-finding strategies based on endophenotypes.

ALDH2, ADH1B and alcohol expectancies: integrating genetic and learning perspectives

The present study evaluated associations of ALDH2 and ADH1B genotypes with alcohol expectancies and drinking behavior in a sample of Asian American young adults. In addition to assessing global alcohol expectancies, the authors developed a measure of physiological expectancies to evaluate an expectancy phenotype specific to the mechanism by which ALDH2 and ADH1B variations presumably influence drinking behavior. Compared with individuals with the ALDH2*1/*1 genotype, those with the ALDH2*2 allele reported greater negative alcohol expectancies, greater expectancies for physiological effects of alcohol and lower rates of alcohol use. ADH1B was not associated with alcohol expectancies or drinking behavior. Hierarchical models showed that demographic factors, ALDH2 genotype, and expectancy variables explained unique variance in drinking outcomes. Mediation tests showed significant indirect effects of ALDH2 on drinking frequency and peak lifetime consumption through expectancies. These results provide support for influences of genetic factors and alcohol sensitivity on alcohol-related learning and suggest the importance of developing biopsychosocial models of drinking behavior in Asian Americans.

Vulnerabilidad social en el síndrome de turner: interacción genes-ambiente

En este trabajo se exponen los fundamentos teóricos que permiten considerar al Síndrome de Turner como un “modelo genético sensible” en el cual analizar asociaciones entre caracteres psicológicos y factores genéticos y ambientales. La investigación en esta línea permitiría dilucidar mecanismos de riesgo ambiental y comprender el grado de “vulnerabilidad” que presentan las mujeres con el síndrome. El Síndrome de Turner es un trastorno genético, no heredable, que se caracteriza por la deleción total o parcial del cromosoma X en el sexo femenino. El estudio de la disfunción social que presentan las mujeres con este síndrome, es decir, de la capacidad para relacionarse con el entorno y la calidad de los vínculos tiene importantes implicaciones en la comprensión de la forma en que actúa el ambiente sobre el desarrollo psicológico, y de cómo a su vez éste se ve afectado por factores genéticos que actúan en interacción.

Genetics of posttraumatic stress disorder: Review and recommendations for future studies

Posttraumatic stress disorder (PTSD) is common and debilitating. Posttraumatic stress disorder is moderately heritable; however, the role of genetic factors in PTSD etiology has been largely neglected by trauma researchers. The goal of this study is to motivate trauma researchers to reflect on the role genetic variation may play in vulnerability and resilience following trauma exposure. Evidence from family, twin, and molecular genetic studies for genetic influences on PTSD is reviewed. Recommendations for future studies are presented with emphasis on study design and assessment issues particular to the field of trauma and PTSD. Clinical implications of PTSD genetic studies are discussed.

Family-based analysis of serotonin transporter gene polymorphisms in migraine with and without aura

Genetic epidemiological twin studies have demonstrated a significant heritability for migraine, with > 60% of liability to migraine either with or without aura coming from additive genetic factors. Because of the essential role of serotonin in the pathophysiology and treatment of migraine, genes of the serotonin system are candidates for involvement in migraine. Consequently, we examined two functional VNTR polymorphisms in the serotonin transporter gene, the 5-HTTLPR and the intron 2 VNTR, in a sample of 212 family trios each with a proband with childhood migraine, 153 with migraine without aura (MoA) and 59 with migraine with aura (MA). For the first time, we used transmission disequilibrium test analysis with the program TDTPHASE to examine the transmission of these two markers and their haplotypes to offspring affected by migraine. We found no significant transmission distortion of any marker, with the common L allele of the 5-HTTLPR transmitted 170 times and not transmitted 178 times, and the S allele 130 vs. 122 times. Likewise, the common 12 allele of the intron 2 VNTR was transmitted 201 times and not transmitted 188 times, and the 10 allele 107 vs. 120 times. The markers were not associated with MoA and MA and none of the haplotypes was associated with overall migraine, MoA or MA. The 5-HTTLPR and the intron 2 VNTRs do not play a major role in susceptibility to migraine.

A dopamine D4 receptor exon 3 VNTR allele protecting against migraine without aura

OBJECTIVE

As dopamine plays an important role in the pathophysiology of migraine and antimigraine drugs have an effect on the dopamine system, the objective of this study was to examine the dopamine D4 receptor gene for involvement in the cause of migraine.

METHODS

We tested a VNTR-polymorphism in the dopamine D4 receptor gene, the exon 3 VNTR, in a sample of 190 family trios each with a proband with childhood migraine by using transmission disequilibrium test tests.

RESULTS

We found a trend for transmission distortion of this marker in migraine, with the common seven-repeat allele of the VNTR transmitted 58 times and not transmitted 82 times (global likelihood ratio score (LRS) = 12.27, degress of freedom (DF) = 6, p = 0.06; for the 7-repeat allele: chi(2) = 5.1, p = 0.02). This effect came only from migraine without aura (145 trios), with the common 7-repeat allele transmitted 45 times and not transmitted 69 times (global LRS = 15.18; DF = 6, p = 0.019; for the 7-repeat allele: chi(2) = 6.4, p = 0.01; odds ratio, 0.47), whereas in migraine with aura (45 trios) there was no transmission distortion of the 7-repeat allele.

INTERPRETATION

We conclude that seven-repeat allele of the dopamine D4 receptor VNTR is a protective factor for migraine without aura. Because migraine is a common disorder, this protective effect may have contributed to the positive selection acting on the dopamine D4 receptor exon 3 VNTR seven-repeat allele in recent human history. We speculate that dopamine function in the lateral parabrachial nucleus is involved in migraine without aura.

Family-based association analysis of functional VNTR polymorphisms in the dopamine transporter gene in migraine with and without aura

Because of the role of dopamine in triggering migraine attacks, genes of the dopamine system are candidates for involvement in migraine. We examined three VNTR polymorphisms in the dopamine transporter, the 5'UTR VNTR, the intron 8 VNTR and the intron 14 VNTR, in a sample of 205 family trios. We used the transmission disequilibirium test (TDT) to examine the transmission of these three markers and their haplotypes to offspring affected by migraine. We found no significant transmission distortion of any marker. Likewise haplotypes of the three markers did not show significant overall or individual association with migraine. Finally we examined migraine with and without aura, and likewise found no association between dopamine transporter VNTRs or their haplotypes and either classification of the disease. We conclude that functional genetic variation in the dopamine transporter does not act as a significant risk factor for migraine.

Child eating patterns and weight regulation: a developmental behaviour genetics framework

There is relatively limited knowledge about the development of child eating patterns and how they may contribute to excess weight gain in early life. Particularly scarce are genetically informative studies that addressed environmental and genetic influences which can be challenging to disentangle. A review of this literature can help identify ongoing themes in the field and may stimulate new ideas for future research. The purpose of this paper is to provide an overview about how select environmental factors (e.g. the portion size of foods) and parental feeding practices (e.g. dietary restriction) can affect children's eating behaviour and weight status. The second part of the review explains in more detail the types of studies that can be employed to assess genetic influences (e.g. heritability estimates) on child food intake and body weight and composition. The review closes with suggestions for future research emphasizing the importance of collaborations among investigators from different disciplines to further elucidate gene-environment interactions in the domains of child eating behaviour and obesity.

The genetic and environmental origins of learning abilities and disabilities in the early school years

Despite the importance of learning abilities and disabilities in education and child development, little is known about their genetic and environmental origins in the early school years. We report results for English (which includes reading, writing, and speaking), mathematics, and science as well as general cognitive ability in a large and representative sample of U.K. twins studied at 7, 9, and 10 years of age. Although preliminary reports of some of these data have been published, the purpose of this monograph is to present new univariate, multivariate, and longitudinal analyses that systematically examine genetic and environmental influences for the entire sample at all ages for all measures for both the low extremes (disabilities) and the entire sample (abilities). English, mathematics, and science yielded similarly high heritabilities and modest shared environmental influences at 7, 9, and 10 years despite major changes in content across these years. We draw three conclusions that go beyond estimating heritability. First, the abnormal is normal: Low performance is the quantitative extreme of the same genetic and environmental influences that operate throughout the normal distribution. Second, continuity is genetic and change is environmental: Longitudinal analyses suggest that age-to-age stability is primarily mediated genetically, whereas the environment contributes to change from age to age. Third, genes are generalists and environments are specialists: Multivariate analyses indicate that genes largely contribute to similarity in performance within and between the three domains--and with general cognitive ability--whereas the environment contributes to differences in performance. These conclusions have far-reaching implications for education and child development as well as for molecular genetics and neuroscience.

The heritability of life history strategy: the K-factor, covitality, and personality

Archival data from the MIDUS survey (Brim et al., 2000), a nationally representative sample, on 309 MZ and 333 DZ twin pairs aged 25-74 years were used to test the psychometrics and behavioral genetics of life history strategy. We organized 253 of the originally administered 2,000 questions into 30 scales measuring life history traits (e.g., quality of family relationships and altruism towards kin), medical symptoms (e.g., thyroid problems), personality traits (e.g., neuroticism, extraversion, conscientiousness), and social background (e.g., financial security). A single higher-order factor, indicating a general life history strategy, composed of three lower-order factors, was replicated. Factor analyses were then performed on the genetic variance-covariance matrices. We found that (a) a single higher-order factor explained the preponderance of the genetic correlations among the scales and (b) this higher-order factor was itself 68 percent heritable and accounted for 82 percent of the genetic variance among the three component lower-order factors.

Gene-environment interactions in psychiatry: joining forces with neuroscience

Gene-environment interaction research in psychiatry is new, and is a natural ally of neuroscience. Mental disorders have known environmental causes, but there is heterogeneity in the response to each causal factor, which gene-environment findings attribute to genetic differences at the DNA sequence level. Such findings come from epidemiology, an ideal branch of science for showing that a gene-environment interactions exist in nature and affect a significant fraction of disease cases. The complementary discipline of epidemiology, experimental neuroscience, fuels gene-environment hypotheses and investigates underlying neural mechanisms. This article discusses opportunities and challenges in the collaboration between psychiatry, epidemiology and neuroscience in studying gene-environment interactions.