儿童青少年智力的双生子研究

目的 应用双生子法探讨遗传和环境因素对儿童青少年智力影响.方法 采用中国修订版-韦氏儿童智力量表评定6～16岁333对双生子的智力特点.应用结构方程模型分析遗传和环境因素对智力的影响.结果 6～16岁儿童青少年的总智商(intelligence quotient,IQ)遗传度为0.43,其中言语智商(verbal intelligence quotient,VIQ)遗传度为0.37,而遗传因素对操作智商(performance intelligence quotient,PIQ)影响甚小.10～16岁的青少年智力遗传度大于6～9岁的儿童(IQ:0.82 vs 0.00,VIQ:0.80 vs 0.00,PIQ:0.51 vs 0.00).男性的言语智商(0.47)受遗传影响大于女性(0.05);而在男性和女性中,操作智商均主要受共享环境的影响.结论 在儿童青少年时期,总智商和言语智商有中度的遗传度,而共享环境因素对操作智商的影响更大;但智商总分及言语智商和操作智商分测试分在年龄较大的青少年的遗传度都明显高于年龄较小的儿童.     

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.     

Family stories: narrative genetics and conceptions of heritability in pregnant women

As our understanding of genetics has grown, and its importance has increased in clinical care, pregnancy and the fetus are often seen through a genetic lens. Clinicians who care for pregnant women are charged with explaining genetic risk and overseeing prenatal screening. For the clinician, genetics represents clearly defined application of a particular kind of scientific knowledge. Further, heritability in clinical terms is understood as purely genetic. Pregnant women themselves, however, may not give these genetic explanations the same primacy or meaning. In order to better understand the way pregnant women actually understand and explain heritability, we completed in-depth interviews with 26 pregnant women, listening as they gave weight and substance to the various factors they describe as influencing the personhood of their unborn children. Two-thirds of our respondents were Hispanic or African American. Most were recruited through programs that serve low-income women. The interviews were coded and analyzed by using categories that emerged directly from the narratives captured in the interviews and that revealed the broad, cross-cutting, overlapping parameters of women's deeply-held beliefs about heritability. These stories represent narratives of heritability that are profoundly familial and cultural. They incorporate belief in the authoritative knowledge of medicine-including any genetic information-into a complex and usually multicultural context, woven together by ancestry, household, and community.     

Heritability of hostility-related emotions,attitudes, and behaviors

Hostility-related variables have been categorized as to kinds of emotions, attitudes, and behaviors. Relatively few studies have explored whether genetic factors contribute to individual differences in these variables. Moreover, the majority of this research has involved male subjects. The present study utilized the twin method to evaluate the influence of genetic factors on hostility-related emotions, namely, trait anger and irritability, hostility-related attitudes, namely cynical hostility and suspiciousness, and hostility-related behaviors, namely, physical, verbal, and indirect aggression in adult women. Responses on the measure of trait anger showed evidence of significant heritability. However, evidence for a genetic component to responses on the irritability scale was less clear. There was no support for the notion of a genetic component to the measure of suspiciousness, and the evidence of a genetic contribution for cynical hostility was not significant. It was expected that due to environmental influences for women, only certain forms of aggression would show genetic variance, namely, verbal and indirect as opposed to physical forms. The results were generally congruent with these expectations.This study was supported, in part, by a General Research Fund Award from the University of Kansas to B. Kent Houston and a Research Improvement Award from the University of Kansas to Michael H. Crawford.     

Behavior genetic differences within and between defined human populations

The small populations of the Caucasus offer a unique opportunity to consider concepts, such as heritability, which are often considered properties of a trait but which are really properties of a population. A comprehensive strategy is outlined for studying intra-and interpopulation genetic structure across a wide range of traits and environments. A threewway association is demonstrated between 12 of 16 psychophysiological traits, attitude, and thet allele for PTC sensitivity. Differences between populations and traits are evaluated in theoretical terms for morphological, physiological, and psychological measures. While decreases in performance with inbreeding are often predicted, in these small, isolated populations the effects are minimal.     

Estimates of asthma heritability in a large twin sample

Background Asthma is a complex disease characterized by symptoms of wheezing, shortness of breath, chest tightness, and cough. Objective To study the relative contribution of genetic and environmental factors in the liability to asthma in a large sample of twins. Methods Data on asthma in 21 135 twin pairs, 3–71 years of age, from the Danish Twin Registry were collected via a multidisciplinary questionnaire survey. Heritability estimates were calculated using variance components models. Results A monozygotic twin had an approximately sixfold increased risk of asthma whereas a dizygotic twin only had an approximately threefold increased risk relative to the general population if his or her co‐twin was affected. The difference was more pronounced among males. Familial aggregation of asthma in children and adolescents was explained mainly by additive genetic factors, but common environment was also important. The heritability of asthma was also substantial in adults aged 20–49 years. In older adults (aged 50–71 years), additive genetic factors did not significantly influence the disease risk. Conclusion Genetic influences on asthma are substantial throughout the life span but the proportion of the disease liability explained by genetic factors is decreased in older adults. Cite this as: S. F. Thomsen, S. van der Sluis, K. O. Kyvik, A. Skytthe, V. Backer, Clinical & Experimental Allergy, 2010 (40) 1054–1061.     

Evaluation of the discriminative accuracy of genomic profiling in the prediction of common complex diseases

Genetic testing for susceptibility to common diseases based on a combination of genetic markers may be needed because the effect size associated with each genetic marker is small. Whether or not a genome profile based on a combination of markers could yield a useful test can be evaluated by assessing the discriminative accuracy. The authors present a simple method to calculate the clinical discriminative accuracy of a genomic profile when the relative risk and genotype frequency of each genotype are known. In addition, the clinical discriminative accuracy of a genetic test is presented for given values of the heritability and prevalence of the disease and for the population-attributable fraction of the combined genetic markers. For given values of relative risk and genotype frequency, the discriminative accuracy increases with increasing heritability but declines with increasing prevalence of the disease. For a given value of population-attributable fraction, the discriminative accuracy increases with increasing relative risks, but declines with increasing genotype frequency. On the basis of population-attributable fraction and estimates of heritability of disease, the number of risk genotypes required to have a reasonable clinical discriminative accuracy is much higher than the genome profiles available at present.     

Lifestyle factors in monozygotic and dizygotic twins

In examining genetic influences on biological variables using twins, it may be important to examine the distribution between and within twin pairs of demographic and lifestyle factors that may themselves affect the biological variable being studied. We explored the distribution of demographic and lifestyle factors that may affect blood lipid levels or ischaemic heart disease (IHD) risk among a sample of 106 monozygotic (MZ) and 94 like-sex dizygotic (DZ) twin pairs. In our sample, MZ twins were statistically significantly different from DZ twins only in marital status, cigarette smoking habits, and the ratio of polyunsaturated to saturated fat (P:S ratio) in their dietary intake. The latter variable was among many dietary variables examined (using 4-day weighed food diaries), and the size of the difference in intake was small. When comparisons were made of the similarities within twin pairs, we found members of MZ twin pairs to be statistically significantly closer than DZ twins in educational achievement, occupation, cigarette smoking, and exercise habits, and the number of days a week on which alcohol was consumed. These last three variables were consistently closer among twins with closer contact than among those with a smaller degree of current shared environment. For 12 of the 13 nutrients examined, the within-pair correlations were higher for MZ than for DZ twins, although our test for significant genetic variance showed statistical significance only for intake of complex carbohydrates. We conclude that MZ twins share demographic and lifestyle factors that might influence the risk of IHD and blood lipid levels to a greater degree than do DZ twins, although it is difficult to say if these similarities in lifestyle result from genetic influences or not. Nevertheless, ascribing differences between correlations in MZ and DZ twin pairs for lipid levels as being purely "genetic"--as implicit in conventional measures of heritability--is likely to overestimate the influence of genetic factors.