Greater Genetic Influence Research Articles

Sub-types of insomnia in adolescents: Insights from a quantitative/molecular twin study.

Insomnia with short sleep duration has been postulated as more severe than that accompanied by normal/long sleep length. While the short duration subtype is considered to have greater genetic influence than the other subtype, no studies have addressed this question. This study aimed to compare these subtypes in terms of: (1) the heritability of insomnia symptoms; (2) polygenic scores (PGS) for insomnia symptoms and sleep duration; (3) the associations between insomnia symptoms and a wide variety of traits/disorders. The sample comprised 4000 pairs of twins aged 16 from the Twins Early Development Study. Twin models were fitted to estimate the heritability of insomnia in both groups. PGS were calculated for self-reported insomnia and sleep duration and compared among participants with short and normal/long sleep duration. Heritability was not significantly different in the short sleep duration group (A=0.13 [95%CI=0.01, 0.32]) and the normal/long sleep duration group (A=0.35 [95%CI=0.29, 0.40]). Shared environmental factors accounted for a substantial proportion of the variance in the short sleep duration group (C=0.19 [95%CI=0.05, 0.32]) but not in the normal/long sleep duration group (C=0.00 [95%CI=0.00, 0.04]). PGS did not differ significantly between groups although results were in the direction expected by the theory. Our results also showed that insomnia with short (as compared to normal/long) sleep duration had a stronger association with anxiety and depression (p<.05)-although not once adjusting for multiple testing. We found mixed results in relation to the expected differences between the insomnia subtypes in adolescents. Future research needs to further establish cut-offs for 'short' sleep at different developmental stages and employ objective measures of sleep.

Age Differences in Heritability of a Latent Dementia Index Score in Men and Women

AbstractBackgroundHeritability estimates of dementia are ∼50‐60% of the total variance across older adulthood. Earlier age of onset, however, might be associated with greater genetic influence whereas older age of onset might be associated with greater environmental influences. The categorical nature of dementia diagnosis outcomes has made testing the relative importance of genetic and environmental influences on dementia difficult due to low statistical power. To overcome this methodological limitation, we tested linear and quadratic effects of age on genetic and environmental variance underlying a continuous measure of dementia likelihood in men and women.MethodThe analytic sample was 5,670 (53% female) pairs of twins from 10 studies in the Interplay of Genes and Environment Across Multiple Studies (IGEMS) consortium. Dementia likelihood is quantified continuously using a latent dementia index measure that is estimated from twins’ available cognitive, memory‐specific, and functional ability measures. Linear and quadratic age differences in genetic and environmental influences on dementia likelihood were tested by modeling univariate correlation between twins’ dementia scores as a linear function of zygosity and age in Mplus. Separate models were estimated for male and female twin groups.ResultsAge moderated genetic and environmental influences on dementia likelihood scores. Both genetic and nonshared environmental variance increased as a function of age, whereas common environmental variance declined. Sex significantly moderated the effect of zygosity on the twin correlations (monozygotic male: .57, monozygotic female: .51, dizygotic male: .19, dizygotic female: .25). Notably, MZ twin correlations were consistent with previously reported heritability estimates for dementia. The pattern of age moderation was the same in men as women, although the linear effect of age on both genetic and common environmental influences was greater in men than women (see Figure 1).ConclusionAge linearly moderated genetic and environmental variance underlying dementia likelihood similarly for both men and women, despite quantitative genetic and environmental sex differences in dementia likelihood. Genetic variance accounted for similar proportions of total variance at younger ages, whereas genetic variance accounted for greater variance in men than in women at older ages.

Teachers’ perception about genes and behavior

Abstract Knowing about teacher perceptions contributes to the understanding of teachers’ attitudes toward the behavior of their students. We evaluated the perceptions of 501 teachers about the genetic and environmental influences on behaviors considered relevant to the educational environment using an original questionnaire from the United Kingdom, adapted to the Portuguese language of Brazil. We found that the teachers attributed genetic and environmental influences evenly regarding personality and learning difficulties; greater genetic influence on intelligence and mental illness; and greater environmental influence on behavioral problems. Most teachers stated that having a student with genetically influenced learning difficulties would affect their method of instructing them.

Insights Gained From the Study of Pediatric Systemic Lupus Erythematosus.

The pathophysiology of systemic lupus erythematosus (SLE) has been intensely studied but remains incompletely defined. Currently, multiple mechanisms are known to contribute to the development of SLE. These include inadequate clearance of apoptotic debris, aberrant presentation of self nucleic antigens, loss of tolerance, and inappropriate activation of T and B cells. Genetic, hormonal, and environmental influences are also known to play a role. The study of lupus in children, in whom there is presumed to be greater genetic influence, has led to new understandings that are applicable to SLE pathophysiology as a whole. In particular, characterization of inherited disorders associated with excessive type I interferon production has elucidated specific mechanisms by which interferon is induced in SLE. In this review, we discuss several monogenic forms of lupus presenting in childhood and also review recent insights gained from cytokine and autoantibody profiling of pediatric SLE.

The etiology of social aggression: a nuclear twin family study.

Social aggression is a form of antisocial behavior in which social relationships and social status are used to damage reputations and inflict emotional harm on others. Despite extensive research examining the prevalence and consequences of social aggression, only a few studies have examined its genetic-environmental etiology, with markedly inconsistent results. We estimated the etiology of social aggression using the nuclear twin family (NTF) model. Maternal-report, paternal-report, and teacher-report data were collected for twin social aggression (N = 1030 pairs). We also examined the data using the classical twin (CT) model to evaluate whether its strict assumptions may have biased previous heritability estimates. The best-fitting NTF model for all informants was the ASFE model, indicating that additive genetic, sibling environmental, familial environmental, and non-shared environmental influences significantly contribute to the etiology of social aggression in middle childhood. However, the best-fitting CT model varied across informants, ranging from AE and ACE to CE. Specific heritability estimates for both NTF and CT models also varied across informants such that teacher reports indicated greater genetic influences and father reports indicated greater shared environmental influences. Although the specific NTF parameter estimates varied across informants, social aggression generally emerged as largely additive genetic (A = 0.15-0.77) and sibling environmental (S = 0.42-0.72) in origin. Such findings not only highlight an important role for individual genetic risk in the etiology of social aggression, but also raise important questions regarding the role of the environment.

Expanding the environment: gene × school‐level SES interaction on reading comprehension

Influential work has explored the role of family socioeconomic status (SES) as an environmental moderator of genetic and environmental influences on cognitive outcomes. This work has provided evidence that socioeconomic circumstances differentially impact the heritability of cognitive abilities, generally supporting the bioecological model in that genetic influences are greater at higher levels of family SES. The present work expanded consideration of the environment, using school-level SES as a moderator of reading comprehension. The sample included 577 pairs of twins from the Florida Twin Project on Reading, Behavior and Environment. Reading comprehension was measured by the Florida Comprehensive Achievement Test (FCAT) Reading in third or fourth grade. School-level SES was measured by the mean Free and Reduced Lunch Status (FRLS) of the schoolmates of the twins. The best-fitting univariate G × E moderation model indicated greater genetic influences on reading comprehension when fewer schoolmates qualified for FRLS (i.e., 'higher' school-level SES). There was also an indication of moderation of the shared environment; there were greater shared environmental influences on reading comprehension at higher school-level SES. The results supported the bioecological model; greater genetic variance was found in school environments in which student populations experienced less poverty. In general, 'higher' school-level SES allowed genetic and probably shared environmental variance to contribute as sources of individual differences in reading comprehension outcomes. Poverty suppresses these influences.

A Behavioral Genetic Investigation of Weekend Drinking Among an Adult Sample

This study examined common and unique genetic and environmental influences on weekend drinking and weekday drinking reported by US male and female adult participants (mean age = 43.9). Data from 96 monozygotic and 82 dizygotic twin pairs were used to estimate bivariate biometric models of daily levels of weekend and weekday drinking volume. Weekend and weekday drinking volume scores were calculated from end-of-day reports of drinking across eight days. As expected, more drinking occurred during weekends. Biometric models provided evidence of significant additive genetic and nonshared environmental influences on both weekend and weekday drinking. Shared environmental influences were nonsignificant. Genetic influences accounted for a greater proportion of drinking variance during weekdays than weekends (0.36 compared to 0.17). However, these apparent differences in heritability—proportion of total variance accounted for by genetic variance—were due to increased nonshared environmental influences on weekend days, rather than greater genetic influences. The study's limitations are noted. Funded by National Institutes of Health/National Institute of Aging and John D. and Catherine T. MacArthur Foundation.

Heritability of Facial Characteristics between Parents and Offsprings: A Photographic Study

Aims and objectives: Facial morphology is influenced by both genetic and environmental factors which interact in complex ways to determine the form and function of the craniofacial complex. Many studies have been done to know the amount of heritability of the skeletal components but hardly are known about the heritability of soft tissue pattern which is compared by everyone as soon as the child born. Cephalometry and photography is used in orthodontics to document the appearance of the face. Considerable progress has been made in the development of its application in orthodontics. Thus, the study was done to know the heritability of soft tissue pattern between parents and their offsprings by using photographs. Materials and methods: The sample consisted of 140 children and their parents. Material was collected from both the genders of children above the age of 16 years. Frontal and right lateral photographs of the entire sample were taken in the standardized pattern. Tracings were made on all the photographs. Twenty-seven parameters of linear and proportional measurements were measured. Results: Statistically significant correlations between parents and their offspring were found. It was found that daughters had greater genetic influence from both the parent than sons. Higher correlation was found for the mandibular position, chin prominence, nasal prominence, nasal width, lip length at philtrum, facial height and lip prominence. Conclusion: The evidence of significant genetic contribution was there for linear and proportional parameters. Sons showed stronger heritability to their mothers than to their fathers while daughter showed heritability from both the parents. Thus, the soft tissue form of offspring can be predicted from parental data and the information from the siblings can also be used.

Abstract 048: Association Analyses of up to ∼263,000 Individuals Provide New Insights into the Biology and Genetic Architecture of the Extremes of Anthropometric Traits

Anthropometric traits have a strong genetic component with heritability estimates between 40–70% for body mass index (BMI) and ∼80% for height; however, established loci only account for a small fraction (1–10%) of the phenotypic variance of these complex traits. It has been hypothesized that the extremes of the distributions of these traits are enriched for genetic loci and may have a distinct genetic architecture compared to the general population. To explore the genetic contribution of the extremes (defined as the upper and lower 5th percentile) of BMI, height, and waist-hip ratio [WHR] adjusted for BMI and clinical classes of obesity (including overweight and obesity classes I, II, and III), we conducted meta-analyses of ∼2.8 million SNPs from 49 genome-wide association studies of European ancestry totaling from 4,774 cases and 5,481 controls (extreme WHR) to 93,015 cases and 65,840 controls (overweight) for these traits. The most promising loci from each meta-analysis (P&lt;5 x 10 −6 ) were taken forward for replication into up to 65,332 cases and 39,294 controls. In meta-analyses of the combined stages, we observed genome-wide significant associations (P&lt;5 x 10 −8 ) for 191 loci (extreme BMI, height and WHR: 10, 96 and 2 loci, respectively; overweight and obesity classes I, II, and III: 25, 33, 24 and 1 loci, respectively). Out of these 191 loci, we identified 9 novel loci that have not been previously associated with anthropometric traits when studying the whole distributions (P&lt;5 x 10 −8 ), including three loci for extreme height ( ZNF36, H6PD , RSRC1 ), three for obesity class II ( OLFM4 , HS6ST3 , AK5/ZZZ3 ), two for obesity class I ( GNAI3/MIR197/GNAT2, HNF4G ), and two for overweight ( RPTOR, HNF4G ). Several loci for obesity were located near genes expressed primarily in the brain (e.g. CACNA1D, AK5 ), suggesting a neuronal influence, whereas the loci for overweight were near genes involved in other processes, such as mTOR signaling (e.g. RPTOR ). All of the novel loci discovered for the extremes and obesity classes were nominally associated with the trait as a continuous measure in the general population (N = 123,865) but at a lesser significance level (P range: 0.003 – 1.4x10 −5 ). A polygenetic risk score including all independent SNPs associated with BMI (at different P-value thresholds) revealed that significantly more of the variance was explained for the extremes of BMI and obesity class II, than for BMI as a continuous measure in the population (variance explained, 20%, 10% and 5%, respectively), suggesting a greater genetic influence on the extremes. Investigations are underway to evaluate haplotypes and additional signals at known BMI and height loci in the extreme samples to explore allelic heterogeneity. In conclusion, this study identifies additional loci and provides novel insights into the genetic architecture of the extremes of anthropometric traits.

Genetic and environmental influences on the size of specific brain regions in midlife: The VETSA MRI study

The impact of genetic and environmental factors on human brain structure is of great importance for understanding normative cognitive and brain aging as well as neuropsychiatric disorders. However, most studies of genetic and environmental influences on human brain structure have either focused on global measures or have had samples that were too small for reliable estimates. Using the classical twin design, we assessed genetic, shared environmental, and individual-specific environmental influences on individual differences in the size of 96 brain regions of interest (ROIs). Participants were 474 middle-aged male twins (202 pairs; 70 unpaired) in the Vietnam Era Twin Study of Aging (VETSA). They were 51–59 years old, and were similar to U.S. men in their age range in terms of sociodemographic and health characteristics. We measured thickness of cortical ROIs and volume of other ROIs. On average, genetic influences accounted for approximately 70% of the variance in the volume of global, subcortical, and ventricular ROIs and approximately 45% of the variance in the thickness of cortical ROIs. There was greater variability in the heritability of cortical ROIs (0.00–0.75) as compared with subcortical and ventricular ROIs (0.48–0.85). The results did not indicate lateralized heritability differences or greater genetic influences on the size of regions underlying higher cognitive functions. The findings provide key information for imaging genetic studies and other studies of brain phenotypes and endophenotypes. Longitudinal analysis will be needed to determine whether the degree of genetic and environmental influences changes for different ROIs from midlife to later life.

Parental genetic effects evaluation of growth-related traits of red common carp in China

Reciprocal differences have been observed widely for given traits in fish breeding programs, but maternal and paternal effects and heritable extranuclear genetic effects have often been omitted in the evaluation of genetic variance. In this study, we have applied a mixed genetic model to conduct a complete diallel cross using three varieties of red common carp (Cyprinus carpio L.), namely, C.carpio. var. singuonensis, C. carpio var. wuyuanensis and C.carpio var. color. Parental and direct (additive and dominance) genetic effects for growth-related traits at 8 and 20 months post-hatch were analyzed. At 8 months post-hatch, only significant additive and dominance variances were observed, while maternal and paternal variances were low and non-significant in the traits evaluated: body weight, total length, standard length, pre-dorsal height, pre-dorsal width, caudal peduncle length, and caudal peduncle height. At 20 months post-hatch, with the exception of significant additive and/or dominance variances, maternal variances were significant for the traits of body weight, pre-dorsal height, pre-dorsal width, and caudal peduncle height, and the paternal variance was significant only for total length. The maternal effects in the common carp had greater genetic influence on offspring than the paternal effects. Female C. carpio var. wuyuanensis were more suitable as brooders than males, but both female and male C. carpio var. color can be used as brooders according to breeding programs of improved traits. Cyprinus carpio var. singuonensis was the worst brooder of the three varieties of common carp evaluated.

Discordance of prenatal and neonatal brain development in twins

Background Discordance of birth weight has been observed in twin pairs, though little is known about prenatal and early neonatal discordance of head and brain size, and the role that zygosity and chorionicity play in discordances of early brain development in twins. Aims To compare prenatal and neonatal discordances of head size in monozygotic–monochorionic (MZ–MC), monozygotic–dichorionic (MZ–DC), and same-sex dizygotic–dichorionic twin pairs (DZ). Study design Subjects prospectively had ultrasounds at 22 and 32 weeks gestational age, and magnetic resonance imaging (MRI) of the brain MRI after birth. Subjects 88 twin pairs recruited from two university hospital prenatal diagnostic clinics; 22 MZ–MC, 17 MZ–DC, and 49 same-sex DZ pairs. Outcome measures Discordance of head circumference (HC) and weight at 22 weeks, 32 weeks and birth, as well as intracranial volume (ICV) on neonatal MRI. Results There were no group differences in discordance of head circumference and weight on the 22 or 32 week ultrasounds, or at birth. MZ–MC twins tended to have numerically greater discordances of HC and weight. There was a significant group difference in ICV on neonatal MRI (ANOVA, p = 0.0143), with DZ twins having significantly greater discordance than MZ–MC ( p = 0.028) or MZ–DC ( p = 0.0131) twins. Conclusions This study indicates that zygosity and chorionicity do not contribute to significant discordances of head size in late prenatal development. DZ twins do have significantly greater discordances of ICV on neonatal MRI, suggesting a relatively greater genetic influence on brain growth in the first weeks after birth.

The use of parental data to evaluate soft tissues in an Anatolian Turkish population according to Holdaway soft tissue norms

The relative influence of genetic and environmental factors in the etiology of malocclusion has long been a matter for discussion. The aim of this study was to compare the soft tissue structures of parents and their prepubertal, pubertal, and postpubertal offspring according to the Holdaway soft tissue norms to determine the similarity among them. Differences related to age and sex between the parents and offspring were also evaluated. Lateral cephalometric radiographs were used to determine the similarities in soft tissue structures in 120 families, which were divided into prepubertal (n = 40), pubertal (n = 40), and postpubertal (n = 40) groups according to the children's skeletal ages. A total of 12 variables (2 angular and 10 linear) were measured according to Holdaway's soft tissue analysis. Pairs were formed between family members (mother to son, mother to daughter, father to son, father to daughter, midparent (mean of the father's and mother's values) to son, and midparent to daughter) in each group. Descriptive statistics and multiple linear regression analysis were performed. Statistically significant correlations between parents and their offspring were found. The parental data showed that a mother's genetic influence on her child's soft tissues was greater than the father's. Moreover, it was found that daughters had greater genetic influences from their parents than did sons. As age increased, the similarity was greater. Soft tissue facial angle (beta: 0.671), soft tissue chin thickness (beta: 0.549), and basic upper lip thickness (beta: 0.537) were the most similar variables between parents and their offspring. A few selected cephalometric measurements of the parents might furnish important data to the clinician in predicting a child's facial growth characteristics and aging process.

A Genetic Analysis of Differential Experiences of Adolescent Siblings Across Three Years

Environmental factors work to make siblings in the same family different from one another rather than similar. The Sibling Inventory of Differential Experience (SIDE; Daniels &amp; Plomin, 1985) was constructed to evaluate how differently siblings perceive their experiences to be across three domains: parental treatment, sibling treatment, and peer characteristics. The goals of the study were threefold: to assess the degree to which siblings agree about their differential experiences; to examine the stability of perceived differential treatment across three years; and to assess genetic and environmental contributions to the SIDE using both the twin design and the stepfamily design. These goals were explored using a genetically sensitive sample of 719 same‐sex sibling pairs ranging from 10 to 18 years of age of whom 94% of eligible pairs were retested three years later. Results indicated moderate agreement between siblings, and considerable stability across 3 years. As in previous research on the SIDE, MZ vs. DZ results indicated greater genetic influence than did results for full siblings vs. genetically unrelated siblings. The results suggest that, although intended as a measure of nonshared environment, the SIDE is not impervious to genetic influence as assessed by the twin design.

Evidence for a genetic etiology of early-onset delinquency.

Age at onset of antisocial behavior discriminates persistent and transitory offenders. The authors proposed that early-onset delinquency has an underlying genetic influence that manifests in problems related to inhibition, whereas late-onset delinquency is more environmentally mediated. To test these notions, they selected 36 early starters, 86 late starters, and 25 nondelinquent controls from a large sample of 11-year-old twins and compared them on several measures related to inhibition and a peer group measure. As expected, early starters had more psychological, behavioral, and emotional problems related to inhibition than late starters and controls. A longitudinal analysis indicated an increase an antisocial behavior among peers of late starters shortly before their delinquency onset. Family history data and a twin analysis provided evidence of greater genetic influence on early-onset than late-onset delinquency.

Reading Disability in Boys and Girls: No Evidence for a Differential Genetic Etiology.

In order to test the hypothesis that genetic influences are moreimportant as a cause of reading disability in girls than in boys,composite reading performance data from identical and fraternal twinpairs were analyzed using both concordance and multiple regressionmethods. The sample included 206 identical (99 male, 107 female), 159same-sex fraternal (90 male, 69 female), and 117 opposite-sex fraternaltwin pairs, in which at least one member of each pair had readingdifficulties. Although the difference between the concordance rates forreading disabilities in female identical and same-sex fraternal twinpairs was somewhat greater (65% for identical twins vs.32% for fraternal twins) than the difference in concordance ratesfor boys (68% vs. 39%), loglinear analysis of thesecategorical data revealed that the interaction between sex, zygosity,and concordance was not significant (p > 0.70). Moreover,the heritability of reading disability(h 2 g) estimated from regression analysisof the reading performance data in males was nearly identical to that infemales (h 2 g = 0.58 and 0.59,respectively; p > 0.90). Thus, results of this studyprovide little or no evidence for the hypothesis of greater geneticinfluence on reading difficulties in girls than in boys.

A genetic study of biomass in Tribolium. I. Path coefficient analysis of base populations.

Biomass, an aggregate trait combining the metric trait 13-day larval weight with the reproductive fitness trait number of larvae per mating, was investigated in two unrelated base populations of Tribolium castaneum, black and pearl.The black population was characterized by smaller 13-day larvae, more larvae per mating due to a higher rate of fecundity, and a smaller biomass than was observed for the pearl population. Both genetic and phenotypic variances were higher in black than in pearl. Heritability estimates for larval weight approached 0.20 in both populations while those for the fitness traits were smaller and seldom exceeded 10%. Non-additive genetic effects as well as maternal influences were observed in both populations. Positive estimates for the genetic correlations between larval weight and number of larvae per mating were observed for both populations (0.47 for black and 0.17 for pearl).Path coefficient analyses revealed that larval number in both populations had greater genetic and phenotypic influences on biomass than did larval weight. In turn, egg number had a greater influence on number of larvae than did larval viability.