Additive Genetic Contributions Research Articles

Bayesian Evaluation of Growth Rates and Kleiber's Ratios in Harnali Sheep: Dissecting Maternal and Additive Genetic Contributions.

Understanding the genetic basis of growth and metabolic traits in sheep is crucial for improving production efficiency and sustainability. The current study aimed to estimate the genetic influences, both direct and maternal, on growth rate and Kleiber's ratio traits in Harnali sheep using pedigree data under Bayesian inference. The data pertained to 2404 animals spanned over 24 years (1998-2021). Fixed factors such as birth period, lamb sex and dam's weight at lambing were considered. The traits studied included average daily gains (ADGs) categorised into ADG1 (birth to weaning age), ADG2 (weaning to 6 months of age) and ADG3 (6-12 months of age), as well as corresponding Kleiber's ratios (KR1, KR2 and KR3). Six single-trait animal models were employed to estimate covariance components and heritabilities, integrating direct additive and maternal effects alongside significant fixed factors using THRGIBBS1F90 and POSTGIBBSF90 programmes. Direct heritability estimates were obtained for ADG1 (0.11 ± 0.05), ADG2 (0.06 ± 0.03), ADG3 (0.03 ± 0.03), KR1 (0.07 ± 0.03), KR2 (0.06 ± 0.03) and KR3 (0.05 ± 0.03). Maternal genetic effects have contributed significant particularly to pre-weaning traits. The study identified an antagonistic relationship between direct additive and maternal genetic effects. Positive genetic and phenotypic correlations emphasised the intricate relationship between growth and metabolic efficiency in Harnali sheep. The current study offers critical insights into the genetic basis of growth and metabolic traits in Harnali sheep, ultimately contributing to more efficient and sustainable sheep production systems.

Heritability of floral traits in Allium cepa L. populations from biparental crosses

AbstractOnions (Allium cepa L.) are one of the main vegetable crops worldwide. As an allogamous species with entomophilous pollination, floral traits play a critical role in seed production. Improving seed yield, especially for hybrid seed production, is very important. In this work, we obtained genetic information for floral traits using segregating populations from three male‐sterile lines and one open‐pollinated variety. Data on 16 floral traits, including perianth, gynoecium, stamens, and receptacle structures, were collected from the parental cultivars, their hybrids, and from segregating populations in the F2 and F3 generations. This dataset underpinned a comprehensive analysis of genetic variability, broad‐ and narrow‐sense heritability estimation, genetic gain predictions, and trait correlations. The evaluated traits exhibited high broad‐sense heritability values (0.08–0.85), but moderate narrow‐sense heritability values (0.01–0.68), implying that the observed phenotypic variance is mainly explained by genetic factors, with a minor additive genetic factors contribution. Consequently, the study revealed effective genetic gain for the analyzed traits. The phenotypic correlations observed in the parental cultivars were not always maintained in the segregating populations, suggesting random correlations. Meanwhile, genetic correlations were moderate to low, suggesting that the analyzed traits can be independently selected without affecting the expression of other floral traits. Notably, correlations among floral traits were significant in stable cultivars but weak in segregating populations, excluding pleiotropic effects. This work has successfully demonstrated the heritability of onion floral traits and provided a sound basis for selecting individuals with desirable attributes, with valuable practical implications for onion breeding and seed production.

Heritability of the glycan clock of biological age.

Immunoglobulin G is posttranslationally modified by the addition of complex N-glycans affecting its function and mediating inflammation at multiple levels. IgG glycome composition changes with age and health in a predictive pattern, presumably due to inflammaging. As a result, a novel biological aging biomarker, glycan clock of age, was developed. Glycan clock of age is the first of biological aging clocks for which multiple studies showed a possibility of clock reversal even with simple lifestyle interventions. However, none of the previous studies determined to which extent the glycan clock can be turned, and how much is fixed by genetic predisposition. To determine the contribution of genetic and environmental factors to phenotypic variation of the glycan clock, we performed heritability analysis on two TwinsUK female cohorts. IgG glycans from monozygotic and dizygotic twin pairs were analyzed by UHPLC and glycan age was calculated using the glycan clock. In order to determine additive genetic, shared, and unique environmental contributions, a classical twin design was applied. Heritability of the glycan clock was calculated for participants of one cross-sectional and one longitudinal cohort with three time points to assess the reliability of measurements. Heritability estimate for the glycan clock was 39% on average, suggesting a moderate contribution of additive genetic factors (A) to glycan clock variation. Remarkably, heritability estimates remained approximately the same in all time points of the longitudinal study, even though IgG glycome composition changed substantially. Most environmental contributions came from shared environmental factors (C), with unique environmental factors (E) having a minor role. Interestingly, heritability estimates nearly doubled, to an average of 71%, when we included age as a covariant. This intervention also inflated the estimates of unique environmental factors contributing to glycan clock variation. A complex interplay between genetic and environmental factors defines alternative IgG glycosylation during aging and, consequently, dictates the glycan clock's ticking. Apparently, environmental factors (including lifestyle choices) have a strong impact on the biological age measured with the glycan clock, which additionally clarifies why this aging clock is one of the most potent biomarkers of biological aging.

Genetics of obsessive-compulsive disorder.

Obsessive-compulsive disorder (OCD) is a psychiatric disorder with multiple symptom dimensions (e.g. contamination, symmetry). OCD clusters in families and decades of twin studies clearly demonstrate an important role for genetics in the etiology of the disorder. In this review, we summarize the genetic epidemiology and molecular genetic studies of OCD and obsessive-compulsive symptoms. OCD is a heritable, polygenic disorder with contributions from both common and rare variants, including de novo deleterious variations. Multiple studies have provided reliable support for a large additive genetic contribution to liability to OCD, with discrete OCD symptom dimensions having both shared and unique genetic risks. Genome-wide association studies have not produced significant results yet, likely because of small sample sizes, but larger meta-analyses are forthcoming. Both twin and genome-wide studies show that OCD shares genetic risk with its comorbid conditions (e.g. Tourette syndrome and anorexia nervosa). Despite significant efforts to uncover the genetic basis of OCD, the mechanistic understanding of how genetic and environmental risk factors interact and converge at the molecular level to result in OCD's heterogeneous phenotype is still mostly unknown. Future investigations should increase ancestral genetic diversity, explore age and/or sex differences in genetic risk for OCD and expand the study of pharmacogenetics, gene expression, gene × environment interactions and epigenetic mechanisms for OCD.

Genetic and environmental components of vertical growth in mono- and dizygotic twins up to 15-18 years of age.

To determine the additive genetic and environmental contributions to the vertical growth of craniofacial structures. The sample consisted of 64 untreated monozygotic (44 male, 20 female) and 61 untreated dizygotic twins (32 male, 29 female). Lateral cephalograms taken at 15 and 18 years of age were traced to analyze the sella-nasion-nasal line angle (SN-NL), nasal line-mandibular line angle (ML-NL), sella-nasion-mandibular line angle (SN-ML), sella-nasion-sella-gnathion angle (Y-axis), posterior face height/anterior face height (PFH/AFH), and lower anterior face height/anterior face height (LAFH/AFH). The genetic and environmental components of variance were analyzed with structural equation modeling for multilevel mixed effects. At 15 years of age, strong dominant genetic control was seen for NL-ML (81%), LAFH/AFH (73%), and Y-axis (57%), whereas strong additive genetic components were found for PFH/AFH (78%), SN-NL (58%), and SN-ML (57%). Unique environmental factors accounted for 18-42% of observed variance, with SN-NL being affected the most (42%). At 18 years of age, only LAFH/AFH (86%) was under strong dominant genetic control, whereas the remainder were under additive genetic influence. The sole exception was SN-NL, which changed from additive to unique environmental influence. Either additive or dominant genetic components were found at 15 or 18 years of age for most vertical variables. Environmental factors accounted for about 10-40%, with SN-NL being mostly affected.

Can a brief intervention alter genetic and environmental influences on psychological traits? An experimental behavioral genetics approach

Mindset interventions are designed to encourage students to adopt a growth mindset, reflecting the belief that one’s intelligence can be improved in an effort to increase academic achievement. How do these interventions exert their effects? We assessed the effects of an online mindset intervention on mindset and four outcome variables, grit, locus of control, challenge-seeking behavior, and cognitive ability test performance in a sample of 1668 twins in 840 families. The mindset intervention successfully induced a growth mindset, but had no effect on the outcome variables. Biometric modeling of self-reported mindset before and after the intervention further revealed that this mean change in mindset was accompanied by changes in its etiology. At baseline, nonshared environmental contributions to individual differences in mindset predominated, while additive genetic contributions were small-to-moderate and shared environmental contributions were negligible. After the intervention, there was an increase in additive genetic contributions to individual differences in mindset. In other words, despite its very brief nature, our simple environmental intervention acted to increase the heritability of mindset. Such findings suggest that interventions may sometimes exert their effects by altering the genetic influences on a trait.

Genetic parameters of morphometric measurements in Criollo horses

The aim of this study was to estimate the genetic parameters for the morphometric measurements of withers height (WH), thoracic circumference (TC) and cannon bone circumference (CBC) of Criollo horses, stratified for maternal and paternal effects. Statistical genetic design of factor crossings was used to evaluate the offspring of full siblings and half-siblings. Fifty stallions were selected (n=50) who had been crossed with six mares each (n=6), to provide 300 parental pairings in which two offspring were born per mare (n=600). WH in females and TC in males were highly influenced by additive genetic effects, while the other morphometric measures were found to be closely related to the general effects of the environment. WH had the greatest additive genetic influence on female offspring (47.06%), while TC presented the greatest additive genetic influence on male offspring (58.73%). When comparing the parental influence on the morphometric characteristics evaluated, TC and CBC had greater additive genetic influence from maternal effects, regardless of offspring sex. However, the WH in female offspring showed greater maternal additive genetic contribution, while in males this characteristic presented greater paternal additive genetic influence. For WH in male offspring, narrow sense heritability ( : 0.26) was more influenced by paternal effects, while for WH in females ( : 0.47), TC in females ( : 0.08) and males ( : 0.59), and CBC in females ( : 0.07) and males ( : 0.05) the maternal effects were the most important. Therefore, the phenotypic expression of WH in males and females and TC in males is influenced by the additive genetic effect of the genes. On the other hand, the TC in female progenies and CBC in progenies of both sexes are closely related to the effects of the environment. The results obtained in this study could be useful in the selection process of Criollo horses.

Abstract A122: Comparison of mutational profiles in primary prostate cancers between men with African and European ancestry

Abstract Background: African American men have more than twice the age-adjusted mortality rate from prostate cancer than European American men. Lower rate of PSA screening, less aggressive treatment, and other socioeconomic factors have been raised as possible reasons for this disparity, but genetic differences between prostate cancers from African and European ancestry have not been fully investigated as most sequencing studies so far have studied the latter group. The goal of this study is to perform a meta-analysis across various publicly available sequencing datasets and identify mutational profiles associated with African American ancestry in prostate cancer. Methods: Whole exome sequencing data from 499 treatment-naive prostate cancers were analyzed from The Cancer Genome Atlas (TCGA). The ethnicity of each patient was inferred using previously published method (1). Our analysis included whole-exome sequencing data from 404 European and 159 African prostate cancers. African American samples were aggregate of TCGA and recently published African American prostate cancer data (2). We looked at previously shown 97 significantly mutated genes in prostate cancer (3). Using coding mutations, a Fisher's exact test was performed for each gene to compare the frequencies between populations. In a separate analysis, these two exome datasets were combined with two other targeted sequencing datasets from Huang et al. (2) (n = 86) and Abida et al. (4) (n = 424) using only genes common to all platforms. Results: Among 97 genes, only KDM6A was significantly enriched in African American samples (p = 0.039). NCOR1, ERF, and AR tended to be more mutated in African American samples. TP53, SPEN, and PIK3CA were more mutated in prostate cancer of European ancestry (p < 0.05). PTEN and CTNNB1 tended to be more mutated in European tumors even though they did not meet statistical significance. For the meta-analysis across both exome and targeted sequencing datasets, we observed that ZFHX3 was significantly more frequent in tumors from African American versus other populations (8% versus 2%, FDR = 0.0001). ZFHX3 was also strongly enriched for loss-of-function mutations (p = 1.2e-9), further supporting its role as a tumor suppressor. Discussion: The contribution of tumor genetics to outcome disparities in African American prostate cancer is under active investigation. Our analysis shows that African American prostate cancers tend to harbor fewer mutations in previously identified prostate cancer genes such as PIK3CA, TP53, PTEN, and CTNNB1 and potentially more mutations in KDM6A and ZFHX3. As prostate cancers have a lower mutation rate, the number of tumors needed to detect low frequency mutations is high. More sequencing of African American prostate cancers may elucidate additional genetic contributions to higher mortality. Citation Format: Eejung Kim, Yusuke Koga, Jian Carrot-Zhang, Joshua D. Campbell, Franklin Huang. Comparison of mutational profiles in primary prostate cancers between men with African and European ancestry [abstract]. In: Proceedings of the Eleventh AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2018 Nov 2-5; New Orleans, LA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl):Abstract nr A122.

A role for genes in the \u2018caregiver stress process\u2019?

The stress that accompanies caring for one’s parent, and the contribution of that stress to adverse physical and mental-health outcomes, is extensively studied and widely acknowledged. Yet there has been almost no attempt to incorporate the well-documented role of genetic variation in psychological distress into research on caregiving. We use phenotypic data from a large, population-based sample linked to extensive genotype data to develop a polygenic risk score (PRS) for depression, and test for both direct and interactive effects of the PRS in a multilevel repeat-measures model of caregiver-related stress. We distinguish three groups: potential caregivers (those with a living parent who does not need care), noncaregivers (those who do not provide care to their parent that needs care), and caregivers. We also obtain separate estimates according to the gender of both the parent and child. We found that a parent’s need for care, and the child’s provision of care, are associated with depression in some but not all cases; in contrast the PRS was significantly associated with the risk for increased depressive symptoms (with P ≤ 0.01) in all cases. These findings support an additive genetic contribution to the diathesis-stress model of depression in the context of caregiving.

Comparison of heritability estimates on resting state fMRI connectivity phenotypes using the ENIGMA analysis pipeline.

We measured and compared heritability estimates for measures of functional brain connectivity extracted using the Enhancing Neuroimaging Genetics through Meta-Analysis (ENIGMA) rsfMRI analysis pipeline in two cohorts: the genetics of brain structure (GOBS) cohort and the HCP (the Human Connectome Project) cohort. These two cohorts were assessed using conventional (GOBS) and advanced (HCP) rsfMRI protocols, offering a test case for harmonization of rsfMRI phenotypes, and to determine measures that show consistent heritability for in-depth genome-wide analysis. The GOBS cohort consisted of 334 Mexican-American individuals (124M/210F, average age = 47.9 ± 13.2 years) from 29 extended pedigrees (average family size = 9 people; range 5-32). The GOBS rsfMRI data was collected using a 7.5-min acquisition sequence (spatial resolution = 1.72 × 1.72 × 3 mm3 ). The HCP cohort consisted of 518 twins and family members (240M/278F; average age = 28.7 ± 3.7 years). rsfMRI data was collected using 28.8-min sequence (spatial resolution = 2 × 2 × 2 mm3 ). We used the single-modality ENIGMA rsfMRI preprocessing pipeline to estimate heritability values for measures from eight major functional networks, using (1) seed-based connectivity and (2) dual regression approaches. We observed significant heritability (h2 = 0.2-0.4, p < .05) for functional connections from seven networks across both cohorts, with a significant positive correlation between heritability estimates across two cohorts. The similarity in heritability estimates for resting state connectivity measurements suggests that the additive genetic contribution to functional connectivity is robustly detectable across populations and imaging acquisition parameters. The overarching genetic influence, and means to consistently detect it, provides an opportunity to define a common genetic search space for future gene discovery studies.

Resting Heart Rate Variability (HRV) in Adolescents and Young Adults from a Genetically-Informed Perspective.

Reduced heart rate variability (HRV) is associated with cardiac morbidity, mortality, and negative psychopathology. Most research concerning genetic influences on HRV has focused on adult populations, with fewer studies investigating the developmental period of adolescence and emerging adulthood. The current study estimated the genetic and environmental contributions to resting HRV in a sample of twins using various HRV time domain metrics to assess autonomic function across two different time measurement intervals (2.5- and 10-min). Five metrics of resting HRV [mean interbeat interval (IBI), the standard deviation of normal IBIs (SDNN), root square mean of successive differences between IBIs (RMSSD), cardiac vagal index (CVI), and cardiac sympathetic index (CSI)] were assessed in 421 twin pairs aged 14-20 during a baseline electrocardiogram. This was done for four successive 2.5-min intervals as well as the overall 10-min interval. Heritability (h2) appeared consistent across intervals within each metric with the following estimates (collapsed across time intervals): mean IBI (h2 = 0.36-0.46), SDNN (h2 = 0.23-0.30), RMSSD (h2 = 0.36-0.39), CVI (h2 = 0.37-0.42), CSI (h2 = 0.33-0.46). Beyond additive genetic contributions, unique environment also was an important influence on HRV. Within each metric, a multivariate Cholesky decomposition further revealed evidence of genetic stability across the four successive 2.5-min intervals. The same models showed evidence for both genetic and environmental stability with some environmental attenuation and innovation. All measures of HRV were moderately heritable across time, with further analyses revealing consistent patterns of genetic and environmental influences over time. This study confirms that in an adolescent sample, the time interval used (2.5- vs. 10-min) to measure HRV time domain metrics does not affect the relative proportions of genetic and environmental influences.

Familial clustering of vitamin D deficiency via shared environment: The Korean National Health and Nutrition Examination Survey 2008–2012

Familial correlation of serum 25-hydroxyvitamin D concentration (25(OH)D) was reported in twin- or parent-offspring studies. However, data on relative contribution of environmental factors on familial clustering of 25(OH)D in extended families are limited. We performed cross-sectional study using data from the Korean National Health and Nutrition Examination Survey (KNHANES) 2008-2012. Familial correlations of 25(OH)D were estimated in 28,551 subjects from 10,882 families. The variance component method was used to assess the relative contribution of additive genetic or environmental contributions to the variation in 25(OH)D level. Logistic regression models with interaction term were built to evaluate the differential influence of parental vitamin D status on the adolescents and adults offspring. Mean serum 25(OH)D concentration of subjects was 44.6 nmol/L (vitamin D insufficiency (30-50 nmol/L), 51%; vitamin D deficiency ( < 30 nmol/L), 17%). Familial clustering explained 40% of the total variation in 25(OH)D. In the variance component model, 4%, 39%, and 57% of the variation in serum 25(OH)D level was attributed to additive genetic, common shared environmental, and individual environmental factors, respectively. The odds of vitamin D deficiency in offspring with both parents with vitamin D deficiency compared with those with both parents with sufficient vitamin D levels was greater in adolescents ( < 19 years) than in adults ( ≥ 19 years) (odds ratio = 41.1 vs. 12.5; p for interaction = 0.03). We found a familial clustering of vitamin D deficiency in a large family-based cohort. Parental influence on vitamin D status of offspring was greater in adolescents than in adults.

Determinants of gestation length in Thoroughbred mares on German stud farms

The aim of the present study was to analyze the effects of stallion and mare, their ages, and maternal lineage on the gestation length (GL) in Thoroughbreds. In addition, additive genetic effects of the dam, stallion and fetus were analyzed. Data were taken from 1993 through 2009, and included 16,226 pregnancies from 5959 Th oroughbred mares mated with 290 different stallions. All analyses were performed using linear mixed models. The GL ranged from 306 to 390 days, with a mean length of 347.0 ± 14.4 days. Mating of mares with stallions aged 17 years and older resulted in a significantly longer GL compared to younger stallions. Furthermore, the GL significantly increased with the increasing age of the mares, and the GL was longer with male foals. The month and year of breeding, as well as the mare´s breeding history (parity and reproductive status) also affected GL. The mare and stallion themselves explained 18% and 4% of the variance in GL. Coefficients of inbreeding of mares and foals had no significant effect on GL. The heritability for the GL was 0.17 for the dam and 0.006 for the fetus, whereas an additive genetic paternal effect was not estimable. The relative proportions among the additive genetic and permanent environmental contributions of the dam were 76.5% and 23.5%. A maternal lineage effect was not obvious.

Heterosis and genetics parameters for yield and nutritional components in half-sibling maize progenies

The growing demand for maize creates a challenge to breeders, requiring the development of higher yielding and higher quality genotypes. The objective of this work was to estimate the most relevant heterosis, variance components and genetic parameters, and to use a multivariate approach to define narrow sense heritability profiles for yield and nutritional components in half-sib maize progenies. The experimental design used was random blocks, with a male parent (hybrid tester), five inbred lines (S5) as maternal parents and the progenies (hybrid Top Cross), totalizing 11 maize genotypes arranged in six replicates. Agronomic and nutritional characters were evaluated. Half-sibling progenies reveal greater additive genetic contribution to phenotypic expression through grain width and thickness, iron content, total flavonoids and carotenoids, soluble solids, and methionine. Narrow sense heritability values between and within progenies are higher for manganese content, glycine, proline and tryptophan. Regardless of the inbreeding line S5 used, heterosis gains are obtained for insertion of spike height, number of grain rows per spike, stem diameter, and zinc content, total carotenoids, soluble solids and pH. Specific heterosis’s evidenced for grain yield, glycine, serine, threonine, and phenylalanine. The multivariate approach used defines eight-character profiles regarding their genetic trends and indicates narrow sense heritability of the progeny mean as the major cause for this distinction.

Maternal-by-environment but not genotype-by-environment interactions in a fish without parental care.

The impact of environmental conditions on the expression of genetic variance and on maternal effects variance remains an important question in evolutionary quantitative genetics. We investigate here the effects of early environment on variation in seven adult life history, morphological, and secondary sexual traits (including sperm characteristics) in a viviparous poeciliid fish, the mosquitofish Gambusia holbrooki. Specifically, we manipulated food availability during early development and then assessed additive genetic and maternal effects contributions to the overall phenotypic variance in adults. We found higher heritability for female than male traits, but maternal effects variance for traits in both sexes. An interaction between maternal effects variance and rearing environment affected two adult traits (female age at maturity and male size at maturity), but there was no evidence of trade-offs in maternal effects across environments. Our results illustrate (i) the potential for pre-natal maternal effects to interact with offspring environment during development, potentially affecting traits through to adulthood and (ii) that genotype-by-environment interactions might be overestimated if maternal-by-environment interactions are not accounted for, similar to heritability being overestimated if maternal effects are ignored. We also discuss the potential for dominance genetic variance to contribute to the estimate of maternal effects variance.

Phenotypic and genetic integration of personality and growth under competition in the sheepshead swordtail, Xiphophorus birchmanni.

Competition for resources including food, physical space, and potential mates is a fundamental ecological process shaping variation in individual phenotype and fitness. The evolution of competitive ability, in particular social dominance, depends on genetic (co)variation among traits causal (e.g., behavior) or consequent (e.g., growth) to competitive outcomes. If dominance is heritable, it will generate both direct and indirect genetic effects (IGE) on resource‐dependent traits. The latter are expected to impose evolutionary constraint because winners necessarily gain resources at the expense of losers. We varied competition in a population of sheepshead swordtails, Xiphophorus birchmanni, to investigate effects on behavior, size, growth, and survival. We then applied quantitative genetic analyses to determine (i) whether competition leads to phenotypic and/or genetic integration of behavior with life history and (ii) the potential for IGE to constrain life history evolution. Size, growth, and survival were reduced at high competition. Male dominance was repeatable and dominant individuals show higher growth and survival. Additive genetic contributions to phenotypic covariance were significant, with the G matrix largely recapitulating phenotypic relationships. Social dominance has a low but significant heritability and is strongly genetically correlated with size and growth. Assuming causal dependence of growth on dominance, hidden IGE will therefore reduce evolutionary potential.

Heritable Variation, With Little or No Maternal Effect, Accounts for Recurrence Risk to Autism Spectrum Disorder in Sweden

BackgroundAutism spectrum disorder (ASD) has both genetic and environmental origins, including potentially maternal effects. Maternal effects describe the association of one or more maternal phenotypes with liability to ASD in progeny that are independent of maternally transmitted risk alleles. While maternal effects could play an important role, consistent with association to maternal traits such as immune status, no study has estimated maternal, additive genetic, and environmental effects in ASD. MethodsUsing a population-based sample consisting of all children born in Sweden from 1998 to 2007 and their relatives, we fitted statistical models to family data to estimate the variance in ASD liability originating from maternal, additive genetic, and shared environmental effects. We calculated sibling and cousin family recurrence risk ratio as a direct measure of familial, genetic, and environmental risk factors and repeated the calculations on diagnostic subgroups, specifically autistic disorder (AD) and spectrum disorder (SD), which included Asperger’s syndrome and/or pervasive developmental disorder not otherwise specified. ResultsThe sample consisted of 776,212 children of whom 11,231 had a diagnosis of ASD: 4554 with AD, 6677 with SD. We found support for large additive genetic contribution to liability; heritability (95% confidence interval [CI]) was estimated to 84.8% (95% CI: 73.1–87.3) for ASD, 79.6% (95% CI: 61.2–85.1) for AD, and 76.4% (95% CI: 63.0–82.5) for SD. ConclusionsThere was modest, if any, contribution of maternal effects to liability for ASD, including subtypes AD and SD, and there was no support for shared environmental effects. These results show liability to ASD arises largely from additive genetic variation.

Genetic and environmental influences on psychological traits and eating attitudes in a sample of Spanish schoolchildren

IntroductionThe heritability of eating disorders has been estimated to range from 22% to over 62%. The aim of this study is to determine the relative influence of genetics and environment that contribute to the drive for thinness, body dissatisfaction, perfectionism, and ineffectiveness, by evaluating sex differences in a sample of adolescent twins from Valencia, Spain. Material and methodsFive hundred eighty-four pairs of adolescent twins between 13 and 18 years of age completed the study. To determine zygosity, teachers responded to a questionnaire on physical similarity. Psychological traits of eating disorders were assessed with four sub-scales of the Eating Disorder Inventory (EDI); drive for thinness, body dissatisfaction, perfectionism, and ineffectiveness. Twin models were used to assess genetic and environmental (common and unique) factors affecting these four psychological traits. ResultsAll four traits showed significant genetic contributions among girls, with heritability estimates of 37.7% for ineffectiveness, 42.8% for perfectionism, 56.9% for drive for thinness, and 65.5% for body dissatisfaction. Among boys, body dissatisfaction showed no additive genetic contributions, indicating significant shared and individual specific environment effects. The three other traits in boys showed significant additive genetic contributions, but were lower than in girls. ConclusionsWith the exception of body dissatisfaction in boys, psychological traits of eating disorders show heritability patterns that differ according to sex.

A Genetic Epidemiological Mega Analysis of Smoking Initiation in Adolescents.

Previous studies in adolescents were not adequately powered to accurately disentangle genetic and environmental influences on smoking initiation (SI) across adolescence. Mega-analysis of pooled genetically informative data on SI was performed, with structural equation modeling, to test equality of prevalence and correlations across cultural backgrounds, and to estimate the significance and effect size of genetic and environmental effects according to the classical twin study, in adolescent male and female twins from same-sex and opposite-sex twin pairs (N = 19 313 pairs) between ages 10 and 19, with 76 358 longitudinal assessments between 1983 and 2007, from 11 population-based twin samples from the United States, Europe, and Australia. Although prevalences differed between samples, twin correlations did not, suggesting similar etiology of SI across developed countries. The estimate of additive genetic contributions to liability of SI increased from approximately 15% to 45% from ages 13 to 19. Correspondingly, shared environmental factors accounted for a substantial proportion of variance in liability to SI at age 13 (70%) and gradually less by age 19 (40%). Both additive genetic and shared environmental factors significantly contribute to variance in SI throughout adolescence. The present study, the largest genetic epidemiological study on SI to date, found consistent results across 11 studies for the etiology of SI. Environmental factors, especially those shared by siblings in a family, primarily influence SI variance in early adolescence, while an increasing role of genetic factors is seen at later ages, which has important implications for prevention strategies. This is the first study to find evidence of genetic factors in liability to SI at ages as young as 12. It also shows the strongest evidence to date for decay of effects of the shared environment from early adolescence to young adulthood. We found remarkable consistency of twin correlations across studies reflecting similar etiology of liability to initiate smoking across different cultures and time periods. Thus familial factors strongly contribute to individual differences in who starts to smoke with a gradual increase in the impact of genetic factors and a corresponding decrease in that of the shared environment.

Ontogentic shifts in genetic and maternal effects on length and survival in Chinook salmon (Oncorhynchus tshawytscha)

Understanding how the interplay between genetic and environmental factors changes over the lifetime of a species is critical when selecting broodstock to optimize production at each life stage and reduce bottlenecks in the production chain. We analyzed changes in environmental, additive genetic, and non-additive genetic contributions in growth and saltwater survival across multiple life stages of Chinook salmon (Oncorhynchus tshawytscha) in an aquaculture facility to assess the importance of each factor throughout life. We used a full-factorial breeding design and followed fish for their entire 3-year life cycle to quantify the dam and sire effect on growth and survival and partition these effects into the respective environmental and genetic components. We show for body size that maternal and non-additive effects are the most important drivers of larval size, explaining a total of 87% of total larval phenotypic variation, but decline with age. Additive genetic effects peak during the juvenile stage, explaining a maximum of 15% of the total variation in size, but are much less important at earlier and later life stages. We saw a similar pattern to saltwater survival—with non-additive effects high (42% of total variance explained) at the earliest stage measured and decreasing in later stages and additive effects playing little role. Unlike growth, there was little maternal influence on survival. Taken together, our results show that maternal and non-additive effects are important drivers of larval size but that additive effects may play a more important role with age. Non-additive effects explained the most phenotypic variance observed for survival, playing a much larger role than maternal or additive effects. Our results add to a growing body of literature suggesting careful crosses of select lines can lead to enhanced growth and survival and that these effects can be tailored to the life stages of most concern for a given system. In this way hatchery managers can best develop breeding lines for specific systems and these lines can have stable effects over many generations. Statement of relevanceThe enclosed manuscript is directly relevant to commercial aquaculture. The study was conducted in a commercial aquaculture facility and the questions we are asking relate to the effects of genetic and non-genetic (maternal) factors in Chinook salmon growth and survival in an aquaculture facility.