The heritability of amyloid burden in older adults: the Older Australian Twins Study

ObjectiveTo determine the proportional genetic contribution to the variability of cerebral β-amyloid load in older adults using the classic twin design.MethodsParticipants (n=206) comprising 61 monozygotic (MZ) twin pairs (68 (55.74%) females; mean age (SD): 71.98 (6.43) years), and 42 dizygotic (DZ) twin pairs (56 (66.67%) females; mean age: 71.14 (5.15) years) were drawn from the Older Australian Twins Study. Participants underwent detailed clinical and neuropsychological evaluations, as well as MRI, diffusion tensor imaging (DTI) and amyloid PET scans. Fifty-eight participants (17 MZ pairs, 12 DZ pairs) had PET scans with 11Carbon-Pittsburgh Compound B, and 148 participants (44 MZ pairs, 30 DZ pairs) with 18Fluorine-NAV4694. Cortical amyloid burden was quantified using the centiloid scale globally, as well as the standardised uptake value ratio (SUVR) globally and in specific brain regions. Small vessel disease (SVD) was quantified using total white matter hyperintensity volume on MRI, and peak width of skeletonised mean diffusivity on DTI. Heritability (h2) and genetic correlations were measured with structural equation modelling under the best fit model, controlling for age, sex, tracer and scanner.ResultsThe heritability of global amyloid burden was moderate (0.41 using SUVR; 0.52 using the centiloid scale) and ranged from 0.20 to 0.54 across different brain regions. There were no significant genetic or environmental correlations between global amyloid burden and markers of SVD.ConclusionAmyloid deposition, the hallmark early feature of Alzheimer’s disease, is under moderate genetic influence, suggesting a major environmental contribution that may be amenable to intervention.

Shared genetic and environmental etiology between substance use disorders and suicidal behavior

Background Previous studies have demonstrated substantial associations between substance use disorders (SUD) and suicidal behavior. The current study empirically assesses the extent to which shared genetic and/or environmental factors contribute to associations between alcohol use disorders (AUD) or drug use disorders (DUD) and suicidal behavior, including attempts and death. Methods The authors used Swedish national registry data, including medical, pharmacy, criminal, and death registrations, for a large cohort of twins, full siblings, and half siblings (N = 1 314 990) born 1960–1980 and followed through 2017. They conducted twin-sibling modeling of suicide attempt (SA) or suicide death (SD) with AUD and DUD to estimate genetic and environmental correlations between outcomes. Analyses were stratified by sex. Results Genetic correlations between SA and SUD ranged from rA = 0.60–0.88; corresponding shared environmental correlations were rC = 0.42–0.89 but accounted for little overall variance; and unique environmental correlations were rE = 0.42–0.57. When replacing attempt with SD, genetic and shared environmental correlations with AUD and DUD were comparable (rA = 0.48–0.72, rC = 0.92–1.00), but were attenuated for unique environmental factors (rE = −0.01 to 0.31). Conclusions These findings indicate that shared genetic and unique environmental factors contribute to comorbidity of suicidal behavior and SUD, in conjunction with previously reported causal associations. Thus, each outcome should be considered an indicator of risk for the others. Opportunities for joint prevention and intervention, while limited by the polygenic nature of these outcomes, may be feasible considering moderate environmental correlations between SA and SUD.

Genetic and environmental correlations between complex phenotypes differ by race/ethnicity and sex

We developed novel closed-form estimators of genetic and environmental correlation coefficients. We applied them to estimate over 4,000 genetic and environmental correlations between multiple phenotypes in a diverse sample from the Trans-Omics in Precision Medicine (TOPMed) program. We found substantial differences in heritabilities, genetic, and environmental correlations of multiple phenotypes and phenotype-pairs between Black, Hispanic/Latino and White populations as well as between sexes. Finally, we quantified genetic and environmental correlations between phenotypic domains, each characterized by multiple phenotypes. Altogether we provide a novel, in-depth framework for examining relations among complex human phenotypes and their determinants.

Divergence in Body Mass, Wing Loading, and Population Structure Reveals Species-Specific and Potentially Adaptive Trait Variation Across Elevations in Montane Bumble Bees

Biogeographic clines in morphology along environmental gradients can illuminate forces influencing trait evolution within and between species. Latitude has long been studied as a driver of morphological clines, with a focus on body size and temperature. However, counteracting environmental pressures may impose constraints on body size. In montane landscapes, declines in air density with elevation can negatively impact flight performance in volant species, which may contribute to selection for reduced body mass despite declining temperatures. We examine morphology in two bumble bee (Hymenoptera: Apidae: Bombus Latreille) species, Bombus vancouverensis Cresson and Bombus vosnesenskii Radoszkowski, across mountainous regions of California, Oregon, and Washington, United States. We incorporate population genomic data to investigate the relationship between genomic ancestry and morphological divergence. We find that B. vancouverensis, which tends to be more specialized for high elevations, exhibits stronger spatial-environmental variation, being smaller in the southern and higher elevation parts of its range and having reduced wing loading (mass relative to wing area) at high elevations. Bombus vosnesenskii, which is more of an elevational generalist, has substantial trait variation, but spatial-environmental correlations are weak. Population structure is stronger in the smaller B. vancouverensis, and we find a significant association between elevation and wing loading after accounting for genetic structure, suggesting the possibility of local adaptation for this flight performance trait. Our findings suggest that some conflicting results for body size trends may stem from distinct environmental pressures that impact different aspects of bumble bee ecology, and that different species show different morphological clines in the same region.

Relations between HEXACO personality and ideology variables are mostly genetic in nature

Existing work indicates that socio-political attitudes (or: ideology) are associated with personality, with Social Dominance Orientation and Right-Wing Authoritarianism relating most strongly to honesty-humility and openness to experience, the two value-related domains of the HEXACO framework. Using a sample of 7067 twins and siblings of twins (including 1376 complete twin pairs), we examined the degree to which these relations arise from common genetic and environmental sources. Heritability estimates for the HEXACO personality and ideology variables ranged from .34 to .58. Environmental factors shared by twins reared together showed negligible effects on individual differences in personality and ideology. At the phenotypic level, Social Dominance Orientation and Right-Wing Authoritarianism dimensions related most strongly to honesty-humility and openness to experience. These associations were mostly explained by genetic factors (48%–93%). Genetic correlations between openness to experience and the ideology scales ranged from –.29 to –.53; those between honesty-humility and the ideology scales ranged from –.31 to –.43. None of the environmental correlations exceeded | r| = .18. These results suggest that the relations between the two value-related domains of the HEXACO personality model and ideology are mostly genetic in nature, and that there is substantial overlap in the heritable components of personality and ideology.

Carbon Dioxide Concentration Mechanisms in Natural Populations of Marine Diatoms: Insights From Tara Oceans

Marine diatoms, the most successful photoautotrophs in the ocean, efficiently sequester a significant part of atmospheric CO2 to the ocean interior through their participation in the biological carbon pump. However, it is poorly understood how marine diatoms fix such a considerable amount of CO2, which is vital information toward modeling their response to future CO2 levels. The Tara Oceans expeditions generated molecular data coupled with in situ biogeochemical measurements across the main ocean regions, and thus provides a framework to compare diatom genetic and transcriptional flexibility under natural CO2 variability. The current study investigates the interlink between the environmental variability of CO2 and other physicochemical parameters with the gene and transcript copy numbers of five key enzymes of diatom CO2 concentration mechanisms (CCMs): Rubisco activase and carbonic anhydrase (CA) as part of the physical pathway, together with phosphoenolpyruvate carboxylase, phosphoenolpyruvate carboxykinase, and malic enzyme as part of the potential C4 biochemical pathway. Toward this aim, we mined >200 metagenomes and >220 metatranscriptomes generated from samples of the surface layer of 66 globally distributed sampling sites and corresponding to the four main size fractions in which diatoms can be found: 0.8–5 μm, 5–20 μm, 20–180 μm, and 180–2,000 μm. Our analyses revealed that the transcripts for the enzymes of the putative C4 biochemical CCM did not in general display co-occurring profiles. The transcripts for CAs were the most abundant, with an order of magnitude higher values than the other enzymes, thus implying the importance of physical CCMs in diatom natural communities. Among the different classes of this enzyme, the most prevalent was the recently characterized iota class. Consequently, very little information is available from natural diatom assemblages about the distribution of this class. Biogeographic distributions for all the enzymes show different abundance hotspots according to the size fraction, pointing to the influence of cell size and aggregation in CCMs. Environmental correlations showed a complex pattern of responses to CO2 levels, total phytoplankton biomass, temperature, and nutrient concentrations. In conclusion, we propose that biophysical CCMs are prevalent in natural diatom communities.

Genetic and environmental architecture of conscientiousness in adolescence

Using a genetically informative design (about 2000 twin pairs), we investigated the phenotypic and genetic and environmental architecture of a broad construct of conscientiousness (including conscientiousness per se, effortful control, self-control, and grit). These four different measures were substantially correlated; the coefficients ranged from 0.74 (0.72–0.76) to 0.79 (0.76–0.80). Univariate genetic analyses revealed that individual differences in conscientiousness measures were moderately attributable to additive genetic factors, to an extent ranging from 62 (58–65) to 64% (61–67%); we obtained no evidence that shared environmental influences were observed. Multivariate genetic analyses showed that for the four measures used to assess conscientiousness, genetic correlations were stronger than the corresponding non-shared environmental correlations, and that a latent common factor accounted for over 84% of the genetic variance. Our findings suggest that individual differences in the four measures of conscientiousness are not distinguishable at both the phenotypic and behavioural genetic levels, and that the overlap was substantially attributable to genetic factors.

PHENOTYPIC, GENETIC AND ENVIRONMENTAL CORRELATIONS BETWEEN BODY WEIGHT AND LINEAR BODY TRAITS OF CHICKEN GENOTYPES

Data from 123, 49, 116, 137, 42 and 64 chickens belonging to Isa Brown x frizzle feathered (IBxF), Isa Brown x naked neck (IBxNa), Isa Brown x normal feathered (IBxN), frizzle feathered x Isa Brown (FxIB), naked neck x Isa Brown (NaxIB) and normal feathered x Isa Brown (NxIB) genotypes, respectively were used to establish phenotypic (rP), genetic (rG) and environmental (rE) correlations between body weight and linear body traits at 2, 10 and 20 weeks of age. Phenotypic correlations were analyzed by Pearson’s Product Moment method. Genetic and environmental correlations were estimated by covariance analysis. The highest rP estimates were obtained between body weight and shank length (SL) in IBxF (0.84) and NxIB (0.87) at 10 weeks, body width (BW) in IBxNa (0.84) and IBxN (0.72), drumstick length (DL) in FxIB (0.71) and NaxIB (0.88) at 20 weeks. Body weight had highest rG estimates with SL in NxIB (0.99), BW in IBxF (2.40), wing length (WL) in BxNa (0.91) and FxIB (7.39) at 10 weeks, body girth (BG) in IBxN (0.97) and BW of NaxIB (4.73) at 20 weeks. However, SL of IBxNa (-5.15), BG of NaxIB (-0.53), keel length (KL) of NxIB (0.35), WL of IBxF (-0.38) and FxIB (-1.41) at 2 weeks and WL of IBxN (-0.43) at 20 weeks had the least rE with body weight. Indirect selection of body weight using the highest phenotypic, genetic and lowest environmental correlated linear traits will result in rapid genetic improvement in these chickens.

Genetic analysis of body weights of Japanese quails (Coturnix japonica) in a semi-arid area of Nigeria

Production and management of Japanese quail is relatively new in Nigeria but the birds have been attracting national attention in the recent times. This study on Japanese quail was conducted to estimate genetic parameters of egg production traits of Japanese quails in a semi-arid area of Nigeria. In a study that lasted for 40 weeks, 40 sires and 120 dams that produced 1267 progenies (743 females and 524) in three batches were used. The mixed model least squares and maximum likelihood programme of Harvey was used to estimate heritability, genetic, phenotypic and environmental correlations for body weights of Japanese quails from 0 – 40 weeks of age. Heritability estimates from sire, dam and, sire plus dam variance components from 0 to 36 weeks were low to moderate ranging from 0.071 to 0.569. Genetic correlations between body weights at the different ages were positive but varied widely from low (0.02) to high (0.977). However, the genetic relationships between body weights from hatch to 8 weeks were high (0.921 to 0.992). This may suggest that selection for final body weight may be based on early weight records. The phenotypic and environmental correlations were generally high, positive and ranged from 0.572 to 0.995 and 0.776 to 0.999, respectively. Though, the magnitude of genetic and phenotypic correlations of body weights decreased with increase in age of Japanese quails. Thus, rapid progress in selection for improvement of body weight of the Japanese quail may be