Faculty Bibliography

Epigenetic modifications of the membrane bound catechol-O-methyltransferase (MB-COMT) gene may affect the enzymatic degradation of dopamine, and consequently, human behavior. This study investigated the association between membrane bound catechol-O-methyltransferase DNA methylation (DNAm) differences in 92 monozygotic (MZ) twins with phenotypic manifestations of cognitive, behavioral, and personality indicators associated with reward-related behaviors and lack of control. We used pyrosequencing to determine DNAm of the regulatory region of membrane bound catechol-O-methyltransferase in saliva DNA. Results of intrapair differences in the percentage of membrane bound catechol-O-methyltransferase DNAm at each of five CpG sites show that there are associations between phenotypic indicators of lack of control and membrane bound catechol-O-methyltransferase DNAm differences on CpG1, CpG2 and CpG4, suggesting the common epigenetic patterns for personality traits, cognitive functions, and risk behaviors.

OBJECTIVE:The main goal of this study was to explore the latent structure and genetic basis of cognitive processes involved in the Wisconsin Card Sorting Task (WCST) within phenotypic, behavioral genetic, and molecular genetic research paradigms. METHOD/METHODS:The sample used in phenotypic and behavioral genetic analyses comprised 468 twins (154 monozygotic and 80 dizygotic twin pairs), while molecular genetic analyses were performed on 404 twins from the same sample. The zygosity of most twin pairs (96.8%) was determined via deoxyribonucleic acid (DNA) analysis of buccal swabs. Trained researchers administered the Wisconsin Card Sorting Test (WCST; Heaton et al., 1993) to the entire sample. RESULTS:Met- genotype. CONCLUSIONS:Met + genotype showed significant main effects on different WCST measures. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Two studies examined genetic and environmental influences on traits proposed by the revised Reinforcement Sensitivity Theory (rRST) of personality. Both quantitative and molecular behavioral genetic methods were applied considering the effects of COMT, DRD2, HTR1A and TPH2 single nucleotide polymorphisms (SNPs). Study one included 274 monozygotic and 154 dizygotic twins for the quantitative behavioral study; and in study two there were 431 twins for the molecular genetic study. The Reinforcement Sensitivity Questionnaire was used to assess basic personality traits defined by the rRST. Univariate biometric modeling suggested that genetic influences accounted for 34-44% of variance of Behavioral Approach System (BAS), Behavioral Inhibition System (BIS) and Fight-Fligh-Freeze System. Molecular genetic analyses proposed the significant main effect of COMT SNP on the BAS and TPH2 SNP on the BIS, and pointed out epistatic effects of COMT x DRD2 on BAS and HTR1A x TPH2 on Fight. Results demonstrated substantial heritability for all rRST constructs, as well as for differences in the molecular genetic basis of both approach-related and avoidance-related dimensions.

The main aim of this study was to explore the etiology of relations between general cognitive ability (g) and different hierarchical phenotypic levels of the Five Factor Model (FFM), including the General Factor of Personality (GFP), the Big Two, the five domains of the FFM, and their 30 facets. The second aim was to detect personality facets that contribute to the prediction of general intelligence. The sample consisted of 424 young adult twins (134 pairs of monozygotic twins) on whom the NEO-PI-R and Advanced Progressive Matrices were administered. The results did not support hierarchical solutions above the FFM. Thus, five-domain and facet level of personality were analyzed, showing that only Openness and Neuroticism had significant genetic or environmental correlations with intelligence. The several facets from all domains had significant associations, among which Ideas and Positive Emotions showed the highest positive correlations, while Order and Modesty showed the highest negative genetic correlations with intelligence. Furthermore, seven facets significantly predicted g factor (35%), with higher genetic (0.52) than environmental (0.13) correlations with intelligence. The results reveal the common genetic basis of narrow traits and intelligence, highlighting the importance of specific traits in the explanation of general cognitive abilities.

The aim of this study was to explore genetic and environmental contributions to laboratory-induced aggressive behavior. On a sample of 478 adult twins (316 monozygotic), the Competitive Reaction Time Task was used for aggression induction. The results showed that the initial, basic level of aggression could be explained by both shared (45%) and nonshared environmental factors (55%), while only nonshared environmental factors (100%) had a significant influence on changes in aggression as provocation increased. Genetic factors had no influence on laboratory-induced aggression. The results highlight the importance of environmental factors in shaping situation-specific aggressive responses to provocation.

The first aim of this study was to explore the aetiology of phenotypic relationships between different measures of executive functions. The second objective was to examine sources of the covariation between different measures of executive functions and the measure of general cognitive ability. The study sample consisted of 468 twins (154 pairs of monozygotic twins and 80 pairs of dizygotic twins) of the same and different gender who grew up together. Executive functions were evaluated by the Wisconsin Card Sorting Test, the Trail Making Test "“ form B, and verbal fluency tests. Raven's Advanced Progressive Matrices were used as a measure of general cognitive ability. The study results suggest a primarily genetic origin of the mutual covariation of different executive measures and their covariation with the general cognitive ability construct. While the shared genetic variance primarily lies in the bases of similarity/unity of the used cognitive measures, their particularity/difference is determined by a specific unshared environment. The obtained result on the presence of a single general genetic factor, which can be singled out in the case of different executive measures, at least partially speaks in favor of the thesis about the unity of various executive measures and the existence of a common basic ability. Together with the specific unshared environment, the specific genetic influence speaks in favor of a difference between each of the individual measures.

This study examines cultural differences in genetic and environmental influences on Five-Factor Model (FFM) across Croatian, German and Serbian cultures. Participants were 1021 monozygotic and 722 dizygotic twin pairs and NEO Five-Factor Inventory"“ NEO-FFI is used to assess FFM personality traits. Results show a similar pattern of genetic and environmental contribution to the variance of all FFM dimensions, indicating that culture has no significant effect on the genetic and environmental variance of personality traits. The best fitted common factor - common AE pathway models show that FFM dimensions are accounted for by the common latent factor. Although FFM dimensions clearly share some common sources of variance, the effects of specific genetic and environmental factors are more pronounced than common ones. Different patterns of genetic and environmental correlations across three samples may reflect the way that the synergy of personality traits responds to the specificities of a particular culture, as well as possible subtle differences in item translation, testing conditions, and measurement error.

Identifying human remains is one of the many responsibilities of forensic scientists. An eye- and skin-color predictor translates genotypic information into phenotypic description. Eight single nucleotide polymorphisms (SNPs) are utilized for this predictor, five for eye, and six for skin coloration. Here, we describe the development and validation of an 8-SNP multiplex assay that consists of a multiplex PCR, followed by a multiplexed single-base primer extension reaction generating fluorescently labeled oligonucleotides of distinct length that are detected by multicolor capillary electrophoresis. Validation of this assay included tests for reproducibility, reliability, sensitivity, species specificity, its performance on degraded DNA, and on forensic samples. It can be concluded that the 8-SNP multiplex assay is robust and can be used on challenging samples, including bones, to reliably determine the genotypes to predict eye and skin color of individuals. This information can assist in the identification of human remains and missing persons.

AIM: To improve the 7-plex system to predict eye and skin color by increasing precision and detailed phenotypic descriptions. METHODS: Analysis of an eighth single nucleotide polymorphism (SNP), rs12896399 (SLC24A4), showed a statistically significant association with human eye color (P=0.007) but a rather poor strength of agreement (kappa=0.063). This SNP was added to the 7-plex system (rs12913832 at HERC2, rs1545397 at OCA2, rs16891982 at SLC45A2, rs1426654 at SLC24A5, rs885479 at MC1R, rs6119471 at ASIP, and rs12203592 at IRF4). Further, the instruction guidelines on the interpretation of genotypes were changed to create a new 8-plex system. This was based on the analysis of an 803-sample training set of various populations. The newly developed 8-plex system can predict the eye colors brown, green, and blue, and skin colors light, not dark, and not light. It is superior to the 7-plex system with its additional ability to predict blue eye and light skin color. RESULTS: The 8-plex system was tested on an additional 212 samples, the test set. Analysis showed that the number of positive descriptions for eye colors as being brown, green, or blue increased significantly (P=6.98e-15, z-score: -7.786). The error rate for eye-color prediction was low, at approximately 5%, while the skin color prediction showed no error in the test set (1% in training set). CONCLUSIONS: We can conclude that the new 8-plex system for the prediction of eye and skin color substantially enhances its former version.

When a forensic DNA sample cannot be associated directly with a previously genotyped reference sample by standard short tandem repeat profiling, the investigation required for identifying perpetrators, victims, or missing persons can be both costly and time consuming. Here, we describe the outcome of a collaborative study using the Identitas Version 1 (v1) Forensic Chip, the first commercially available all-in-one tool dedicated to the concept of developing intelligence leads based on DNA. The chip allows parallel interrogation of 201,173 genome-wide autosomal, X-chromosomal, Y-chromosomal, and mitochondrial single nucleotide polymorphisms for inference of biogeographic ancestry, appearance, relatedness, and sex. The first assessment of the chip's performance was carried out on 3,196 blinded DNA samples of varying quantities and qualities, covering a wide range of biogeographic origin and eye/hair coloration as well as variation in relatedness and sex. Overall, 95 % of the samples (N = 3,034) passed quality checks with an overall genotype call rate >90 % on variable numbers of available recorded trait information. Predictions of sex, direct match, and first to third degree relatedness were highly accurate. Chip-based predictions of biparental continental ancestry were on average ~94 % correct (further support provided by separately inferred patrilineal and matrilineal ancestry). Predictions of eye color were 85 % correct for brown and 70 % correct for blue eyes, and predictions of hair color were 72 % for brown, 63 % for blond, 58 % for black, and 48 % for red hair. From the 5 % of samples (N = 162) with <90 % call rate, 56 % yielded correct continental ancestry predictions while 7 % yielded sufficient genotypes to allow hair and eye color prediction. Our results demonstrate that the Identitas v1 Forensic Chip holds great promise for a wide range of applications including criminal investigations, missing person investigations, and for national security purposes.