Brazilian Twin Studies: A Scoping Review.

The current study was motivated by an interest in deepening understanding of Brazilian twin research, which is underrepresented internationally, in an effort to rectify this situation. Our aim was threefold: (1) to carry out a comprehensive investigation of Brazilian research on twins according to the area of knowledge; (2) to evaluate the representation of research in the field of psychology in comparison with other areas; (3) to evaluate characteristics of the research that may have contributed to its exclusion from the comprehensive meta-analysis of 50 years of twin research. A scoping review was performed according to PRISMA guidelines. Titles and abstracts were searched up to 2022 in six databases: CAPES, BDLTD, PePSIC, PubMed, Google Scholar, and SciELO, using selected keywords both in Portuguese and in English (e.g., 'twins' and 'Brazil'; 'twinning' and 'Brazil'; 'gemelaridade' [twinning], and 'gêmeos' [twins]). Three hundred and forty publications were included in the review. Approximately half (53.8‰) used the classic twin design to investigate the heritability of several traits, and the other half (46.2%) used other research designs. The scoping review showed that the number of publications doubled approximately every 10 years. Most publications were from the health area, with medicine accounting for approximately half of the studies, followed by psychology, odontology, and biology. We found that the interest in studying twins among Brazilian scientists is increasing over the years and there are reasons to be enthusiastic about the potential impact of this trend in the global scenario.

Hunting for Genes Underlying Emotionality in the Laboratory Rat: Maps, Tools and Traps.

Scientists have systematically investigated the hereditary bases of behaviors since the 19th century, moved by either evolutionary questions or clinically-motivated purposes. The pioneer studies on the genetic selection of laboratory animals had already indicated, one hundred years ago, the immense complexity of analyzing behaviors that were influenced by a large number of small-effect genes and an incalculable amount of environmental factors. Merging Mendelian, quantitative and molecular approaches in the 1990s made it possible to map specific rodent behaviors to known chromosome regions. From that point on, Quantitative Trait Locus (QTL) analyses coupled with behavioral and molecular techniques, which involved in vivo isolation of relevant blocks of genes, opened new avenues for gene mapping and characterization. This review examines the QTL strategy applied to the behavioral study of emotionality, with a focus on the laboratory rat. We discuss the challenges, advances and limitations of the search for Quantitative Trait Genes (QTG) playing a role in regulating emotionality. For the past 25 years, we have marched the long journey from emotionality-related behaviors to genes. In this context, our experiences are used to illustrate why and how one should move forward in the molecular understanding of complex psychiatric illnesses. The promise of exploring genetic links between immunological and emotional responses are also discussed. New strategies based on humans, rodents and other animals (such as zebrafish) are also acknowledged, as they are likely to allow substantial progress to be made in the near future.

Association of a locus on rat chromosome 4 with anxiety-related behaviors in two selectively bred rat lines

The Floripa H and L rat lines, selected for high and low locomotion in the central aversive area of an open field, a widely used emotionality test, were proposed as a model for studying the genetic basis of anxiety. The present study aimed to verify if the QTL Ofil1, mapped to rat chromosome 4 and previously identified as being related to emotionality in another population of rats, contributes to the behavioral variability observed in the Floripa rat lines. To this purpose, rats of five generations of selective breeding were genotyped for two polymorphic markers, D4RAT59 and D4MGH27, flanking Ofil1. Changes in genotype and allele frequencies throughout generations were evaluated in both H and L lines, in order to assess if the bidirectional selection based on behavioral scores induced divergent changes in the genotype of this genome region. There were significant changes in genotype frequencies for both molecular markers, however, only the genotype variations of the D4RAT59 marker were significantly correlated with the variations in the selected phenotype. This result suggests that the region of the genome near D4RAT59 contains one or more genes contributing to the interindividual variation in central locomotion in the open field test.

Beyond the "Cinderella effect" : Life history theory and child maltreatment.

A central thesis of this paper is that understanding the nature of child maltreatment is so complex that no one disciplinary specialty is likely to be sufficient for the task. Although life history theory is the guiding principle for our analysis, we argue that an evolutionary explanation adds precision by incorporating empirical findings originating from the fields of anthropology; clinical, developmental, and social psychology; and sociology. Although evolutionary accounts of child maltreatment have been largely limited to the role of the coefficient of relatedness, the prospective reproductive value of a child, and the residual reproductive potential of parents, a case is made for expanding this basic application. An explanatory model is presented that describes how ecological conditions as well as parental and child traits interact to influence the degree of parental investment. As shown in the model, these various "marker variables" alter parental perceptions of the benefits and costs associated with child care and promote low-investment parenting, which leads to disrupted family management practices and to a downward-spiraling, self-perpetuating system of coercive family interaction, increased parental rejection of the child, and even lower parental investment. Child maltreatment is the ultimate outcome of this downward trajectory of family relations.