INDIRECT GENETIC EFFECTS ON SOCIAL BEHAVIOR AND PARALLELLED CHANGES IN METHYLATION PATTERNS IN ZEBRAFISH

The social environment, more particularly the genetic makeup of conspecifics, may influence individuals' social behavior, a phenomenon known as indirect genetic effects (IGEs). Previous work demonstrated how genetic variation in the social environment affects the behavior of the zebrafish oxytocin receptor mutants (OXTR). It was found that the interaction between an individual's genotype and the genotype of the group affects social behaviors, indicating that the social environment can either rescue or promote phenotypes associated with specific genes. Nevertheless, the mechanisms underlying this behavioral plasticity remain poorly understood. In the present study, we used the same experimental paradigm of growing fish in different environmental conditions (1 wild-type in a group of mutants; 1 mutant in a group of wild-type and the respective controls) to explore the mechanism that regulates the interaction between genes and environment. Following behavioral assays, forebrains were collected for sequencing to assess both epigenetic and transcriptional changes. Our results confirm that group genotypic composition significantly influences social interactions in a genotype-dependent manner, affecting both individual behavior and group dynamics. Preliminary genomic analyses revealed a differentially methylated CpG island in a gene expressed in the mesolimbic reward system and dopaminergic pathways that appears to be involved in emotional learning and reward processing. Together, these data support a model in which social context drives molecular changes in the brain, with epigenetic regulation acting as potential mediators of socially induced phenotypic variation.