Natural variation in brain gene expression profiles of aggressive and nonaggressive individual sticklebacks

Abstract

Within many species, some individuals are consistently more aggressive than others. We examine whether there are differences in brain gene expression between aggressive versus nonaggressive behavioural types of individuals within a natural population of male three-spined sticklebacks (Gasterosteus aculeatus). We compared gene expression profiles of aggressive male sticklebacks to nonaggressive males in four regions of the brain (brainstem, cerebellum, diencephalon and telencephalon). Relatively few genes were differentially expressed between behavioural types in telencephalon, cerebellum and diencephalon, but hundreds of genes were differentially expressed in brainstem, a brain area involved in detecting threats. Six genes that were differentially expressed in response to a territorial intrusion in a previous study were also differentially expressed between behavioural types in this study, implying primarily non-shared but some shared molecular mechanisms. Our findings offer new insights into the molecular causes and correlates of behavioural plasticity and individual variation in behaviour.

Keywords: animal personality; behavioural syndromes; sociogenomics.

Figure 1

Differences in aggressive behaviour (latency to bite the intruder) between aggressive (red) and nonaggressive (green) individuals. Each line represents the behaviour of a different individual across the four observation periods. This figure is published in colour in the online edition of this journal, which can be accessed via http://booksandjournals.brillonline.com/content/journals/1568539x.

Figure 2

Differences in aggressive behaviour (number of bites at the intruder) between aggressive (red) and nonaggressive (green) individuals. Each line represents the behaviour of a different individual across the four observation periods. This figure is published in colour in the online edition of this journal, which can be accessed via http://booksandjournals.brillonline.com/content/journals/1568539x.

Figure 3

Venn diagram showing numbers of differentially expressed transcripts between aggressive and nonaggressive individuals within each brain region, and the overlap between them. BS: brainstem; C: cerebellum; D: diencephalon; T: telencephalon. This figure is published in colour in the online edition of this journal, which can be accessed via http://booksandjournals.brillonline.com/content/journals/1568539x.

Figure 4

GO results. Molecular functions and biological processes enriched in the set of genes that were differentially expressed between aggressive and nonaggressive individuals in brainstem. The bubble scatter plots show GO clusters with representatives noted. Similarity within clusters represents functional similarity computed among two GO terms using ‘simRel’ scores (Supek et al., 2011). The X and Y axes were calculated by applying multidimensional scaling to a matrix of the GO terms’ similarities. Color represents −log(p-value), whereas size corresponds to GO size (frequency) in the GOA database. This figure is published in colour in the online edition of this journal, which can be accessed via http://booksandjournals.brillonline.com/content/journals/1568539x.