QTL Mapping of Behaviour in the Zebrafish

The study of complex traits is one of the greatest current challenges in biology, and the exact mechanism whereby individual genes cause small quantitative variation in any given trait still remains largely unresolved. In the case of behavioural traits, with lower heritabilities and repeatabilities as compared to other character-types, this problem is exacerbated even further. One of the principal forms of genetic analysis for quantitative traits is via QTL (quantitative trait loci) mapping, with the power of this approach even greater in model organisms due to the array of genomic tools available. These tools give a genuine possibility of identifying the actual causative genes or nucleotides responsible for the variation (the quantitative trait nucleotide, or QTN). The zebrafish displays a range of behaviours that are both complex and bear a striking similarity to some of the behavioural measurements performed in other model organisms, notably affecting anxiety and social aggregation. The combination of the behavioural variation present in the zebrafish and the genetic and genomic advantages to QTL mapping available for this species paves the way for its use in generating a new model for the genetic dissection of such trait types. This chapter aims to first discuss the zebrafish as a behavioural model suitable for QTL mapping, focussing in particular on the behaviours of shoaling and predator inspection, before giving an overview of what is contained in a QTL study and the types of crossings, analysis and their relevance to behavioural QTL mapping. Finally two case studies are presented, one of anxiety behaviour in mice, one of shoaling and boldness behaviour in zebrafish.