Summer blog series together with the 3RCC Part 1: Bacterial Balance: Unravelling the Influence of Gut Microbiota on Zebrafish Social Behaviour

Neurodevelopmental disorders, such as autism spectrum disorder, which are characterized by impaired social behaviour, are highly prevalent worldwide. Recently, scientists have started to understand the role that gut health plays in the symptoms of these disorders, how these symptoms are triggered and how they can be improved.

While it’s hard to observe early social behaviour development in the prenatal brains of mammals, it’s much easier in transparent larval zebrafish. Due to their transparency, neurodevelopment is readily visualized without the need for invasive techniques or complex imaging procedures. To study this topic, Joseph Bruckner and colleagues from the University of Oregon thus raised zebrafish larvae in a germ-free environment (through which the absence of their normal gut bacteria was facilitated) until they were seven days old. They used a behavioural test to evaluate the sociability of adult zebrafish and investigate how their behaviour differed in the presence or absence of their normal gut bacteria. Normally, zebrafish raised together would show specific social behaviours, such as swimming in parallel and turning towards each other. The scientists measured this behaviour by using fish tanks separated with a special film that can turn transparent when needed. When a fish sees another fish in the adjacent tank, they usually interact and move toward each other. Larvae raised in the germ-free conditions and thus without their normal gut bacteria did not however display these normal social behaviours. When examining the brains of these germ-free zebrafish the researchers discovered that the gut bacteria exerted influence over their brain development, particularly in the forebrain region critical for social behaviour.  

These findings suggest that having the right gut bacteria might help to prevent certain brain disorders. Utilizing the zebrafish as a model for investigating the microbiota-gut-brain axis, as was done in this study, presents a promising avenue for enhancing our understanding of neurodevelopmental disorders.

Authors : Christopher Cederroth, Jessica Lampe & Robbie I’Anson Price, Swiss 3R Competence Centre

Reference: Bruckner JJ, Stednitz SJ, Grice MZ, Zaidan D, Massaquoi MS, Larsch J, et al. (2022) The microbiotapromotes social behavior by modulating microglial remodeling of forebrain neurons. PLoS Biol 20(11):e3001838. https://doi.org/10.1371/journal.pbio.3001838