Zebrafish Lacking Neurexin Genes Develop Lasting Social and Anxiety Changes, Offering New Route to Psychiatric Research

Young zebrafish that lack certain genes look, for a while, like any other young zebrafish. They swim, they develop, they behave in ways that give researchers no obvious reason to worry. Then they reach the juvenile stage, and something changes.

That delay is the central finding of a study from Griffith University's Institute for Biomedicine and Glycomics. The team built what it describes as the world's first complete collection of zebrafish models, each missing members of the neurexin gene family. Neurexins are among the strongest groups of genes linked to psychiatric disorders in people.

In the early part of their lives, the fish showed no obvious changes in brain development or behaviour. As they matured, though, the picture shifted. The animals developed profound, permanent and highly specific behavioural changes. The researchers report alterations in social behaviour, anxiety and aggression, all of which are also affected in patients with conditions such as schizophrenia and autism.

The timing is what the researchers find most striking. Many psychiatric conditions in humans do not announce themselves at birth; they emerge later, after a period of apparently typical development. The fish follow a comparable path, which the team says strikingly mimics human disease trajectories.

Dr Jean Giacomotto, who commented on the work, said the results challenge assumptions about how much biological complexity is needed for behaviours tied to mental health. He noted that the animals function and behave remarkably normally early in life, and that removing specific neurexin genes led to profound changes as they mature. He suggested that even highly complex behaviours may arise from deeply conserved biological and genetic programs.

He also pointed to a common way of thinking about social behaviour, as something shaped mainly by experience, environment and learning. Changing a single family of genes, he said, was enough to profoundly and permanently reshape how these animals interact with others and respond to their surroundings.

The practical interest lies in what the fish can reveal about the period before symptoms appear. Zebrafish, according to the team, offer a window into the silent neuronal changes that precede mental health conditions. Because the models follow the human trajectory, Giacomotto said, researchers can work backwards to identify when brain circuits begin to diverge, what triggers that transition, and whether an intervention before severe behavioural changes emerge is possible. He also raised the prospect of reversing changes after they have appeared.

The models are also meant to serve as a platform for finding treatments that could prevent, delay or reverse these changes. Giacomotto described the ultimate goal as moving from genes, to mechanisms, to treatments. For now the work sits at the first of those steps: a set of fish that show, in a simple animal, how the loss of one gene family can quietly reshape behaviour as it grows up.