Fish with larger brains and higher intelligence had higher expression of Angiopoietin-1 (Ang-1), and when expression levels of Ang-1 were experimentally reduced, brains shrunk. These trends were seen in two unrelated species of fish – guppies (Poecilia reticulata) and zebra fish (Danio rerio). The trends indicate that expression of Ang-1 is important for brain growth and development in fish generally.

“Other genes may be involved in brain growth in young, developing fish but no other genes were found to vary in their expression in adult fish other than Ang-1. Future studies will aim to investigate the role of Ang-1 and possibly other genes in the formation of differently sized brains in developing embryos”, says Dr Niclas Kolm, Stockholm University.

The study, published in Proceedings of the Royal Society B, identified the underlying genetics of natural variation in brain size and cognitive abilities in fish. Ang-1 could play an important role in the brain development of other vertebrates, including humans, but future research is required to establish this, say the scientists involved.

The protein encoded by Ang-1 is known to play an important role in growing new blood vessels and forming new brain cells in mice, which may indicate an important role of Ang-1 in brain growth of other animals, even in humans.

“We don’t yet know if Ang-1 is important in human brain development – it isn’t on the list of genes typically studied in relation to human brain size – but as it plays a role in forming new blood vessels in humans, there may be a connection as large brains need a bigger blood supply, particularly during growth and for many brain functions. This presents us with an exciting opportunity to investigate the role of Ang-1 across different vertebrates”, says Professor Judith E. Mank, University College of London.

The work was funded by the European Research Council, the Swedish Research Council, the Austrian Science Fund, Academy of Finland and the Sigrid Juselius Foundation.

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