The tale of a missing rainbow trout gene

Breaking new ground 15. jun 2023 3 min Postdoctoral Fellow William Joyce Written by Morten Busch

A scientist has made a groundbreaking discovery while studying salmonid fish that could provide fascinating answers about the evolution of genes and genomes. In a new study, the researcher discovered that a gene that is crucial for human cardiovascular function is missing in rainbow trout. This finding not only enhances understanding of fish physiology and evolution but also has implications for fish farming, research on human health and environmental conservation.

Adrenergic receptors strongly influence how the human body responds to adrenaline – the hormone that gets your body ready for a fight-or-flight response. However, not much is known about how these genes evolved. In an exciting new study, a scientist studied the genes in salmonid fish. The research provides fundamental knowledge about fish physiology and evolution and can have broader implications for fields such as understanding human health and disease, drug development and environmental conservation.

“I have found a specific gene, an adrenergic receptor, that is essential for humans but absent in rainbow trout, where it has been lost in evolution. Understanding the fate of genes during duplication is important not only to understand functional differences and adaptations between species but also because rainbow trout and zebrafish have been valuable as model organisms in research. Thus, considering these limitations and carefully interpreting the findings are important when these organisms are used as models for human biology,” explains William Joyce, Postdoctoral Fellow from the Section of Zoophysiology of the Department of Biology at Aarhus University.

Highly lethal when absent in mammals

To unravel the complex genetic make-up of rainbow trout, William Joyce analysed extensive genomic data. By specifically exploring the gene expression patterns and the presence of specific receptors, he aimed to understand more about how adrenergic regulation affects the rainbow trout’s cardiovascular system.

“I extensively mined protein sequence data and surprisingly found that an adrenergic receptor gene known as the b1-adrenergic receptor, which is vital for cardiovascular function among humans and many other vertebrates, was completely absent in the rainbow trout.”

This prompted William Joyce to delve deeper into the genome and use bioinformatics tools to confirm the absence of the gene and how this might have evolved. He performed a comprehensive genome survey of six salmonid species spanning five genera: lake whitefish, huchen, salmon, brown trout, lake trout and rainbow trout. The study revealed a fascinating finding.

“The absence of this gene in rainbow trout suggests an intriguing phenomenon related to whole-genome duplication in which additional gene copies compensate for the loss of specific genes, enabling functional redundancy and evolutionary adaptation. The salmonid lineage experienced a specific whole-genome duplication at the same time that they lost the b1-adrenergic receptor, meaning that an enhanced repertoire of other adrenergic genes could compensate for the loss.”

Interpreting the findings cautiously

However, there is a balance between the advantages and disadvantages of gene duplication. Understanding these complexities can shed light on the fate of genes during evolutionary events and how this affects the genome as a whole. Rainbow trout are the first known group among vertebrates to lack this essential gene.

“The absence of this gene has been shown to be highly lethal in mammals, since it plays a vital role in various physiological processes, including cardiovascular function. The finding suggests that the rainbow trout’s duplicated genome has enabled them to compensate for the loss and develop alternative mechanisms.”

Fish, especially rainbow trout and zebrafish, have been widely used as model organisms in physiological studies for several decades. They are used to understand various aspects of fish physiology, including cardiovascular regulation, which is crucial for growth and nutrient transport.

“They can provide valuable insights into human studies and drug development. By studying the absence of this gene in fish, we can obtain insight into the potential effects of the loss and how other genes compensate for its absence.”

This knowledge may contribute to improving understanding of human genetic disorders or diseases associated with gene loss or dysfunction.

“However, with the new results, exercising caution in interpreting the findings is even more important, considering the complex nature of evolutionary processes and the variation in gene duplication and loss effects.”

Highly relevant to study the effects of climate change

William Joyce emphasises that the research is driven by curiosity to unravel the mysteries of evolution and advance understanding of the natural world. Although the direct translational applications of this research to humans are not yet evident, it contributes greatly to the knowledge of fish biology and evolutionary processes—and importantly, their unique genetic adaptations.

“This can prove relevant to both aquaculture practices and environmental monitoring. Further investigations into the missing adrenergic receptor gene in rainbow trout could offer valuable insight into the potential limitations or adaptations associated with its absence. I am currently focusing on investigating potential drawbacks or limitations associated with the absence of the adrenergic receptor gene in rainbow trout.”

Specifically, the aim is to determine whether certain conditions, such as high temperatures or exposure to pollutants, pose challenges for the fish lacking the b1-adrenergic receptor. Studying the effects of climate change on fish is highly relevant, especially given the role of adrenergic stimulation in cardiovascular responses.

“Investigating the potential limitations or advantages of gene loss in response to environmental changes can provide valuable information for assessing how climate change affects various species and ecosystems.”

Evolutionary loss of the b1-adrenergic receptor in salmonids” was published in General and Comparative Endocrinology. William Joyce received a postdoctoral fellowship for study abroad from the Novo Nordisk Foundation.

Researchers at the Department of Biology contribute through research and collaboration to dealing with the major societal challenges formulated in the...

© All rights reserved, Sciencenews 2020