With a mate and a nest to protect, the male threespined stickleback is a fierce fish, chasing and biting other males until they go away.
Now researchers are mapping the genetic underpinnings of the stickleback's aggressive behavior. Armed with tools that allow them to see which genes are activated or deactivated in response to social encounters, a team from the University of Illinois has identified broad patterns of gene activity that correspond to aggression in this fish.
A paper describing their work appears in the Proceedings of the Royal Society: Biological Sciences.
"The molecular mechanisms underlying complex behaviors such as aggression are a challenge to study because hundreds of genes are involved, and in order to study them, we have to delve into arguably the most complex tissue: the brain," said Illinois animal biology professor Alison Bell, who led the study.
The researchers looked at brain gene expression – the pattern of genes that were activated or deactivated – across four brain regions in the nesting stickleback fish shortly after it encountered an intruder. They compared the brains of nesting stickleback males that did and did not encounter an intruder, to identify how the experience of fending off a challenger changed gene expression in the brain.
"Territorial aggression and other behaviors in sticklebacks have been well-studied by astute observers of animal behavior for almost a century, but complex behaviors in wild animals require the use of powerful tools to understand them," Bell said. "Until recently we have not had sophisticated computational and genomics tools to delve into the causes of aggression in real organisms in natural populations."
The analysis revealed that hundreds of genes were upregulated (activated at higher levels than normal) or downregulated in different regions of the stickleback brain after it encountered an intruder. The upregulated genes were being transcribed and translated into proteins at higher levels to perform specific tasks within the brain.
An analysis of the types of genes that responded when a stickleback male faced an intruder revealed that many molecular and cellular processes were affected. Genes involved in immunity, metabolism and regulation of normal body states were recruited or put to bed. Many of these genes had never before been implicated in studies of aggression or territorial defense, Bell said.
Some of the genes that were downregulated are associated with metabolism and sexual behavior.
"For ages we've known that there are costs of aggression for things like immunity, and conflicts between aggression and other functions such as courtship behavior," Bell said. "This study begins to identify some of the molecular mechanisms that mediate these tradeoffs."
The greatest changes in gene expression were seen in the diencephalon (a region deep in the brain that is involved in relaying sensory information, emotions and motor signals to other brain regions and helps regulate consciousness, sleep, alertness and circadian rhythm, among other things) and the cerebellum (which receives sensory signals and plays a role in motor coordination). A significant number of these genes were regulated in opposite directions in these two brain regions (up in one and down in the other), the researchers report.
One gene, which codes for a protein hormone known as CGA, was the most highly upregulated in the diencephalon and the most highly downregulated in the cerebellum. CGA is known to play a role in reproductive changes and is associated with aging in males and females.
"That the same gene was expressed in opposite directions in different brain regions suggests that there are complex patterns of gene regulation," Bell said.
The researchers also found evidence that some proteins, called transcription factors, which regulate the expression of networks of genes, are regulated differently in different brain regions in response to a territorial threat.
"This suggests that complex transcription regulatory networks are involved in the behavioral response of territorial animals to an intrusion," Bell said.
The new study offers a glimpse into the regulatory mechanisms that govern brain responses to perceived threats, Bell said.
"It lays the stepping-stones to the ultimate characterization of the neurogenomic states underlying complex decision-making in response to social challenges," said postdoctoral researcher Yibayiri Osee Sanogo, the lead author on the paper.
"This study shows how computational approaches can help solve complex problems of molecular biology," said computer science professor Saurabh Sinha, a co-author on the study. "Only powerful computational tools – in combination with new approaches in genomics – can begin to address the complexity of the brain and behavior."
University of Illinois at Urbana-Champaign: http://www.uiuc.edu
This press release was posted to serve as a topic for discussion. Please comment below. We try our best to only post press releases that are associated with peer reviewed scientific literature. Critical discussions of the research are appreciated. If you need help finding a link to the original article, please contact us on twitter or via e-mail.
Pigs ‘edited’ with a warthog gene to resist African swine fever could help spawn GM animal farms in the UK
Mouse House to make naturalist biopic, six years after box-office failure of Creation, starring Paul Bettany
International team spends 10 years making inroads into treatment of bacterium which kills up to half of those it infects
You may not know it, but you probably have some Neanderthal in you. For people around the world, except sub-Saharan Africans, about 1 to 3 percent of their DNA comes from Neanderthals, our close cousins who disappeared roughly 39,000 years ago.
Research at Yale plotted what happened in the brains of two scientists as they held a conversation
From medicines to jet fuel, we have so many reasons to celebrate the microbes we live with every day
Genome sequencing indicates Kennewick Man is Native American, reopening the bitter battle over whether he should be reburied or studied
In the article on the discovery of dinosaurs (They’re back, Review, 6 June) you state: “In Sussex, a local doctor uncovered fragmentary remains of what appeared to be two more species of colossal extinct land reptiles.” You grossly underplay the contribution of Lewes-born Gideon Mantell, geologist and palaeontologist, author and diarist, friend to princes and international scholars as well as local doctor. Mantell not only discovered (aided by his wife) the first remains of the iguanodon in 1824 but named it – as it resembled the tooth of an iguana. This was the first known land dinosaur, Mary Anning having identified the first sea-living dinosaur.Mantell went on to put together more pieces of the jigsaw with extra fossil discoveries. In contrast to Richard Owen, whose models form the basis for the Crystal Palace dinosaurs, Mantell stated correctly that iguanodon would have walked on their back legs, using their forearms to fight or gather food. He did, however, attribute the thumb spike to a nose horn though later corrected this assumption. The Natural History Museum has a display on Gideon and his wife Mary’s contribution as well as the large “Mantell-piece” of Iguanodon fossils that he had on show in his museum in Brighton. He sold it, along with many more priceless items, to the British Museum in 1838. Gideon Mantell’s reputation deserves better than your throwaway remark. Debby MatthewsLewes, East Sussex Continue reading...
Unique triangular hairs help keep Saharan silver ants cool at 70°C by manipulating the physics of light
Most animals wouldn't confront a fearsome predator like a lion. But through sophisticated group work, hyenas launch successful raids