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Burmese python study could bring better understanding into how vertebrates control organ growth and function

Wednesday, June 10, 2015

Media Contact: Bridget Lewis

News Topics: biology, research

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A new study led by biologists from The University of Texas at Arlington has found that dramatic changes in the anatomy and physiology of the Burmese python after it eats a large meal are controlled by a series of alterations in gene expression.

The research is detailed in the paper, “Rapid changes in gene expression direct rapid shifts in intestinal form and function in the Burmese python after feeding,” that is published in the May edition of the journal Physiological Genomics. It analyzes the changes that occur in the reptile’s small intestine in the days after it ingests a meal following a long period of fasting. The authors believe that their work could shed new light on how vertebrates control organ growth and function.

Todd Castoe, an assistant professor of biology in the UT Arlington College of Science and corresponding author of the paper, said the study is a breakthrough because it delves explicitly into how genes are utilized in creating the stunning changes that take place in the Burmese python’s organs.

A previous paper published in 2013, which was led by Castoe, showed that massive changes in gene expression underlie organ regenerative growth upon feeding in pythons.

“This new paper is the first one to dive into the details,” Castoe said. “Our paper is the first to really show the link between the extreme changes in the python’s organs, specifically the small intestine, with gene expression. It’s also the first one to show that these changes occur very quickly upon feeding – much more quickly than anyone had previously imagined.”

The Burmese python’s physiology undergoes massive changes every time it eats. It has an extraordinary ability for what researchers call “physiological remodeling.” Physiological remodeling refers to the process by which pythons are able to digest meals much larger than their own size by ramping up their metabolism and increasing the mass of their heart, liver, small intestine and kidneys.

Within two days after eating, the snake’s organs expand up to more than double their original size and its metabolism and digestive processes increase 10- to 44-fold. Ten days after eating, the snake’s meal is digested and these changes have reversed, allowing the body to shrink and return back to its pre-meal state.

The new paper explains that when a Burmese python eats, the rapid changes in its small intestine are triggered by alterations in the expression of at least 2,000 genes, equivalent to 10 percent of all genes in the python genome. Moreover, the vast majority of the changes occur within the first six hours after the snake eats, which was a surprise to the researchers.

Castoe said that the intestine rapidly expands in size thanks to cell division. One developmental pathway associated with cell division, called WNT signaling, is utilized by the snake’s intestine during the process.

“The python turns WNT on and turns it back off around four days later, and it winds down,” Castoe said. “They create all these new cells and then when they’re no longer needed, there is a round of programmed cell death, sort of like hitting the self-destruct button on cells. So they grow all these cells and a week later, they kill them so they don’t have to feed them.”

Audra Andrew, lead author of the paper and a Ph.D. student in Castoe’s laboratory, said that researchers found that these WNT genes are the same variety involved in intestinal and other cancers, suggesting that the python’s small intestine may represent a valuable model for studying the interactions of metabolism with the regulation of cell division/death and WNT signaling relevant to cancer.

“Exploring these extreme physiological changes and the shifts will allow us to gain new insights into how snakes may have co-opted pathways for the expression of such extreme body shapes,” she said.  

Castoe added that many types of cancer cells, such as colon cancer, use WNT.

“Basically, the WNT gets stuck in the ‘on’ position and won’t shut off, so the cancer cells just keep on multiplying,” he explained. “With our findings in this study, we’re very excited about the python intestine as a potential model for colon cancer.”  

The study is a collaboration between UT Arlington, the University of Colorado School of Medicine in Aurora, Colo., and the University of Alabama in Tuscaloosa, Ala. In addition to Andrew and Castoe, other co-authors from UT Arlington include Daren Card, Drew Schield and Richard Adams, all Ph.D. students in Castoe’s laboratory. Additional co-authors are Robert Ruggiero and David Pollock of the University of Colorado School of Medicine, and Stephen Secor of the University of Alabama.

-- Greg Pederson, contributing writer

About The University of Texas at Arlington

The University of Texas at Arlington is a comprehensive research institution of more than 50,000 students in campus-based and online degree programs and is the second largest institution in The University of Texas System. The Chronicle of Higher Education ranked UT Arlington as the seventh fastest-growing public research university in 2013. U.S. News & World Report ranks UT Arlington fifth in the nation for undergraduate diversity. Visit www.uta.edu to learn more, and find UT Arlington rankings and recognition at www.uta.edu/uta/about/rankings.php.

 

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