BPA overrides temperature to decide turtle sex

The environmental build-up of bisphenol A (BPA) can result in a life-changing shift for aquatic animals.

For painted turtles, exposure to this chemical can disrupt sexual differentiation,, according to new research in the  General and Comparative Endocrinology.

Scientists at the University of Missouri have teamed up to show how low levels of certain endocrine disruptors like BPA can cause males to possess female gonadal structures in newly-hatched turtles. This collaboration between MU, Westminster College, the U.S. Geological Survey (USGS) and the Saint Louis Zoo exposed turtle eggs to levels of BPA similar to those currently found in the environment.

“It’s important because this is one of the first times we’ve seen low doses of BPA causing disorganization or reorganization of the male gonad to resemble females,” said Dawn Holliday, adjunct assistant professor of pathology & anatomical sciences at MU’s School of Medicine and assistant professor of biology at Westminster College. “We’re not sure what this means in terms of population-level effects, but certainly it can cause some reproductive dysfunction for turtles.”

Painted turtle eggs were brought from a hatchery in Louisiana, candled to ensure embryo viability and then incubated at male-permissive temperatures in a bed of vermiculite. Those exposed to BPA developed deformities to testes that held female characteristics.  Photo by Roger Meissen | © 2015 - MU Bond Life Sciences Center

Painted turtle eggs were brought from a hatchery in Louisiana, candled to ensure embryo viability and then incubated at male-permissive temperatures in a bed of vermiculite. Those exposed to BPA developed deformities to testes that held female characteristics.
Photo by Roger Meissen | © 2015 – MU Bond Life Sciences Center

Endocrine disruptors leach into rivers and streams and concern scientists because of potential effects on animals and humans. While BPA is used as a hardening agent in plastics, it also is used to line cans and in manufacturing where more than 15 billion tons are produced each year.

In the case of painted turtles, these chemicals have potential to alter sex ratios, which are normally regulated by temperature during incubation. Eggs exposed to cooler temperatures normally produce males and those hatched at warmer temperatures produce females.

Turtle eggs incubated at cooler temperatures result in male hatchlings while warmer temperatures cause females. Researchers are measuring the temperature and weight of this turtle. Photo by Roger Meissen | © 2015 - MU Bond Life Sciences Center

Turtle eggs incubated at cooler temperatures result in male hatchlings while warmer temperatures cause females. Researchers are measuring the temperature and weight of this turtle. Photo by Roger Meissen | © 2015 – MU Bond Life Sciences Center

In this experiment, turtle eggs were incubated at temperatures known to rear males and dosed with low, medium and high levels of BPA. BPA-exposed turtles were compared to hatchlings not exposed to chemicals as well as a group exposed to high levels of ethinyl estradiol — an endocrine disruptor found in birth control — at the USGS Columbia Environmental Research Center.

These doses resulted in turtle sex organs that should have been male , but abnormally contained female gonadal elements. The low dose represented BPA concentrations found in fields where turtles can nest while the mid and high doses approximate BPA levels near contaminated sites like landfills.

“We exposed the eggs for a limited amount of time right when they were most vulnerable to the effects,” said Cheryl Rosenfeld, a researcher at MU’s Bond Life Sciences Center and an associate professor of biomedical sciences in the College of Veterinary Medicine. “We found that we got partial feminization in more than 30 percent of turtle eggs exposed to BPA despite being incubated at male-permissive temperatures.”

Dawn Holliday (left), Caitlin Jandegian and Cheryl Rosenfeld examine turtle gonadal tissue to determine if BPA affected proper sexual development. Photo by Roger Meissen | © 2015 - MU Bond Life Sciences Center

Dawn Holliday (left), Caitlin Jandegian and Cheryl Rosenfeld examine turtle gonadal tissue to determine if BPA affected proper sexual development. Photo by Roger Meissen | © 2015 – MU Bond Life Sciences Center

These results give the team a look into what real-world exposure levels might mean in the wild and a starting point for comparison.

“Turtles are the most endangered vertebrate taxa and they have all sorts of conservation issues coming at them from people harvesting them to disease, and endocrine disruptors are another potentially big whammy they have against their conservation status,” said Sharon Deem, director of the Saint Louis Zoo’s Institute for Conservation Medicine. “This research is a stepping stone, and we are hoping we can apply these results to populations of turtles throughout the state and use these results as a marker to look at endocrine disruptors in the wild.”

Future studies plan to look at the underlying mechanisms behind sexual disruption and will extend the study to animals including fish and mammals. Rosenfeld’s laboratory is in the process of examining how early exposure of turtles to endocrine disruptors might affect cognitive behaviors, including spatial navigation ability.

Fred vom Saal, Curators Professor of Biological Sciences in the College of Arts and Science at MU, Don Tillitt, an adjunct professor of biological sciences at MU and a research toxicologist with the USGS, Ramji Bhandari, an assistant research professor of biological sciences and a visiting scientist with the USGS at MU and Caitlin Jandegian, a senior research technician at MU, all collaborated on the study.

Candling helps determine whether the painted turtle embryo is viable for the experiment. Photo by Roger Meissen | © 2015 - MU Bond Life Sciences Center

Candling helps determine whether the painted turtle embryo is viable for the experiment. Photo by Roger Meissen | © 2015 – MU Bond Life Sciences Center

Funding was provided by Mizzou Advantage, an MU initiative that fosters interdisciplinary collaboration among faculty, staff, students and external partners to solve real-world problems in four areas of strength identified at the University of Missouri. These areas include Food for the Future, Sustainable Energy, Media for the Future and One Health/One Medicine.

Five Bond LSC undergraduates win Arts and Sciences Scholarships

Five undergraduate researchers at Bond LSC were awarded arts and sciences scholarships to help them continue their education. Congratulations to each of the winners.

Hannah Baldwin/Bond LSC MU undergraduate Wade Dismukes gathers plants from a growing room in Bond LSC to prepare for an experiment about plant evolution on Thursday, April 9, 2015. Dismukes, who won an arts and sciences scholarship, is a researcher in Dr. Chris Pires’ lab. He is a double major in biology and math.

Hannah Baldwin/Bond LSC
MU undergraduate Wade Dismukes gathers plants from a growing room in Bond LSC to prepare for an experiment about plant evolution on Thursday, April 9, 2015. Dismukes, who won an arts and sciences scholarship, is a researcher in Dr. Chris Pires’ lab. “I got into science because I had good mentors,” he said.

Wade Dismukes started his career as an undergraduate researcher at Bond LSC in Dr. Jack Schultz’s lab almost four years ago. He started out studying how plants, specifically grape vines, reacted to being eaten by insects, specifically phylloxera. About two years ago, he joined Dr. Chris Pires’ lab in order to learn to read a transcriptome, which is a way of looking at all the genes an organism expresses, Dismukes said. A senior with one year of school left, Dismukes is double majoring in math and biology. He plans to go to graduate school and eventually become a research scientist. He’ll stick to plant science, he said. Dismukes credits his interest in science to good mentors.

Hannah Baldwin/Bond LSC MU junior Nathan Coffey works in Dr. Dawn Cornelison's lab on an experiment involving muscle tissue on Thursday, April 9, 2015. Coffey, a winner of an arts and sciences scholarship, said his research focuses on how different types of muscle work within the body. He said that he hopes to complete an MDPhD one day so he can be a researcher and physician. This summer, he will intern at the National Institute on Alcohol Abuse and Alcoholism (NIAAA), which is part of the National Institutes of Health (NIH), in Bethesda, Md.

Hannah Baldwin/Bond LSC
MU junior Nathan Coffey works in Dr. Dawn Cornelison’s lab on an experiment involving muscle tissue on Thursday, April 9, 2015. Coffey, a winner of an arts and sciences scholarship, said his research focuses on how different types of muscle work within the body. He said that he hopes to complete an MDPhD one day so he can be a researcher and physician. This summer, he will intern at the National Institute on Alcohol Abuse and Alcoholism (NIAAA), which is part of the National Institutes of Health (NIH), in Bethesda, Md.

MU junior Nathan Coffey thought he would study physical therapy. Then, he tore his ACL playing soccer. He became interested in medicine and switched majors to biological sciences. He has been an undergraduate researcher in Dr. D. Cornelison’s lab since his sophomore year. This summer, he will intern at the National Institute of Alcohol Abuse and Alcoholism in Bethesda, Md., where he will work on a research project. Currently, he researchers how different types of muscle work within the human body. Coffey says he would like to pursue an MDPhD so he can become a research physician once he finishes his bachelor’s degree.

Hannah Baldwin/Bond LSC MU junior Kevin Bird inspects plants in a greenhouse on Monday, Feb. 23, 2015. Bird, who won an arts and science scholarship, is a student in Dr. Chris Pires' lab studying how plants express genes.

Hannah Baldwin/Bond LSC
MU junior Kevin Bird inspects plants in a greenhouse on Monday, Feb. 23, 2015. Bird, who won an arts and science scholarship, is a student in Dr. Chris Pires’ lab studying how plants express genes.

MU junior Kevin Bird said a heart defect he was born with made him interested in genetics from a young age. Now, the biology and philosophy major works in Dr. Chris Pires’ lab to understand the genetics behind why Brassica rapa — a species that include napa cabbage, mizuna, turnips, bok choy and field mustard — is nutritious. He uses genomics and quantitative genetics to conduct his research. Bird said he wants to continue to study plant genetics in a doctoral program and eventually become a professor so he can teach and research plant molecular evolution and systems biology.

Courtesy of Morgan Seibert MU sophomore Morgan Seibert is a researcher in Dr. D. Cornelison's lab at Bond LSC. She is a winner of an arts and sciences scholarship.

Courtesy of Morgan Seibert
MU sophomore Morgan Seibert is a researcher in Dr. D. Cornelison’s lab at Bond LSC. She is a winner of an arts and sciences scholarship.

Morgan Seibert has been interested in science since she was kid, farming with her father. The Mu sophomore currently studies rhabdomyosarcoma, the type of skeletal muscle cancer that  occurs most often in children, alongside Dr. D. Cornelison and a graduate student. Seibert plans to continue researching independently throughout the summer and fall. Her research in the coming months will focus on the role of receptors known as Ephs and ephrins in the nuclei of cancer cells. The research may lead to new treatments for cancer. Seibert said she hopes to either go to medical school or continue her research in graduate school.

###

MU undergraduate Badr Almadi, a researcher in Dr. Anand Chandrasekhar’s lab could not be reached for an interview or photograph. He is also a winner of an arts and sciences scholarship.

Life Sciences Week preview: Doing more with less

Gehrke 2015 flyerA simple virtue lies at the heart of Xuemin (Sam) Wang’s research: thrift.

“A good way to think of it is how to increase output without demanding more inputs,” Wang said.

Wang, the E. Desmond Lee and Family Fund endowed professor at the University of Missouri-St. Louis and a principal investigator at the Donald Danforth Plant Science Center, studies plant membrane lipids. His lab is focused on understanding the relationship between oil production and plant stresses such as drought and nutrient deficiency.

Wang will speak during the 31st annual Missouri Life Sciences Week, a yearly celebration of MU’s research and an exploration of public policy, entrepreneurship and science outreach.

Wang’s lab uses Arabidopsis, the lab mouse of the plant world, as a discovery tool but also works with crops such as soybean and the Camelina species. Camelina was widely grown in Europe before it was supplanted by canola, but Wang and others are working to develop Camelina as a productive oil crop.

The lab studies how lipids — the fatty acids that make up cell membranes — help regulate cell function. For example, they’re trying to figure out how a cell senses water and nutrients and then “determines whether it should grow faster or store more lipid or carbohydrates,” Wang said.

By understanding those processes, future research might develop plants that do more with less. That could mean less water and chemical fertilizer needed for the same or greater yield. Wang pointed to reliance on fertilizers as a major problem.

“Not only does it drive up agriculture production costs, but there can be major environmental consequences.”

Ultimately, Wang’s research could improve plant oil and biomass production while decreasing our dependence on fertilizers and abundant water.

Wang’s presentation on “Lipids as Molecular Switches in plant stress signaling and metabolic integration” constitutes this year’s Charles W. Gehrke distinguished lecture. Gehrke, a MU professor of Biochemistry who died in 2009, was instrumental in advancing the field of chromatography and helped analyze rock samples retrieved from the moon during the Apollo 11 mission. Gehrke grew up in poverty during the great depression and worked in melon fields during his youth before studying at Ohio State University.

Missouri Life Sciences Week is an annual event. In addition to Wang’s talk, this year’s line-up will also focus on HIV and emerging diseases and highlight more than 300 undergraduate and graduate research projects at its poster sessions.

Check out the full schedule of events here.