Researcher Studies Link Between Chemical Toxicity Exposure in Developing Embryos and Later in Life Diseases
Jennifer L. Freeman, PhD
Assistant Professor of Toxicology
Director, School of Health Sciences Undergraduate Honors Program
Postdoctoral Fellow, Harvard Medical School and Brigham and Women's Hospital, Boston, 2005-07
PhD, University of Illinois, Urbana, 2005
Molecular Cytogenetics and Environmental Toxicology
BS, University of Illinois, Urbana, 2000
Cell and Structural Biology
Symposium Chair: "Application of Systems Biology to Identify Molecular Mechanisms and Biomarkers of Lead (Pb) Neurotoxicity: Implications in a Developmental Origin of Alzheimer's Disease." Society of Toxicology Conference, March 10-14, 2013, San Antonio.
Colgate-Palmolive Grants in Alternative Research Award, Society of Toxicology, 2012
Purdue Charles B. Murphy Outstanding Undergraduate Teaching Award Nominee, College of Health and Human Sciences, 2012-13
Robert R. Landolt Award for Excellence in Teaching, School of Health Sciences, 2010
Society of Toxicology; International Neurotoxicology Association; Environmental Mutagenesis and Genomics Society; Society of Environmental Toxicology and Chemistry; Rosalind Franklin Society
Jennifer Freeman, PhD, has this big picture in plain view: understanding how exposures to heavy metals and other environmental chemical contaminants affect our life and health. Not just our own, but our offspring's and perhaps for generations to come.
Freeman, assistant professor of toxicology in the School of Health Sciences, and her laboratory investigate the underlying genetic and epigenetic mechanisms of toxicity of a developmental exposure to the heavy metal lead and the herbicide atrazine. Epigenetics is the study of alterations in the genome that do not involve changes in DNA sequences that potentially get passed down from one generation to the next.
Freeman's laboratory specifically looks at low-dose chemical exposures and questions if there is a threshold dose at which toxicity initially presents. Drilling down further, Freeman investigates how lead affects the brain and whether exposure to a developing embryo can make one more susceptible to diseases, such as Alzheimer's, later in life. Her laboratory also studies atrazine, commonly used in agriculture, as an endocrine-disrupting chemical (EDC) and a potential carcinogen. She cites other studies that show that EDCs can cause irreversible changes in tissue formation, decreased reproductive tissue formation, decreased reproductive potential, obesity and cancer.
"Atrazine has been used in agriculture since the 1950s to control and prevent weeds from growing among crops, especially in corn in the Midwestern United States. It is an effective herbicide that is regulated by the EPA since it is often found contaminating drinking water supplies," says Freeman. "The adverse health effects of atrazine, especially at concentrations present in our drinking water supplies, are not well understood, and our ongoing studies are investigating the endocrine disrupting properties of this herbicide."
Enter the Zebrafish
Freeman's laboratory uses the zebrafish model system to investigate toxicity. Researchers use zebrafish because molecular events of development are similar to humans. In addition, female zebrafish lay large quantities of eggs, and the embryos develop outside of the mother's body, so there is easy access to them. Because the embryos are transparent, researchers can watch development as it happens.
"Life stages are also shorter," she notes. "Embryonic development is complete after three days. In just three to four months we can have multiple generations, and we can complete a full lifespan study in about a year." Freeman's laboratory cares for and maintains thousands of zebrafish.
In the lead study, she exposed zebrafish to low doses and analyzed changes at various developmental points. The hypothesis was that they would see changes in genes associated with the central nervous system. "That turned out to be true at 72 hours, while at 120 hours, when most of brain development is complete, very few genes associated with the central nervous system were changed," she explains. "We can use this information to guide us as to sensitive developmental stages to lead neurotoxicity."
A similar approach was taken with a range of atrazine concentrations to establish toxicity. "Overall, this study identified genetic targets altered in response to a developmental atrazine exposure to further define the mechanisms of toxicity," she says.
Freeman notes that data collected from both the lead and atrazine studies are being used to link the developmental exposure to adult disease susceptibility.
Freeman's interest in genetics began in high school when she was introduced to the work of Gregor Mendel, considered the father of genetics. "I was fascinated by it," she recalls. As an undergraduate her interests grew to include cytogenetics and toxicology.
The author of more than 25 published manuscripts, her professional passions extend beyond the research to include mentoring students. She graduated her first PhD student last year. She currently mentors three graduate students and several undergraduate researchers in her laboratory.
"Since joining Purdue I have worked with a number of undergraduates in my laboratory, and all of them were involved in independent research projects. I really enjoy mentoring the undergraduate student researchers and am proud of the work they are accomplishing," she says.