An important goal in improving human health is to understand how exposure to environmental toxicants during gestation and childhood leads to disease later in adulthood. It is also vital to determine whether a single early toxicant exposure can affect the health of subsequent generations. Understanding and identifying these risks will positively impact human health. My research focus is to use zebrafish to understand two toxic responses seen in adults exposed during development to 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD, dioxin), at the parts per trillion (ppt) level. Our published work and my preliminary results indicate that a single exposure during development can cause skeletal malformation and reproductive toxicity in the adults, and various forms of toxicity in the subsequent F1 and F2 generations. F0 adult toxicity includes an apparent male feminization in which fish with female secondary sex characteristics have testes. A goal is to determine whether TCDD alters gonadal fate, changing ovaries to testes, or feminizes the body of males. Another major sign of toxicity in adults exposed during early development is malformations in the axial skeleton resembling human scoliosis. I will identify the source of these changes in skeletal development examining bone and collagen by staining and measuring alterations in gene expression. Down-regulation of the sox9b gene is the cause of TCDD-induced jaw malformation in zebrafish. The human sox9 gene is a master regulator of both skeletal formation and sex specification: sox9 is thought to be the target of the male Y-chromosome sry gene. I have also observed sox9b expression at the site of vertebral development in zebrafish. Therefore, I will examine the expression of both zebrafish homologs of human sox9: sox9a and sox9b in developing bone and gonad of TCDD-treated zebrafish. I find reproducible toxicity in F1 and F2 offspring of F0 fish that were exposed only briefly during development. I will better characterize this transgenerational toxicity, measuring changes in global gene expression in affected tissues from each generation and will use both gene- specific and global techniques to examine alterations in DNA methylation and chromatin structure induced by TCDD exposure and transmitted into F1 and F2 fish. In year 3 of this project, I plan to use the results from this work as preliminary data to apply for an R21 or R03 grant. Transgenerational work, even in zebrafish, takes several years to mature, so the proposed work would allow a future grant to focus on mechanisms driving my results. As a K01 recipient, I will follow a career development plan with very specific research and development milestones for each award year. I will meet regularly with my mentors and advisory committee to strengthen my ability to link translational and mechanistic research. I will obtain experiential training in areas needed for a successful career in translational research, including project planning, manuscript and grant writing, and identification and mastery of cellular and molecular techniques needed to move my research forward. I have a clinical background with a research emphasis. I will gain experience in mechanistic, hypothesis testing driven research. This plan will stretch my research expertise and enhance my training in developmental toxicology research. The University of Wisconsin has numerous NIH-sponsored training programs, core facilities and funded researchers making it an ideal training environment for me to develop as an independent scientist.

Public Health Relevance

An important public health concern is that exposure to certain chemicals during fetal development or early in childhood can have long-lasting adverse health consequences in adulthood and even in subsequent generations. Our goal is to determine if this occurs in zebrafish exposed to TCDD and assess adverse effects on the skeleton. Zebrafish are an ideal model system because they grow rapidly to adulthood making them ideal for transgenerational studies, their organ systems have similarities to humans, and they are sensitive to TCDD toxicity.

National Institute of Health (NIH)
Office of The Director, National Institutes of Health (OD)
Research Scientist Development Award - Research & Training (K01)
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Special Emphasis Panel (ZTR1-CM-6 (01))
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Contreras, Miguel A
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University of Wisconsin Madison
Schools of Pharmacy
United States
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Gawdzik, Joseph C; Yue, Monica S; Martin, Nathan R et al. (2018) sox9b is required in cardiomyocytes for cardiac morphogenesis and function. Sci Rep 8:13906
Meyer, Danielle N; Baker, Bridget B; Baker, Tracie R (2018) Ancestral TCDD Exposure Induces Multigenerational Histologic and Transcriptomic Alterations in Gonads of Male Zebrafish. Toxicol Sci 164:603-612
Baker, Bridget B; Yee, Jeremiah S; Meyer, Danielle N et al. (2016) Histological and Transcriptomic Changes in Male Zebrafish Testes Due to Early Life Exposure to Low Level 2,3,7,8-Tetrachlorodibenzo-p-Dioxin. Zebrafish 13:413-23
Baker, Tracie R; King-Heiden, Tisha C; Peterson, Richard E et al. (2014) Dioxin induction of transgenerational inheritance of disease in zebrafish. Mol Cell Endocrinol 398:36-41
Baker, Tracie R; Peterson, Richard E; Heideman, Warren (2014) Adverse effects in adulthood resulting from low-level dioxin exposure in juvenile zebrafish. Endocr Disruptors (Austin) 2:
Plavicki, Jessica S; Baker, Tracie R; Burns, Felipe R et al. (2014) Construction and characterization of a sox9b transgenic reporter line. Int J Dev Biol 58:693-9
Baker, Tracie R; Peterson, Richard E; Heideman, Warren (2014) Using zebrafish as a model system for studying the transgenerational effects of dioxin. Toxicol Sci 138:403-11
Baker, Tracie R; Peterson, Richard E; Heideman, Warren (2013) Early dioxin exposure causes toxic effects in adult zebrafish. Toxicol Sci 135:241-50
Baker, Tracie R; Baker, Bridget B; Johnson, Stephen M et al. (2013) Comparative analgesic efficacy of morphine sulfate and butorphanol tartrate in koi (Cyprinus carpio) undergoing unilateral gonadectomy. J Am Vet Med Assoc 243:882-90