@article{watson_carmona baez_jima_reif_ding_roberts_kullman_2022, title={TCDD alters essential transcriptional regulators of osteogenic differentiation in multipotent mesenchymal stem cells}, volume={11}, ISSN={["1096-0929"]}, url={https://doi.org/10.1093/toxsci/kfac120}, DOI={10.1093/toxsci/kfac120}, abstractNote={Differentiation of multipotent mesenchymal stem cells into bone-forming osteoblasts requires strict coordination of transcriptional pathways. Aryl hydrocarbon receptor (AhR) ligands, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), have been shown to alter osteoblast differentiation in vitro and bone formation in multiple developmental in vivo models. The goal of the present study was to establish a global transcriptomic landscape during early, intermediate, and apical stages of osteogenic differentiation in vitro in response to TCDD exposure. Human bone-derived mesenchymal stem cells (hBMSC) were cultured in growth media (GM), osteogenic differentiation media (ODM), or osteogenic differentiation media containing 10 nM TCDD (ODM+TCDD), thus enabling a comparison of the transcriptomic profiles of undifferentiated, differentiated, and differentiated -TCDD-exposed hBMSCs, respectively. In this test system, exposure to TCDD attenuated differentiation of hBMSCs into osteoblasts as evidenced by reduced alkaline phosphatase activity and mineralization. At various timepoints, we observed altered expression of genes that play a role in the Wnt, FGF, BMP/TGF-β developmental pathways, as well as pathways related to extracellular matrix organization and deposition. Reconstruction of gene regulatory networks with the iDREM analysis revealed modulation of transcription factors (TF) including POLR3G, NR4A1, RDBP, GTF2B, POU2F2 and ZEB1, which may putatively influence osteoblast differentiation and the requisite deposition and mineralization of bone extracellular matrix. We demonstrate that the combination of RNA-Seq data in conjunction with the iDREM regulatory model, captures the transcriptional dynamics underlying mesenchymal stem cell differentiation under different conditions in vitro. Model predictions are consistent with existing knowledge and provides a new tool to identify novel pathways and transcription factors that may facilitate a better understanding of the osteoblast differentiation process, perturbation by exogenous agents, and potential intervention strategies targeting those specific pathways.}, journal={TOXICOLOGICAL SCIENCES}, author={Watson, AtLee T. D. and Carmona Baez, Aldo and Jima, Dereje and Reif, David and Ding, Jun and Roberts, Reade and Kullman, Seth W.}, year={2022}, month={Nov} }
 @article{watson_planchart_mattingly_winkler_reif_kullman_2016, title={From the Cover: Embryonic Exposure to TCDD Impacts Osteogenesis of the Axial Skeleton in Japanese medaka,Oryzias latipes}, volume={155}, ISSN={1096-6080 1096-0929}, url={http://dx.doi.org/10.1093/toxsci/kfw229}, DOI={10.1093/toxsci/kfw229}, abstractNote={Recent studies from mammalian, fish, and in vitro models have identified bone and cartilage development as sensitive targets for dioxins and other aryl hydrocarbon receptor ligands. In this study, we assess how embryonic 2,3,7,8-tetrachlorochlorodibenzo-p-dioxin (TCDD) exposure impacts axial osteogenesis in Japanese medaka (Oryzias latipes), a vertebrate model of human bone development. Embryos from inbred wild-type Orange-red Hd-dR and 3 transgenic medaka lines (twist:EGFP, osx/sp7:mCherry, col10a1:nlGFP) were exposed to 0.15 nM and 0.3 nM TCDD and reared until 20 dpf. Individuals were stained for mineralized bone and imaged using confocal microscopy to assess skeletal alterations in medial vertebrae in combination with a qualitative spatial analysis of osteoblast and osteoblast progenitor cell populations. Exposure to TCDD resulted in an overall attenuation of vertebral ossification characterized by truncated centra, and reduced neural and hemal arch lengths. Effects on mineralization were consistent with modifications in cell number and cell localization of transgene-labeled osteoblast and osteoblast progenitor cells. Endogenous expression of osteogenic regulators runt-related transcription factor 2 (runx2) and osterix (osx/sp7), and extracellular matrix genes osteopontin (spp1), collagen type I alpha I (col1), collagen type X alpha I (col10a1), and osteocalcin (bglap/osc) was significantly diminished at 20 dpf following TCDD exposure as compared with controls. Through global transcriptomic analysis more than 590 differentially expressed genes were identified and mapped to select pathological states including inflammatory disease, connective tissue disorders, and skeletal and muscular disorders. Taken together, results from this study suggest that TCDD exposure inhibits axial bone formation through dysregulation of osteoblast differentiation. This approach highlights the advantages and sensitivity of using small fish models to investigate how xenobiotic exposure may impact skeletal development.}, number={2}, journal={Toxicological Sciences}, publisher={Oxford University Press (OUP)}, author={Watson, AtLee T. D. and Planchart, Antonio and Mattingly, Carolyn J. and Winkler, Christoph and Reif, David M. and Kullman, Seth W.}, year={2016}, month={Nov}, pages={485–496} }
 @article{conley_watson_xie_buchwalter_2014, title={Dynamic Selenium Assimilation, Distribution, Efflux, and Maternal Transfer in Japanese Medaka Fed a Diet of Se-enriched Mayflies}, volume={48}, ISSN={["1520-5851"]}, DOI={10.1021/es404933t}, abstractNote={Selenium (Se) trafficking in oviparous species remains understudied and a major source of uncertainty in developing sound Se regulations. Here, we utilized (75)Se to follow Se through a simulated natural food chain (water, periphyton, mayflies (Centroptilum triangulifer), fish (Japanese medaka)). We specifically examined Se assimilation efficiency, tissue distribution, efflux rate, and maternal transfer in medaka. Selenium assimilation efficiency (AE) averaged 63.2 ± 8.8% from mayfly diets and was not affected by mayfly [Se] across a dietary range of 5.6-38.7 μg g(-1) (dry wt). However, AE decreased significantly as mayfly larva size increased. Efflux rate constants (ke) were consistent between reproductively inactive (0.066 d(-1)) and spawning females (0.069 d(-1)). Total Se loss rate constant (ke+egg; efflux and egg deposition) was 0.17 d(-1) in spawning females. Interestingly, medaka appeared to rapidly shuttle Se to their eggs directly from their diet via the ovary, as opposed to mobilization from surrounding tissues, resulting in dynamic egg [Se] that was more attributable to recent dietary Se ingestion than female whole body [Se] in this asynchronous spawning fish. Spawning strategy likely plays a large role in the process of fish egg Se deposition and requires further attention to understand risk and toxicity of Se to fish.}, number={5}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Conley, Justin M. and Watson, AtLee T. D. and Xie, Lingtian and Buchwalter, David B.}, year={2014}, month={Mar}, pages={2971–2978} }