title: Effects of methylmercury exposure on neuronal differentiation of mouse and human embryonic stem cells.
abstract: The establishment of more efficient in vitro approaches has been widely acknowledged as a critical need for toxicity testing. In this study, we examined the effects of methylmercury (MeHg), which is a well-known developmental neurotoxicant, in two neuronal differentiation systems of mouse and human embryonic stem cells (mESCs and hESCs, respectively). Embryoid bodies were generated from gathering of mESCs and hESCs using a micro-device and seeded onto ornithine-laminin-coated plates to promote proliferation and neuronal differentiation. The cells were exposed to MeHg from the start of neuronal induction until the termination of cultures, and significant reductions of mESCs and hESCs were observed in the cell viability assays at 1,10,100 and 1000nM, respectively. Although the mESC derivatives were more sensitive than the hESC derivatives to MeHg exposure in terms of cell viability, the morphological evaluation demonstrated that the neurite length and branch points of hESC derivatives were more susceptible to a low concentration of MeHg. Then, the mRNA levels of differentiation markers were examined using quantitative RT-PCR analysis and the interactions between MeHg exposure and gene expression levels were visualized using a network model based on a Bayesian algorithm. The Bayesian network analysis showed that a MeHg-node was located on the highest hierarchy in the hESC derivatives, but not in the mESC derivatives, suggesting that MeHg directly affect differentiation marker genes in hESCs. Taken together, effects of MeHg were observed in our neuronal differentiation systems of mESCs and hESCs using a combination of morphological and molecular markers. Our study provided possible, but limited, evidences that human ESC models might be more sensitive in particular endpoints in response to MeHg exposure than that in mouse ESC models. Further investigations that expand on the findings of the present paper may solve problems that occur when the outcomes from laboratory animals are extrapolated for human risk evaluation.
authors.affiliation: Division of Environmental Health Sciences, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan.
authors.forename: Xiaoming
authors.initials: X
authors.lastname: He
authors.forename: Satoshi
authors.initials: S
authors.lastname: Imanishi
authors.forename: Hideko
authors.initials: H
authors.lastname: Sone
authors.forename: Reiko
authors.initials: R
authors.lastname: Nagano
authors.forename: Xian-Yang
authors.initials: XY
authors.lastname: Qin
authors.forename: Jun
authors.initials: J
authors.lastname: Yoshinaga
authors.forename: Hiromi
authors.initials: H
authors.lastname: Akanuma
authors.forename: Junko
authors.initials: J
authors.lastname: Yamane
authors.forename: Wataru
authors.initials: W
authors.lastname: Fujibuchi
authors.forename: Seiichiroh
authors.initials: S
authors.lastname: Ohsako
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D053595:Embryonic Stem Cells / Q000166:cytology / Q000187:drug effects*; D020869:Gene Expression Profiling; D006801:Humans; D007150:Immunohistochemistry; D008767:Methylmercury Compounds / Q000633:toxicity*; D051379:Mice; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000648:ultrastructure; D060888:Real-Time Polymerase Chain Reaction
chemical_list: D008767:Methylmercury Compounds