title: Effects of low-dose embryonic thyroid disruption and rearing temperature on the development of the eye and retina in zebrafish.
abstract: Thyroid hormones are required for vertebrate development, and disruption of the thyroid system in developing embryos can result in a large range of morphologic and physiologic changes, including in the eye and retina. In this study, our anatomic analyses following low-dose, chronic thyroid inhibition reveal that both methimazole (MMI) exposure and rearing temperature affect eye development in a time- and temperature-dependent fashion. Maximal sensitivity to MMI for external eye development occurred at 65 hr postfertilization (hpf) for zebrafish reared at 28°C, and at 69 hpf for those reared at 31°C. Changes in eye diameter corresponded to changes in thickness of two inner retinal layers: the ganglion cell layer and the inner plexiform layer, with irreversible MMI-induced decreases in layer thickness observed in larvae treated with MMI until 66 hpf at 28°C. We infer that maximal sensitivity to MMI between 65 and 66 hpf at 28°C indicates a critical period of thyroid-dependent eye and retinal development. Furthermore, our results support previous work that shows spontaneous escape from MMI-induced effects potentially due to embryonic compensatory actions, as our data show that embryos treated beyond the critical period generally resemble controls.
authors.affiliation: Department of Biology, American University, Washington, District of Columbia.
authors.forename: Masha
authors.initials: M
authors.lastname: Reider
authors.forename: Victoria P
authors.initials: VP
authors.lastname: Connaughton
mesh_terms: D000818:Animals; D013956:Antithyroid Agents / Q000494:pharmacology*; D004625:Embryo, Nonmammalian / Q000187:drug effects; D007037:Hypothyroidism / Q000139:chemically induced; D008713:Methimazole / Q000494:pharmacology*; D012160:Retina / Q000196:embryology* / Q000502:physiology*; D013696:Temperature; D013961:Thyroid Gland / Q000502:physiology; D013963:Thyroid Hormones; D015027:Zebrafish / Q000196:embryology*
chemical_list: D013956:Antithyroid Agents; D013963:Thyroid Hormones; D008713:Methimazole
keywords: development; methimazole; retina; thyroid; zebrafish