Early Zebrafish Development, a Screening Model to Identify Effects of Endocrine Disrupting Chemicals

Abstract

The exposure of mammalian foetus to endocrine disrupting chemicals (EDCs) has been hypothesized to increase the propensity of offspring to develop organ dysfunction or diseases in adult life. Since fetal development is recognized as the most susceptible stage to be affected by different kinds of stress, there is a pressing need to understand the effects of EDCs on this critical developmental window. However, the understanding of the mechanistic basis of this cause-effect relationship is in fact stunningly complex, largely hampered by the complexity of the mammalian developmental processes. Zebrafish, an excellent model widely used in the field of developmental biology, provides an invaluable tool to the field of developmental toxicology. Furthermore, zebrafish was used in classical toxicological studies in sublethal or lethal toxicity test by exposure to different types of chemical contaminants. However, these studies did not provide information on the mechanistic action of the contaminants at realistic exposure dosages. In this study, the approach of using standard whole-mount in situ hybridization screening method was adopted to determine early developmental defects in zebrafish embryos exposed to the ubiquitous contaminant, bisphenol A (BPA) at three critical early developmental stages (60–75% epiboly, 8–10 somite, and prim-5). This screening strategy provided an important evidence to illustrate the effects of BPA on dorsal-ventral (DV) patterning, segmentation, and brain development in zebrafish embryos within 24 hours of the exposure.