Transient Exposure to Ethanol during Zebrafish Embryogenesis Results in Defects in Neuronal Differentiation: An Alternative Model System to Study FASD

Abstract

BackgroundThe exposure of the human embryo to ethanol results in a spectrum of disorders involving multiple organ systems, including the impairment of the development of the central nervous system (CNS). In spite of the importance for human health, the molecular basis of prenatal ethanol exposure remains poorly understood, mainly to the difficulty of sample collection. Zebrafish is now emerging as a powerful organism for the modeling and the study of human diseases. In this work, we have assessed the sensitivity of specific subsets of neurons to ethanol exposure during embryogenesis and we have visualized the sensitive embryonic developmental periods for specific neuronal groups by the use of different transgenic zebrafish lines.Methodology/Principal FindingsIn order to evaluate the teratogenic effects of acute ethanol exposure, we exposed zebrafish embryos to ethanol in a given time window and analyzed the effects in neurogenesis, neuronal differentiation and brain patterning. Zebrafish larvae exposed to ethanol displayed small eyes and/or a reduction of the body length, phenotypical features similar to the observed in children with prenatal exposure to ethanol. When neuronal populations were analyzed, we observed a clear reduction in the number of differentiated neurons in the spinal cord upon ethanol exposure. There was a decrease in the population of sensory neurons mainly due to a decrease in cell proliferation and subsequent apoptosis during neuronal differentiation, with no effect in motoneuron specification.ConclusionOur investigation highlights that transient exposure to ethanol during early embryonic development affects neuronal differentiation although does not result in defects in early neurogenesis. These results establish the use of zebrafish embryos as an alternative research model to elucidate the molecular mechanism(s) of ethanol-induced developmental toxicity at very early stages of embryonic development.

Comparison of molecular marker expression in early zebrafish brain development following chronic ethanol or morpholino treatment

“…With regard to pax2a , our data confirm earlier studies that showed this MHB marker was not affected by early ethanol exposure (Coffey et al, 2013; Joya et al, 2014), although Coffey et al (2013) showed decreased pax2 a expression following later exposure to ethanol. Pax2a MHB expression was only lost in a small subset of aldh1a3 morphants and in fgf8a morphants in the present study.…”

Effects of embryonic ethanol exposure at low doses on neuronal development, voluntary ethanol consumption and related behaviors in larval and adult zebrafish: Role of hypothalamic orexigenic peptides

“…These effects, evident in the anterior and posterior regions of the hypothalamus, are induced by both concentrations of ethanol, 0.25% and 0.5%. While neurogenesis in the brain of zebrafish has yet to examined in fish exposed as embryos to low concentrations of ethanol, moderate to high ethanol concentrations have been tested and found to have very different effects in fish, causing an increase in cell death and morphological malformations in the brain and also a decrease in neuronal differentiation in the spinal cord [58, 59]. Thus, the concentration of ethanol during embryonic development is critical for the outcome, with low concentrations stimulating neurogenesis in the hypothalamus as demonstrated here in larval zebrafish.…”

Fishing for Fetal Alcohol Spectrum Disorders: Zebrafish as a Model for Ethanol Teratogenesis

“…Due to the large number of transgenic backgrounds available, new insights are being gained into how ethanol disrupts neural development in zebrafish. Exposure to 1% ethanol reduces the number of elavl3-positive neural progenitors 54 and 100 mM (0.6%) increases the branching of secondary motor neurons and decreased the diameter of Mauthner axons. 55 In addition, Zhang et al 56 reported that 0.5% ethanol exposure leads to disruption of the mid-hindbrain boundary.…”