Effects of Nicotine on Embryological Neural Development

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The Ohio State University

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Over 1 million women, approximately 12-22% of the U.S. population, smoke while pregnant (Centers for Disease Control). Nicotine, the primary toxin in cigarette smoke has been associated with altered neural structure and functioning in rats (Roy, 2002) and premature birth, low birth weight, cognitive defects, and behavioral problems in humans (DiFranza and Lew,1995; Sexton, 1990; Olds, 1994). The actions of nicotine are mediated by neuronal nicotinic acetylcholine receptors (nAChRs) which then influence synaptic transmission in many part of the vertebrate nervous system. In this study, zebrafish are being developed as a model for determining the effects of prenatal exposure to nicotine on motor neuron development through examination of genes expressed in the motor neuron pathway. Zebrafish provide the ideal molecular model as embryos are transparent, small, and are accessible at early ages. Recently it has been shown that transient exposure of zebrafish embryos to nicotine delays the development of secondary motor neurons (Svoboda et al., 2002).The mechanism of this action is not known. This study examines the effect of nicotine on the expression of the LIM homeodomain-containing transcription factor Islet-1 (Isl-1), which is important for motor neuron differentiation (Pfaff et al., 1997). Consequently, we hypothesize that nicotine may affect motor neuron development by altering Islet-1 gene expression within motor neurons. To view anatomical expression patterns, in situ hybridization was used to compare control and nicotine treated embryos of the same ages. Further characterization of the effects of nicotine on gene expression may be carried out focusing on the gene sonic hedgehog (SHH) which is expressed even earlier within the motor neuron pathway. The application of these findings may be used to solidify the link between smoking and motor neuron defects and diseases.


1st Place in Denman Undergraduate Research Forum


Nicotine, motor neuron development