Date of Defense

3-21-2014

Date of Graduation

4-2014

Department

Speech Pathology and Audiology

First Advisor

Bharti Katbamna

Second Advisor

Charles Ide

Abstract

In this study, we used the African clawed frog, Xenopus laevis, as a model of fetal alcohol syndrome to study how alcohol may impact two genes, engrailed 2 (en2) and connexin 43 (cx43) that set up the stage for partitioning of the brain during early development. Xenopus embryos at stages 10-12 (before neural tube closure) were exposed to 2% alcohol or no alcohol (control) for 24 hours, raised to stages 46/47 (approximately day 5) and fixed overnight in 4% paraformaldehyde. Four specimens from each group were then embedded, sectioned and stained with the en2 and cx43 markers. Analysis of imaged sections showed that en2 expression was reduced, but evident in the midbrain-hindbrain junction, and lost or significantly diminished in the hindbrain segments in alcohol treated animals. Likewise, cx43 expression was displaced from its normal locations and scattered laterally away from the ventricular zone in alcohol exposed animals. These findings indicate that alcohol disrupts early events that lay the foundations for partitioning of the midbrain and hindbrain structures and that such a disruption may impede migration of cells to their final places of destination, thereby producing malformations of structures emerging from these regions. Thus, abnormalities of the ear and adjacent facial and vestibuloauditory cranial ganglia documented in earlier work may be attributed to aberrant patterning of en2 and cx43 in the midbrain and hindbrain.

Access Setting

Honors Thesis-Restricted

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