Fetal Alcohol Spectrum Disorders (FASD) describes a wide array of ethanol-induced developmental defects, including craniofacial dysmorphology, such as lower jaw hypoplasia and cleft palate. It affects approximately 1 in 100 children born in the United States each year. Although fetal exposure to alcohol causes FASD, virtually nothing of the genetics behind these ethanol-induced craniofacial defects is understood. The majority of the craniofacial skeleton is generated by cranial neural crest cells in part through complex interactions with epithelial tissues. These interactions are orchestrated by, among others, the Bone Morphogenetic Protein (Bmp) signaling pathway. My preliminary data demonstrates that Bmp signaling, specific to the endoderm, is required for lower jaw morphogenesis, while Bmp signaling regulates palate morphogenesis in part through the transcription factor, gata3. These results suggest a model where Bmp signaling regulates anterior craniofacial morphogenesis via multiple signaling pathways. Growing evidence supports that genetic predisposition plays a role in these ethanol-induced defects, yet little is understood about these gene-ethanol interactions. The Eberhart lab has helped pioneer genetic screens to identify these ethanol-sensitive genetic loci. From these screens, I have compiled a set of mutants with ethanol induced defects suggesting that ethanol interacts with a genetic hierarchy regulating anterior craniofacial development. First, through a screen of available zebrafish mutants, I found that several members of the Bmp signaling pathway exhibit ethanol-induced defects to the embryonic lower jaw and palate. Second, in a forward genetic screen I recovered ethanol-sensitive mutants that phenocopy specific aspects of the Bmp phenotype. These findings support the hypothesis that Bmp signaling regulates a novel ethanol-sensitive pathway regulating morphogenesis of the anterior craniofacial skeleton.
In Specific Aim 1, I will 1) determine how ethanol disrupts a Bmp mediated endoderm-oral ectoderm- neural crest pathway using 4D confocal analyses and 2) elucidate the target of ethanol action the Bmp pathway.
In Specific Aim 2, I will 1) clone and characterize the ethanol sensitivity of au15, au24 and au25, 2) analyze neural crest cell behaviors in ethanol-treated au15 mutants and 3) characterize the mechanism of ethanol action in au15 mutant embryos.
In Specific Aim 3, I will a) clone and characterize au26, b) visualize palate morphogenesis in ethanol-treated Bmp mutants and au26 embryos and c) characterize the epistatic relationship between Bmp-pathway members, au26 and gata3. Overall, the work outlined in this proposal will provide insight into ethanol-sensitive pathways regulating anterior craniofacial development and the gene- ethanol interactions that underlie these pathways. Because of the conservation of gene function between zebrafish and humans, this work will directly translate to studies of candidate genes in human populations and allow for better diagnosis and treatment of FASD.
The purpose of this proposal is to elucidate the genetics and mechanisms underlying the variability of defects found in patients with Fetal Alcohol Spectrum Disorders (FASD). Results obtained from this proposal will greatly increase our understanding of gene-ethanol interactions and the etiology of FASD.
