Browsing by Subject "Fetal Alcohol Syndrome"
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Item Ethanol-kat6a interaction induces mandibular arch defects during craniofacial development(2024-04-28) Liu, Joanna; Eberhart, Johann K.Prenatal alcohol exposure can induce a variety of developmental defects characterized as “Fetal alcohol spectrum disorders” (FASD). FASD remains a significant health concern and yet little is known about the mechanism of alcohol-induced birth defects. These defects are often concentrated around the craniofacial region which are developed from transient structures called pharyngeal arches. This research aims to investigate how loss of one or both functional copy of the lysine acetyltransferase 6A (kat6a) gene can modulate the alcohol-induced craniofacial phenotype during zebrafish development. The kat6a gene is a chromatin modifier that regulates hox gene expression. The hox genes are expressed in the second and posterior-pharyngeal-arches but not in the first pharyngeal arch compartment. Thus, the zebrafish kat6a mutants exhibit second arch patterning defects, disrupting jaw support skeleton, while the jaw and palatal skeleton, derived from the first arch remains largely unaffected. However, when the developing embryos are exposed to ethanol, kat6a mutants also exhibit defects in the first pharyngeal arch skeletal elements. Measurements of pharyngeal arch elements in control versus ethanol-treated samples revealed significant shortening and often loss of first-pharyngeal arch elements in the ethanol-treated kat6a mutants and heterozygotes. Mutants were also exposed to ethanol at various developmental windows to determine the stage post-fertilization most susceptible to ethanol-induced effects. This revealed 10-24 hpf as the shortest exposure window which caused significant ethanol-induced effects . Furthermore, I also found that the lowest dose of ethanol that caused defects was 0.25% EtOH. Overall, my thesis demonstrates how an interplay between alcohol and kat6a can exacerbate craniofacial defects. This work also suggests a novel role of kat6a in the morphogenesis of the first pharyngeal arch. In the future, I aim to understand how the kat6a-alcohol interaction impacts cellular processes and gene expression patterns in the first pharyngeal arch during zebrafish development.Item Genetic and bioinformatic approaches to characterize ethanol teratogenesis(2019-09-11) Sidik, Alfire; Eberhart, Johann K.; Harris, R. A; Iyer, Vishwanath R; Sullivan, Christopher S; Wallingford, John BAlcohol consumption during pregnancy is the most preventable cause of birth defects, yet approximately 2-5% of children are afflicted with Fetal Alcohol Spectrum Disorders (FASD). FASD describes the complex and highly variable deleterious phenotypes caused by prenatal alcohol exposure. Twin studies suggest a genetic predisposition, contributing to the variation in risk for FASD. Despite this, we lack a basic understanding of 1) the factors that protect or predispose an individual to FASD and 2) how these genetic factors interact in ethanol teratogenesis. Results from a genetic “shelf” screen revealed vangl2, a member of the Wnt/planar cell polarity (PCP) pathway that mediates convergent extension movements that narrow and elongate the body axis, as an ethanol-sensitive genetic locus. Untreated vangl2 mutants displayed a relatively intact craniofacial skeleton. Ethanol-exposed vangl2 heterozygotes and mutants, displayed cyclopean and midfacial defects. To assess the relative level of variation of the transcriptional response to ethanol, I performed single embryo RNA-seq during early embryonic stages. Individual zebrafish embryos were exposed to a subteratogenic dose of 1% ethanol in embryo media. My data suggests that the effect of ethanol is subtle; time is the most important variable driving variation in fold coverage across all samples. Despite this, I find a number of differentially expressed genes in response to ethanol. Transcriptional changes due to ethanol are indicative of increased oxidative stress and ion transport and reduced DNA replication and cell division. Using a bioinformatic approach, I find cyclopamine, a Hedgehog pathway inhibitor, interacts with ethanol. Further genetic analyses shows that ethanol disrupts convergent extension of the mesoderm, which in turn disrupts localization of shh in the axial mesoderm, a signal necessary to separate the eye field. I find this effect to be further exacerbated in the vangl2 mutant background. Together these data yield important insight necessary to advance understanding and treatment for FASD