Pdgfra protects against ethanol-induced craniofacial defects in a zebrafish model of FASD

Abstract

Human birth defects are highly variable and this phenotypic variability can be influenced by both the environment and genetics. However, the synergistic interactions between these two variables are not well understood. Fetal alcohol spectrum disorders (FASD) is the umbrella term used to describe the wide range of deleterious outcomes following prenatal alcohol exposure. Although FASD are caused by prenatal ethanol exposure, FASD are thought to be genetically modulated, although the genes regulating sensitivity to ethanol teratogenesis are largely unknown. To identify potential ethanol-sensitive genes, we tested five known craniofacial mutants for ethanol sensitivity: cyp26b1, gata3, pdgfra, smad5 and smoothened. We found that only platelet-derived growth factor receptor alpha (pdgfra) interacted with ethanol during zebrafish craniofacial development. Analysis of the PDGF family in a human FASD genome-wide dataset links PDGFRA to craniofacial phenotypes in FASD, prompting a mechanistic understanding of this interaction. In zebrafish, untreated pdgfra mutants have cleft palate due to defective neural crest cell migration, whereas pdgfra heterozygotes develop normally. Ethanol-exposed pdgfra mutants have profound craniofacial defects that include the loss of the palatal skeleton and hypoplasia of the pharyngeal skeleton. Furthermore, ethanol treatment revealed latent haploinsufficiency, causing palatal defects in ∼62% of pdgfra heterozygotes. Neural crest apoptosis partially underlies these ethanol-induced defects in pdgfra mutants, demonstrating a protective role for Pdgfra. This protective role is mediated by the PI3K/mTOR pathway. Collectively, our results suggest a model where combined genetic and environmental inhibition of PI3K/mTOR signaling leads to variability within FASD.

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

“…28,52 However, in our analyses discussed below, we have found that 1% ethanol merely sensitizes embryos to craniofacial defects, 53 differences that may be due to genetic background. Due to the large number of transgenic backgrounds available, new insights are being gained into how ethanol disrupts neural development in zebrafish.…”

“…Pdgfra acts through the PI3K/ mTOR pathway to regulate cell survival, proliferation, and growth, 99,100 and we found that this pathway mediates the pdgfra-ethanol interaction. 53 Pdgfra function is conserved among zebrafish, mice, and human 94,96,97 and, in human, we identified single-nucleotide polymorphisms in PDGFRA and PDGFRB that significantly associated ethanol-induced changes in outer canthal width and midfacial depth, respectively. 53 This suggests that growth factor signaling as a target of ethanol teratogenesis and that studies in animal models can predict gene-ethanol interactions in human FASD.…”

“…Of these, only pdgfra interacted with ethanol and this interaction was highly synergistic. 53 In zebrafish, mice, and human, loss of pdgfra results in cleft palate, and in model organisms, this has been shown to be due to disrupted neural crest cell migration. [95][96][97][98] When treated with ethanol, pdgfra mutant zebrafish have massive reductions of the entire craniofacial skeleton.…”

“…[95][96][97][98] When treated with ethanol, pdgfra mutant zebrafish have massive reductions of the entire craniofacial skeleton. 53 In addition, over two-thirds of pdgfra heterozygous embryos had craniofacial defects. These ethanol-induced defects proved to be due to elevated cell death.…”

Pvr receptor tyrosine kinase promotes tissue closure by coordinating corpse removal and epidermal zippering

“…For instance, zebrafish pdgfra directs morphogenesis of the craniofacial skeleton, and its activity is sensitive to genetic and environmental perturbations suspected in the etiology of mammalian clefting disorders (Eberhart et al, 2008;McCarthy et al, 2013). Similarly, mutations in murine Pdgfc ligand and Pdgfra receptor result in facial and palate clefts due to both reduced cell proliferation and inadequate migration of neural crest derivatives (Ding et al, 2004;He and Soriano, 2013;Smith and Tallquist, 2010).…”