Project description:Gene expression was measured using microarrays in 8 hour postfertilization embryos, comparing control versus ethanol-treated (2 to 8 hours postfertilization) embryos. This experiment was performed to determine the gene expression changes that occur in response to ethanol treatment as a model of fetal alcohol spectrum disorder. Fetal alcohol spectrum disorder (FASD) occurs when pregnant mothers consume alcohol, causing embryonic ethanol exposure and characteristic birth defects that include craniofacial, neural and cardiac defects. Gastrulation is a particularly sensitive developmental stage for teratogen exposure, and zebrafish is an outstanding model to study gastrulation and FASD. Epiboly (spreading blastomere cells over the yolk cell), prechordal plate migration and convergence/extension cell movements are sensitive to early ethanol exposure. Here, experiments are presented to characterize mechanisms of ethanol toxicity on epiboly and gastrulation. Epiboly mechanisms include blastomere radial intercalation cell movements and yolk cell microtubule cytoskeleton pulling the embryo to the vegetal pole. Both of these processes were disrupted by ethanol exposure. Ethanol effects on cell migration also indicated that cell adhesion was affected, which was confirmed by cell aggregation assays. E-cadherin cell adhesion molecule expression and distribution, which control epiboly and gastrulation, were not affected. Gene expression microarray analysis was used to identify potential causative factors for early development defects, and expression of the cell adhesion molecule protocadherin-18a (pcdh18a), which controls epiboly, was significantly reduced in ethanol-exposed embryos. Injecting pcdh18a synthetic mRNA in ethanol-treated embryos partially rescued epiboly cell movements, including enveloping layer cell shape changes. Together, data show that epiboly and gastrulation defects induced by ethanol are multifactorial, and include yolk cell (extraembryonic tissue) microtubule cytoskeleton disruption and blastomere adhesion defects, in part caused by reduced pcdh18a expression. Control vs. ethanol-treated zebrafish embryos that were treated from 2 to 8 hours postfertilization. Total RNA from control and ethanol-treated embryos were harvested at 8 hours postfertilization.

Project description:Gene expression was measured using microarrays in 8 hour postfertilization embryos, comparing control versus ethanol-treated (2 to 8 hours postfertilization) embryos. This experiment was performed to determine the gene expression changes that occur in response to ethanol treatment as a model of fetal alcohol spectrum disorder. Fetal alcohol spectrum disorder (FASD) occurs when pregnant mothers consume alcohol, causing embryonic ethanol exposure and characteristic birth defects that include craniofacial, neural and cardiac defects. Gastrulation is a particularly sensitive developmental stage for teratogen exposure, and zebrafish is an outstanding model to study gastrulation and FASD. Epiboly (spreading blastomere cells over the yolk cell), prechordal plate migration and convergence/extension cell movements are sensitive to early ethanol exposure. Here, experiments are presented to characterize mechanisms of ethanol toxicity on epiboly and gastrulation. Epiboly mechanisms include blastomere radial intercalation cell movements and yolk cell microtubule cytoskeleton pulling the embryo to the vegetal pole. Both of these processes were disrupted by ethanol exposure. Ethanol effects on cell migration also indicated that cell adhesion was affected, which was confirmed by cell aggregation assays. E-cadherin cell adhesion molecule expression and distribution, which control epiboly and gastrulation, were not affected. Gene expression microarray analysis was used to identify potential causative factors for early development defects, and expression of the cell adhesion molecule protocadherin-18a (pcdh18a), which controls epiboly, was significantly reduced in ethanol-exposed embryos. Injecting pcdh18a synthetic mRNA in ethanol-treated embryos partially rescued epiboly cell movements, including enveloping layer cell shape changes. Together, data show that epiboly and gastrulation defects induced by ethanol are multifactorial, and include yolk cell (extraembryonic tissue) microtubule cytoskeleton disruption and blastomere adhesion defects, in part caused by reduced pcdh18a expression.

Project description:Defects in blood development are a major contributor to complex congenital anomalies. Thrombocytopenia-Absent Radius (TAR) Syndrome is a rare congenital disease presenting with reduced blood platelets (megakaryocytic thrombocytopenia) and forelimb anomalies, concurrent with variable heart and kidney defects caused by hypomorphic RBM8A/Y14 gene function. RBM8A encodes a component of the ubiquitous exon junction complex involved in mRNA splicing, transport, and nonsense-mediated decay. How perturbing a general mRNA-processing factor causes the distinct phenotypes of TAR Syndrome remains unknown. Here, we connect zebrafish rbm8a perturbation to early hematopoiesis defects via attenuated planar cell polarity (PCP) signaling involved in controlling developmental cell arrangements. Combining different genetic means to reduce rbm8a function, we find a significant reduction of cd41-positive thrombocytes in hypomorphic rbm8a larvae. Transcriptomics analysis documents rbm8a-mutant zebrafish embryos already after gastrulation accumulate mRNAs with erroneously included introns, a hallmark of defective nonsense-mediated decay. Affected mRNAs include transcripts encoding components of the non-canonical Wnt pathway involved in PCP signaling, and rbm8a mutant-embryos show hallmarks of Wnt/PCP-dependent, early convergent extension defects. We establish that reduced rbm8a function synergizes with perturbations in Wnt/PCP pathway genes including wnt5b, wnt11f2, fzd7a, and vangl2. Following axis formation, rbm8a perturbation impairs the migration and architecture of the lateral plate mesoderm (LPM) that forms the hematopoietic, cardiovascular, kidney, and forelimb skeleton progenitors. Subsequently, rbm8a perturbation impairs expression of early hematopoietic/endothelial genes including runx1a, kdrl, sox7, and the megakaryocyte regulator gfi1aa. Lastly, we document similar hematopoietic defects upon loss of vangl2. Together, our data link reduced rbm8a function to LPM migration and hematopoietic defects via attenuated Wnt/PCP signaling. Our findings establish a developmental framework that connects the complex TAR Syndrome phenotypes to a potential LPM origin.

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Dynamic Optima In Cell Sizes Enable Normal Gastrulation Movements In Zebrafish Embryos During Early Development

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