Alcohol is a potent neurotoxicant and prenatal alcohol exposure is a leading cause of mental disability. One affected population is the neural crest. Clinically relevant ethanoi levels (20-80 mM) cause neural crest (NC) apoptosis. Our past work under this award showed that the apoptosis results from an ethanol-stimulated intracellular calcium (Ca2+) transient originating from the CPy-mediated activation of PLC-IP3. The current award shows that the Ca2+ transient activates CaMKII, which in turn destabilizes the transcriptional effector beta-catenin, which mediates canonical Wnt signaling and NC survival. Proposed studies directly extend this work to ask How does beta-catenin loss cause neural crest apoptosis? We will test the hypothesis that beta- catenin maintains NC cell adhesion and expression ofthe survival factor snail2 (formerly slug). We further posit that the ethanol-mediated loss of beta-catenin initiates premature NC cell delamination and suppresses snail2, thus activating NC apoptosis.
Aim 1 tests whether snail2 loss directly initiates NC apoptosis because it controls the expression ofthe apoptosis regulators bcl2 and bax.
Aim 2 tests the role of beta-catenin in NC cell adhesion and whether beta-catenin loss stimulates precocious NC delamination and apoptosis.
Aim 3 extends our work to test if acute ethanoi exposure similarly destabilizes beta-catenin and its transcriptional activity in other neuronal populations in which p-catenin controls cell fate, specifically the fetal brain and adult hippocampus. Finally, our ARRA supplement performs high-throughput RNA-Seq of ethanol-sensitive and - resistant NC to identify calcium-dependent factors upstream of beta-catenin that govern NC survival.
Aim 4 tests the efficacy of these candidate genes in controlling NC responses to ethanoi. This work is a logical extension ofthe current award. We continue using our established chick embryo model, which replicates the alcohol responses of mammals including humans, has well-described NC development, and is amenable to genetic manipulation. Beta-Catenin dysregulation contributes to several neuropathologies, suggesting it may also modulate alcohol action in the fetus and the adult.
Fetal alcohol spectrum disorders (FASD) are a major cause of cognitive and behavioral disability in children. How ethanoi damages the embryo and fetus is incompletely understood. Because it is difficult to prevent gestational alcohol abuse, there is increased interest in strategies to blunt ethanol's damage. Identification of its toxicity mechanism suggests targets for intervention, i.e. pharmacological agents that stabilize beta-catenin.
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