Role of Microglial Fractalkine Signaling in Altered Dopaminergic Wiring in FASD

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PROJECT SUMMARY/ABSTRACT Despite public awareness campaigns, Fetal Alcohol Spectrum Disorders (FASD) remain prevalent due to alcohol consumption by women that are pregnant or of child-bearing age. Prenatal alcohol exposure disrupts (1) dopaminergic mesocorticolimbic projections which is likely related to the executive dysfunction, attention deficits, and increased risk for substance use disorders that characterize FASD, (2) the subpallium, a critical intermediate target during axon formation, and (3) guidance cues and signaling pathways that drive axon formation. In this study, we test the hypothesis that binge prenatal alcohol exposure hinders dopaminergic axon outgrowth in the subpallium through reduced signaling between dopamine axons and microglial cells via fractalkine. Our experiments aim to (1) define the developmental timing of alcohol-induced alterations in fractalkine signaling and (2) determine the role of these alterations in microglial number, activation, and regulation of dopaminergic axon guidance. To determine the developmental timing of alcohol effects on fractalkine signaling, we will measure in vivo levels of mRNA and protein fractalkine (CX3CL1), its receptor (CX3CR1), and resultant cytokines (IL-1β, TNFα, IL-6, MIP-1α, and MCP-1) before, during, and after microglial guidance of dopaminergic axons. To visualize alcohol effects on microglial activation in the subpallium, we will count immunostained microglia and perform 3D reconstructions to analyze morphology using Imaris and Halo technologies. To measure dopaminergic axon outgrowth, we will trace tyrosine hydroxylase (TH) immunostained axons. To confirm the requirement of fractalkine signaling in these effects, we will utilize CX3CR1eGFP/eGFP mice which serve as functional knockouts of the fractalkine receptor. Our anticipated findings will reveal the impact of developmental alcohol exposure on cellular and molecular mechanisms that are required for proper nervous system wiring, an area that is currently understudied. This work will enhance understanding of neurobiological underpinnings of neuroinflammation and dampened dopamine function that are observed in human FASD.