Changes in the astrocyte translatome induced by developmental ethanol mediate dysregulation of neuronal development: role of the extracellular matrix and relevance to Fetal Alcohol Spectrum Disorders

Background: Fetal Alcohol Spectrum Disorders (FASD) cause life-long cognitive and behavioral impairment and are highly prevalent across the world. The effects of developmental ethanol exposure on astrocyte functions in vivo are poorly understood. To fill this gap, we assessed changes in the astrocyte translatome following in vivo developmental ethanol exposure and mechanistically linked some of these changes to altered neuronal development. Methods: The translating RNA from hippocampal astrocytes of neonatal Aldh1l1-EGFP-Rpl10a mice exposed to ethanol was isolated by Translating Ribosomal Affinity Purification and sequenced; neuronal dendritic morphology was assessed by Golgi-Cox staining and morphometric analysis; chondroitin sulfate glycosaminoglycan (CS-GAG) disaccharides were measured by Liquid Chromatography/Mass Spectrometry; neurite outgrowth was assessed in in vitro hippocampal neurons incubated in the presence of astrocyte-conditioned medium prepared from control and Chpf2-silenced astrocytes. Results: Translatome results suggested that ethanol alters mechanisms of astrocyte-neuron interactions involved in neuronal development. Moreover, ethanol increased dendritic arborization in hippocampal pyramidal neurons, inhibited the astrocyte translation of enzymes involved in the biosynthesis of inhibitory CS-GAGs, and decreased the levels of disaccharides forming CS-GAGs in vivo. Lastly, the silencing of CS-GAG biosynthetic enzyme Chpf2 in astrocyte cultures increased neurite branching of hippocampal neuron in vitro. Conclusions: Translatome analysis revealed novel effects of developmental ethanol exposure on astrocytes and provided mechanistic insights into altered brain development possibly relevant to the pathophysiology of FASD. We also identified a novel mechanism by which ethanol-induced reduction of astrocyte-produced inhibitory extracellular matrix components CS-GAGs increases dendritic arborization.