ABSTRACT Prenatal alcohol exposure (PAE) is a leading cause of preventable neurodevelopmental disability. One contributing factor is impaired corticogenesis through alcohol’s suppression of neural progenitor cell (NPC) proliferation. Ribosome biogenesis (RBG) is a critical regulator of cell cycle progression and its disruption causes nucleolar stress and cell cycle arrest. Using whole-transcriptome sequencing and KEGG pathway analysis, I identified ribosome biogenesis (RBG) as the single greatest downregulated pathway within the alcohol-exposed fetal brain cortex (60 out of 70 ribosomal genes; p-adj = 1.86E-49). Transcriptional suppression of RBG occurs through DNA methylation in CpG regulatory regions of ribosomal protein (RP)- encoding genes and ribosomal DNA (rDNA). I found that 36 RP-encoding genes having attenuated expression in the alcohol-exposed fetal cortex were also hypermethylated in their 5’ upstream regulatory regions. Choline is an essential nutrient required for NPC proliferation and provides methyl groups for DNA methylation. Prenatal supplemental choline restored methylation of cytosines in these RP-encoding genes. I hypothesize that alcohol impairs NPC proliferation, at least in part, through hypermethylation of CpG regulatory regions in RP-encoding genes and rDNA, and this leads to suppressed RBG, whereas prenatal choline supplementation prevents these changes. To test this, I will administer alcohol, with and without choline supplementation, to pregnant Nestin-CFPnuc transgenic mice during the peak proliferative phase of fetal cortical neurogenesis (E10.5 – E14.5); I will study their NPCs at E14.5. Nestin-CFPnuc mice express cyan fluorescent protein (CFP) specifically in NPCs, to facilitate their identification and isolation. In Aim 1, I will quantify proliferation and monitor cell cycle progression in alcohol-exposed Nestin-CFP+ NPCs, and I will assess the ability of prenatal choline to normalize their proliferation. In Aim 2, I will quantify RBG and nucleolar stress in alcohol-exposed nestin-CFP+ NPCs and will assess whether prenatal choline reduces their nucleolar stress. Using targeted knockdown, I will also confirm that reduced RBG is sufficient to decrease proliferation in otherwise-normal NPCs. In Aim 3, I will quantify DNA methylation within the CpG regulatory regions of RP-encoding genes and rDNA in alcohol-exposed NPCs and test the ability of choline to normalize their methylation. These studies offer novel mechanistic insight into how PAE impairs NPC proliferation, and informs our understanding of how prenatal choline may improve neurodevelopmental outcomes in PAE. Studies herein will develop my skills in preclinical models of PAE and will deepen my expertise as an investigator with a niche in epigenetic and nutrient interactions in PAE.