Transcriptomic analyses of gastrulation-stage C57BL/6J and C57BL/6NHsd mouse embryos with differential susceptibility to alcohol

Fetal Alcohol Spectrum Disorders (FASD) are a serious public health concern, affecting approximately 5% of live births in the US. The more severe craniofacial and central nervous system malformations characteristic of FASD are caused by alcohol exposure during gastrulation (embryonic day 7 in mice; 3rd week of human pregnancy). Genetics are a known contributor to differences in alcohol sensitivity in humans and in animal models of FASD. Our study profiled gene expression in gastrulation-stage embryos from two commonly used, genetically similar mouse substrains, C57BL/6J and C57BL/6NHsd, that differ in alcohol sensitivity. First, we established normal gene expression patterns at three finely resolved timepoints during gastrulation and developed a web-based interactive tool. Baseline transcriptional differences across strains were associated with immune signaling, indicative of their molecular divergence. Second, we examined the gene networks impacted by alcohol in each strain. Alcohol was associated with a more pronounced transcriptional effect in the 6J's vs. 6N's, matching the 6J's increased susceptibility. The 6J strain exhibited down-regulation of cell proliferation and morphogenic signaling pathways and up-regulation of pathways related to cell death and craniofacial defects, while 6N's show enrichment of hypoxia (up) and cellular metabolism (down) pathways. Collectively, these datasets 1) provide insight into the changing transcriptional landscape across gastrulation in two commonly used mouse strains, 2) establish a valuable resource that enables the discovery of candidate genes that may modify susceptibility to prenatal alcohol exposure that can be validated in humans, and 3) identify novel pathogenic mechanisms potentially involved in alcohol's impact on development.