Transcriptomic analysis of neurulation and early organogenesis in rat embryos: an in vivo and ex vivo comparison

Cultured embryos mimic the morphological developmental progression of embryos (in vivo) undergoing neurulation and early organogenesis. Using available genomics technologies, comparative molecular-based assessments between cultured embryos and in vivo models may further clarify commonalities and dissimilarities, which contribute to differences between systems. Therefore, in this study, using a transcriptomic approach, we compared cultured whole rat embryos and embryos in vivo at comparable time points in development (gestational day (GD) 10 + 2-48 h, GD 0 = copulatory plug) to assess for commonalities and differences in gene expression in relation to morphology. We reveal strong parallels in time-dependent expression of genes in terms of magnitude, directionality, and functionality between whole embryo culture (WEC) and in vivo (rat). Genes changing in expression over time resemble previously hypothesized mechanisms underlying early development in mammalian systems. Furthermore, at the gene and functional level, we identify genes, which differ in expression between models, including genes related to development, oxygen transport, and metabolism. In summary, our results support the use of WEC for toxicological studies aimed at representing in vivo development during this time window at the molecular level. Additionally, we indicate genes, which differ in expression between models, providing possible insights for improvement of culture conditions.