Transcription Landscape of the Early Developmental Biology in Pigs

SIMPLE SUMMARY: A complete and exploratory landscape of developmental biology during mammalian organogenesis is needed to improve livestock production and contribute with comparative developmental studies in other relative species, including humans. Since transcriptome analysis is suitable to understand systemic context and genomic interactions, we evaluated the main transcriptional changes during overall organogenesis comparing fetal and embryonic stages through RNA-seq analysis, using the pig as model. The differentially expressed genes between pig fetuses and embryos highlight the main biological events and pathways required for primary organs and body structure development at the embryonic stage, the biological events and pathways related to growth and specialization of these organs at the fetal stage, as well as the molecular mechanisms involved in embryonic to fetal transition. This exploratory transcriptional landscape contributes to improving our knowledge of the crucial biological events during normal prenatal development, which is relevant in prenatal programing studies as well as in livestock production. ABSTRACT: Since pre- and postnatal development are programmed during early prenatal life, studies addressing the complete transcriptional landscape during organogenesis are needed. Therefore, we aimed to disentangle differentially expressed (DE) genes between fetuses (at 35 days old) and embryos (at 25 days old) through RNA-sequencing analysis using the pig as model. In total, 1705 genes were DE, including the top DE IBSP, COL6A6, HBE1, HBZ, HBB, and NEUROD6 genes, which are associated with developmental transition from embryos to fetuses, such as ossification, skeletal muscle development, extracellular matrix organization, cardiovascular system, erythrocyte differentiation, and neuronal system. In pathway analysis, embryonic development highlighted those mainly related to morphogenic signaling and cell interactions, which are crucial for transcriptional control during the establishment of the main organs in early prenatal development, while pathways related to myogenesis, neuronal development, and cardiac and striated muscle contraction were enriched for fetal development, according to the greater complexity of organs and body structures at this developmental stage. Our findings provide an exploratory and informative transcriptional landscape of pig organogenesis, which might contribute to further studies addressing specific developmental events in pigs and in other mammals.