Global transcriptome analysis identifies regulated transcripts and pathways activated during oogenesis and early embryogenesis in Atlantic cod.
Bottom Line: During early vitellogenesis, several of the most upregulated genes are linked to nervous system signaling, suggesting increasing requirements for ovarian synaptic signaling to stimulate the rapid growth of oocytes.One of the genes with the highest upregulation in the ovulated egg is involved in oxidative phosphorylation, reflecting increased energy requirements during fertilization and the first rapid cell divisions of early embryogenesis.In conclusion, this study provides a large-scale presentation of the Atlantic cod's maternally controlled transcriptome in ovarian follicles through oogenesis, ovulated eggs, and early embryos.
Affiliation: Institute of Marine Research, Bergen, Norway.Show MeSH
Related in: MedlinePlus
Mentions: Differentially expressed genes (DEGs) detected in this study were linked to KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways in order to identify their systems-level function. An overview of the pathways represented by the highest numbers (≥10) of DEGs can be seen in Supplemental material (Additional File 2). “Housekeeping” pathways tend to encompass a large proportion of the DEGs, whereas smaller pathways that might be mainly up- or downregulated will be masked due to their lower contribution of DEGs. As we consider pathways that are clearly activated or silenced, and therefore represented by mostly up- or downregulated genes, respectively, we focused on the ratio between the number of upregulated and downregulated genes within each specific pathway. In addition, we applied a cutoff for this ratio in order to limit the long list of pathways annotated to the DEGs: up/down ≥5 for upregulated pathways, and down/up ≥5 for downregulated pathways. We added “1” to all “numbers of genes” within a pathway to avoid arithmetic errors that would otherwise result from division by pathways with zero genes. Figure 3 shows an overview of the up- and downregulated pathways. As few genes were differentially expressed from ovulated eggs to blastula embryos, this group was not included. The most up- and downregulated (based on fold change (FC)) genes from one stage to the next are shown in Figure 4, and are also presented with associated KEGG pathways in the following sections.