Transferase activity function and system development process are critical in cattle embryo development

Microarray gene expression experiments often consider specific developmental stages, tissue sources, or reproductive technologies. This focus hinders the understanding of the cattle embryo transcriptome. To address this, four microarray experiments encompassing three developmental stages (7, 25, 280 days), two tissue sources (embryonic or extra-embryonic), and two reproductive technologies (artificial insemination or AI and somatic cell nuclear transfer or NT) were combined using two sets of meta-analyses. The first set of meta-analyses uncovered 434 genes differentially expressed between AI and NT (regardless of stage or source) that were not detected by the individual-experiment analyses. The molecular function of transferase activity was enriched among these genes that included ECE2, SLC22A1, and a gene similar to CAMK2D. Gene POLG2 was over-expressed in AI versus NT 7-day embryos and was under-expressed in AI versus NT 25-day embryos. Gene HAND2 was over-expressed in AI versus NT extra-embryonic samples at 280 days yet under-expressed in AI versus NT embryonic samples at 7 days. The second set of meta-analyses uncovered enrichment of system, organ, and anatomical structure development among the genes differentially expressed between 7- and 25-day embryos from either reproductive technology. Genes PRDX1and SLC16A1 were over-expressed in 7- versus 25-day AI embryos and under-expressed in 7- versus 25-day NT embryos. Changes in stage were associated with high number of differentially expressed genes, followed by technology and source. Genes with transferase activity may hold a clue to the differences in efficiency between reproductive technologies.