Embryo

Search for the Bovine Homolog of the Murine Ped Gene and Characterization of Its Messenger RNA Expression During Bovine Preimplantation Development

Abstract
In mice, a gene (Ped: preimplantation embryo development) that regulates preimplantation embryonic growth, including cleavage rate and embryo survivability, has been described. The objective of the current study was to identify the bovine homolog of the Ped gene and to characterize the mRNA expression pattern of this gene during bovine preimplantation embryo development. The NCBI GenBank/EBI expressed sequence tags (EST) databases were searched for bovine ESTs that were homologous to the murine Ped gene, the resulting ESTs were aligned and assembled into a contiguous sequence. The homology of the sequence to the murine Ped gene was confirmed. Primers were designed for the sequence and the mRNA expression pattern was characterized during bovine preimplantation embryo development in vivo and in vitro. In vitro produced bovine zygotes were cultured either in vitro, in synthetic oviduct fluid, or in vivo, in the ewe oviduct for 1 to 7 days and processed for quantitative real time PCR. Transcript abundance increased at each stage of development. However, the expression levels were consistently higher in in vivo cultured embryos at all stages; with in vivo cultured embryos showing a 9-fold increase in relative transcript abundance during culture from the zygote to the blastocyst stage in contrast to a 3-fold increase during the same culture period in vitro. The mRNA expression pattern of the gene was investigated in early- and late-cleaving 2-cell embryos collected at 25, 28, 32 & > 36 h post insemination (pi). Transcript relative abundance was highest in those embryos that had cleaved by 28 hpi and decreased almost 3-fold thereafter. In conclusion, we have identified a potential bovine homolog of the murine Ped gene. We have characterized the mRNA expression pattern of this gene during preimplantation embryo development in cattle and shown that a greater relative abundance of the gene transcript is associated with embryos of higher quality (in vivo cultured) and greater developmental potential (early cleaving).

Key words: Embryo • Early development • Gene regulation • In vitro fertilization

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