Submitted to: Animal Reproduction Congress Proceedings
Publication Type: Proceedings
Publication Acceptance Date: July 1, 2002
Publication Date: May 1, 2003
Citation: Serial analysis of gene expression (sage) in preimplantation stage swine embryos. (2004). IN: Biological Resource Management in Agriculture: Mammalian Embryo Genomics, Watson, A., Editor, OECD Publications, Paris, France, pp. 47-85.
Mammalian embryo development represents a continuum of molecular and cellular interactions whereby early events dictate or influence subsequent developmental outcomes. For example, conditions under which oocytes are matured can dramatically impact the rates of pronuclear and blastocyst development after in vitro fertilization and embryo culture . Swine often exhibit high rates (>30%) of early embryonic mortality following either artificial insemination or natural mating . The efficiencies of producing swine embryos in vitro are also poor compared to other livestock species. Typically, approximately 20% of transferred in vitro produced swine embryos develop into live offspring after embryo transfer . The long-term objective of the present study is to establish comprehensive gene expression profiles from the 4 critical stages of porcine embryo development depicted in Figure 1. Development from the 2- to 4-cell stages (day 2 (D2) after insemination) coincides the transition from maternal to embryonic genome expression within the embryo . The blastocyst stage (D6) represents the earliest stage at which cellular polarity and morphologic differentiation occur within the embryo. Blastocyst stage embryos are also the stage most commonly transferred and cryopreserved in swine [5, 6]. The maternal recognition of pregnancy combined with the dramatic embryo elongation that occurs between day 11 (D11) and day 12 (D12) of gestation denote critical stages in porcine development that immediately precede tight adherence of the embryo to the uterine endometrial epithelium [7, 8]. Serial analysis of gene expression (SAGE) enables both qualitative and quantitative analysis of gene expression on a whole-transcriptome level . The SAGE process consists of extracting mRNA template from cells of interest and performing a series of manipulations to isolate and sequence a population of 10-12 base-pair nucleotide `tags¿ (i.e. a SAGE library) wherein each tag is uniquely representative of an individual transcript represented in the original mRNA population. Bioinformatic analysis of SAGE tag sequence data identifies and quantitates the occurrence of each tag; the tag frequency is correlated to the frequency at which its respective transcript occurs in the mRNA population. We performed SAGE on in vivo-derived D11 and D12 porcine embryos to identify and characterize critical gene expression events that occur during and between these key stages of early porcine embryo development.