Global gene expression profiling of preimplantation embryos

Abstract

Preimplantation development is marked by four major events: the transition of maternal transcripts to zygotic transcripts, compaction, the first lineage differentiation into inner cell mass and trophectoderm, and implantation. The scarcity of the materials of preimplantation embryos, both in size (diameter < 100 microm) and in quantity (only a few to tens of oocytes from each ovulation), has hampered molecular analysis of preimplantation embryos. Recent progress in RNA amplification methods and microarray platforms, including genes unique to preimplantation embryos, allow us to apply global gene expression profiling to the study of preimplantation embryos. Our gene expression profiling during preimplantation development revealed the distinctive patterns of maternal RNA degradation and embryonic gene activation, including two major transient waves of de novo transcription. The first wave corresponds to zygotic genome activation (ZGA). The second wave, mid-preimplantation gene activation (MGA), contributes dramatic morphological changes during late preimplantation development. Further expression profiling of embryos treated with inhibitors of transcription or translation revealed that the translation of maternal RNA is required for the initiation of ZGA, suggesting a cascade of gene activation from maternal RNA/protein sets to ZGA gene sets and thence to MGA gene sets. To date, several reports of microarray experiments using mouse and human preimplantation embryos have been published. The identification of a large number of genes and multiple signaling pathways involved at each developmental stage by such global gene expression profiling accelerates understanding of molecular mechanisms underlining totipotency/pluripotency and programs of early mammalian development.

Early embryonic lethality in gene trap mice with disruption of the Arfgef2 gene

“…Zygotic genome activation (ZGA) occurs very early during embryonic development. In the mouse, a minor burst of ZGA toward the end of the one-cell stage is followed by a major burst during the two-cell to four-cell stages and then the mid-preimplantation gene activation (MGA) occurs (Latham et al 1992;Vernet et al 1992;Aoki et al 1997;Thompson et Schultz, 2002;Hamatani et al 2006). The Arfgef2 zygotic activation belongs to the major ZGA at 4-cell stage.…”

Characterization of Maternal Antigen That Embryos Require (MATER/NLRP5) Gene and Protein in Pig Somatic Tissues and Germ Cells

“…More recently, the RNA and protein were observed up to the 16-cell stage in bovine embryos [24,25], the 8-cell stage in a non-human primate [26] and in germinal vesicles in humans [27]. The transcript can be detected during oocyte growth from primary follicles, accumulates during oocyte development and decreases after fertilization [28,29]. NLRP5-null female mice present a normal phenotype regarding folliculogenesis, ovulation and fertilization; however, their embryos do not develop beyond the 2-cell stage coincident with maternal-to-embryo transition [15].…”

Analysis of Permissive and Repressive Chromatin Markers in In Vitro Fertilized Bovine Embryos Just After Embryonic Genome Activation

“…Nonetheless, embryonic genome must suffer a third wave of transcription activation at the 4cell stage. This wave represents the second major transition of gene expression profile, and is named mid pre-implantational gene activation (Hamatani et al, 2006). At this point, genes associated with critical function in early embryos, such as key regulators for epiblast (EPI) and trophectoderm (TE) specification, are activated.…”