Effect of intra-cytoplasmic sperm injection (ICSI) on gene expression and development of mouse preimplantation embryos

Background: In vitro culture of preimplantation mouse embryos is associated with changes in gene expression. It is however not known if the method of fertilization affects the global pattern of gene expression. Method: We compared gene expression and development of mouse blastocysts produced by intra-cytoplasmic sperm injection and cultured in Whittens medium (ICSIWM) or KSOM medium with amino acids (ICSIKSOMaa) with control blastocysts flushed out of the uterus on post coital day 3.5 (In vivo). Global pattern of gene expression was assessed using the Affymetrix 430 2.0 chip. In addition we compared gene expression in embryos generated in IVF or ICSI using WM. Results: Blastocysts resulting from ICSI fertilization have a reduction in the number of trophoblastic and inner cell mass cells compared to in vivo generated embryos. Approximately 1000 genes are different between ICSI blastocyst and in vivo blastocysts; proliferation, apoptosis and morphogenetic pathways are the most common pathways altered after in vitro culture. Unexpectedly, only 41 genes were statistically different between embryo cultured in suboptimal conditions (WM) or optimal conditions (KSOMaa). Conclusion: The method of fertilization plays a more important role in shaping the transcriptome of the developing mouse embryo than the culture media used.

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