Decreased growth factor expression through RNA interference inhibits development of mouse preimplantation embryos.

Mitogenic growth factors play an important role in cellular development and differentiation. The purpose of this study was to assess the extent to which epidermal growth factor (EGF) and transforming growth factor alpha (TGFalpha) and their cognate receptor (EGFR) are crucial for normal preimplantation embryo development. We used RNA interference to decrease expression of growth factors in preimplantation mouse embryos. We microinjected 1-cell mouse embryos individually with short interfering RNA (siRNA) specific to EGF, TGFalpha, and EGFR and then analyzed temporal and spatial gene expression patterns at different stages of development before implantation. Transfection with siRNA significantly reduced growth factor expression in 1-cell, 2-cell, morula, early-blastocyst, and late-blastocyst embryos to levels similar to those in untreated 'cloned' embryos derived through intracytoplasmic nuclear injection. In addition, siRNA effectively decreased expression of maternally inherited genes between 24 and 72 h after transfection, with recovery of gene expression during late-blastocyst stage at 96 h after transfection. Furthermore, siRNA significantly decreased blastocyst formation, increased the number of apoptotic cells, and reduced the total number of differentiated cells in blastocysts; these changes were greatest after decreasing EGFR and of both EGF and TGFalpha simultaneously. These results support our hypothesis that EGF and TGFalpha are crucial for embryo survival and development. Further, dysregulated expression of growth factors is associated with poor development of cloned mouse embryos.