Expression of the insulin-like growth factor-1 gene and its receptor in preimplantation mouse embryos; is it a marker of embryo viability?

Overview

Recent studies have demonstrated the importance of insulin-like growth factors (IGF) in mouse preimplantation development. We examined IGF-1 and IGF-1 receptor (IGF-1R) gene expression in a single blastomere of an early mouse embryo and compared it with subsequent embryo development in culture. Fertilized eggs and 2-cell embryos were obtained by tubal flushing in superovulated and mated female mice. Single cells were removed from embryos at cleavage stage between 3 and 8 cells using the standard embryo biopsy techniques. Individual blastomeres from each embryo were then assayed for the presence of IGF-1 and IGF-1R mRNA using reverse transcription-polymerase chain reaction. The biopsied embryos were washed in medium and placed in co-culture with murine endometrial cells. Embryonic development in culture was assessed and blastocyst grading was performed. IGF-1 gene expression was then examined for an association with in-vitro development. Eighty-seven embryos were biopsied. IGF-1R gene expression was detected in the majority of embryos tested and IGF-1 gene expression was detected in 34 of 81 (42%) embryos. A significant association between IGF-1 expression and blastocyst formation in vitro was found (P < 0.01). There was no association between IGF-1R expression and subsequent embryo development. We conclude that IGF-1 gene expression could potentially be used as a marker of embryo quality.