Oligonucleotide-based inhibition of embryonic gene expression

We describe a technique to define gene function using antisense oligonucleo tide (AS-ODN) inhibition of gene expression in mice. A single intravenous i njection of an AS-ODN targeting vascular endothelial growth factor (VEGF) i nto pregnant mice between E7.5-8.5 resulted in a lack of primary angiogenes is. This enabled us to define the critical window required to inhibit VEGF expression and recapitulate the primary loss of function phenotype observed in VEGF (-/-) embryos. This phenotype was sequence-specific and time- and dose-dependent. Injection of an AS-ODN targeting a second gene, E-cadherin, into pregnant mice at E10 confirmed a hypothesized secondary phenotype. Th is is the first report of AS-ODN inhibition of gene expression in utero and provides a new strategy for target validation in functional genomics.