Insulin-like growth factors, imprinting and embryonic growth control

Abstract

Mutations introduced into the genes encoding the insulin-like growth factors (IGF) and their receptors indicate that these molecules play critical roles in regulating embryonic growth from mid-gestation onwards. Studies of compound mutations show that IGFI, interacting with the IGF type-1 receptor (IGF1R), has important growth promoting activities in the embryo. Similarly while IGFII signals proliferation via binding to the IGF1R, it also interacts with a second unidentified receptor to ensure normal placental growth. Finally, the growth promoting effects of IGFII during embryogenesis appear to be tightly regulated both by imprinting phenomena associated with the Igf2 locus, and through interactions with the IGF2R/MPR.