Hypermethylation of INS Promoter in the Developing Liver of Cattle

Insulin (INS) and insulin-like growth factor 2 (IGF2) are both important for the milk synthesis in human and dairy cattle. Liver is a source of growth factors that play an important role in the regulation of milk synthesis in the mammary gland in influence its composition. Occurrence of common INS-IGF transcript and imprinting regulation in some human tissues suggests close interaction between both genes. Here, we analyzed the DNA methylation pattern of the INS promoter and IGF2 expression at six different pre- and postnatal developmental stages of bovine liver. We found stage-independent DNA hypermethylation (93%) of the INS promoter. In contrast, we observed a 4-fold decrease of the IGF2 expression in 12-month-old adult animals compared to 2-month-old fetuses. We therefore suggest that DNA methylation at the INS promoter does not directly regulate the IGF2 expression in the bovine liver.