Developmental regulation of genomic imprinting of the IGF2 gene in human liver.

Control of the expression of the human insulin-like growth factor II gene is known to be complex, displaying both tissue-specific and developmental regulation. Insulin-like growth factor II is expressed at high levels in most tissues in the human fetus and appears to be important in fetal growth. In adult life, high levels of expression are found chiefly in liver, kidney, skin, nerve, and muscle tissue. Recent studies in the human fetus have demonstrated that in all tissues examined, including liver, the human insulin-like growth factor II gene is imprinted, with the paternally inherited allele expressed and the maternally inherited allele silent. The present study demonstrates that while the insulin-like growth factor gene is imprinted in human fetal liver, imprinting is relaxed in the second half of the first year of postnatal life, and thereafter the insulin-like growth factor gene is biallelically expressed.