Parental imprinting and the IGF2 gene

The phenomenon of parental imprinting has become increasingly important in disciplines such as evolution, genetics, molecular biology, embryology and pathology. Principally, parental imprinting refers to a parent-of-origin dependent expression of a subset of autosomal loci, independent of the sex of the offspring. Today, at least seven such loci have been identified, including the human IGF2 gene. It appears that the set of imprinted genes is not always identical between the species, although the importance of maintaining this kind of gene regulation is evolutionarily conserved. It is particularly interesting from the clinical point of view that a number of human diseases, such as the Beckwith-Wiedemann and Prader-Willi/Angelman syndromes, appear to involve unbalanced parental contributions of imprinted loci. We show here that the four different human IGF2 promoters are expressed mono- and/or biallelically in complex patterns in postnatal liver specimens.