The level of H19 expression in the mole was similar to that in normal placentae, which is compatible with the finding that half of the H19 gene was methylated and the remaining one was hypomethylated en masse in the complete mole.
In situ hybridization analysis shows strong expression of the H19 gene in eight complete hydatidiform moles, hyperplastic tissues consisting of trophoblasts which contain only paternally derived genetic material, indicating that H19 is not functionally imprinted in this tissue.
We suggest that the expression of the maternally expressed H19 gene in the androgenetic tissue of complete hydatidiform mole represents relaxation of imprinting and may be associated with its malignant potential.