Application of gene amplification by polymerase chain reaction to genetic analysis of molar mitochondrial DNA: the detection of anuclear empty ovum as the cause of complete mole.

To investigate the pathogenesis of complete hydatidiform mole (complete mole), we employed a newly developed gene amplification method by polymerase chain reaction (PCR) for the restriction fragment length polymorphism (RFLPs) analysis of extranuclear DNA (mitochondrial DNA) of complete mole. Whole cellular DNA was extracted from six molar tissues and from peripheral blood mononuclear cells of parents. Two hyperpolymorphic regions of mitochondrial DNA, a 1.5-kb-long fragment and a 1.9-kb-long fragment, were selectively amplified from the extracted DNA by the PCR method. The amplification products amounted to over 10 micrograms after 30 cycles of PCR. The PCR products were digested with endonucleases (HaeIII, HinfI, AluI, and TaqI) and then electrophoresed on agarose gel. The electrophoretic pattern of digested DNA showed that the RFLPs of molar mitochondrial DNA coincided with those of the patient, indicating that the mitochondrial DNA of complete mole was inherited from the ovum. As it has been identified that the intranuclear DNA of complete mole is transmitted only from the spermatozoa, our results verify that complete mole results from the fertilization of an anuclear "empty" ovum with normal sperm at the molecular level.