The human chorionic gonadotrophin alpha subunit gene in gestational trophoblastic disease. 1. Restriction fragment length polymorphisms in hydatidiform moles.

The distribution of EcoR1 and HindIII restriction fragment length polymorphisms in the region of the gene coding for the alpha subunit of human chorionic gonadotrophin have been examined in 71 normal controls, six families, and 65 cases of hydatidiform mole, all of European origin. In control samples the genotypes generated by the presence or absence of the restriction sites, fitted a Hardy Weinberg distribution while in family studies the two polymorphisms showed Mendelian inheritance. The distribution of the genotypes in hydatidiform moles differed from that in control samples. However, the frequency of the alternative alleles R+, R- and H+, H- was not significantly different in the two populations and differences in the distribution of genotypes could be explained in terms of the unique origin of hydatidiform moles. The frequency of the rare homozygous genotype R-R-,H+H+, which has previously been suggested to be associated with the development of choriocarcinoma, was similar in those complete moles which resolved spontaneously (35 per cent) and those which progressed to trophoblastic tumours (27 per cent). No association was found between the genotype of the hydatidiform mole and the subsequent clinical outcome of the patient. Thus the pattern of restriction fragment length polymorphisms associated with the human chorionic gonadotrophin alpha subunit gene would not appear to be an appropriate marker of clinical outcome in patients with hydatidiform moles.