The frequency of an inactivating point mutation (C-566 -> T) of the human follicle-stimulating hormone receptor gene in four populations using allele-specific hybridization and time-resolved fluorometry

We have described previously in the Finnish population an inactivating poin t mutation (C-566-->T) in the human FSH receptor (FSHR) gene. In women, thi s mutation causes hypergonadotropic ovarian failure with arrest of follicul ar maturation and infertility, whereas in men, there is variable suppressio n of spermatogenesis, but no absolute infertility. To determine whether the same FSHR mutation occurs in other populations, its frequency was determin ed in Finland, Switzerland, Denmark, and the Chinese population of Singapor e. The mutation was screened for using genomic DNA extracted from whale blo od or dried blood spots. Exon 7 of the FSHR gene was first amplified using a pair of biotinylated primers. The PCR products were then immobilized on s treptavidin-coated microtitration wells and hybridized using short allele-s pecific oligonucleotide probes labeled with europium. Time-resolved fluorom etry was used for europium signal detection. To test the reliability of thi s method, 40 isolated DNA samples and 35 dried blood spot samples were blin dly tested for the C-566-->T FSHR mutation. The analyses yielded identical results with denaturing gradient gel electrophoresis and allele-specific re striction enzyme digestion of the same samples, thus demonstrating the reli ability of the tested method. Automation of this procedure allows the scree ning of large numbers of samples, which was subsequently carried out to inv estigate the frequency of the C-566-->T mutation in the study populations. A total of 4981 samples from the above-mentioned 4 countries were analyzed. The frequency of the C-566-->T mutation was 0.96% for all Finnish samples (n = 1976), with a strong enrichment of the mutant allele in the northeaste rn part of the country. Only 1 mutation carrier was identified in the sampl es from Switzerland (n = 1162), whereas none was found in samples from Denm ark (n = 1094) and the Singapore Chinese (n = 540). These results suggest t hat the C-566-->T mutation of the FSHR gene is enriched in Finland, but is uncommon in other populations.