Title: Follicle-stimulating-hormone receptor and twinning
Abstract: Ayman Al-Hendy and colleagues1Al-Hendy A Moshynska O Saxena A Feyles V Association between mutations of the follicle-stimulating-hormone receptor and repeated twinning.Lancet. 2000; 356: 914Summary Full Text Full Text PDF PubMed Google Scholar suggest that homozygosity for two linked mutations (G/G homozygosity) at the FSHR gene in women produces a presumably more sensitive FSHR and is associated with repeated spontaneous twinning. They based their conclusion on one index case, homozygous for the G variant, and on the fact that no other female member of her family nor any of the other 14 female controls (data not shown) had homozygosity at this locus, which suggests that these mutations are not a common polymorphism of the FSHR locus in women in this population. As part of a project of the East Flanders Prospective Twin Survey2Loos R Derom C Vlietinck R Derom R The East Flanders Prospective Twin Survey (Belgium): a population-based register.Twin Res. 1998; 1: 167-175PubMed Google Scholar we have collected data on Flemish pedigrees with many spontaneous dizygotic twins. Two families showed repeated spontaneous dizygotic twinning (figure). The pregnancies were conceived without the use of fertility medication and the zygosity of the twins were proven by sex, zygosity questionnaires, DNA polymorphisms, or a combination of these. The proband in family 19, who gave birth to three pairs of dizygotic twins from different husbands, gave a strong family history of twinning (data not shown). This was not the case in family 18. We isolated peripheral-blood DNA from the most informative people and amplified the terminal segment of exon 10 of the FSHR gene with primers (5′CTTTCTTTGCCATTTCTGC C3′ and 5′AAAGGCAAGGACTGA ATTATC3′). According to Al-Hendy and colleagues, the A-to-G mutation at nucleotide 2039 created a new BsrI restriction-enzyme site and is linked to a second mutation at nucleotide 307. The two mutations, the G variant, always segregate together. The A variant is the wild-type phenotype. The results of the genotyping of these two families are shown in the figure. We also genotyped 27 female controls: all Flemish mothers of at least three children with no familial history of twinning. Of these women, nine were A/A, five G/G, and 13 A/G. This distribution corresponds to a frequency of the G-allele in our Flemish population of 0·43. The frequencies of the different genotypes are in accordance with a Hardy-Weinberg equilibrium. From these data, and contrary to the findings of Al-Hendy and colleagues, we can conclude that in the Flemish population, the G variant is common and that G/G homozygosity is certainly not the main cause of repeated spontaneous dizygotic twinning. Indeed, in family 19, all mothers of dizygotic twins are of the A/G phenotype and in family 18 all descendants, whether carriers or non-carriers, show the G/G phenotype with exception of one, who shows the A/G phenotype. These findings are not surprising since we found in the reported sequence of Genbank (X91747) a G nucleotide located at position 2039 and are confirming the dictation of Lewis and colleagues3Lewis CM Healy SC Martin NG Genetic contribution to DZ twinning.Am J Med Genet. 1995; 61: 237-246Crossref Scopus (39) Google Scholar that dizygotic twinning could be a tractable (though far from ideal) trait for linkage studies through which genes that have a major effect on female fertility and infertility might be detected. Follicle-stimulating-hormone receptor and twinningAuthors' reply Full-Text PDF
Publication Year: 2001
Publication Date: 2001-01-01
Language: en
Type: letter
Indexed In: ['crossref', 'pubmed']
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Cited By Count: 7
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