FRAXA premutations are not a cause of familial premature ovarian failure

Anna Marozzi1, Leda Dalprà and Enrico Ginelli

Department of Biology and Genetics for Medical Sciences, University of Milan, Italy

Maria Grazia Tibiletti

Pathology Laboratory, Department of Clinical and Biological Sciences, University of Pavia, Varese, Italy

Pier Giorgio Crosignani

First Department of Obstetrics and Gynaecology, University of Milan, Italy

Dear Sir,

Conway et al. (1998) report that the transmission of premature ovarian failure (POF) (MIM 311360) was associated with fragile X (FRAXA) premutation in three out of 23 pedigrees. POF is defined as secondary amenorrhoea with high gonadotrophin values occurring before the age of 40. From a population of 71 women affected by POF and attending the Reproductive Endocrinology Service of the Departments of Obstetrics and Gynaecology in Milan and Varese (Vegetti et al., 1998Go), we selected a sample of 29 families showing the transmission of the condition. Pedigree analysis suggested a dominant pattern of inheritance through maternal or paternal relatives and, in five families, through both. The analysis of 29 probands indicated that the median age at POF onset was 38 years (range 20–40 years), and that menarche occurred at 12 years (range 10–18 years). Within each family the proband and all of the relatives affected by POF were phenotypically normal; women with a family history of mental retardation were excluded from the study. Furthermore, proband chromosome analysis based on high resolution banding, failed to reveal any structural anomalies. To test the possible association between POF and the fragile X premutation, peripheral blood DNA from the probands was digested with EcoRI or EcoRI/EagI, and hybridized with the StB12.3 probe, as described by Rousseu et al. (1991). Southern blot analysis revealed a FRAXA premutation in only one out of the 29 affected females (see Figure 1Go). However, the hybridization intensity of the fragment corresponding to the FRAXA premutation (5.6 kb) in the proband (II-4) was less than that observed in the premutated control (PC). This result suggests the occurrence of a post-zygote event leading to a mosaic condition in which case the FRAXA premutation can be considered a sporadic event. Moreover, the mother (I-8) showed a normal number of CCG repeats. Our data agree with the results of Kenneson et al. (1998) (who found no evidence of FRAXA premutation in a sample of 17 cases of familial POF and 108 sporadic cases, but one premutated allele in one of the control women) but differ from those reported by Conway et al. (1998) which indicate a higher than expected (Sherman, 1995Go) prevalence of FRAXA carriers among women with POF. The discrepancy between the two studies may lie in the different criteria used for the sampling, including family history and median age at menopause. Since it has been reported that the onset of menopause is earlier in FRAXA carriers (Partington et al., 1996Go), pedigrees showing the transmission of fragile X syndrome (as reported by Conway et al., 1998Go) should probably be avoided when investigating the possible association between FRAXA premutation and POF. Furthermore, Conway et al. (1998) reported a median age at menopause onset of 26, which differs from the 38 years found in our study. This difference in median age may reflect the occurence of subpopulations of women affected by POF, who may be characterised by a different aetiopathogenesis. In conclusion, any assessment as to whether FRAXA carriers are at greater risk of developing early menopause requires studies with more controlled parameters.



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Figure 1. Pedigree and Southern Blot analysis of the identified fragile X (FRAXA) carrier and her mother. I-5 and II-4 respectively ceased menstruation at 29 and 40 years. II-3 was not available for analysis, but had regular menses at the age of 48. PC = premutated FRAXA control.

 

Notes

1 To whom correspondence should be addressed Back

References

Conway, G.S., Payne, N.N., Webb, J. et al. (1998) Fragile X premutation screening in women with premature ovarian failure. Hum. Reprod., 13, 1184–1187.[Abstract]

Kenneson, A., Cramer, D.W. and Warren, S.T. (1998) Fragile X premutations are not a major cause of early menopause. Am. J. Hum. Genet., 61, 1362–1369.[ISI]

Partington, M.W., York Moore, D. and Turner, G.M. (1996) Confirmation of early menopause in fragile X carriers. Am. J. Med. Genet., 64, 370–372.[ISI][Medline]

Rousseu, F., Heitz, D., Biancalana, V et al. (1991) Direct diagnosis by DNA analysis of the fragile X syndrome of mental retardation. N. Engl. J. Med., 325, 1673–1681.[Abstract]

Sherman, S.L. (1995) The high prevalence of fragile X premutation carriers female: is this frequency unique to the French Canadian population? Am. J. Hum. Genet., 57, 991–993.[ISI][Medline]

Vegetti, W., Tibiletti, M.G., Testa, G. et al. (1998) Inheritance in idiopathic premature ovarian failure: analysis of 71 cases. Hum. Reprod., 13, 1796–1800.[Abstract]


 
Gerard S. Conway

The Middlesex Hospital, Mortimer Street, London W1N 8AA, UK

Dear Sir,

In their letter Dr Marozzi et al. present the third series of women with premature ovarian failure in whom screening for Fragile X (FRAXA) premutations has been undertaken. Neither Marozzi et al. nor Kenneson et al. (1997) detected an excess of FRAXA premutations in their studies, as was the case in our own series (Conway et al., 1998Go). The reason for these discrepancies is simply related to the difference in the age of onset of ovarian failure in each study population. The median age of menopause in the Marozzi series was 38 while in the study of Kenneson et al. (1997) only a minority of women in fact had premature menopause at all as 85% of women in their series experienced the menopause between the ages of 40 and 47. In our own series the median age of onset of amenorrhoea was 26 years (range 11–39) and in the seven women with premature ovarian failure (POF) and FRAXA permutations the median age of onset was 24 years (11–35). Quite obviously, very few women in this age group were included in either the Marrozzi or the Kenneson study.

While we did not select our patients on the basis of age, our clinic is a tertiary referral centre based in a Reproductive Endocrine unit rather than a routine menopause clinic and as such it tends to attract a younger age group. I would suggest though, that if one is studying the pathogenesis of a premature menopause it would be unhelpful to focus on the 35–40 year old age group, most of whom will form the young end of the physiological menopausal process being only 2SD below the mean age menopause at 50.8 years.

One method of verifying our observation that women with POF have an excess of FRAXA premutations is to perform the reverse experiment – screening for early ovarian failure in women known to transmit Fragile X syndrome. This in fact has been undertaken by an international consortium which found that women with FRAXA premutations but not, intriguingly, those with a full mutation, experienced an early menopause (Allingham-Hawkins, 1998). Clearly there is more to this association than can be explained by the FMRI protein alone.

References

Allingham-Hawkins, D./International Collaborative POF in Fragile X Study (1999) Fragile X premutation is a significant risk factor for premature ovarian failure. Am. J. Med. Genet., in press.

Conway, G.S., Payne, N.N., Webb, J. et al. (1998) Fragile X premutation screening in women with premature ovarian failure. Hum. Reprod., 13, 1184–1187.[Abstract]

Kenneson, A., Cramer, D.W. and Warren, S.T. (1997) Fragile X premutations are not a major cause of early menopause. Am. J. Hum. Genet., 61, 1362–1369.[ISI][Medline]