Increased serum FSH in female fragile X premutation carriers with either regular menstrual cycles or on oral contraceptives

Molecular Pathogenesis and Peripheral Monitoring of Adult Fragile X-Associated Syndromes

Abnormal trinucleotide expansions cause rare disorders that compromise quality of life and, in some cases, lifespan. In particular, the expansions of the CGG-repeats stretch at the 5’-UTR of the Fragile X Mental Retardation 1 (FMR1) gene have pleiotropic effects that lead to a variety of Fragile X-associated syndromes: the neurodevelopmental Fragile X syndrome (FXS) in children, the late-onset neurodegenerative disorder Fragile X-associated tremor-ataxia syndrome (FXTAS) that mainly affects adult men, the Fragile X-associated primary ovarian insufficiency (FXPOI) in adult women, and a variety of psychiatric and affective disorders that are under the term of Fragile X-associated neuropsychiatric disorders (FXAND). In this review, we will describe the pathological mechanisms of the adult “gain-of-function” syndromes that are mainly caused by the toxic actions of CGG RNA and FMRpolyG peptide. There have been intensive attempts to identify reliable peripheral biomarkers to assess disease progression and onset of specific pathological traits. Mitochondrial dysfunction, altered miRNA expression, endocrine system failure, and impairment of the GABAergic transmission are some of the affectations that are susceptible to be tracked using peripheral blood for monitoring of the motor, cognitive, psychiatric and reproductive impairment of the CGG-expansion carriers. We provided some illustrative examples from our own cohort. Understanding the association between molecular pathogenesis and biomarkers dynamics will improve effective prognosis and clinical management of CGG-expansion carriers.

The RNA-binding fragile-X mental retardation protein and its role beyond the brain

It is well-established that variations of a CGG repeat expansion in the gene FMR1, which encodes the fragile-X mental retardation protein (FMRP), cause the neurocognitive disorder, fragile-X syndrome (FXS). However, multiple observations suggest a general and complex regulatory role of FMRP in processes outside the brain: (1) FMRP is ubiquitously expressed in the body, suggesting it functions in multiple organ systems; (2) patients with FXS can exhibit a physical phenotype that is consistent with an underlying abnormality in connective tissue; (3) different CGG repeat expansion lengths in FMR1 result in different clinical outcomes due to different pathogenic mechanisms; (4) the function of FMRP as an RNA-binding protein suggests it has a general regulatory role. This review details the complex nature of FMRP and the different CGG repeat expansion lengths and the evidence supporting the essential role of the protein in a variety of biological and pathological processes.

Does the presence of AGG interruptions within the CGG repeat tract have a protective effect on the fertility phenotype of female FMR1 premutation carriers?

PURPOSE

While FMR1 premutation carriers (CGG 55-200) were shown to have reduced success with IVF treatment (lower oocyte yield), studies reporting on the association between the number of CGG repeats and patients' response to controlled ovarian hyperstimulation (COH) are inconsistent. In the present study, we aim to explore whether the number of CGG repeats in women with premutation in FMR1 gene, undergoing COH for IVF, correlates with COH variables and whether the number of AGG interruptions may function as a "protective factor" by improving the ovarian response to COH.

METHODS

Retrospective study, in an academic IVF-PGD unit. Fifty-seven consecutive FMR1 premutation carriers who underwent 285 IVF treatment cycles were included. The numbers of CGG repeats and AGG interruptions were retrieved and correlated to the demographics and COH variables.

RESULTS

There were no significant association between the numbers of CGG or the AGG interruptions and the number of oocyte retrieved or the peak estradiol levels. The lack of association was also observed when including all the IVF treatment cycles or only the first or last IVF treatment cycle. Moreover, no associations were found between the number of CGG repeats or AGG interruptions and other COH variables, i.e., duration of stimulation, the total dose of gonadotropin used, or the number of top-quality embryos.

CONCLUSIONS

No associations were observed between the number of CGG repeats or AGG interruptions and any of the COH variables. Further studies are required to identify early biomarkers of POI to empower FMR1 premutation carriers with risk assessment tools to consider procedures such as fertility preservation.

Pharmacological Reactivation of the Silenced FMR1 Gene as a Targeted Therapeutic Approach for Fragile X Syndrome

More than ~200 CGG repeats in the 5′ untranslated region of the FMR1 gene results in transcriptional silencing and the absence of the FMR1 encoded protein, FMRP. FMRP is an RNA-binding protein that regulates the transport and translation of a variety of brain mRNAs in an activity-dependent manner. The loss of FMRP causes dysregulation of many neuronal pathways and results in an intellectual disability disorder, fragile X syndrome (FXS). Currently, there is no effective treatment for FXS. In this review, we discuss reactivation of the FMR1 gene as a potential approach for FXS treatment with an emphasis on the use of small molecules to inhibit the pathways important for gene silencing.

Fragile X syndrome and fragile X-associated tremor ataxia syndrome

Fragile X-associated disorders encompass several conditions, which are caused by expansion mutations in the fragile X mental retardation 1 (FMR1) gene. Fragile X syndrome is the most common inherited etiology of intellectual disability and results from a full mutation or >200 CGG repeats in FMR1. It is associated with developmental delay, autism spectrum disorder, and seizures. Fragile X-associated tremor/ataxia syndrome is a progressive neurodegenerative disease that occurs in premutation carriers of 55-200 CGG repeats in FMR1 and is characterized by kinetic tremor, gait ataxia, parkinsonism, executive dysfunction, and neuropathy. Fragile X-associated primary ovarian insufficiency also occurs in premutation carrier women and manifests with infertility and early menopause. The diseases constituting fragile X-associated disorders differ mechanistically, due to the distinct molecular properties of premutation versus full mutations. Fragile X syndrome occurs when there is a lack of fragile X mental retardation protein (FMRP) due to FMR1 methylation and silencing. In fragile X-associated tremor ataxia syndrome, a toxic gain of function is postulated with the production of excess CGG repeat-containing FMR1 mRNA, abnormal translation of the repeat sequence leading to production of polyglycine, polyalanine, and other polypeptides and to outright deficits in translation leading to reduced FMRP at larger premutation sizes. The changes in underlying brain chemistry due to FMR1 mutations have led to therapeutic studies in these disorders, with some progress being made in fragile X syndrome. This paper also summarizes indications for testing, genetic counseling issues, and what the future holds for these disorders.

Implications of the FMR1 Premutation for Children, Adolescents, Adults, and Their Families

BACKGROUND AND OBJECTIVES

Given the nature of FMR1 gene expansions, most biological mothers, and often multiple other family members of children with fragile X syndrome (FXS), will have a premutation, which may increase individual and family vulnerabilities. This article summarizes important gaps in knowledge and notes potential implications for pediatric providers with regard to developmental and medical risks for children and adolescents with an FMR1 premutation, including possible implications into adulthood.

METHODS

A structured electronic literature search was conducted on FMR1 pre- and full mutations, yielding a total of 306 articles examined. Of these, 116 focused primarily on the premutation and are included in this review.

RESULTS

Based on the literature review, 5 topic areas are discussed: genetics and epidemiology; phenotypic characteristics of individuals with the premutation; implications for carrier parents of children with FXS; implications for the extended family; and implications for pediatricians.

CONCLUSIONS

Although the premutation phenotype is typically less severe in clinical presentation than in FXS, premutation carriers are much more common and are therefore more likely to be seen in a typical pediatric practice. In addition, there is a wide range of medical, cognitive/developmental, and psychiatric associated features that individuals with a premutation are at increased risk for having, which underscores the importance of awareness on the part of pediatricians in identifying and monitoring premutation carriers and recognizing the impact this identification may have on family members.

Study of the Genetic Etiology of Primary Ovarian Insufficiency: FMR1 Gene

Menopause is a period of women’s life characterized by the cessation of menses in a definitive way. The mean age for menopause is approximately 51 years. Primary ovarian insufficiency (POI) refers to ovarian dysfunction defined as irregular menses and elevated gonadotrophin levels before or at the age of 40 years. The etiology of POI is unknown but several genes have been reported as being of significance. The fragile X mental retardation 1 gene (FMR1) is one of the most important genes associated with POI. The FMR1 gene contains a highly polymorphic CGG repeat in the 5′ untranslated region of exon 1. Four allelic forms have been defined with respect to CGG repeat length and instability during transmission. Normal (5–44 CGG) alleles are usually transmitted from parent to offspring in a stable manner. The full mutation form consists of over 200 repeats, which induces hypermethylation of the FMR1 gene promoter and the subsequent silencing of the gene, associated with Fragile X Syndrome (FXS). Finally, FMR1 intermediate (45–54 CGG) and premutation (55–200 CGG) alleles have been principally associated with two phenotypes, fragile X tremor ataxia syndrome (FXTAS) and fragile X primary ovarian insufficiency (FXPOI).

FMR1 premutation: not only important in premature ovarian failure but also in diminished ovarian reserve

It is recognized that FMR1 premutation expansions are associated with premature ovarian failure (POF), but their role in diminished ovarian reserve (DOR) is not clearly established. Moreover, the impact of smaller repeats at the boundary of premutation and normal is less clear. Therefore, we have compared the frequency of these intermediate (45-54 repeats) and premutation (>55) sized FMR1 CGG repeats among a patients group including 188 DOR and 173 POF women and 200 controls. FSH and LH concentrations were also compared between intermediate and premutation ranges in patients. The 5' UTR of FMR1 gene was amplified using PCR. The numbers of trinucleotide repeats were confirmed by the Sanger sequencing method. The frequency of premutation was higher in POF and DOR patients in comparison with controls, but the difference in the incidence of intermediate alleles was not statistically significant among these groups. The mean level of serum FSH was higher in patients with premutation than patients with intermediate alleles. Based on the current evidence, we concluded that intermediate-sized FMR1 CGG repeat alleles should not be considered as a high-risk factor for POF and DOR.

Präimplantationsdiagnostik in den Niederlanden

Im Jahr 1995 wurde die Präimplantationsdiagnostik (PID) auf experimenteller Ebene in Maastricht eingeführt. Seit 2003 ist sie Bestandteil des Erstattungssystems des niederländischen Ministry Public Health, Welfare and Sport.

PID wird nur Paaren ermöglicht, die mit einem Risiko für eine schwerwiegende monogene Erkrankung, strukturellen Chromosomenanomalien oder mitochondrialen Erkrankungen bei ihren Nachkommen rechnen müssen. Ein Aneuploidiescreening zur Verbesserung der Erfolgsraten und assistierte Reproduktionstechnologien wie In-vitro-Fertilisation (IVF) oder Intrazytoplasmatische Spermieninjektion (ICSI) waren nie Gegenstand des PID-Programms.

2008 beschloss die niederländische Regierung, eine „National Indications Commission“ einzurichten, die bei neuen Krankheitsentitäten prüfen soll, ob die Kriterien für die Zulassung einer PID erfüllt sind: 1. die Schwere und Art der Erkrankung, 2. bestehende Möglichkeiten für Prävention und Behandlung, 3. zusätzliche medizinische Kriterien und 4. psychologische und ethische Faktoren.

Geschlechtsbestimmung (aus sozialen Gründen) ist auch in den Niederlanden, wie in den meisten europäischen Ländern, nicht erlaubt. Eine PID für die Diagnose sog. Rettungskinder ist nur dann erlaubt, wenn unabhängig hiervon eine Indikation für eine PID der genetischen Erkrankung besteht. HLA-Typisierung ohne Indikation für eine genetische Erkrankung ist hingegen nicht zulässig.

Das Maastricht University Medical Center (UMC) übernimmt die gesamte genetische Diagnostik und verfügt über die mit den Universitäten von Utrecht, Groningen und Amsterdam abgestimmten (University Medical Centre (UMC) Utrecht, University Medical Centre (UMC) Groningen and the Amsterdam Medical Centre (AMC)) SOPs für die PID-Transporte.

Zwischen 1995 und 2015 wurden insgesamt 2870 Zyklen bei 1430 Paaren durchgeführt. Der häufigste Grund für eine Überweisung zur PID war die Huntington-Krankheit, gefolgt von erblichem Brust- und Eierstockkrebs. Unter den weiteren Indikationen sind weit mehr autosomal-dominante genetisch bedingte Erkrankungen als autosomal-rezessive. Unter den zuletzt genannten stehen an erster Stelle Mukoviszidose und danach die spinale Muskelatrophie (SMA). Die Erfolgsrate liegt bei 20 % pro Zyklusbeginn und bei 25 % pro Embryonentransfer. Die Anzahl der Behandlungszyklen pro Paar liegt fast exakt bei 2,0.

Endocrine Dysfunction in Female FMR1 Premutation Carriers: Characteristics and Association with Ill Health

Female FMR1 premutation carriers (PMC) have been suggested to be at greater risk of ill health, in particular endocrine dysfunction, compared to the general population. We set out to review the literature relating to endocrine dysfunction, including premature ovarian insufficiency (POI), in female PMCs, and then to consider whether endocrine dysfunction in itself may be predictive of other illnesses in female PMCs. A systematic review and pilot data from a semi-structured health questionnaire were used. Medline, Embase, and PsycInfo were searched for papers concerning PMCs and endocrine dysfunction. For the pilot study, self-reported diagnoses in females were compared between PMCs with endocrine dysfunction (n = 18), PMCs without endocrine dysfunction (n = 14), and individuals without the premutation (n = 15). Twenty-nine papers were identified in the review; the majority concerned POI and reduced fertility, which are consistently found to be more common in PMCs than controls. There was some evidence that thyroid dysfunction may occur more frequently in subgroups of PMCs and that those with endocrine difficulties have poorer health than those without. In the pilot study, PMCs with endocrine problems reported higher levels of fibromyalgia (p = 0.03), tremor (p = 0.03), headache (p = 0.01) and obsessive-compulsive disorder (p = 0.009) than either comparison group. Further larger scale research is warranted to determine whether female PMCs are at risk of endocrine disorders other than those associated with reproduction and whether endocrine dysfunction identifies a high-risk group for the presence of other health conditions.

Is FMR1 CGG repeat length a predictor of in vitro fertilization stimulation response or outcome?

OBJECTIVE

To study a broad range of FMR1 CGG repeat lengths and assisted reproduction technology (ART) outcomes.

DESIGN

Retrospective cohort study.

SETTING

Private ART practice.

PATIENT(S)

Fresh autologous ART stimulation cycles.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Oocyte yield, live birth.

RESULT(S)

We screened 14,088 fresh autologous ART cycles from 2012 to 2015, of which 4,690 cycles in 3,290 patients met the inclusion criteria. The FMR1 repeat length was statistically significantly but weakly associated with oocyte yield and other markers of ovarian response. The receiver operating characteristic curve analysis suggested extremely limited predictive ability. Moreover, the FMR1 repeat length was not statistically significantly associated with outcomes in multivariable models, including other markers of ovarian reserve. The FMR1 repeat length was not associated with embryo quality or live birth. Only patient age had a strong ability to predict live birth.

CONCLUSION(S)

The FMR1 repeat length is associated with ART response, but only weakly. It provides no incremental predictive ability beyond the conventionally used predictors, including patient age, antimüllerian hormone concentration, antral follicle count, and follicle-stimulating hormone level. These data suggest a possible role of the FMR1 repeat length within the normal range in ovarian response but demonstrate no clinically relevant indication for testing FMR1 as a predictor of ART outcomes.

FMR6 may play a role in the pathogenesis of fragile X-associated premature ovarian insufficiency

The aim of this study was to evaluate whether long noncoding RNA accumulation play a role in the pathophysiology of fragile X-associated premature ovarian insufficiency (FXPOI). The study population consisted of 22 consecutive fragile X mental retardation 1 (FMR1) premutation carriers (CGGn 55-199 repeats) undergoing in vitro fertilization and pre-implantation genetic diagnosis (IVF-PGD) treatment. The control group consists of 11 patients, with <55 CGG repeats, undergoing IVF-ICSI for male factor infertility, matched by age, treated in the same period. After oocyte retrieval, granulosa cells from follicular fluid were washed and stored at -80 °C. RNA was transcribed to generate cDNA and the RNA levels were measured using RT-PCR. Transcripts levels in granulosa cells of long noncoding RNA's FMR4 and FMR6 were measured. In FMR1 premutation carriers there was a significant nonlinear association between the number of CGG repeats and the levels of FMR6 (p = 0.03), but not FMR4. The highest level of FMR6 was seen in women with mid-size CGG repeats (80-120). In addition, a significant negative linear correlation was observed between the number of oocytes retrieved and the RNA levels in granulosa cells of FMR6 (r = -0.53, p = 0.01) but not FMR4. Our study supports previous findings suggesting RNA toxic gain-of-function as one of the possible pathophysiologic mechanisms underlying FXPOI.

Health and reproductive experiences of women with an FMR1 premutation with and without fragile X premature ovarian insufficiency

Recently, research has indicated an increased risk for greater medical and emotional comorbidity and physical health symptoms among women with an FMR1 expansion. However, these studies have generally been limited in their ability to model multiple risk factors associated with these symptoms by small numbers (n = 112–146) of participants. This study used survey methodology to examine the health experiences of 458 adult women with the premutation with and without a history of a fragile X primary ovarian insufficiency (FXPOI) diagnosis. Results suggest similar findings to those reported in the literature with regard to the frequency of medical, emotional, and reproductive experiences of women with the premutation. In addition to expected reproductive differences, women with a diagnosis of FXPOI were also more likely to experience dizziness, nausea, and muscle weakness than women without a diagnosis of FXPOI. Women with and without FXPOI were more likely to have used reproductive assistance and were more likely to have experienced preeclampsia during at least one pregnancy than is reported in the general population. Having comorbid depression and anxiety was predictive of increased medical conditions and increased daily physical health symptoms.

Elevated levels of FMR1 mRNA in granulosa cells are associated with low ovarian reserve in FMR1 premutation carriers

Aim

To assess the role of mRNA accumulation in granulosa cells as the cause of low ovarian response among FMR1 premutation carriers undergoing pre-implantation genetic diagnosis (PGD).

Design

Case control study in an academic IVF unit. Twenty-one consecutive FMR1 premutation carriers and 15 control women were included. After oocyte retrieval the granulosa cells mRNA levels of FMR1 was measured using RT-PCR.

Results

In FMR1 premutation carriers, there was a significant non-linear association between the number of CGG repeats and the number of retrieved oocytes (p<0.0001) and a trend to granulosa cells FMR1 mRNA levels (p = 0.07). The lowest number of retrieved oocytes and the highest level of mRNA were seen in women with mid-size CGG repeats (80–120). A significant negative linear correlation was observed between the granulosa cells FMR1 mRNA levels and the number of retrieved oocytes (R² linear = 0.231, P = 0.02).

Conclusion

We suggest that there is a no-linear association between the number of CGG repeats and ovarian function, resulting from an increased granulosa cells FMR1 mRNA accumulation in FMR1 carriers in the mid-range (80–120 repeats).

Use of model systems to understand the etiology of fragile X-associated primary ovarian insufficiency (FXPOI)

Fragile X-associated primary ovarian insufficiency (FXPOI) is among the family of disorders caused by the expansion of a CGG repeat sequence in the 5' untranslated region of the X-linked gene FMR1. About 20% of women who carry the premutation allele (55 to 200 unmethylated CGG repeats) develop hypergonadotropic hypogonadism and cease menstruating before age 40. Some proportion of those who are still cycling show hormonal profiles indicative of ovarian dysfunction. FXPOI leads to subfertility and an increased risk of medical conditions associated with early estrogen deficiency. Little progress has been made in understanding the etiology of this clinically significant disorder. Understanding the molecular mechanisms of FXPOI requires a detailed knowledge of ovarian FMR1 mRNA and FMRP’s function. In humans, non-invasive methods to discriminate the mechanisms of the premutation on ovarian function are not available, thus necessitating the development of model systems. Vertebrate (mouse and rat) and invertebrate (Drosophila melanogaster) animal studies for the FMR1 premutation and ovarian function exist and have been instrumental in advancing our understanding of the disease phenotype. For example, rodent models have shown that FMRP is highly expressed in oocytes where it is important for folliculogenesis. The two premutation mouse models studied to date show evidence of ovarian dysfunction and, together, suggest that the long repeat in the transcript itself may have some pathological effect quite apart from any effect of the toxic protein. Further, ovarian morphology in young animals appears normal and the primordial follicle pool size does not differ from that of wild-type animals. However, there is a progressive premature decline in the levels of most follicle classes. Observations also include granulosa cell abnormalities and altered gene expression patterns. Further comparisons of these models are now needed to gain insight into the etiology of the ovarian dysfunction. Premutation model systems in non-human primates and those based on induced pluripotent stem cells show particular promise and will complement current models. Here, we review the characterization of the current models and describe the development and potential of the new models. Finally, we will discuss some of the molecular mechanisms that might be responsible for FXPOI.

Approaches to identify genetic variants that influence the risk for onset of fragile X-associated primary ovarian insufficiency (FXPOI): a preliminary study

Fragile X-associated primary ovarian insufficiency (FXPOI) is due to an X-linked mutation that results from the expansion of a CGG repeat sequence located in the 5′ untranslated region of the FMR1 gene (premutation, PM). About 20% of women who carry the PM have cessation of menses before age 40, a clinical condition known as premature ovarian failure (POF). This leads to a 20-fold increased risk over women in the general population. Thus, this single gene mutation has a major effect on reducing a woman's reproductive life span. Based on survival analysis of about 1300 women, we showed that the mean age at menopause among PM carriers is reduced compared with noncarriers, even after removing women who reported POF. This suggests that the majority of women with the PM, not just a subset, experience ovarian insufficiency earlier than noncarriers. To better understand the underlying mechanism of the PM and to identify genes that modify the variable expressivity of FXPOI, we conducted two pilot studies. The first focused on five common variants known to reduce age at menopause. We genotyped these SNPs in 72 women with a PM who experienced menopause and found a significant association with the total SNP risk burden and age at menopause. This suggests that these SNPs influence onset of FXPOI, after adjusting for the effect of the PM allele. In the second approach, we conducted whole genome sequencing on 10 PM carriers, five with onset of FXPOI prior to age 30 and five who experienced menopause after age 47 years. Although only a pilot study, we describe our preliminary approach to identify potential variants that may play a role in modifying onset of FXPOI and potentially play a role in idiopathic primary ovarian insufficiency. The overarching goal of both approaches is to identify predictor variants that may identify women predisposed to early onset FXPOI and to further identify genes involved in defining a woman's reproductive life span.

Associated features in females with an FMR1 premutation

Changes in the fragile X mental retardation 1 gene (FMR1) have been associated with specific phenotypes, most specifically those of fragile X syndrome (FXS), fragile X tremor/ataxia syndrome (FXTAS), and fragile X primary ovarian insufficiency (FXPOI). Evidence of increased risk for additional medical, psychiatric, and cognitive features and conditions is now known to exist for individuals with a premutation, although some features have been more thoroughly studied than others. This review highlights the literature on medical, reproductive, cognitive, and psychiatric features, primarily in females, that have been suggested to be associated with changes in the FMR1 gene. Based on this review, each feature is evaluated with regard to the strength of evidence of association with the premutation. Areas of need for additional focused research and possible intervention strategies are suggested.

The FMR1 gene, infertility, and reproductive decision-making: a review

The strongest association between FMR1 and the ovary in humans is the increased risk of premature ovarian failure (POF) in women who carry the premutation level of CGG repeats (55–199 CGGs). Research on the FMR1 gene has extended to other endpoints of relevance in the OB/GYN setting for women, including infertility and ovarian hormones. After reviewing the nomenclature changes that have occurred in recent years, this article reviews the evidence linking the length of the FMR1 repeat length to fertility and ovarian hormones (follicle stimulating hormone and anti-mullerian hormone as the primary methods to assess ovarian reserve in clinical settings). The literature is inconsistent on the association between the FMR1 trinucleotide repeat length and infertility. Elevated levels of follicle stimulating hormone have been found in women who carry the premutation; however the literature on the relationship between anti-mullerian hormone and the CGG repeat length are too disparate in design to make a summary statement. This article considers the implications of two transgenic mouse models (FXPM 130R and YAC90R) for theories on pathogenesis related to ovarian endpoints. Given the current screening/testing recommendations for reproductive age females and the variability of screening protocols in clinics, future research is recommended on pretest and posttest genetic counseling needs. Future research is also needed on ovarian health measurements across a range of CGG repeat lengths in order to interpret FMR1 test results in reproductive age women; the inconsistencies in the literature make it quite challenging to advise women on their risks related to FMR1 repeat length.

Study of FMR1 gene association with ovarian dysfunction in a sample from the Basque Country

Premature ovarian failure (POF) is defined as cessation of menses before the age of 40. The most significant single gene associated with POF is the Fragile X Mental Retardation 1 gene (FMR1). In the present work we screened women with fertility problems from the Basque Country in order to determine, whether in these women, FMR1 CGG repeat size in the intermediate and premutation range was associated with their pathology, and whether intermediate and premutation carriers had endocrine signs of diminished ovarian function, using the most established measure of ovarian reserve, the gonadotropin FSH. A patient sample of 41 women with ovarian insufficiency and a control sample of 32 women with no fertility problems from the Basque Country were examined. The patient sample was classified into three categories according to the results of the retrospective assessment of their ovarian function. In group 2 of patients, women with irregular cycles, reduced fecundity and FSH levels ≥ 10IU/l, there is a significant increase in the number of intermediate and premutation FMR1 alleles (35-54 CGG repeats). In group 3 of patients, women with amenorrhea for at least four consecutive months and FSH levels ≥ 10IU/l, a significant increase in the number of intermediate FMR1 alleles (35-54 CGG repeats) was found in patients compared with controls. In this group all the patients had a serum concentration > 40 IU/l. The results suggest that in the analysed Basque sample the FMR1 gene has a role in the aetiology of POF. However, elevated FSH levels are more related to the menstrual cycle pattern than to the CGG repeat size.

Fragile X syndrome: a pilot proton magnetic resonance spectroscopy study in premutation carriers

Purpose

There is increasing evidence that neurodevelopmental differences in people with Fragile X syndrome (FraX) may be explained by differences in glutamatergic metabolism. Premutation carriers of FraX were originally considered to be unaffected although several recent reports demonstrate neuroanatomical, cognitive, and emotional differences from controls. However there are few studies on brain metabolism in premutation carriers of FraX.

Methods

We used proton magnetic resonance spectroscopy to compare neuronal integrity of a number of brain metabolites including N-Acetyl Aspartate, Creatine + Phosphocreatinine, Choline, myoInositol, and Glutamate containing substances (Glx) in 17 male premutation carriers of FraX and 16 male healthy control individuals.

Results

There was no significant between-group difference in the concentration of any measured brain metabolites. However there was a differential increase in N-acetyl aspartate with aging in premutation FraX individuals compared to controls.

Conclusions

This is the first ¹ H-MRS study to examine premutation FraX individuals. Although we demonstrated no difference in the concentration of any of the metabolites examined between the groups, this may be due to the large age ranges included in the two samples. The differential increase in NAA levels with aging may reflect an abnormal synaptic pruning process.

FMR1 premutation carrier frequency in patients undergoing routine population-based carrier screening: insights into the prevalence of fragile X syndrome, fragile X-associated tremor/ataxia syndrome, and fragile X-associated primary ovarian insufficiency in the United States

PURPOSE

Fragile X syndrome is caused by expansion and methylation of a CGG tract in the 5' untranslated region of the FMR1 gene. The estimated frequency of expanded alleles (≥55 repeats) in the United States is 1:257-1:382, but these estimates were not calculated from unbiased populations. We sought to determine the frequency of fragile X syndrome premutation (55-200 repeats) and full mutation (>200 repeats) alleles in nonselected, unbiased populations undergoing routine carrier screening for other diseases.

METHODS

A previously validated laboratory-developed test using triplet-primed polymerase chain reaction was used to detect premutation and full mutation alleles in an unselected series of 11,759 consecutive cystic fibrosis carrier screening samples and 2011 samples submitted for screening for genetic diseases prevalent among the Ashkenazi Jewish population.

RESULTS

Premutations were identified in 48 cystic fibrosis screening samples (1:245) and 15 samples (1:134) from the Ashkenazi Jewish population. Adjusted for the ethnic mix of the US population and self-reported ethnicity in our screening population, the estimated female premutation carrier frequency in the United States was 1:178. The calculated frequency of full mutation alleles was 1:3335 overall, and the calculated premutation frequency in males was 1:400. Based on frequency of larger, ≥70 repeat alleles, and reported penetrance, the calculated fragile X-associated tremor and ataxia syndrome, and fragile X-associated primary ovarian insufficiency frequencies is 1:4848 and 1:3560, respectively.

CONCLUSION

Our calculated fragile X syndrome carrier rate is higher than previous estimates for the US population and warrants further consideration of population-based carrier screening.

Fragile X-associated disorders: a clinical overview

Fragile X Syndrome (FraX) is the most common inherited cause of learning disability worldwide. FraX is an X-linked neuro-developmental disorder involving an unstable trinucleotide repeat expansion of cytosine guanine guanine (CGG). Individuals with the full mutation of FraX have >200 GG repeats with premutation carriers having 55-200 GG repeats. A wide spectrum of physical, behavioural, cognitive, psychiatric and medical problems have been associated with both full mutation and premutation carriers of FraX. In this review, we detail the clinical profile and examine the aetiology, epidemiology, neuropathology, neuroimaging findings and possible management strategies for individuals with both the full mutation and premutation of FraX.

Increased frequency of occult fragile X-associated primary ovarian insufficiency in infertile women with evidence of impaired ovarian function

BACKGROUND

The FMR1 premutation is associated with overt primary ovarian insufficiency (POI). However, its prevalence in women with occult POI (i.e. menstrual cycles, but impaired ovarian response) has not been examined. We hypothesized that both the FMR1 premutation and intermediate allele is more frequent in infertile women with occult POI than in controls, and that a repeat length cutoff might predict occult POI.

METHODS

All subjects were menstruating women <42 years old and with no family history of unexplained mental retardation, autism or fragile X syndrome. Cases had occult POI defined by elevated FSH or poor response to gonadotrophin therapy (n = 535). Control subjects (n = 521) had infertility from other causes or were oocyte donors. Prevalence of the FMR1 premutation and intermediate alleles was examined and allele length was compared between controls and women with occult POI.

RESULTS

The frequency of the premutation (7/535 versus 1/521; P< 0.05) and intermediate alleles (17/535 versus 7/521; P< 0.05) was higher in women with occult POI than in controls. The allele with the greatest number of CGG repeats was longer in women with occult POI compared with controls (32.7 ± 7.1 versus 31.6 ± 4.3; P < 0.01). A receiver operating characteristic curve examining repeat length as a test for occult POI had an area of 0.56 ± 0.02 (P < 0.01). A repeat cutoff of 45 had a specificity of 98%, but a sensitivity of only 5% to identify occult POI. The positive predictive value was only 21% for a fertility population that has ∼ 22% of its patients with occult POI.

CONCLUSIONS

The data suggest that FMR1 premutations and intermediate alleles are increased in women with occult POI. Thus, FMR1 testing should be performed in these women as some will have fragileX-associated POI. Although the FMR1 repeat lengths were longer in women with occult POI, the data do not support the use of a repeat length cutoff to predict occult POI.

Intra-individual stability over time of standardized anti-Mullerian hormone in FMR1 premutation carriers

BACKGROUND

Carriers of a premutation (CGG repeat length 55-200) in the fragile X mental retardation (FMR1) gene are at risk for primary ovarian insufficiency (FXPOI). The anti-Müllerian hormone (AMH) level acts as a useful marker of ovarian follicle reserve and, thus, may serve to predict when this ovarian reserve becomes too low to sustain ovarian function. We investigated the intra-individual variation of AMH levels over time for premutation carriers compared with non-carriers.

METHODS

We determined AMH levels in blood samples from 240 women ascertained through fragile X families, of which 127 were premutation carriers and 113 were non-carriers. Linear mixed models were used to assess the effect of age and premutation status on AMH levels and to determine a modeled AMH value. The stability over time of the deviation of observed AMH levels from modeled levels, referred to as standardized AMH values, was assessed through correlation coefficients of 41 longitudinal samples.

RESULTS

At all ages, premutation carriers exhibited lower AMH levels. For all women, AMH was found to decrease by 10% per year. The added effect of having a premutation decreased AMH levels by 54%. The deviation of an individual's AMH level from the modeled value showed a reasonable intra-individual correlation. The Pearson correlation coefficient of two samples taken at different ages was 0.36 (P = 0.05) for non-carriers and 0.69 (P = 0.01) for carriers.

CONCLUSIONS

We developed a unique standardized AMH value, taking FMR1 premutation status and the subject's age into account, which appears to be stable over time and may serve as a predictor for FXPOI after further longitudinal assessment.

FMR1 genotype with autoimmunity-associated polycystic ovary-like phenotype and decreased pregnancy chance

The FMR1 gene partially appears to control ovarian reserve, with a specific ovarian sub-genotype statistically associated with a polycystic ovary (PCO)- like phenotype. Some forms of PCO have been associated with autoimmunity. We, therefore, investigated in multiple regression analyses associations of ovary-specific FMR1 genotypes with autoimmunity and pregnancy chances (with in vitro fertilization, IVF) in 339 consecutive infertile women (455 IVF cycles), 75 with PCO-like phenotype, adjusted for age, race/ethnicity, medication dosage and number of oocytes retrieved. Patients included 183 (54.0%) with normal (norm) and 156 (46%) with heterozygous (het) FMR1 genotypes; 133 (39.2%) demonstrated laboratory evidence of autoimmunity: 51.1% of het-norm/low, 38.3% of norm and 24.2% het-norm/high genotype and sub-genotypes demonstrated autoimmunity (p = 0.003). Prevalence of autoimmunity increased further in PCO-like phenotype patients with het-norm/low genotype (83.3%), remained unchanged with norm (34.0%) and decreased in het-norm/high women (10.0%; P<0.0001). Pregnancy rates were significantly higher with norm (38.6%) than het-norm/low (22.2%, p = 0.001). FMR1 sub-genotype het-norm/low is strongly associated with autoimmunity and decreased pregnancy chances in IVF, reaffirming the importance of the distal long arm of the X chromosome (FMR1 maps at Xq27.3) for autoimmunity, ovarian function and, likely, pregnancy chance with IVF.

Relevance of triple CGG repeats in the FMR1 gene to ovarian reserve

Most individuals demonstrate 29-30 CGG triple repeats on the FMR1 gene. This may functionally represent a normal range in regard to ovarian reserve. Higher counts reflect risk towards premature ovarian senescence, but lower counts have not been investigated before and, therefore, were the principal subject of this investigation. Amongst 316 consecutive infertility patients, 94 demonstrated <28 repeats (group A), 163 28-33 repeats (group B, considered normal repeat numbers) and 59 > or =34 repeats (group C). The three groups did not differ in age, FSH or anti-Müllerian hormone (AMH) concentrations. Neither FSH nor AMH correlated in linear regression with <28 CGG repeats. In logistic regression, AMH of < or =0.8 ng/ml (indicative of diminished ovarian reserve at all ages) was, however, significantly associated with number of repeats (P < 0.001). Every decrease by five CGG repeats in group A increased the likelihood of diminished ovarian reserve by 40%, while every increase by five CGG repeats in group C increased risk by 50% (both P < 0.002). AMH of < or =0.8 ng/ml statistically correlated overall with decreasing triple CGG repeats throughout all ranges (P < 0.001). Approximately 29-30 CGG repeats appear reflective of normal ovarian reserve, with higher and lower counts denoting similar risks towards premature ovarian senescence.

Ovarian reserve determinations suggest new function of FMR1 (fragile X gene) in regulating ovarian ageing

With regard to ovarian reserve, 26-34 triple CGG repeats on the FMR1 gene denote 'normal'. This study explores whether two-allele analyses reflects risk towards diminished ovarian reserve based on age in consecutive patients (34 oocyte donors and 305 infertility patients), longitudinally and cross-sectionally. Box and whisker plots confirmed the normal range of CGG counts. Patients were then defined as normal with both alleles in range, as heterozygous with one allele outside and as homozygous with both alleles outside of range. Ovarian reserve was assessed by anti-Müllerian hormone (AMH). Normals at young ages exhibited significantly higher AMH concentrations than either heterozygous or homozygous females (P=0.009). By approximately age 35, heterozygous women have higher AMH concentrations than normal women, while homozygous women exceed normal women shortly before age 50 years. These data support a control function of the FMR1 gene over ovarian reserve, thus defining life-long ovarian reserve patterns. Heterozygous and homozygous abnormal CGG counts reduce ovarian reserve at younger ages and improve ovarian reserve at older ages. They, thus, at expense of reduced fertility in the young, preserve fertility into older age. This function of potential evolutionary importance may explain the preservation of the FMR1 gene despite its, at times, severe neuropsychiatric risks.

The significance of the number of CGG repeats and autoantibodies in premature ovarian failure

The objective of this study was to determine whether there was a threshold for the number of CGG repeats in the FMR1 (fragile X) gene in premature ovarian ageing and premature ovarian failure and to investigate the association of this sequence with serum concentrations of anti-Müllerian hormone (AMH), inhibin B, anti-thyroid and anti-adrenal autoantibodies. In this prospective randomized controlled preliminary study, the number of triple CGG repeats and serum concentrations of FSH, AMH and aforementioned autoantibodies were evaluated in 79 women who were younger than 40 years old. FSH concentrations were between 12 and 50 IU/ml (premature ovarian ageing) in 30 women and were higher than 50 IU/ml (premature ovarian failure) in nine women; FSH concentrations were normal in 40 women. All women whose FSH concentrations were higher than 12 IU/ml had CGG repeats greater than 30. No women whose FSH concentrations were normal had a repeat number above 30. There was no significant relationship between the levels of antibodies and either CGG repeat numbers or FSH concentrations. In conclusion, the number of CGG repeats between 30 and 40 might be used to predict premature ovarian ageing and premature ovarian failure in infertile women.

Effects of race/ethnicity on triple CGG counts in the FMR1 gene in infertile women and egg donors

This cross-sectional cohort study investigated 385 females (344 infertile women and 41 oocyte donors), the numbers of CGG repeats on the FMR1 gene and differences between races/ethnicities. Traditional definitions of neuropsychiatric risks are classified as common, intermediate, premutation and full mutation ranges. Normal CGG count range was here, however, defined by box and whisker plot as 26-32 repeats (median 30). Distribution of abnormal outliers in CGG counts from this normal range was then compared between women of Caucasian, African and Asian descent. African and Asian women demonstrated a higher prevalence of two normal count alleles (65%) than Caucasians (54.3%; P=0.03). Caucasians demonstrated the highest rate of allele abnormalities (43.3%) and were the only race/ethnicity also demonstrating abnormalities in both FMR1 alleles. Asian women demonstrated significantly fewer low outlier counts than Caucasians (P=0.002) and Africans (P=0.03). This study, thus, suggests significant racial/ethnic differences in triple CGG counts on the FMR1 gene between races/ethnicities. Since CGG counts on FMR1 are associated with ovarian reserve, these findings may reflect potential differences between races/ethnicities in ovarian function and female fertility reported in the literature.

The effect of CGG repeat number on ovarian response among fragile X premutation carriers undergoing preimplantation genetic diagnosis

OBJECTIVE

To assess ovarian response among carriers of FMR1 premutation who undergo preimplantation genetic diagnosis (PGD).

DESIGN

Retrospective study.

SETTING

Academic IVF unit.

PATIENT(S)

Of 18 carriers of FMR1 premutation referred to PGD, eight had <100 CGG repeats and ten had >or=100 CGG repeats.

INTERVENTION(S)

Controlled ovarian stimulation (COH) and PGD.

MAIN OUTCOME MEASURE(S)

Correlation between the number of CGG repeats and the level of E2 at day of hCG administration, number of retrieved oocytes, number of two-pronuclear (2PN) zygotes, and dose of recombinant FSH.

RESULT(S)

There was a positive correlation between CGG repeats and the level of E2 at day of hCG administration, number of retrieved oocytes, and number of 2PN zygotes. There was a negative correlation between number of CGG repeats and the total dose of gonadotropins. The E2 level and the number of retrieved oocytes and 2PN zygotes were significantly higher and the dose of gonadotropins significantly lower for premutation patients with >or=100 CGG repeats compared with <100 CGG repeats.

CONCLUSION(S)

There is a positive correlation between E2 level, retrieved oocytes, 2PN zygotes, and number of CGG repeats. Premutation carriers with <100 CGG repeats suffer from impaired ovarian response and decreased fertilization rate.

Intermediate and premutation FMR1 alleles in women with occult primary ovarian insufficiency

OBJECTIVE

To compare the prevalence of intermediate and premutation FMR1 alleles in women with occult primary ovarian insufficiency (oPOI) and in controls.

DESIGN

Observational study.

SETTING

Division of Infertility and Service of Genetic Medicine, Geneva University Hospitals.

PATIENT(S)

The study group consisted of 27 infertile women with oPOI referred by infertility specialists for FMR1 testing in 2005-6 because of unexplained poor response to controlled ovarian hyperstimulation or altered hormonal profiles. The control group consisted of 32 women undergoing genetic testing for conditions unrelated to mental retardation or ovarian function. The DNA samples were anonymized.

INTERVENTION(S)

In the study group, data were collected concerning reproductive/family history, hormonal markers, possible fertility treatment outcomes, and results of karyotype and FMR1 testing. In the control group, FMR1 gene testing was done. The only clinical data available in controls were sex and indication for genetic testing.

MAIN OUTCOME MEASURE(S)

Distribution of FMR1 alleles.

RESULT(S)

Six (22%) of 27 women with oPOI had FMR1 alleles of >40 repeats (intermediate to premutation range), compared with one (3%) of 32 controls.

CONCLUSION(S)

These results suggest that women with oPOI might be at risk of carrying alleles in the intermediate and premutation range.

Fragile X-associated primary ovarian insufficiency: evidence for additional genetic contributions to severity

The fragile X mental retardation gene (FMR1) contains a CGG repeat sequence in its 5' untranslated region that can become unstable and expand in length from generation to generation. Alleles with expanded repeats in the range of approximately 55-199, termed premutation alleles, are associated with an increased risk for fragile-X-associated primary ovarian insufficiency (FXPOI). However, not all women who carry the premutation develop FXPOI. To determine if additional genes could explain variability in onset and severity, we used a random-effects Cox proportional hazards model to analyze age at menopause on 680 women from 225 families who have a history of fragile X syndrome and 321 women from 219 families from the general population. We tested for the presence of a residual additive genetic effect after adjustment for FMR1 repeat length, race, smoking, body mass index, and method of ascertainment. Results showed significant familial aggregation of age at menopause with an estimated additive genetic variance of 0.55-0.96 depending on the parameterization of FMR1 repeat size and definition of age at menopause (P-values ranging between 0.0002 and 0.0027). This is the first study to analyze familial aggregation of FXPOI. This result is important for proper counseling of women who carry FMR1 premutation alleles and for guidance of future studies to identify additional genes that influence ovarian insufficiency.

Reproductive health of adolescent girls who carry the FMR1 premutation: expected phenotype based on current knowledge of fragile x-associated primary ovarian insufficiency

The fragile X mental retardation 1 (FMR1) gene, located on the X chromosome, is characterized by a dynamic CGG repeat expansion in the 5' untranslated region. It has long been known that female carriers of the FMR1 premutation allele (55-199 CGG) are at risk for passing the FMR1 full mutation (> or =200 repeats) to their offspring, which results in a common form of mental retardation known as fragile X syndrome. The FMR1 premutation allele, however, also places female carriers at significantly increased risk for prematurely diminished ovarian function, which we refer to as fragile X-associated primary ovarian insufficiency (FXPOI). Although of particular concern for younger women, to date, studies of FXPOI have been restricted to women > or =18 years of age and have not specifically addressed ovarian reserve and menstrual cycle characteristics among adolescent carriers. We discuss the expected reproductive phenotype among FMR1 premutation carriers during adolescence, the associated health considerations based on our current understanding of FXPOI, and the directions for future studies.

Altered hypothalamus-pituitary-adrenal gland axis regulation in the expanded CGG-repeat mouse model for fragile X-associated tremor/ataxia syndrome

The human FMR1 gene contains an unstable CGG-repeat in its 5' untranslated region. The repeat length in the normal population is polymorphic (5-54 CGG-repeats). Individuals carrying lengths beyond 200 CGGs (i.e. the full mutation) show hypermethylation and as a consequence gene silencing of the FMR1 gene. The absence of the gene product FMRP causes the fragile X syndrome, the most common inherited form of mental retardation. Elderly carriers of the premutation (PM), which is defined as a repeat length between 55 and 200 CGGs, can develop a progressive neurodegenerative syndrome: fragile X-associated tremor/ataxia syndrome (FXTAS). The high FMR1 mRNA levels observed in cells from PM carriers have led to the hypothesis that FXTAS is caused by a pathogenic RNA gain-of-function mechanism. Apart from tremor/ataxia, specific psychiatric symptoms have been described in PM carriers with or without FXTAS. Since these symptoms could arise from elevated stress hormone levels, we investigated hypothalamic-pituitary-adrenal (HPA) axis regulation using a knock-in mouse model with an expanded CGG-repeat in the PM range (>98 repeats) in the Fmr1 gene, which shows repeat instability, and displays biochemical, phenotypic and neuropathological characteristics of FXTAS. We show elevated levels of corticosterone in serum and ubiquitin-positive inclusions in both the pituitary and adrenal gland of 100-week-old animals. In addition, we demonstrate ubiquitin-positive inclusions in the amygdala from aged expanded CGG-repeat mice. We hypothesize that altered regulation of the HPA axis and the amygdala and higher stress hormone levels in the mouse model for FXTAS may explain associated psychological symptoms in humans.

Anti-Mullerian hormone indicates early ovarian decline in fragile X mental retardation (FMR1) premutation carriers: a preliminary study

BACKGROUND

Women who carry the fragile X mental retardation (FMR1) premutation are at risk for fragile X-associated primary ovarian insufficiency. Past studies have shown that carriers who are still cycling have increased levels FSH compared with non-carriers. As anti-Mullerian hormone (AMH) has been shown as an excellent marker of ovarian decline, we examined AMH levels among premutation carriers to characterize their ovarian function.

METHODS

We determined the level of FSH and AMH in serum samples collected during early follicular phase from women who carried longer FMR1 repeat alleles (defined as >or=70 repeats, n = 40) and those with shorter repeat alleles (<70 repeats, n = 75), identified by DNA analysis. Comparisons were made stratified by age and carrier status.

RESULTS

For all age groups, AMH levels were significantly lower among longer repeat allele carriers compared to shorter repeat allele carriers (P = 0.002, 0.006 and 0.020 for women ages 18-30, 31-40 and 41-50 years, respectively). In contrast, increased FSH indicative of early ovarian decline was only evident for longer repeat allele carriers aged 31-40 years (P = 0.089, 0.001 and 0.261 for women ages 18-30, 31-40 and 41-50 years, respectively).

CONCLUSIONS

These preliminary data suggest that AMH levels indicate early ovarian decline among women with longer FMR1 repeat alleles; moreover, AMH appears to be a better marker than FSH in identifying this early decline.

Fragile X-associated tremor/ataxia syndrome: clinical features, genetics, and testing guidelines

Fragile X-associated tremor/ataxia syndrome (FXTAS) is a neurodegenerative disorder with core features of action tremor and cerebellar gait ataxia. Frequent associated findings include parkinsonism, executive function deficits and dementia, neuropathy, and dysautonomia. Magnetic Resonance Imaging studies in FXTAS demonstrate increased T2 signal intensity in the middle cerebellar peduncles (MCP sign) in the majority of patients. Similar signal alterations are seen in deep and subependymal cerebral white matter, as is general cortical and subcortical atrophy. The major neuropathological feature of FXTAS is the presence of intranuclear, neuronal, and astrocytic, inclusions in broad distribution throughout the brain and brainstem. FXTAS is caused by moderate expansions (55-200 repeats; premutation range) of a CGG trinucleotide in the fragile X mental retardation 1 (FMR1) gene, the same gene which causes fragile X syndrome when in the full mutation range (200 or greater CGG repeats). The pathogenic mechanism is related to overexpression and toxicity of the FMR1 mRNA per se. Although only recently discovered, and hence currently under-diagnosed, FXTAS is likely to be one of the most common single-gene disorders leading to neurodegeneration in males. In this report, we review information available on the clinical, radiological, and pathological features, and prevalence and management of FXTAS. We also provide guidelines for the practitioner to assist with identifying appropriate patients for DNA testing for FXTAS, as well as recommendations for genetic counseling once a diagnosis of FXTAS is made.

Rising follicle-stimulating hormone levels with age accelerate female reproductive failure

Rising serum FSH levels is one of the earliest signs of human female reproductive aging. Whether or not elevated FSH remains a passive reflection of a diminishing ovarian follicle pool or actively contributes to declining female fertility with age has not been established. We therefore investigated female reproduction in mice expressing progressively rising serum levels of transgenic human FSH (Tg-FSH, 2.5-10 IU/liter) independently of follicle depletion. We show that serum LH and estradiol levels and uterine size remained normal in Tg-FSH females, whereas ovarian weight and corpora lutea number were significantly increased up to 1.3- and 5-fold, respectively. Furthermore, the monotrophic FSH rise produced a striking biphasic effect on female fertility. Tg-FSH females less than 22 wk old delivered increased litter sizes, then beyond 23 wk, litter sizes decreased rapidly culminating in premature infertility despite continued ovary follicle development, and increased ovulation and uterine embryo implantation sites as well as normal serum levels of anti-Mullerian hormone, a marker of ovarian follicle reserve. We found that rising circulating Tg-FSH produced premature infertility by increasing embryo-fetal resorption and parturition failure with age. Thus, our Tg-FSH mice present a novel paradigm to investigate selective contributions of elevated FSH to age-related female infertility, which revealed that rising FSH levels, despite no exhaustion of ovarian reserve, actively accelerates female reproductive aging primarily by postimplantation reduction of embryo-fetal survival.

Examination of reproductive aging milestones among women who carry the FMR1 premutation

BACKGROUND

The fragile X premutation is characterized by a large CGG repeat track (55-199 repeats) in the 5' UTR of the FMR1 gene. This X-linked mutation leads to an increased risk for premature ovarian failure; interestingly, the association of repeat size with risk is non-linear. We hypothesize that the premutation-associated ovarian insufficiency is due to a diminished oocyte pool and examined reproductive aging milestones by repeat size group to determine if the same non-linear association is observed.

METHODS

We analyzed cross-sectional reproductive history questionnaire data from 948 women with a wide range of repeat sizes.

RESULTS

We have confirmed the non-linear relationship among premutation carriers for ovarian insufficiency. The mid-range repeat size group (80-100 repeats), not the highest group, had an increased risk for: altered cycle traits (shortened cycle length, irregular cycles and skipped cycles), subfertility and dizygotic twinning. Smoking, a modifiable risk, decreased the reproductive lifespan of women with the premutation by about 1 year, similar to its effect on non-carriers. As expected, premutation carriers were found to be at an increased risk for osteoporosis.

CONCLUSIONS

Possible molecular mechanisms to explain the non-linear repeat size risk for ovarian insufficiency are discussed.

Recommendations from Multi-disciplinary Focus Groups on Cascade Testing and Genetic Counseling for Fragile X-associated Disorders

The purpose of this paper is to report the outcome of a collaborative project between the Fragile X Research and Treatment Center at the Medical Investigation of Neurodevelopmental Disorders (M.I.N.D.) Institute at the University of California at Davis, the National Fragile X Foundation (NFXF), and the Centers for Disease Control and Prevention (CDC). The objective of this collaboration was to develop and disseminate protocols for genetic counseling and cascade testing for the multiple disorders associated with the fragile X mental retardation 1 (FMR1) mutation. Over the last several years, there has been increasing insight into the phenotypic range associated with both the premutation and the full mutation of the FMR1 gene. To help develop recommendations related to screening for fragile X-associated disorders, four, two day advisory focus group meetings were conducted, each with a different theme. The four themes were: (1) fragile X-associated tremor/ataxia syndrome (FXTAS); (2) premature ovarian failure (POF) and reproductive endocrinology; (3) psychiatric, behavioral and psychological issues; and (4) population screening and related ethical issues.

The FMR1 premutation and reproduction

OBJECTIVE

To update clinicians on the reproductive implications of premutations in FMR1 (fragile X mental retardation 1). Fragile X syndrome, a cause of mental retardation and autism, is due to a full mutation (>200 CGG repeats). Initially, individuals who carried the premutation (defined as more than 55 but less than 200 CGG repeats) were not considered at risk for any clinical disorders. It is now recognized that this was incorrect, specifically with respect to female reproduction.

DESIGN AND SETTING

Literature review and consensus building at two multidisciplinary scientific workshops.

CONCLUSION(S)

Convincing evidence now relates the FMR1 premutation to altered ovarian function and loss of fertility. An FMR1 mRNA gain-of-function toxicity may underlie this altered ovarian function. There are major gaps in knowledge regarding the natural history of the altered ovarian function in women who carry the FMR1 premutation, making counseling about reproductive plans a challenge. Women with premature ovarian failure are at increased risk of having an FMR1 premutation and should be informed of the availability of fragile X testing. Specialists in reproductive medicine can provide a supportive environment in which to explain the implications of FMR1 premutation testing, facilitate access to testing, and make appropriate referral to genetic counselors.

X-linked premature ovarian failure: a complex disease

Involvement of the X chromosome in premature ovarian failure was demonstrated by the relatively frequent chromosomal rearrangements in patients, but the requirement of two X chromosomes for ovarian function was quite unexplained until recently. Review of the data on chromosomal rearrangements suggests that several genes along the X chromosomes contribute to ovarian function. In most instances, no single X chromosome gene has a causative role in premature ovarian failure, and the phenotype is likely to derive from the additive effect of X-linked and non-X-linked factors. Recent data on a small group of balanced X-autosome translocations showed that X-linked premature ovarian failure might also be caused by a different mechanism, namely position effect of the X chromosome on non-X-linked genes, and suggest a peculiar organization of the X chromosome during oogenesis.

The Fragile X premutation: new insights and clinical consequences

The Fragile X syndrome (FXS, MIM 309550) is still the most prevalent cause of heritable mental retardation, with a frequency of 1/4000 males and 1/6000 females. The syndrome and its particular pattern of heredity are caused by a dynamic mutation, involving an unstable expansion of a trinucleotide (CGG) repeat at the 5' UTR of the FMR1 gene, located at Xq27.3. Expansion of this repeat region greater than 200 repeats leads to methylation-coupled silencing of the gene and absence of the Fragile X mental retardation protein (FMRP), causing the classical FXS. Individuals with expanded repeat lengths varying from 50 to 200 repeats do not exhibit the classical FXS phenotype, but are considered as fragile X premutation (PM) carriers. These premutation alleles may become unstable, only through maternal transmission, with further expansion in the next generations. For long-time, male and female premutation carriers were considered as asymptomatic. This view was, however, gradually challenged with the description and reports of different premutation-associated clinical phenotypes over the last decade.

Fragile X syndrome

Fragile X syndrome, the most common genetic disorder associated with mental retardation is caused by an expansion of the unstable CGG repeat within the FMR1 gene. Although overgrowth is not the main hallmark of this condition, the fragile X syndrome is usually included in the differential diagnosis of children with mental retardation and excess growth. This review highlights the most recent advances in the field of fragile X research.

Genetic studies to identify genes underlying menopausal age

Menopausal age is important as a retrospective marker for ovarian senescence, an early menopausal age is associated with an increased risk of cardiovascular diseases and osteoporosis, whereas a later menopausal age has been associated with an increased risk of breast cancer. The worldwide average for age at natural menopause is approximately 51 years and is more or less normally distributed with a range roughly between 40 and 60 years. Environmental factors explain only a small part of the variance and it has been proposed that genetic factors are the main source of variation. Menopausal age may be considered a continuous complex trait. Complex traits are defined as traits that are influenced by both multiple genetic and environmental factors. A category of complex traits comprises those that are measured on a continuous scale. The genomic loci that make up the genetic component are called 'quantitative trait loci' or QTLs. The first linkage study on menopausal age suggests that the involvement of the X-chromosome may not be limited to premature ovarian failure (POF), but may influence the broader spectrum of menopausal age. A potentially new locus for variation in menopausal age was allocated to chromosome 9. Further studies need to identify new candidate genes to help unravel the pathophysiology of menopausal age. It is becoming increasingly clear that, in any speciality, it should be acknowledged that genetic factors are involved in many traits and that uncovering these factors may provide insight into pathogenesis and ultimately advance prevention and treatment of disease. In this review we discuss methods and basic principles of gene finding for such traits, exemplified by menopausal age as phenotype. Furthermore, we give an overview of the state of the art of candidate gene studies and linkage studies.