Pathological Effects of the FMR1 CGG-Repeat Polymorphism (5-55 Repeat Numbers): Systematic Review and Meta-Analysis

Ovarian reserve in patients with FMR1 gene premutation and the role of fertility preservation

INTRODUCTION

Women with premutation (PM) of the FMR1 gene may suffer from reduced ovarian reserve or even premature ovarian insufficiency (POI). We studied hormonal and ultrasound ovarian reserve, fertility and fertility preservation outcomes in these patients.

PATIENTS AND METHOD

Retrospective cohort study of 63 female FMR1 premutation carriers.

RESULTS

Sixty-three female patients bearing an FMR1 premutation were included. Median age was 30 years [26.5-35]. Median number of CGG triplets was 83 [77.2-92]. Before diagnosis of PM, 19 women (30%) had had in all 35 pregnancies, resulting in 20 births, including 7 affected children. After diagnosis of PM, 17 women (26.1%) had in all 23 pregnancies, at a median age of 34.5 years [32.2-36.0]: 2 after pre-implantation genetic diagnosis, 3 after oocyte donation, 18 spontaneously, and 5 ending in medical termination for fragile X syndrome. Thirty-three patients (52.4%) had POI diagnosis (median age, 30 years [27-34]) with median FSH level 84 IU/L [50.5-110] and median AMH level 0.08ng/mL [0.01-0.19]. After POI diagnosis, 8 women had in all 9 pregnancies: 3 following oocyte donation, and 6 spontaneous in 5 women (15.1%). Eight of the 9 pregnancies resulted in a live birth (including 2 affected children) and 1 in medical termination for trisomy 13. The median age of the 30 patients without POI was 31 years [25.2-35.0]. Thirteen women (20.6%) underwent fertility preservation, at a median age of 29 years [24-33]: FSH 7.7 IU/L [6.8-9.9], AMH 1.1ng/mL [0.95-2.1], antral follicle count 9.5 [7.7-14.7]. A median 15 oocytes [10-26] were cryopreserved in a median 2 cycles [1-3]. At the time of writing, no oocytes had yet been thawed for in-vitro fertilization.

CONCLUSIONS

This study shows the importance of early fertility preservation after diagnosis of FMR1 premutation in women, due to early deterioration of ovarian reserve. Genetic counseling is essential in these patients, as spontaneous pregnancies are not uncommon, even in cases of impaired ovarian reserve, and can lead to birth of affected children.

Cytosine-guanine-guanine repeats of FMR1 gene negatively affect ovarian reserve and response in Chinese women

RESEARCH QUESTION

Do cytosine-guanine-guanine (CGG) repeats of the FMR1 gene affect ovarian function, ovarian response and assisted reproductive technology (ART) outcomes in Chinese women?

DESIGN

A retrospective cohort study of 5869 women who underwent 8932 ART cycles at Women's Hospital, School of Medicine, Zhejiang University between January 2018 and June 2021. Basic hormone level, oocyte yield, embryo quality and the rate of live birth were considered as main outcome measures to evaluate the effects of CGG repeats on ovarian function, ovarian response and ART outcomes.

RESULTS

The CGG repeats were negatively related to serum anti-Müllerian hormone (AMH), oestradiol, antral follicle count (AFC) and oocyte yield. A significant association was found between serum AMH, oestradiol and AFC even after age was controlled for. No statistically significant association, however, was found between CGG repeats and embryo quality or live birth rate. Ovarian function mediated the association between CGG repeats and ovarian response.

CONCLUSION

Increased CGG repeats on the FMR1 gene were associated with diminished ovarian function and poor ovarian response, and ovarian function played an intermediary role in the relationship between CGG repeats and ovarian response.

Searching for female reproductive aging and longevity biomarkers

Female reproductive aging is, in a way, a biological phenomenon that develops along canonical molecular pathways; however, it has particular features. Recent studies revealed complexity of the interconnections between reproductive aging and aging of other systems, and even suggested a cause-effect uncertainty between them. It was also shown that reproductive aging can impact aging processes in an organism at the level of cells, tissues, organs, and systems. Women at the end of their reproductive lives are characterized by the accelerated incidence of age-related diseases. Timing of the onset of menarche and menopause and variability in the duration of reproductive life carry a latent social risk: not having enough information about the reproductive potential, women keep on postponing childbirth. Identification and use of the most accurate and sensitive aging biomarkers enable the prediction of menopause timing and quantification of the true biological and reproductive ages of an organism. We discuss current views on reproductive aging and peculiarities of using available biomarkers of aging. We also consider latest advances in the search for potential genetic markers of reproductive aging. Finally, we posit the importance of determining the female biological age and highlight potential research directions in this area.

Mitochondrial ROS, uncoupled from ATP synthesis, determine endothelial activation for both physiological recruitment of patrolling cells and pathological recruitment of inflammatory cells

Mitochondrial reactive oxygen species (mtROS) are signaling molecules, which drive inflammatory cytokine production and T cell activation. In addition, cardiovascular diseases, cancers, and autoimmune diseases all share a common feature of increased mtROS level. Both mtROS and ATP are produced as a result of electron transport chain activity, but it remains enigmatic whether mtROS could be generated independently from ATP synthesis. A recent study shed light on this important question and found that, during endothelial cell (EC) activation, mtROS could be upregulated in a proton leak-coupled, but ATP synthesis-uncoupled manner. As a result, EC could upregulate mtROS production for physiological EC activation without compromising mitochondrial membrane potential and ATP generation, and consequently without causing mitochondrial damage and EC death. Thus, a novel pathophysiological role of proton leak in driving mtROS production was uncovered for low grade EC activation, patrolling immunosurveillance cell trans-endothelial migration and other signaling events without compromising cellular survival. This new working model explains how mtROS could be increasingly generated independently from ATP synthesis and endothelial damage or death. Mapping the connections among mitochondrial metabolism, physiological EC activation, patrolling cell migration, and pathological inflammation is significant towards the development of novel therapies for inflammatory diseases and cancers.