The prevalence of CGG repeat expansion mutation in FMR1 gene in the northern Chinese women of reproductive age

Strategic Implementation of Fragile X Carrier Screening in China: A Focused Pilot Study

Fragile X syndrome is the leading genetic cause of intellectual disability and autism spectrum disorders. Female premutation carriers exhibit no obvious symptoms during reproductive age, but the premutation allele can expand to full mutation when transmitted to the fetus. Given the relatively low prevalence but large population, the distinct health care system, the middle-income economic status, and low awareness among public and medical professionals, the optimal genetic screening strategy remains unknown. We conducted a pilot study of Fragile X carrier screening in China, involving 22,245 pregnant women and women with childbearing intentions, divided into control and pilot groups. The prevalence of Fragile X carriers in the control group was 1 of 850, similar to East Asian populations. Strikingly, the prevalence of Fragile X carriers in the pilot group was 1 of 356, which can be attributed to extensive medical training, participant education, and rigorous genetic counseling and testing protocols. Cost-effectiveness analyses of four strategies-no screening, population-based screening, targeted screening, and our pilot screening-indicated that our pilot screening was the most cost-effective option. A follow-up survey revealed that 55% of respondents reported undergoing screening because of their family history. We have successfully established a standardized system, addressing the challenges of low prevalence, limited awareness, and genetic testing complexities. Our study provides practical recommendations for implementing Fragile X carrier screening in China.

Attitudes of medical professionals toward fragile X carrier screening and genetic counseling in China

Fragile X syndrome is the most common inherited cause of intellectual disability. Considering China's low prevalence, distinct healthcare system, middle-income economic status, and unique culture, China cannot simply replicate the screening systems in European and American countries. In this study, we investigated the attitudes of 450 Chinese medical professionals who received fragile X training on fragile X carrier screening and genetic counseling. Before the training, 57.6% of the respondents were unfamiliar with FXS. After the training, 7.3% of participants are unable to fully master the knowledge. Furthermore, 71.8% believe that the absence of phenotypes during the reproductive age and the availability of simple and feasible testing methods are prerequisites for screening. The presence of the phenotype would still require screening. Regarding the target population, over 90% of the participants support fragile X carrier screening in high-risk pregnant women. As for influencing factors, they consider cost as the most influential factor in pregnant women's decision to undergo screening. The acceptable price range for screening is determined to be ￥200-1000 ($30-150). In terms of the issues and challenges of screening, most medical professionals support the need for genetic counseling for intermediate alleles and 55-60 repeat premutation results. Additionally, some respondents believe that informing patients' family members of positive screening results is necessary. It is also recognized that positive results may lead to anxiety for patients. The findings of this study will provide valuable information for the establishment of fragile X carrier screening system, particularly for low-prevalence or middle-income countries.

Carrier Screening Programs for Cystic Fibrosis, Fragile X Syndrome, Hemoglobinopathies and Thalassemia, and Spinal Muscular Atrophy: A Health Technology Assessment

Background

We conducted a health technology assessment to evaluate the safety, effectiveness, and cost-effectiveness of carrier screening programs for cystic fibrosis (CF), fragile X syndrome (FXS), hemoglobinopathies and thalassemia, and spinal muscular atrophy (SMA) in people who are considering a pregnancy or who are pregnant. We also evaluated the budget impact of publicly funding carrier screening programs, and patient preferences and values.

Methods

We performed a systematic literature search of the clinical evidence. We assessed the risk of bias of each included study using the Cochrane Risk of Bias tool and the Risk of Bias Assessment tool for Non-randomized Studies (RoBANS), and the quality of the body of evidence according to the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) Working Group criteria. We performed a systematic economic literature search and conducted cost-effectiveness analyses comparing preconception or prenatal carrier screening programs to no screening. We considered four carrier screening strategies: 1) universal screening with standard panels; 2) universal screening with a hypothetical expanded panel; 3) risk-based screening with standard panels; and 4) risk-based screening with a hypothetical expanded panel. We also estimated the 5-year budget impact of publicly funding preconception or prenatal carrier screening programs for the given conditions in Ontario. To contextualize the potential value of carrier screening, we spoke with 22 people who had sought out carrier screening.

Results

We included 107 studies in the clinical evidence review. Carrier screening for CF, hemoglobinopathies and thalassemia, FXS, and SMA likely results in the identification of couples with an increased chance of having an affected pregnancy (GRADE: Moderate). Screening likely impacts reproductive decision-making (GRADE: Moderate) and may result in lower anxiety among pregnant people, although the evidence is uncertain (GRADE: Very low).We included 21 studies in the economic evidence review, but none of the study findings were directly applicable to the Ontario context. Our cost-effectiveness analyses showed that in the short term, preconception or prenatal carrier screening programs identified more at-risk pregnancies (i.e., couples that tested positive) and provided more reproductive choice options compared with no screening, but were associated with higher costs. While all screening strategies had similar values for health outcomes, when comparing all strategies together, universal screening with standard panels was the most cost-effective strategy for both preconception and prenatal periods. The incremental cost-effectiveness ratios (ICERs) of universal screening with standard panels compared with no screening in the preconception period were $29,106 per additional at-risk pregnancy detected and $367,731 per affected birth averted; the corresponding ICERs in the prenatal period were about $29,759 per additional at-risk pregnancy detected and $431,807 per affected birth averted.We estimated that publicly funding a universal carrier screening program in the preconception period over the next 5 years would require between $208 million and $491 million. Publicly funding a risk-based screening program in the preconception period over the next 5 years would require between $1.3 million and $2.7 million. Publicly funding a universal carrier screening program in the prenatal period over the next 5 years would require between $128 million and $305 million. Publicly funding a risk-based screening program in the prenatal period over the next 5 years would require between $0.8 million and $1.7 million. Accounting for treatment costs of the screened health conditions resulted in a decrease in the budget impact of universally provided carrier screening programs or cost savings for risk-based programs.Participants value the perceived potential positive impact of carrier screening programs such as medical benefits from early detection and treatment, information for reproductive decision-making, and the social benefit of awareness and preparation. There was a strong preference expressed for thorough, timely, unbiased information to allow for informed reproductive decision-making.

Conclusions

Carrier screening for CF, FXS, hemoglobinopathies and thalassemia, and SMA is effective at identifying at-risk couples, and test results may impact preconception and reproductive decision-making.The cost-effectiveness and budget impact of carrier screening programs are uncertain for Ontario. Over the short term, carrier screening programs are associated with higher costs, and also higher chances of detecting at-risk pregnancies compared with no screening. The 5-year budget impact of publicly funding universal carrier screening programs is larger than that of risk-based programs. However, accounting for treatment costs of the screened health conditions results in a decrease in the total additional costs for universal carrier screening programs or in cost savings for risk-based programs.The people we spoke with who had sought out carrier screening valued the potential medical benefits of early detection and treatment, particularly the support and preparation for having a child with a potential genetic condition.

Molecular subtype identification and predictive power of N6-methyladenosine regulator in unexplained recurrent pregnancy loss

The etiology of recurrent pregnancy loss (RPL) is complicated and effective clinical preventive measures are lacking. Identifying biomarkers for RPL has been challenging, and to date, little is known about the role of N6-methyladenosine (m6A) regulators in RPL. Expression data for m6A regulators in 29 patients with RPL and 29 healthy controls were downloaded from the Gene Expression Omnibus (GEO) database. To establish a diagnostic model for unexplained RPL, differential gene expression analysis was conducting for 36 m6A regulators using least absolute shrinkage and selection operator (LASSO) regression. Unsupervised cluster analysis was conducted on hub genes, and probable mechanisms were explored using gene set enrichment analysis (GSEA) and gene ontology (GO) analysis. Correlations between m6A-related differentially expressed genes and immune infiltration were analyzed using single-sample GSEA. A total of 18 m6A regulators showed significant differences in expression in RPL: 10 were upregulated and eight were downregulated. Fifteen m6A regulators were integrated and used to construct a diagnostic model for RPL that had good predictive efficiency and robustness in differentiating RPL from control samples, with an overall area under the curve (AUC) value of 0.994. Crosstalk was identified between 10 hub genes, miRNAs, and transcription factors (TFs). For example, YTHDF2 was targeted by mir-1-3p and interacted with embryonic development-related TFs such as FOXA1 and GATA2. YTHDF2 was also positively correlated with METTL14 (r = 0.5983, p < 0.001). Two RPL subtypes (Cluster-1 and Cluster-2) with distinct hub gene signatures were identified. GSEA and GO analysis revealed that the differentially expressed genes were mainly associated with immune processes and cell cycle signaling pathway (normalized enrichment score, NES = -1.626, p < 0.001). Immune infiltration was significantly higher in Cluster-1 than in Cluster-2 (p < 0.01). In conclusion, we demonstrated that m6A modification plays a critical role in RPL. We also developed and validated a diagnostic model for RPL prediction based on m6A regulators. Finally, we identified two distinct RPL subtypes with different biological processes and immune statuses.

Fragile X Syndrome Secondary to in Vitro Fertilization With a Family Egg Donor: A Case Report and Review of the Literature

Objective: To evidence the need for screening fragile X syndrome (FXS) in egg donors in assisted reproduction protocols.

Case report: This is the report of a boy with FXS who inherited the mutated allele from an ovule donated by the mother´s sister through an assisted reproduction protocol. Identifying premutation (PM) carriers of FXS amongst gamete donors isn’t part of the obligatory genetic analysis for donors and is only considered by most of the in vitro fertility societies and guidelines as part of the extension screening tests.

Conclusion: It is cost-effective to do pre-conceptional screening for the PM or full mutation (FM) of the FMR1 gene affected in FXS in every woman undergoing assisted reproductive methods, including gamete donors even without a positive family history of intellectual disabilities. This case supports the need of rethinking the guidelines on the necessary gamete donor screening tests in assisted reproduction protocols.

Risk of intellectual disability and maternal history of spontaneous abortion: a nationwide cohort study

AIM

To investigate the association between a maternal history of spontaneous abortion and intellectual disability in children.

METHOD

This cohort study included 1 778 786 children (913 340 males, 865 085 females, 361 missing data; mean age 15y 2mo, SD 8y 11mo, range birth to 40y) born in Denmark between 1977 and 2016. Cox proportional hazard regression was used to estimate the hazard ratios (HRs) of intellectual disability.

RESULTS

The overall HR of intellectual disability for children with a maternal history of spontaneous abortion was 1.17 (95% confidence interval [CI] 1.12-1.22) and the risk for multiple spontaneous abortions (HR=1.30, 95% CI 1.20-1.40) was higher than for a single spontaneous abortion (HR=1.13, 95% CI 1.07-1.18). When only cases of inpatient intellectual disability were included, the estimates increased slightly: the overall HR was 1.22 (95% CI 1.12-1.32), the HR for multiple spontaneous abortions was 1.37 (95% CI 1.20-1.58), and the HR for a single spontaneous abortion was 1.17 (95% CI 1.07-1.28). The risks were similar regardless of whether spontaneous abortion occurred before or after the index delivery. Estimates were nearly unchanged after adjusting for preterm birth, low birthweight, or Apgar score.

INTERPRETATION

Children born to mothers with spontaneous abortion, especially multiple spontaneous abortions, may be at a higher risk of intellectual disability in later life, regardless of whether spontaneous abortion occurred before or after the index delivery. The findings have clinical implications for targeted early intervention of children with intellectual disability. What this paper adds A maternal history of spontaneous abortion was associated with a risk of intellectual disability in offspring. The risk was higher in children whose mothers previously had multiple spontaneous abortions. Similar risks were observed regardless of whether spontaneous abortion occurred before or after childbirth.

Population-based carrier screening and prenatal diagnosis of fragile X syndrome in East Asian populations

Identification of carriers of fragile X syndrome (FXS) with the subsequent prenatal diagnosis and knowledge of FXS-associated genetic profiles are essential for intervention in specific populations. We report the results of carrier screening of 39,458 East Asian adult women and prenatal diagnosis from 87 FXS carriers. The prevalence of FXS carriers and full mutation fetuses was estimated to be 1/581 and 1/3124 in East Asian populations, respectively. We confirmed the validity of the current threshold of CGG trinucleotide repeats for FMR1 categorization; the integral risks of full mutation expansion were approximately 6.0%, 43.8%, and 100% for premutation alleles with 55-74, 75-89, and ≥90 CGG repeats, respectively. The protective effect of AGG (adenine-guanine-guanine nucleotides) interruption in East Asian populations was validated, which is important in protecting premutation alleles with 75-89 CGG repeats from full mutation expansion. Finally, family history was shown not an effective indicator for FXS carrier screening in East Asian populations, and population-based screening was more cost-effective. This study provides an insight into the largest carrier screening and prenatal diagnosis for FXS in East Asian populations to date. The FXS-associated genetic profiles of East Asian populations are delineated, and population-based carrier screening is shown to be promising for FXS intervention.

Inequities in diagnosis of Fragile X syndrome in Colombia

BACKGROUND

Fragile X syndrome (FXS) is the most common cause of inherited intellectual disability and autism spectrum disorder (ASD). In Colombia, there are no screening or testing protocols established for the diagnosis of FXS. In this study, we aimed to describe the diagnostic trends of FXS in Colombia.

METHODS

Data were included on 1322 individuals obtained based on data from the only 2 databases available. Sociodemographic information and data related to the diagnostic process were obtained and included in this study.

RESULTS

The average age at the time of diagnosis for individuals with the full mutation (FM) was of 26.9 ± 2.57 years and was strongly dependent on sex and socioeconomic status. Most individuals with a molecular diagnosis were from the main cities.

CONCLUSION

The overall age of diagnosis of FXS is later in life than reports from other countries. Restricted access to molecular testing through the national health system might explain this discrepancy in Colombia.

The significance of FMR1 CGG repeats in Chinese women with premature ovarian insufficiency and diminished ovarian reserve

BACKGROUND

Previous studies have shown that there is an association between FMR1 CGG repeats and ovarian dysfunction. The aim of this study is to assess the association between the number of CGG repeats in FMR1 in Chinese patients with premature ovarian insufficiency (POI) and diminished ovarian reserve (DOR).

METHODS

This is a cross-sectional, case-control study, which enrolled 124 patients with POI, 57 patients with DOR and 111 normal menopausal controls. The demographic details along with other clinical data were recorded. The FMR1 CGG repeats were analyzed by polymerase chain reaction and microfluidic capillary electrophoresis.

RESULTS

We could detect two premutation carriers in the POI group (1.6%) and one in the control group (0.9%). No premutation carriers were identified in the DOR group. The frequency of FMR1 premutations was not different between POI or DOR and controls. The most common CGG repeat was 29 and 30, and the repeat length for allele 2 had a secondary peak around 36-39 repeats. The CGG repeats were divided into groups of five consecutive values, and the distribution of allele 1 in the POI group was different from that in the control group (P < 0.001). No statistically significant differences were found for allele 1 between DOR group vs. controls, and for allele 2 between three groups (P > 0.05).

CONCLUSIONS

The study shows that the frequency of FMR1 premutations is relatively low (1.6%) in Chinese women with POI. The distribution of allele 1 CGG repeat in patients with POI showed difference from that in healthy women.

Development of Chinese genetic reference panel for Fragile X Syndrome and its application to the screen of 10,000 Chinese pregnant women and women planning pregnancy

BACKGROUND

Fragile X syndrome (FXS) is the most common inherited form of intellectual disability caused by a CGG repeat expansion in the 5' untranslated region of the FMR1 gene. When the number of repeats exceeds 200, the gene becomes hypermethylated and is transcriptionally silenced, resulting in FXS. Other allelic forms of the gene that are studied because of their instability or phenotypic consequence include intermediate alleles (45-54 CGG repeats) and premutation alleles (55-200 repeats). Normal alleles are classified as having <45 CGG repeats. Population screening studies have been conducted among American and Australian populations; however, large population-based studies have not been completed in China.

METHODS AND RESULTS

In this work we present FXS screening results from 10,145 women of childbearing age from China. We first created and tested a standard panel that was comprised of normal, intermediate, premutation, and full mutation samples, and we performed the screening after confirming the consistency of genotyping results among laboratories.

CONCLUSION

Based on our findings, we have determined the intermediate and premutation carrier prevalence of 1/130 and 1/634, respectively, among Chinese women.