Prevalence of CGG expansions of the FMR1 gene in a US population-based sample

Population-based FMR1 carrier screening among reproductive women

PURPOSE

Fragile X syndrome (FXS) is a neurodevelopmental disorder, caused by an CGG repeat expansion (FM, > 200 CGG) in the fragile X messenger ribonucleoprotein 1 (FMR1) gene. Female carriers of a premutation (PM; 55-200 CGG) can transmit the PM allele, which, depending on the CGG allele size, can expand to an allele in the FM range in the offspring.

METHODS

Carrier screening for FMR1 PM is not available in Thailand. This study aimed to investigate the prevalence of PM carriers among Thai reproductive women at the tertiary hospital. A total of 1250 females participated in this study; ages ranged from 20 to 45 years, mean of 30 years (S.D. = 6.27).

RESULTS

Two carriers of a premutation allele, with 32,62 and 32,69 CGG repeats respectively, were identified. This corresponds to 1 in 600 women or 0.17% of the population. Further, three women carrying a gray zone allele (45-54 CGG repeats) were identified (29,51; 29,49; and 30,47 CGG repeats) which equals to 1:400 women or 0.25% of the population. No FM case was detected.

CONCLUSIONS

This study heightens the importance of PM carrier screening of women of reproductive age, particularly for the higher risk of developing fragile X-associated primary ovarian insufficiency (FXPOI). Early identification of PM carrier status enhances family planning and fecundity alternatives and improves reproductive health outcomes leading to a better life.

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.

Social Communication Delay in an Unbiased Sample of Preschoolers With the FMR1 Premutation

PURPOSE

The Fragile X Messenger Ribonucleoprotein-1 (FMR1) premutation (FXpm) is a genetic variant that is common in the general population and is associated with health symptoms and disease in adulthood. However, poor understanding of the clinical phenotype during childhood has hindered the development of clinical practice guidelines for screening and intervention. Given that social communication difficulties have been widely documented in adults with the FXpm and are linked with reduced psychosocial functioning, the present study aimed to characterize the communication profile of the FXpm during early childhood.

METHOD

Eighteen children with the FXpm who were identified through cascade testing (89%) or screening at birth (11%) were compared to 21 matched typically developing children, aged 2-4 years. Participants completed standardized assessments of language (Mullen Scales of Early Learning) and adaptive communication (Vineland Adaptive Behavior Scales-II). Social communication was rated from seminaturalistic interaction samples using the Brief Observation of Social Communication Change.

RESULTS

Children with the FXpm showed delayed social communication development, with the magnitude of group differences highlighting social communication as a feature that distinguishes children with the FXpm from their peers (p = .046, ηp2 = .12). The groups did not differ on the standardized language and adaptive communication measures (ps > .297, ηp2s < .03).

CONCLUSIONS

Early screening and treatment of social communication delays may be key to optimizing outcomes for children with the FXpm. Further research is needed to replicate findings in a larger sample, delineate the trajectory and consequences of social communication difficulties across the life span in the FXpm, and determine the potential epidemiological significance of FMR1 as a mediator of developmental communication differences within the general population.

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.

Autistic Traits Associated with the Fragile X Premutation Allele: The Neurodevelopmental Profile

Although most individuals who carry the Fragile X premutation allele, defined as 55-200 CGG repeats on the X-linked FMR1 gene (Fragile X Messenger Ribonucleoprotein 1 gene), do not meet diagnostic criteria for autism spectrum disorder, there is a suggestion of increased behaviors associated with subtle autistic traits. More autism associated characteristics have been reported among adults than children. This may highlight a possible worsening developmental trajectory, variable findings due to research quality or differences in number of studies done in adults vs children, rather than true developmental changes. This review is designed to examine the neurodevelopmental profile associated with the premutation allele from a developmental perspective, focused on autistic traits.

A Comprehensive Review of Fragile X Syndrome and Fragile X Premutation Associated Conditions in Africa

Fragile X syndrome (FXS) is a genetic disorder caused by a mutation in the fragile X messenger ribonucleoprotein 1 (FMR1) gene and known to be a leading cause of inherited intellectual disability globally. It results in a range of intellectual, developmental, and behavioral problems. Fragile X premutation-associated conditions (FXPAC), caused by a smaller CGG expansion (55 to 200 CGG repeats) in the FMR1 gene, are linked to other conditions that increase morbidity and mortality for affected persons. Limited research has been conducted on the burden, characteristics, diagnosis, and management of these conditions in Africa. This comprehensive review provides an overview of the current literature on FXS and FXPAC in Africa. The issues addressed include epidemiology, clinical features, discrimination against affected persons, limited awareness and research, and poor access to resources, including genetic services and treatment programs. This paper provides an in-depth analysis of the existing worldwide data for the diagnosis and treatment of fragile X disorders. This review will improve the understanding of FXS and FXPAC in Africa by incorporating existing knowledge, identifying research gaps, and potential topics for future research to enhance the well-being of individuals and families affected by FXS and FXPAC.

"We are not a typical family anymore": Exploring the experiences and support needs of fathers of children with Fragile X syndrome in Australia

A diagnosis of the X-linked condition Fragile X syndrome (FXS) in a child commonly reveals the mother's carrier status. Previous research focused on the genetic counseling process for the child and maternal family, despite calls for more research on the support needs of fathers. This study explored experiences and support needs of fathers at least 1 year after their child's FXS diagnosis to understand barriers and enablers and optimize health outcomes for the family. In-depth interviews were conducted with 11 fathers recruited through the Australian Genetics of Learning Disability Service and the Fragile X Association. Deidentified transcripts were analyzed using thematic analysis guided by an inductive approach. Four themes emerged: (1) making life easier through understanding-yesterday and today, (2) the path to a new normal-today and tomorrow, (3) seeking information and support, and (4) what men want. Fathers reported diagnostic odysseys, postdiagnostic grief, and challenges adjusting. They highlighted difficulties in understanding their child's unique behaviors and needs, responding to their partner's psychological support needs, planning for their child's future, and navigating complex health and disability systems. Participants suggested health professionals facilitate father-to-father support and psychological counseling. These findings highlight the unmet needs of fathers and suggest that a strengths-based approach is critically important given the recognized mental health impact.

Stratification of the risk of ovarian dysfunction by studying the complexity of intermediate and premutation alleles of the FMR1 gene

FMR1 premutation female carriers are at risk of developing premature/primary ovarian insufficiency (POI) with an incomplete penetrance. In this study, we determined the CGG repeat size among 1095 women with diminished ovarian reserve (DOR) / POI and characterized the CGG/AGG substructure in 44 women carrying an abnormal FMR1 repeat expansion number, compared to a group of 25 pregnant women carrying an abnormal FMR1 CGG repeat size. Allelic complexity scores of the FMR1 gene were calculated and compared between the two groups. In the DOR/POI cohort, 2.1% of women presented with an intermediate repeat size and 1.9% with a premutation. Our results suggest that the risk of POI is highest in the mid-range of CGG repeats. We observed that the allelic score is significantly higher in POI women compared to the pregnant women group (p-value = 0.02). We suggest that a high allelic score due to more than 2 AGG interspersions in the context of an intermediate number of repetitions could favor POI. Larger studies are still needed to evaluate the relevance of this new tool for the determination of the individual risk of developing POI in women with abnormal number of CGG repeats.

Mortality in Women across the FMR1 CGG Repeat Range: The Neuroprotective Effect of Higher Education

Higher education has been shown to have neuroprotective effects, reducing the risk of Alzheimer's and Parkinson's diseases, slowing the rate of age-related cognitive decline, and is associated with lower rates of early mortality. In the present study, the association between higher education, fragile X messenger ribonucleoprotein 1 (FMR1) cytosine-guanine-guanine (CGG) repeat number, and mortality before life expectancy was investigated in a population cohort of women born in 1939. The findings revealed a significant interaction between years of higher education and CGG repeat number. Counter to the study's hypothesis, the effects of higher education became more pronounced as the number of CGG repeats increased. There was no effect of years of higher education on early mortality for women who had 25 repeats, while each year of higher education decreased the hazard of early mortality by 8% for women who had 30 repeats. For women with 41 repeats, the hazard was decreased by 14% for each additional year of higher education. The interaction remained significant after controlling for IQ and family socioeconomic status (SES) measured during high school, as well as factors measured during adulthood (family, psychosocial, health, and financial factors). The results are interpreted in the context of differential sensitivity to the environment, a conceptualization that posits that some people are more reactive to both negative and positive environmental conditions. Expansions in CGG repeats have been shown in previous FMR1 research to manifest such a differential sensitivity pattern.

Atypical vocal quality in women with the FMR1 premutation: an indicator of impaired sensorimotor control

Women with the FMR1 premutation are susceptible to motor involvement related to atypical cerebellar function, including risk for developing fragile X tremor ataxia syndrome. Vocal quality analyses are sensitive to subtle differences in motor skills but have not yet been applied to the FMR1 premutation. This study examined whether women with the FMR1 premutation demonstrate differences in vocal quality, and whether such differences relate to FMR1 genetic, executive, motor, or health features of the FMR1 premutation. Participants included 35 women with the FMR1 premutation and 45 age-matched women without the FMR1 premutation who served as a comparison group. Three sustained /a/ vowels were analyzed for pitch (mean F0), variability of pitch (standard deviation of F0), and overall vocal quality (jitter, shimmer, and harmonics-to-noise ratio). Executive, motor, and health indices were obtained from direct and self-report measures and genetic samples were analyzed for FMR1 CGG repeat length and activation ratio. Women with the FMR1 premutation had a lower pitch, larger pitch variability, and poorer vocal quality than the comparison group. Working memory was related to harmonics-to-noise ratio and shimmer in women with the FMR1 premutation. Vocal quality abnormalities differentiated women with the FMR1 premutation from the comparison group and were evident even in the absence of other clinically evident motor deficits. This study supports vocal quality analyses as a tool that may prove useful in the detection of early signs of motor involvement in this population.

Large-Scale Whole Genome Sequence Analysis of >22,000 Subjects Provides no Evidence of FMR1 Premutation Allele Involvement in Autism Spectrum Disorder

Expansion of a CGG repeat in the Fragile X Messenger Ribonucleoprotein 1 (FMR1) gene on the X chromosome is the cause of Fragile X Syndrome (FXS). The repeat length of unaffected individuals varies between 5-40 repeats, whereas >200 repeats are observed in cases of FXS. The intermediate range between 55-200 repeats is considered the premutation range and is observed in roughly 1:300 females and 1:900 males in the general population. With the availability of large-scale whole genome sequence (WGS) data and the development of computational tools to detect repeat expansions, we systematically examined the role of FMR1 premutation alleles in autism spectrum disorder (ASD) susceptibility, assess the prevalence, and consider the allelic stability between parents and offspring. We analyzed the WGS data of 22,053 subjects, including 32 FXS positive controls, 1359 population controls, and 5467 ASD families. We observed no FMR1 full mutation range repeats among the ASD parent-offspring families but identified 180 family members with premutation range alleles, which represents a higher prevalence compared to the independent WGS control sample and previous reports in the literature. A sex-specific analysis between probands and unaffected siblings did not reveal a significant increase in the burden of premutation alleles in either males or females with ASD. PCR validation, however, suggests an overestimation of the frequency of FMR1 premutation range alleles through computational analysis of WGS data. Overall, we show the utility of large-scale repeat expansion screening in WGS data and conclude that there is no apparent evidence of FMR1 premutation alleles contributing to ASD susceptibility.

Maternal FMR1 alleles expansion in newborns during transmission: a prospective cohort study

INTRODUCTION

The CGG repeats in the 5' untranslated region of the fragile X mental retardation 1 gene (FMR1) gene shows increased instability upon maternal transmission. Maternal FMR1 intermediate (45-54 repeats) and premutation (PM: 55-<200 repeats) alleles usually expand to full mutation (>200 repeats) alleles in offspring and consequently, cause fragile X syndrome (FXS) in them.

METHODS

In a prospective cohort study, Pakistani pregnant women in prenatal care were first screened for FMR1 expanded alleles. In the follow-up, pregnancy outcomes in women carrying FMR1 expanded alleles were recorded and their newborn offspring were also screened for FXS.

RESULTS

In a total of 1950 pregnant women, 89 (4.6%) were detected carriers for FMR1 expanded alleles; however, rates of detection of expanded alleles were found significantly high in women with a history of FXS. In addition, miscarriages and birth of affected newborns with FXS were significantly more common in women carrying large size PM alleles and had a history of FXS (P = 0.0494 and P = 0.0494, respectively).

CONCLUSIONS

The current study provides the first evidence of screening Pakistani pregnant women for FMR1 expanded alleles in prenatal care. Moreover, the miscarriage was also detected as a clinical predictor for FXS.

IMPACT

Offspring would have a higher risk of developing FXS due to maternal FMR1 alleles expansions during transmission. This is the first prospective cohort study in Pakistan for finding FMR1 allelic status of pregnant women and their newborn offspring in follow-up. The robust offspring risk for FXS estimated in this study may be valuable information for genetic counseling of women carriers for FMR1 expanded alleles. The family history and miscarriage were detected as effective indicators for FXS carrier screening in Pakistani women.

FMR1 CGG Repeats and Stress Influence Self-Reported Cognitive Functioning in Mothers

Variation in the FMR1 gene may affect aspects of cognition, such as executive function and memory. Environmental factors, such as stress, may also negatively impact cognitive functioning. Participants included 1,053 mothers of children with and without developmental disabilities. Participants completed self-report measures of executive function, memory, and stress (i.e., life events, parenting status), and provided DNA to determine CGG repeat length (ranging from 7 to 192 CGGs). Stress exposure significantly predicted greater self-reported difficulties in executive function and the likelihood of memory problems. Cubic CGG effects independently predicted executive function and memory difficulties, suggesting effects of both genetic variation and environmental stress exposure on cognitive functioning.

The diagnostic experience of women with fragile X-associated primary ovarian insufficiency (FXPOI)

PURPOSE

The fragile X premutation occurs when there are 55-200 CGG repeats in the 5' UTR of the FMR1 gene. An estimated 1 in 148 women carry a premutation, with 20-30% of these individuals at risk for fragile X-associated primary ovarian insufficiency (FXPOI). Diagnostic experiences of FXPOI have not previously been included in the literature, limiting insight on experiences surrounding the diagnosis. This study identifies barriers and facilitators to receiving a FXPOI diagnosis and follow-up care, which can inform care and possibly improve quality of life.

METHODS

We conducted qualitative interviews with 24 women with FXPOI exploring how FMR1 screening, physician education, and supportive care impacted their experience. Three subgroups were compared: women diagnosed through family history who have biological children, women diagnosed through family history who do not have biological children, and women diagnosed through symptoms of POI.

RESULTS

Themes from interviews included hopes for broader clinician awareness of FXPOI, clear guidelines for clinical treatment, and proper fertility workups to expand reproductive options prior to POI onset. Participants also spoke of difficulty finding centralized sources of care.

CONCLUSIONS

Our results indicate a lack of optimal care of women with a premutation particularly with respect to FMR1 screening for molecular diagnosis, short- and long-term centralized treatment, and clinical and emotional support. The creation of a "FXPOI health navigator" could serve as a centralized resource for the premutation patient population, assisting in connection to optimal treatment and appropriate referrals, including genetic counseling, mental health resources, advocacy organizations, and better-informed physicians.

Ovarian Reserve Disorders, Can We Prevent Them? A Review

The ovarian reserve is finite and begins declining from its peak at mid-gestation until only residual follicles remain as women approach menopause. Reduced ovarian reserve, or its extreme form, premature ovarian insufficiency, stems from multiple factors, including developmental, genetic, environmental exposures, autoimmune disease, or medical/surgical treatment. In many cases, the cause remains unknown and resulting infertility is not ultimately addressed by assisted reproductive technologies. Deciphering the mechanisms that underlie disorders of ovarian reserve could improve the outcomes for patients struggling with infertility, but these disorders are diverse and can be categorized in multiple ways. In this review, we will explore the topic from a perspective that emphasizes the prevention or mitigation of ovarian damage. The most desirable mode of fertoprotection is primary prevention (intervening before ablative influence occurs), as identifying toxic influences and deciphering the mechanisms by which they exert their effect can reduce or eliminate exposure and damage. Secondary prevention in the form of screening is not recommended broadly. Nevertheless, in some instances where a known genetic background exists in discrete families, screening is advised. As part of prenatal care, screening panels include some genetic diseases that can lead to infertility or subfertility. In these patients, early diagnosis could enable fertility preservation or changes in family-building plans. Finally, Tertiary Prevention (managing disease post-diagnosis) is critical. Reduced ovarian reserve has a major influence on physiology beyond fertility, including delayed/absent puberty or premature menopause. In these instances, proper diagnosis and medical therapy can reduce adverse effects. Here, we elaborate on these modes of prevention as well as proposed mechanisms that underlie ovarian reserve disorders.

Low normal FMR1 genotype in older adult women: Psychological well-being and motor function

The FMR1 gene plays a key role in adult neurogenesis and neuroplasticity, and thus may contribute to age-related health in the population. The current study focused on the "low normal" FMR1 genotype, defined by lower-than-typical numbers of FMR1 CGG repeats (<26), as a potential genetic determinant of age-related health. We characterized the effect of the low normal FMR1 genotype on psychological well-being and motor function in a racially diverse non-clinical sample of older adult women. Women with low CGG repeats were distinguished from those with CGGs falling within the mid-high end of the normal range by reduced performance on multimodal assessments of motor function and psychological well-being, with large effect sizes. Robust continuous associations were also detected between lower CGG repeat length and reduced psychological well-being, balance, and dexterity. Findings suggest that FMR1 may represent an important mediator of individual differences in age-related health; larger epidemiological studies are needed. Given that approximately 23-35% of females carry the low normal genotype, efforts to understand its clinical effects have relevance a broad swath of the aging population.

The effect of college degree attainment on neurodegenerative symptoms in genetically at-risk women

Using longitudinal data, the present study examined the association between college degree attainment and the manifestation of neurodegenerative symptoms among women (n = 93) at elevated genetic risk. The neurodegenerative symptoms investigated in this study are due to FXTAS (Fragile X-associated Tremor/Ataxia Syndrome), a condition with onset after age 50. Those at risk for FXTAS have a mutation of a single gene found on the X chromosome. FXTAS is characterized by intention tremor, gait ataxia, executive function deficits, memory issues, and neuropathy. College degree attainment has been shown to provide neuroprotective effects in the general population, delaying the development of neurodegenerative conditions such as Alzheimer's disease. For this reason, college degree attainment is a potentially salient resource for those at risk of FXTAS. The results of the present research indicated significantly more severe FXTAS symptoms in women who did not attain a college degree as compared with those who were college graduates, although the two groups were similar in age, genetic risk, household income, health behaviors, and general health problems. Furthermore, symptoms in those who did not attain a college degree worsened over the 9-year study period at a significantly faster rate than the college graduates. The association between college degree attainment and FXTAS symptoms was significantly mediated by depression, which was lower among the graduates than those who did not attain a college degree. Thus, the present research is an example of how a sociodemographic factor can mitigate neurodegenerative conditions in genetically at-risk adults.

Verbal inhibition declines among older women with high FMR1 premutation expansions: A prospective study

The FMR1 premutation has been associated with difficulties in executive functioning, including verbal inhibition. However, little is known about the longitudinal profiles of verbal inhibition among FMR1 premutation carriers, particularly in women, and how individual factors such as aging and CGG repeat length may contribute to changes in verbal inhibition over time. The present study examined verbal inhibition performance (i.e., inhibition errors) on the Hayling Sentence Completion Task in a cohort of 92 women with the FMR1 premutation across two timepoints approximately three years apart. We examined the effects of age, CGG repeat length, and their interactions on verbal inhibition over time. We also evaluated whether response latency affected verbal inhibition errors. We found no significant change in verbal inhibition in the full cohort during the three-year study period. However, a subset of FMR1 premutation carriers, namely older participants with higher CGG repeats, evidenced greater declines in verbal inhibition over time. Longer response latencies did not compensate for verbal inhibition errors. The findings suggest that a subset of women with the FMR1 premutation may be at earlier, increased risk for changes in executive functioning, which if confirmed, should be considered as part of the clinical profile associated with the premutation.

Cognitive Dysfunction in Repeat Expansion Diseases: A Review

With the development of the sequencing technique, more than 40 repeat expansion diseases (REDs) have been identified during the past two decades. Moreover, the clinical features of these diseases show some commonality, and the nervous system, especially the cognitive function was affected in part by these diseases. However, the specific cognitive domains impaired in different diseases were inconsistent. Here, we survey literature on the cognitive consequences of the following disorders presenting cognitive dysfunction and summarizing the pathogenic genes, epidemiology, and different domains affected by these diseases. We found that the cognitive domains affected in neuronal intranuclear inclusion disease (NIID) were widespread including the executive function, memory, information processing speed, attention, visuospatial function, and language. Patients with C9ORF72-frontotemporal dementia (FTD) showed impairment in executive function, memory, language, and visuospatial function. While in Huntington's disease (HD), the executive function, memory, and information processing speed were affected, in the fragile X-associated tremor/ataxia syndrome (FXTAS), executive function, memory, information processing speed, and attention were impaired. Moreover, the spinocerebellar ataxias showed broad damage in almost all the cognitive domains except for the relatively intact language ability. Some other diseases with relatively rare clinical data also indicated cognitive dysfunction, such as myotonic dystrophy type 1 (DM1), progressive myoclonus epilepsy (PME), Friedreich ataxia (FRDA), Huntington disease like-2 (HDL2), and cerebellar ataxia, neuropathy, vestibular areflexia syndrome (CANVAS). We drew a cognitive function landscape of the related REDs that might provide an aspect for differential diagnosis through cognitive domains and effective non-specific interventions for these diseases.

Family history of FXTAS is associated with age-related cognitive-linguistic decline among mothers with the FMR1 premutation

BACKGROUND

Women who carry a premutation allele of the FMR1 gene are at increased vulnerability to an array of age-related symptoms and disorders, including age-related decline in select cognitive skills. However, the risk factors for age-related decline are poorly understood, including the potential role of family history and genetic factors. In other forms of pathological aging, early decline in syntactic complexity is observed and predicts the later onset of neurodegenerative disease. To shed light on the earliest signs of degeneration, the present study characterized longitudinal changes in the syntactic complexity of women with the FMR1 premutation across midlife, and associations with family history of fragile X-associated tremor/ataxia syndrome (FXTAS) and CGG repeat length.

METHODS

Forty-five women with the FMR1 premutation aged 35-64 years at study entry participated in 1-5 longitudinal assessments spaced approximately a year apart (130 observations total). All participants were mothers of children with confirmed fragile X syndrome. Language samples were analyzed for syntactic complexity and participants provided information on family history of FXTAS. CGG repeat length was determined via molecular genetic testing.

RESULTS

Hierarchical linear models indicated that women who reported a family history of FXTAS exhibited faster age-related decline in syntactic complexity than those without a family history, with that difference emerging as the women reached their mid-50 s. CGG repeat length was not a significant predictor of age-related change.

CONCLUSIONS

Results suggest that women with the FMR1 premutation who have a family history of FXTAS may be at increased risk for neurodegenerative disease, as indicated by age-related loss of syntactic complexity. Thus, family history of FXTAS may represent a personalized risk factor for age-related disease. Follow-up study is needed to determine whether syntactic decline is an early indicator of FXTAS specifically, as opposed to being a more general age-related cognitive decline associated with the FMR1 premutation.

Fragile X Premutation: Medications, Therapy and Lifestyle Advice

The fragile X premutation is characterized by 55–200 CGG repeats in the 5ʹ untranslated region of FMR1, whereas full fragile X mutation has greater than 200 repeats and full methylation, which manifests as fragile X syndrome (FXS). The premutation spectrum of clinical involvement includes fragile X-associated tremor/ataxia syndrome (FXTAS), fragile X-associated primary ovarian insufficiency (FXPOI), and fragile X-associated neuropsychiatric disorders (FXAND). In addition, premutation carriers also suffer from various other health problems such as endocrine abnormalities and autoimmune problems. In this paper, we have discussed different health issues faced by the carriers and interventions including medications, therapy and lifestyle changes that could improve their health.

Maternal well-being and family adaptation during COVID-19 in fragile X syndrome

Mothers of children with fragile X syndrome are at increased risk of experiencing anxiety and depression due to potential genetic risk and to stress associated with parenting a child with significant behavioral, emotional, and educational support needs. During the initial shutdown and subsequent restrictions of the COVID-19 pandemic, mothers of children with fragile X reported experiencing elevated levels of anxiety and depression relative to their usual levels of well-being. Many indicated that the negative consequences of exposure to COVID-19 and related stressors, as well as the impacts of the pandemic on their family, directly affected their anxiety and depression. Mothers reported on specific sources of distress as well as potential sources of resilience and positive adaptation that occurred during the first year of the COVID-19 pandemic.

Screening for FMR1 CGG Repeat Expansion in Thai Patients with Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a complex disorder with a heterogeneous etiology. Fragile X syndrome (FXS) is recognized as the most common single gene mutation associated with ASD. FXS patients show some autistic behaviors and may be difficult to distinguish at a young age from autistic children. However, there have been no published reports on the prevalence of FXS in ASD patients in Thailand. In this study, we present a pilot study to analyze the CGG repeat sizes of the FMR1 gene in Thai autistic patients. We screened 202 unrelated Thai patients (168 males and 34 females) with nonsyndromic ASD and 212 normal controls using standard FXS molecular diagnosis techniques. The distributions of FMR1 CGG repeat sizes in the ASD and normal control groups were similar, with the two most common alleles having 29 and 30 CGG repeats, followed by an allele with 36 CGG repeats. No FMR1 full mutations or premutations were found in either ASD individuals or the normal controls. Interestingly, three ASD male patients with high normal CGG and intermediate CGG repeats (44, 46, and 53 CGG repeats) were identified, indicating that the prevalence of FMR1 intermediate alleles in Thai ASD patients was approximately 1% while these alleles were absent in the normal male controls. Our study indicates that CGG repeat expansions of the FMR1 gene may not be a common genetic cause of nonsyndromic ASD in Thai patients. However, further studies for mutations other than the CGG expansion in the FMR1 gene are required to get a better information on FXS prevalence in Thai ASD patients.

Cyclic mismatch binding ligands interact with disease-associated CGG trinucleotide repeats in RNA and suppress their translation

Fragile X-associated tremor/ataxia syndrome (FXTAS) is a late-onset neurodegenerative disorder caused by a limited expansion of CGG repeats in the FMR1 gene. Degeneration of neurons in FXTAS cell models can be triggered by accumulation of polyglycine protein (FMRpolyG), a by-product of translation initiated upstream to the repeats. Specific aims of our work included testing if naphthyridine-based molecules could (i) block FMRpolyG synthesis by binding to CGG repeats in RNA, (ii) reverse pathological alterations in affected cells and (iii) preserve the content of FMRP, translated from the same FMR1 mRNA. We demonstrate that cyclic mismatch binding ligand CMBL4c binds to RNA structure formed by CGG repeats and attenuates translation of FMRpolyG and formation of nuclear inclusions in cells transfected with vectors expressing RNA with expanded CGG repeats. Moreover, our results indicate that CMBL4c delivery can reduce FMRpolyG-mediated cytotoxicity and apoptosis. Importantly, its therapeutic potential is also observed once the inclusions are already formed. We also show that CMBL4c-driven FMRpolyG loss is accompanied by partial FMRP reduction. As complete loss of FMRP induces FXS in children, future experiments should aim at evaluation of CMBL4c therapeutic intervention in differentiated tissues, in which FMRpolyG translation inhibition might outweigh adverse effects related to FMRP depletion.

Genetic determination of the ovarian reserve: a literature review

The ovarian reserve is one of the most important indicators of female fertility. It allows for the evaluation of the number of viable oocytes. This parameter is actively used in pregnancy planning and in assisted reproductive technology application, as it determines chances of successful fertilization and healthy pregnancy. Due to increased attention towards diagnostic tests evaluating the ovarian reserve, there has been a growing interest in factors that influence the state of the ovarian reserve. True reasons for pathological changes in the ovarian reserve and volume have not yet been explored in depth, and current diagnostic screening methods often fall short in efficacy. In the following review we analyze existing data relating to the study of the ovarian reserve through genetic testing, determining specific characteristics of the ovarian reserve through genetic profiling. We explore existing studies dedicated to finding specific genetic targets influencing the state of the ovarian reserve.

The Phenotypic Profile Associated With the FMR1 Premutation in Women: An Investigation of Clinical-Behavioral, Social-Cognitive, and Executive Abilities

The FMR1 gene in its premutation (PM) state has been linked to a range of clinical and subclinical phenotypes among FMR1 PM carriers, including some subclinical traits associated with autism spectrum disorder (ASD). This study attempted to further characterize the phenotypic profile associated with the FMR1 PM by studying a battery of assessments examining clinical-behavioral traits, social-cognitive, and executive abilities in women carrying the FMR1 PM, and associations with FMR1-related variability. Participants included 152 female FMR1 PM carriers and 75 female controls who were similar in age and IQ, and screened for neuromotor impairments or signs of fragile X-associated tremor/ataxia syndrome. The phenotypic battery included assessments of ASD-related personality and language (i.e., pragmatic) traits, symptoms of anxiety and depression, four different social-cognitive tasks that tapped the ability to read internal states and emotions based on different cues (e.g., facial expressions, biological motion, and complex social scenes), and a measure of executive function. Results revealed a complex phenotypic profile among the PM carrier group, where subtle differences were observed in pragmatic language, executive function, and social-cognitive tasks that involved evaluating basic emotions and trustworthiness. The PM carrier group also showed elevated rates of ASD-related personality traits. In contrast, PM carriers performed similarly to controls on social-cognitive tasks that involved reliance on faces and biological motion. The PM group did not differ from controls on self-reported depression or anxiety symptoms. Using latent profile analysis, we observed three distinct subgroups of PM carriers who varied considerably in their performance across tasks. Among PM carriers, CGG repeat length was a significant predictor of pragmatic language violations. Results suggest a nuanced phenotypic profile characterized by subtle differences in select clinical-behavioral, social-cognitive, and executive abilities associated with the FMR1 PM in women.

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.

Family as a Context for Child Development: Mothers with the FMR1 Premutation and Their Children with Fragile X Syndrome

Fragile X syndrome (FXS) is a genetic disorder caused by changes of the FMR1 gene that is passed along among families. A range of developmental processes may be impacted with wide variation in abilities across individuals with FXS. Mothers of children with FXS are often carriers of a "premutation" expansion on the FMR1 gene, which is associated with its own clinical phenotype. These maternal features may increase individual and family vulnerabilities, including increased risk for depression and anxiety disorders and difficulties in social and cognitive ability. These characteristics may worsen with age, and potentially interact with a child's challenging behaviors and with family dynamics. Thus, families of children with FXS may experience unique challenges related to genetic risk, manifested across both children and parents, that should be considered in therapeutic planning to optimize outcomes for children and their families. In this article, we review core features of the FMR1 premutation as expressed in mothers and aspects of the family environment that interface with developmental outcomes of children with FXS. Recommendations for family-centered support services are discussed.

Men with an FMR1 premutation and their health education needs

Men who carry an FMR1 premutation are at-risk to develop a late-onset neurodegenerative disorder called fragile X-Associated Ataxia/Tremor syndrome (FXTAS). However, little is known about their health informational needs. This qualitative study is the first to describe diagnostic experiences and identify specific health information needs of male premutation carriers. In-depth qualitative interviews were conducted by phone with ten men who carry an FMR1 premutation. Interviews were analyzed using direct content analysis. Saturation was assessed through use of the Comparative Method for Themes Saturation in qualitative interviews (CoMeTS). Five themes were identified: diagnosis experience, sources of health information, desired health information, barriers to obtaining health information, and facilitators to desired health information. Participants desired information about inheritance, symptoms, expectations for disease, and actions available to slow progression. Facilitators to obtaining health information included healthcare provider knowledge, positive experiences with providers, beneficial family dynamics, participating in research, and access to experts. Barriers to obtaining health information included lack of personal knowledge, lack of healthcare provider knowledge, negative experiences with providers, and uncertainty. Addressing the educational needs of men with/at-risk for FXTAS could improve the quality of life of men who carry a fragile X premutation.

Men with FMR1 premutation alleles of less than 71 CGG repeats have low risk of being affected with fragile X-associated tremor/ataxia syndrome (FXTAS)

Fragile X-associated tremor/ataxia syndrome (FXTAS) is a late-onset condition characterised by cerebellar ataxia and intention tremor, usually found in individuals with FMR1 premutation alleles (PM-CGG expansion of 55-199 repeats). Population studies estimate that between 1 in 250 and 1 in 1600 men have a PM, with up to 45% of these men suggested to develop FXTAS by age 80. We used a Bayesian approach to compare the probability of finding a specific PM genotype in an ataxia population to a population control group and found an estimated penetrance of <1% (0.031%; CI 0.007% to 0.141%) for men with ≤70 CGGs. These findings suggest that men with a PM of ≤70 CGGs, who comprise the vast majority of those with a PM, have a much lower risk of being affected with FXTAS than previously suggested. This is an issue of growing importance for accurate genetic counselling, as those with a PM of ≤70 CGGs are increasingly detected through community carrier screening or neurodevelopmental assessment programmes.

Stress and genetics influence hair cortisol in FMR1 premutation carrier mothers of children with fragile X syndrome

To investigate genetic and environmental influences on cortisol levels, mothers of children with fragile X syndrome (FXS) were studied four times over a 7.5-year period. All participants (n = 84) were carriers of the FMR1 "premutation", a genetic condition associated with impaired HPA axis functioning. Genetic variation was indicated by expansions in the number of CGG (cytosine-guanine-guanine) repeats in the FMR1 gene (67-138 repeats in the present sample). The environmental factor was cumulative exposure to adverse life events during the study period. Cortisol was measured at the beginning of the study via saliva samples and at the end of the study via hair samples; hormone values from these two specimen types were significantly correlated. The interactions between CGG repeat number and adverse life events significantly predicted hair cortisol concentration, including after accounting for the initial salivary cortisol level. For those with fewer CGG repeats, stress exposure was associated with elevated cortisol, the expected response to stress, although women with a higher number of CGGs had a reduced cortisol response to adverse events, which might be related to HPA dysfunction. These results indicate that both exogenous and endogenous factors affect HPA functioning in this population of women.

Mild Neurological Signs in FMR1 Premutation Women in an Unselected Community-Based Cohort

BACKGROUND

Premutation-sized (55-200) CGG repeat expansions in the FMR1 gene cause fragile X-associated tremor/ataxia syndrome (FXTAS). Most studies of premutation carriers utilized reverse ascertainment to identify patients, leading to a selection bias for larger repeats. As shorter CGG premutation repeats are common in the population, understanding their impact on health outcomes has a potentially large public health footprint.

OBJECTIVE

The study's objective was to compare an unselected group of premutation carriers (n = 35, 55-101 CGG repeats) with matched controls (n = 61, 29-39 CGG repeats) with respect to FXTAS-type signs using structured neurological assessments.

METHODS

Three neurologists independently rated signs, using an adapted version of the FXTAS Rating Scale (Leehey MA, Berry-Kravis E, Goetz CG, et al. FMR1 CGG repeat length predicts motor dysfunction in premutation carriers. Neurology. 2008). This was a double-blind study, as genetic status (premutation vs. control) was known neither by the participants nor by any of the neurologists. Analyses controlled potentially confounding comorbid conditions in the electronic health record (eg, osteoarthritis and stroke) and probed the association of age with signs.

RESULTS

Although there was no overall difference between carriers and controls, among individuals without any potentially confounding comorbid diagnoses, there was a statistically significant age-associated elevation in FXTAS-type signs in premutation carriers compared to controls.

CONCLUSIONS

Among those who do not have other comorbid diagnoses, women who have CGG repeats at the lower end of the premutation range may be at greater risk for ataxia and parkinsonism than their age peers, although their overall risk of developing such clinical features is low. This study should provide reassurance to those who share characteristics with the present cohort. © 2021 International Parkinson and Movement Disorder Society.

Relationships between motor scores and cognitive functioning in FMR1 female premutation X carriers indicate early involvement of cerebello-cerebral pathways

BACKGROUND

Smaller expansions of CGG trinucleotide repeats in the FMR1 X-linked gene termed 'premutation' lead to a neurodegenerative disorder: Fragile X Associated Tremor/Ataxia Syndrome (FXTAS) in nearly half of aged carrier males, and 8-16% females. Core features include intention tremor, ataxia, and cognitive decline, and white matter lesions especially in cerebellar and periventricular locations. A 'toxic' role of elevated and expanded FMR1 mRNA has been linked to the pathogenesis of this disorder. The emerging issue concerns the trajectory of the neurodegenerative changes: is the pathogenetic effect confined to overt clinical manifestations? Here we explore the relationships between motor and cognitive scale scores in a sample of 57 asymptomatic adult female premutation carriers of broad age range.

METHODS

Three motor scale scores (ICARS-for tremor/ataxia, UPDRS-for parkinsonism, and Clinical Tremor) were related to 11 cognitive tests using Spearman's rank correlations. Robust regression, applied in relationships between all phenotypic measures, and genetic molecular and demographic data, identified age and educational levels as common correlates of these measures, which were then incorporated as confounders in correlation analysis.

RESULTS

Cognitive tests demonstrating significant correlations with motor scores were those assessing non-verbal reasoning on Matrix Reasoning (p-values from 0.006 to 0.011), and sequencing and alteration on Trails-B (p-values from 0.008 to 0.001). Those showing significant correlations with two motor scores-ICARS and Clinical Tremor- were psychomotor speed on Symbol Digit Modalities (p-values from 0.014 to 0.02) and working memory on Digit Span Backwards (p-values from 0.024 to 0.011).

CONCLUSIONS

Subtle motor impairments correlating with cognitive, particularly executive, deficits may occur in female premutation carriers not meeting diagnostic criteria for FXTAS. This pattern of cognitive deficits is consistent with those seen in other cerebellar disorders. Our results provide evidence that more than one category of clinical manifestation reflecting cerebellar changes - motor and cognitive - may be simultaneously affected by premutation carriage across a broad age range in asymptomatic carriers.

Ectopic expression of CGG-repeats alters ovarian response to gonadotropins and leads to infertility in a murine FMR1 premutation model

Women heterozygous for an expansion of CGG repeats in the 5'UTR of FMR1 risk developing fragile X-associated primary ovarian insufficiency (FXPOI) and/or tremor and ataxia syndrome (FXTAS). We show that expanded CGGs, independent of FMR1, are sufficient to drive ovarian insufficiency and that expression of CGG-containing mRNAs alone or in conjunction with a polyglycine-containing peptide translated from these RNAs contribute to dysfunction. Heterozygous females from two mouse lines expressing either CGG RNA-only (RNA-only) or CGG RNA and the polyglycine product FMRpolyG (FMRpolyG+RNA) were used to assess ovarian function in aging animals. The expression of FMRpolyG+RNA led to early cessation of breeding, ovulation and transcriptomic changes affecting cholesterol and steroid hormone biosynthesis. Females expressing CGG RNA-only did not exhibit decreased progeny during natural breeding, but their ovarian transcriptomes were enriched for alterations in cholesterol and lipid biosynthesis. The enrichment of CGG RNA-only ovaries for differentially expressed genes related to cholesterol processing provided a link to the ovarian cysts observed in both CGG-expressing lines. Early changes in transcriptome profiles led us to measure ovarian function in prepubertal females that revealed deficiencies in ovulatory responses to gonadotropins. These include impairments in cumulus expansion and resumption of oocyte meiosis, as well as reduced ovulated oocyte number. Cumulatively, we demonstrated the sufficiency of ectopically expressed CGG repeats to lead to ovarian insufficiency and that co-expression of CGG-RNA and FMRpolyG lead to premature cessation of breeding. However, the expression of CGG RNA-alone was sufficient to lead to ovarian dysfunction by impairing responses to hormonal stimulation.

Refining the risk for fragile X-associated primary ovarian insufficiency (FXPOI) by FMR1 CGG repeat size

Purpose

Approximately 20–30% of women with an FMR1 premutation experience fragile X–associated primary ovarian insufficiency (FXPOI); however, current risk estimates based on repeat size only identify women with the midrange of repeats to be at the highest risk.

Methods

To better understand the risk by repeat size, we collected self-reported reproductive histories on 1,668 women and divided them into high-resolution repeat size bins of ~5 CGG repeats to determine a more accurate risk for FXPOI in relation to CGG repeat length.

Results

As previously reported, women with 70–100 CGG repeats were at the highest risk for FXPOI using various statistical models to compare average age at menopause and risk of FXPOI, with women with 85–89 repeats being at the highest risk. Importantly, women with <65 repeats or >120 repeats did not have a significantly increased risk for FXPOI compared to women with <45 repeats.

Conclusion

Using a large cross-section study on 1,668 women, we have provided more personalized risk assessment for FXPOI using high-resolution repeat size bins. Understanding the variability in risk has important implications for family planning and overall health among women with a premutation.

A Unique Visual Attention Profile Associated With the FMR1 Premutation

Atypical visual attention patterns have been observed among carriers of the fragile X mental retardation gene (FMR1) premutation (PM), with some similarities to visual attention patterns observed in autism spectrum disorder (ASD) and among clinically unaffected relatives of individuals with ASD. Patterns of visual attention could constitute biomarkers that can help to inform the neurocognitive profile of the PM, and that potentially span diagnostic boundaries. This study examined patterns of eye movement across an array of fixation measurements from three distinct eye-tracking tasks in order to investigate potentially overlapping profiles of visual attention among PM carriers, ASD parents, and parent controls. Logistic regression analyses were conducted to examine whether variables constituting a PM-specific looking profile were able to effectively predict group membership. Participants included 65PM female carriers, 188 ASD parents, and 84 parent controls. Analyses of fixations across the eye-tracking tasks, and their corresponding areas of interest, revealed a distinct visual attention pattern in carriers of the FMR1 PM, characterized by increased fixations on the mouth when viewing faces, more intense focus on bodies in socially complex scenes, and decreased fixations on salient characters and faces while narrating a wordless picture book. This set of variables was able to successfully differentiate individuals with the PM from controls (Sensitivity = 0.76, Specificity = 0.85, Accuracy = 0.77) as well as from ASD parents (Sensitivity = 0.70, Specificity = 0.80, Accuracy = 0.72), but did not show a strong distinction between ASD parents and controls (Accuracy = 0.62), indicating that this set of variables comprises a profile that is unique to PM carriers. Regarding predictive power, fixations toward the mouth when viewing faces was able to differentiate PM carriers from both ASD parents and controls, whereas fixations toward other social stimuli did not differentiate PM carriers from ASD parents, highlighting some overlap in visual attention patterns that could point toward shared neurobiological mechanisms. Results demonstrate a profile of visual attention that appears strongly associated with the FMR1 PM in women, and may constitute a meaningful biomarker.

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.

Fragile X premutation and associated health conditions: A review

Fragile X syndrome (FXS) is the most common single gene disorder, which causes autism and intellectual disability. The fragile X mental retardation 1 (FMR1) gene is silenced when cytosine-guanine-guanine (CGG) triplet repeats exceed 200, which is the full mutation that causes FXS. Carriers of FXS have a CGG repeat between 55 and 200, which is defined as a premutation and transcription of the gene is overactive with high levels of the FMR1 mRNA. Most carriers of the premutation have normal levels of fragile X mental retardation protein (FMRP) and a normal intelligence, but in the upper range of the premutation (120-200) the FMRP level may be lower than normal. The clinical problems associated with the premutation are caused by the RNA toxicity associated with increased FMR1 mRNA levels, although for some mildly lowered FMRP can cause problems associated with FXS. The RNA toxicity causes various health problems in the carriers including but not limited to fragile X-associated tremor/ataxia syndrome, fragile X-associated primary ovarian insufficiency, and fragile X-associated neuropsychiatric disorders. Since some individuals with neuropsychiatric problems do not meet the severity for a diagnosis of a "disorder" then the condition can be labeled as fragile X premutation associated condition (FXPAC). Physicians must be able to recognize these health problems in the carriers and provide appropriate management.

Differential Progression of Motor Dysfunction Between Male and Female Fragile X Premutation Carriers Reveals Novel Aspects of Sex-Specific Neural Involvement

Expansions of the CGG repeat in the non-coding segment of the FMR1 X-linked gene are associated with a variety of phenotypic changes. Large expansions (>200 repeats), which cause a severe neurodevelopmental disorder, the fragile x syndrome (FXS), are transmitted from the mothers carrying smaller, unstable expansions ranging from 55 to 200 repeats, termed the fragile X premutation. Female carriers of this premutation may themselves experience a wide range of clinical problems throughout their lifespan, the most severe being the late onset neurodegenerative condition called "Fragile X-Associated Tremor Ataxia Syndrome" (FXTAS), occurring between 8 and 16% of these carriers. Male premutation carriers, although they do not transmit expanded alleles to their daughters, have a much higher risk (40-50%) of developing FXTAS. Although this disorder is more prevalent and severe in male than female carriers, specific sex differences in clinical manifestations and progress of the FXTAS spectrum have been poorly documented. Here we compare the pattern and rate of progression (per year) in three motor scales including tremor/ataxia (ICARS), tremor (Clinical Tremor Rating scale, CRST), and parkinsonism (UPDRS), and in several cognitive and psychiatric tests scores, between 13 female and 9 male carriers initially having at least one of the motor scores ≥10. Moreover, we document the differences in each of the clinical and cognitive measures between the cross-sectional samples of 21 female and 24 male premutation carriers of comparable ages with FXTAS spectrum disorder (FSD), that is, who manifest one or more features of FXTAS. The results of progression assessment showed that it was more than twice the rate in male than in female carriers for the ICARS-both gait ataxia and kinetic tremor domains and twice as high in males on the CRST scale. In contrast, sex difference was negligible for the rate of progress in UPDRS, and all the cognitive measures. The overall psychiatric pathology score (SCL-90), as well as Anxiety and Obsessive/Compulsive domain scores, showed a significant increase only in the female sample. The pattern of sex differences for progression in motor scores was consistent with the results of comparison between larger, cross-sectional samples of male and female carriers affected with the FSD. These results were in concert with sex-specific distribution of MRI T2 white matter hyperintensities: all males, but no females, showed the middle cerebellar peduncle white matter hyperintensities (MCP sign), although the distribution and severity of these hyperintensities in the other brain regions were not dissimilar between the two sexes. In conclusion, the magnitude and specific pattern of sex differences in manifestations and progression of clinically recorded changes in motor performance and MRI lesion distribution support, on clinical grounds, the possibility of certain sex-limited factor(s) which, beyond the predictable effect of the second, normal FMR1 alleles in female premutation carriers, may have neuroprotective effects, specifically concerning the cerebellar circuitry.

Autistic traits and mental health in women with the fragile-X premutation: maternal status versus genetic risk

BACKGROUND

Research on women with the fragile-X premutation (FX-p) has been underrepresented within the field of behavioural phenotypes.

AIMS

To understand whether the FX-p confers risk for autistic traits, depression and anxiety, independent of maternal status.

METHOD

In study 1, mothers of children with fragile-X syndrome (M-FXp; n = 51, mean age 43 years (s.d. = 5.80)) were compared with mothers of autistic children (M-ASD; n = 59, mean age 42 (s.d. = 5.80)), mothers of children with Smith-Magenis syndrome (M-SMS; n = 27, mean age 39 (s.d. = 7.20)) and mothers of typically developing children (M-TD; n = 44, mean age 40 (s.d. = 4.90)). In study 2, the M-FXp group were compared with non-mothers with the FX-p (NM-FXp; n = 17, mean age 32 (s.d. = 9.20)), typically developed non-mothers (NM-TD; n = 28, mean age 31 (s.d. = 6.80)) and the M-TD group. All participants completed an online survey, including measures of IQ, autistic traits, anxiety, depression and positive affect.

RESULTS

In study 1: the M-FXp group reported more autistic traits than the M-TD group (P < 0.05, η2 = 0.046). Anxiety and parental stress were elevated in the M-FXp, M-SMS and M-ASD groups relative to the M-TD group (all P ≤ 0.003, η2 = 0.079-0.322). In study 2: a main effect of premutation status indicated that women with the FX-p report elevated autistic traits and anxiety (P ≤ 0.007, η2 = 0.055-0.060); this did not interact with maternal status.

CONCLUSIONS

The findings indicate that women with the FX-p show an increased risk for autistic traits and anxiety. This risk is specific to the presence of the FX-p and is not fully accounted for by maternal status or the stress of caring for children with neurodevelopmental disorders.

Maternal Mental Health and Parenting Stress and Their Relationships to Characteristics of the Child With Fragile X Syndrome

Although previous research supports the notion that characteristics of both the child and the mother impact maternal well-being and parenting stress in mothers of children with FXS, more work is needed in which self-report measures are supplemented by physiological measures of stress and well-being. The inclusion of physiological measures, such as heart rate variability (HRV), may provide a window into the biological origins and consequences of maternal perceptions of their experiences, including the challenges of raising a child with developmental challenges. The proposed project, therefore, involved the collection of multimodal assessment data from mothers and their school-aged children with FXS. Further, given the importance of understanding how mothers of youth with FXS are faring in their everyday environment, the present study collected all data using telehealth procedures and wearable technology. Participants were 20 biological mothers and their children with FXS between the ages of 6 and 11 years. We measured maternal mental health and parenting stress through self-report as well as through HRV as a more objective measure of psychological well-being. We also examined the associations between these variables and child characteristics such as externalizing and internalizing behaviors as well as autism symptomatology. We found significant support for an elevated rate of depressive symptoms in the sample of mothers (35%) and some potential indicators for heightened rates of anxiety (15%) when compared to normed samples and rates in the general population. We also found that the mothers presented with an atypical HRV profile akin to those experiencing depression or chronic stress, although limitations of the present measure suggest the need for additional confirmatory research. Further, we found that child externalizing behaviors were the primary correlates of maternal well-being. These findings contribute to the growing body of literature regarding the unique challenges faced by these mother-child dyads and supports the importance of increasing the availability of services available to these mothers, not only for meeting the needs of their children's development and behavior, but in supporting their own well-being as well.

Is FMR1 CGG Repeat Number Polymorphism Associated With Phenotypic Variation in the General Population? Report From a Cohort of 5,499 Adults

FMR1 CGG repeat length was assayed in 5499 research participants (2637 men and 2862 women) in the Wisconsin Longitudinal Study (WLS), a population-based cohort. Most past research has focused on clinically-ascertained individuals with expansions in CGG repeats, either those with fragile X syndrome (> 200 CGG repeats), the FMR1 premutation (55-200 repeats), or in the gray zone (variously defined as 45-54 or 41-54 repeats). In contrast, the WLS is a unique source of data that was obtained from an unselected cohort of individuals from the general population for whom FMR1 CGG repeat length was assayed. The WLS is a random sample of one-third of all high school seniors in the state of Wisconsin in 1957. The most recent round of data collection was in 2011; thus, the study spanned over 50 years. Saliva samples were obtained from 69% of surviving members of the cohort in 2008 and 2011, from which CGG repeats were assayed. With one exception, the CGG repeat length of all members of this cohort was below 100 (ranging from 7 to 84). The present study evaluated the genotype-phenotype associations of CGG repeat number and IQ, college graduation, age at menopause, number of biological children, having a child with intellectual or developmental disabilities, and the likelihood of experiencing an episode of depression during adulthood. Linear and curvilinear effects were probed. Although effect sizes were small, significant associations were found between CGG repeat length and high school IQ score, college graduation, number of biological children, age at menopause, and the likelihood of having an episode of depression. However, there was no significant association between repeat length and having a child diagnosed with an IDD condition. This study demonstrates a continuum of phenotype effects with FMR1 repeat lengths and illustrates how research inspired by a rare genetic condition (such as fragile X syndrome) can be used to probe genotype-phenotype associations in the general population.

Experiences of the Molecular Diagnosis of Fragile X Syndrome in Ecuador

Fragile X syndrome (FXS) is the most common cause of hereditary intellectual disability and the second most common cause of intellectual disability of genetic etiology. This complex neurodevelopmental disorder is caused by an alteration in the CGG trinucleotide expansion in fragile X mental retardation gene 1 (FMR1) leading to gene silencing and the subsequent loss of its product: fragile X mental retardation protein 1 (FMRP). Molecular diagnosis is based on polymerase chain reaction (PCR) screening followed by Southern blotting (SB) or Triplet primer-PCR (TP-PCR) to determine the number of CGG repeats in the FMR1 gene. We performed, for the first time, screening in 247 Ecuadorian male individuals with clinical criteria to discard FXS. Analysis was carried out by the Genetics Service of the Hospital de Especialidades No. 1 de las Fuerzas Armadas (HE-1), Ecuador. The analysis was performed using endpoint PCR for CGG fragment expansion analysis of the FMR1 gene. Twenty-two affected males were identified as potentially carrying the full mutation in FMR1 and thus diagnosed with FXS that is 8.1% of the sample studied. The average age at diagnosis of the positive cases was 13 years of age, with most cases from the geographical area of Pichincha (63.63%). We confirmed the familial nature of the disease in four cases. The range of CGG variation in the population was 12-43 and followed a modal distribution of 27 repeats. Our results were similar to those reported in the literature; however, since it was not possible to differentiate between premutation and mutation cases, we can only establish a molecular screening approach to identify an expanded CGG repeat, which makes it necessary to generate national strategies to optimize molecular tests and establish proper protocols for the diagnosis, management, and follow-up of patients, families, and communities at risk of presenting FXS.

Response Inhibition Deficits in Women with the FMR1 Premutation are Associated with Age and Fall Risk

One in 113-178 females worldwide carry a premutation allele on the FMR1 gene. The FMR1 premutation is linked to neurocognitive and neuromotor impairments, although the phenotype is not fully understood, particularly with respect to age effects. This study sought to define oculomotor response inhibition skills in women with the FMR1 premutation and their association with age and fall risk. We employed an antisaccade eye-tracking paradigm to index oculomotor inhibition skills in 35 women with the FMR1 premutation and 28 control women. The FMR1 premutation group exhibited longer antisaccade latency and reduced accuracy relative to controls, indicating deficient response inhibition skills. Longer response latency was associated with older age in the FMR1 premutation and was also predictive of fall risk. Findings highlight the utility of the antisaccade paradigm for detecting early signs of age-related executive decline in the FMR1 premutation, which is related to fall risk. Findings support the need for clinical prevention efforts to decrease and delay the trajectory of age-related executive decline in women with the FMR1 premutation during midlife.

Large scale in silico characterization of repeat expansion variation in human genomes

Significant progress has been made in elucidating single nucleotide polymorphism diversity in the human population. However, the majority of the variation space in the genome is structural and remains partially elusive. One form of structural variation is tandem repeats (TRs). Expansion of TRs are responsible for over 40 diseases, but we hypothesize these represent only a fraction of the pathogenic repeat expansions that exist. Here we characterize long or expanded TR variation in 1,115 human genomes as well as a replication cohort of 2,504 genomes, identified using ExpansionHunter Denovo. We found that individual genomes typically harbor several rare, large TRs, generally in non-coding regions of the genome. We noticed that these large TRs are enriched in their proximity to Alu elements. The vast majority of these large TRs seem to be expansions of smaller TRs that are already present in the reference genome. We are providing this TR profile as a resource for comparison to undiagnosed rare disease genomes in order to detect novel disease-causing repeat expansions.

Quantification of Neural Activity in FMR1 Premutation Carriers during a Dynamic Sway Task using Source Localization

Fragile X-associated Tremor/Ataxia Syndrome is a genetic neurodegenerative disorder affecting carriers of the FMR1 premutation. Not all carriers develop the condition and the age of onset is somewhat variable. A greater understanding of disease progression would be beneficial. Eight carriers and five controls matched by age, sex, and dominant hand volunteered to perform a sway task on a force platform while EEG was simultaneously recorded. Sway parameters were extracted from the movement data at important timepoints throughout their sway cycles and matched to their EEG activity. Distributed source analysis was applied. While there initially appeared to be differences in neural activity between the two groups in the anterior lobe, the right posterior lobe, the right superior parietal lobule and the right parietal lobe, these differences did not survive correction for multiple comparisons.

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.

Open-label pilot clinical trial of citicoline for fragile X-associated tremor/ataxia syndrome (FXTAS)

Fragile X-associated tremor/ataxia syndrome (FXTAS) is a late onset neurodegenerative disorder that is characterized by tremor, cerebellar ataxia, frequent falls, cognitive decline, and progressive loss of motor function. There are currently no approved treatments for this disorder. The purpose of this study was to determine if citicoline was safe for the treatment of tremor and balance abnormalities and to stabilize cognitive decline in patients with FXTAS. Ten participants with diagnosed FXTAS were administered 1000 mg of citicoline once daily for 12 months. Outcome measures and neurological examination were performed at baseline, 3 months, 6 months, and 12 months. The primary outcome was the FXTAS Rating Scale score. Secondary outcomes included change in a battery of neuropsychological tests, an instrumented Timed up and go test, computerized dynamic posturography, 9-hole pegboard test, and balance confidence and psychiatric symptom questionnaires. Safety was also evaluated. Citicoline treatment resulted in minimal adverse events in all but one subject over the course of the study. There was a significant improvement in the Beck Anxiety Inventory (p = 0.03) and the Stroop Color-Word test (p = 0.03), with all other measures remaining stable over the course of 12 months. This open-label pilot trial of citicoline for individuals with FXTAS showed that it is safe and well tolerated in this population. Registration: This trial was registered at ClinicalTrials.gov. Identifier: NCT0219710.

Physiological regulation and social-emotional processing in female carriers of the FMR1 premutation

The FMR1 gene is associated with a wide range of clinical and cognitive phenotypes, ranging from intellectual disability and autism symptoms in fragile X syndrome (caused by the FMR1 full mutation), to a more varied, and still poorly understood range of clinical and cognitive phenotypes among carriers of the gene in its premutation state. Because the FMR1 premutation is relatively common among women (as high as 1 in 150), investigations of its phenotypic impact could have broad implications for understanding gene-behavior relationships underlying complex human traits, with potential clinical implications. This study investigated physiological regulation measured by pupillary responses, along with fixation patterns while viewing facial expressions among women who carry the FMR1 premutation (PM group; n = 47), to examine whether the FMR1 gene may relate to physiological regulation, social-emotional functioning, and social language skills (where subclinical differences have been previously reported among PM carriers that resemble those documented in autism-related conditions). Relative to controls (n = 25), the PM group demonstrated atypical pupillary responses and fixation patterns, controlling for IQ. In the PM group, pupillary response and fixation patterns were related to social cognition, social language abilities, and FMR1-related variation. Results indicate a pattern of atypical attention allocation among women who carry the FMR1 PM that could reflect different emotion-processing strategies mediated by autonomic dysregulation and the FMR1 gene. These findings lend insight into the FMR1 gene's potential contributions to complex human traits such as social emotional processing and social language.