Static and dynamic postural control deficits in aging fragile X mental retardation 1 (FMR1) gene premutation carriers

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

INTRODUCTION

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

PATIENTS AND METHOD

Retrospective cohort study of 63 female FMR1 premutation carriers.

RESULTS

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

CONCLUSIONS

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

Digital Measures of Postural Sway Quantify Balance Deficits in Spinocerebellar Ataxia

BACKGROUND

Maintaining balance is crucial for independence and quality of life. Loss of balance is a hallmark of spinocerebellar ataxia (SCA).

OBJECTIVE

The aim of this study was to identify which standing balance conditions and digital measures of body sway were most discriminative, reliable, and valid for quantifying balance in SCA.

METHODS

Fifty-three people with SCA (13 SCA1, 13 SCA2, 14 SCA3, and 13 SCA6) and Scale for Assessment and Rating of Ataxia (SARA) scores 9.28 ± 4.36 and 31 healthy controls were recruited. Subjects stood in six test conditions (natural stance, feet together and tandem, each with eyes open [EO] and eyes closed [EC]) with an inertial sensor on their lower back for 30 seconds (×2). We compared test completion rate, test-retest reliability, and areas under the receiver operating characteristic curve (AUC) for seven digital sway measures. Pearson's correlations related sway with the SARA and the Patient-Reported Outcome Measure of Ataxia (PROM ataxia).

RESULTS

Most individuals with SCA (85%-100%) could stand for 30 seconds with natural stance EO or EC, and with feet together EO. The most discriminative digital sway measures (path length, range, area, and root mean square) from the two most reliable and discriminative conditions (natural stance EC and feet together EO) showed intraclass correlation coefficients from 0.70 to 0.91 and AUCs from 0.83 to 0.93. Correlations of sway with SARA were significant (maximum r = 0.65 and 0.73). Correlations with PROM ataxia were mild to moderate (maximum r = 0.56 and 0.34).

CONCLUSION

Inertial sensor measures of extent of postural sway in conditions of natural stance EC and feet together stance EO were discriminative, reliable, and valid for monitoring SCA. © 2024 International Parkinson and Movement Disorder Society.

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.

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.

Optimal time lags from causal prediction model help stratify and forecast nervous system pathology

Traditional clinical approaches diagnose disorders of the nervous system using standardized observational criteria. Although aiming for homogeneity of symptoms, this method often results in highly heterogeneous disorders. A standing question thus is how to automatically stratify a given random cohort of the population, such that treatment can be better tailored to each cluster's symptoms, and severity of any given group forecasted to provide neuroprotective therapies. In this work we introduce new methods to automatically stratify a random cohort of the population composed of healthy controls of different ages and patients with different disorders of the nervous systems. Using a simple walking task and measuring micro-fluctuations in their biorhythmic motions, we combine non-linear causal network connectivity analyses in the temporal and frequency domains with stochastic mapping. The methods define a new type of internal motor timings. These are amenable to create personalized clinical interventions tailored to self-emerging clusters signaling fundamentally different types of gait pathologies. We frame our results using the principle of reafference and operationalize them using causal prediction, thus renovating the theory of internal models for the study of neuromotor control.

Genomic, Clinical, and Behavioral Characterization of 15q11.2 BP1-BP2 Deletion (Burnside-Butler) Syndrome in Five Families

The 15q11.2 BP1-BP2 deletion (Burnside-Butler) syndrome is emerging as the most common cytogenetic finding in patients with neurodevelopmental or autism spectrum disorders (ASD) presenting for microarray genetic testing. Clinical findings in Burnside-Butler syndrome include developmental and motor delays, congenital abnormalities, learning and behavioral problems, and abnormal brain findings. To better define symptom presentation, we performed comprehensive cognitive and behavioral testing, collected medical and family histories, and conducted clinical genetic evaluations. The 15q11.2 BP1-BP2 region includes the TUBGCP5, CYFIP1, NIPA1, and NIPA2 genes. To determine if additional genomic variation outside of the 15q11.2 region influences expression of symptoms in Burnside-Butler syndrome, whole-exome sequencing was performed on the parents and affected children for the first time in five families with at least one parent and child with the 15q1l.2 BP1-BP2 deletion. In total, there were 453 genes with possibly damaging variants identified across all of the affected children. Of these, 99 genes had exclusively de novo variants and 107 had variants inherited exclusively from the parent without the deletion. There were three genes (APBB1, GOLGA2, and MEOX1) with de novo variants that encode proteins evidenced to interact with CYFIP1. In addition, one other gene of interest (FAT3) had variants inherited from the parent without the deletion and encoded a protein interacting with CYFIP1. The affected individuals commonly displayed a neurodevelopmental phenotype including ASD, speech delay, abnormal reflexes, and coordination issues along with craniofacial findings and orthopedic-related connective tissue problems. Of the 453 genes with variants, 35 were associated with ASD. On average, each affected child had variants in 6 distinct ASD-associated genes (x¯ = 6.33, sd = 3.01). In addition, 32 genes with variants were included on clinical testing panels from Clinical Laboratory Improvement Amendments (CLIA) approved and accredited commercial laboratories reflecting other observed phenotypes. Notably, the dataset analyzed in this study was small and reported results will require validation in larger samples as well as functional follow-up. Regardless, we anticipate that results from our study will inform future research into the genetic factors influencing diverse symptoms in patients with Burnside-Butler syndrome, an emerging disorder with a neurodevelopmental behavioral phenotype.

Delineating the Relationships Between Motor, Cognitive-Executive and Psychiatric Symptoms in Female FMR1 Premutation Carriers

Introduction: Premutation expansions (55-200 CGG repeats) of the Fragile X Mental Retardation 1 (FMR1) gene on the X chromosome are associated with a range of clinical features. Apart from the most severe - Fragile X-Associated Tremor/Ataxia Syndrome (FXTAS) - where the most typical white matter changes affect cerebellar peduncles, more subtle changes may include impairment of executive functioning, affective disorders and/or subtle motor changes. Here we aimed to examine whether performance in selected components of executive functioning is associated with subclinical psychiatric symptoms in non-FXTAS, adult females carrying the FMR1 premutation. Methods and Sample: A total of 47 female premutation carriers (sub-symptomatic for FXTAS) of wide age range (26-77 years; M = 50.3; SD = 10.9) were assessed using standard neuropsychological tests, three motor rating scales and self-reported measures of psychiatric symptoms using the Symptom Checklist-90-Revised (SCL-90-R). Results: After adjusting for age and educational level where appropriate, both non-verbal reasoning and response inhibition as assessed on the Stroop task (i.e., the ability to resolve cognitive interference) were associated with a range of primary psychiatric symptom dimensions, and response inhibition uniquely predicted some primary symptoms and global psychiatric features. Importantly, lower scores (worse performance) in response inhibition were also strongly correlated with higher (worse) scores on standard motor rating scales for tremor-ataxia and for parkinsonism. Conclusion: These results provide evidence for the importance of response inhibition in the manifestation of psychiatric symptoms and subtle tremor-ataxia motor features, suggestive of the presence of early cerebellar changes in female premutation carriers.

Upper and Lower Limb Movement Kinematics in Aging FMR1 Gene Premutation Carriers

Fragile X-associated tremor/ataxia syndrome (FXTAS) is a neurodegenerative disorder associated with a premutation cytosine-guanine-guanine (CGG) trinucleotide repeat expansion of the FMR1 gene. FXTAS is estimated to be the most common single-gene form of ataxia in the aging population. Gait ataxia and intention tremor are the primary behavioral symptoms of FXTAS, though clinical evaluation of these symptoms often is subjective, contributing to difficulties in reliably differentiating individuals with FXTAS and asymptomatic premutation carriers. This study aimed to clarify the extent to which quantitative measures of gait and upper limb kinematics may serve as biobehavioral markers of FXTAS degeneration. Nineteen premutation carriers (aged 46-77 years), including 9 with possible, probable, or definite FXTAS and 16 sex- and IQ-matched healthy controls, completed tests of non-constrained walking and reaching while both standing (static reaching) and walking (dynamic reaching) to quantify gait and upper limb control, respectively. For the non-constrained walking task, participants wore reflective markers and walked at their preferred speed on a walkway. During the static reaching task, participants reached and lifted boxes of different sizes while standing. During the dynamic reaching task, participants walked to reach and lift the boxes. Movement kinematics were examined in relation to clinical ratings of neuromotor impairments and CGG repeat length. During non-constrained walking, individuals with FXTAS showed decreased stride lengths and stride velocities, increased percentages of double support time, and increased variabilities of cadence and center of mass relative to both asymptomatic premutation carriers and controls. While individuals with FXTAS did not show any static reaching differences relative to the other two groups, they showed multiple differences during dynamic reaching trials, including reduced maximum reaching velocity, prolonged acceleration time, and jerkier movement of the shoulder, elbow, and hand. Gait differences during non-constrained walking were associated with more severe clinically rated posture and gait symptoms. Reduced maximum reaching velocity and increased jerkiness during dynamic reaching were each related to more severe clinically rated kinetic dysfunction and overall neuromotor symptoms in FMR1 premutation carriers. Our findings suggest kinematic alterations consistent with gait ataxia and upper limb bradykinesia are each selectively present in individuals with FXTAS, but not asymptomatic aging premutation carriers. Consistent with neuropathological and magnetic resonance imaging (MRI) studies of FXTAS, these findings implicate cerebellar and basal ganglia degeneration associated with neuromotor decline. Our results showing associations between quantitative kinematic differences in FXTAS and clinical ratings suggest that objective assessments of gait and reaching behaviors may serve as critical and reliable targets for detecting FXTAS risk and monitoring progression.

Cerebellar-cortical function and connectivity during sensorimotor behavior in aging FMR1 gene premutation carriers

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FMR1 premutation carriers show increased variability in motor control.

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Premutation carriers show reduced extrastriate activation during motor behavior.

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Premutation carriers show reduced extrastriate-cerebellar functional connectivity.

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Reduced extrastriate-cerebellar functional connectivity is related to motor issues.

Introduction

Premutation carriers of the FMR1 gene are at risk of developing fragile X-associated tremor/ataxia syndrome (FXTAS), a neurodegenerative disease characterized by motor, cognitive, and psychiatric decline as well as cerebellar and cerebral white matter pathology. Several studies have documented preclinical sensorimotor issues in aging premutation carriers, but the extent to which sensorimotor brain systems are affected and may represent early indicators of atypical neurodegeneration has not been determined.

Materials and methods

Eighteen healthy controls and 16 FMR1 premutation carriers (including five with possible, probable, or definite FXTAS) group-matched on age, sex, and handedness completed a visually guided precision gripping task with their right hand during fMRI. During the test, they used a modified pinch grip to press at 60% of their maximum force against a custom fiber-optic transducer. Participants viewed a horizontal white force bar that moved upward with increased force and downward with decreased force and a static target bar that was red during rest and turned green to cue the participant to begin pressing at the beginning of each trial. Participants were instructed to press so that the white force bar stayed as steady as possible at the level of the green target bar. Trials were 2-sec in duration and alternated with 2-sec rest periods. Five 24-sec blocks consisting of six trials were presented. Participants’ reaction time, the accuracy of their force relative to the target force, and the variability of their force accuracy across trials were examined. BOLD signal change and task-based functional connectivity (FC) were examined during force vs. rest.

Results

Relative to healthy controls, premutation carriers showed increased trial-to-trial variability of force output, though this was specific to younger premutation carriers in our sample. Relative to healthy controls, premutation carriers also showed reduced extrastriate activation during force relative to rest. FC between ipsilateral cerebellar Crus I and extrastriate cortex was reduced in premutation carriers compared to controls. Reduced Crus I-extrastriate FC was related to increased force accuracy variability in premutation carriers. Increased reaction time was associated with more severe clinically rated neurological abnormalities.

Conclusions

Findings of reduced activation in extrastriate cortex and reduced Crus I-extrastriate FC implicate deficient visual feedback processing and reduced cerebellar modulation of corrective motor commands. Our results are consistent with documented cerebellar pathology and visual-spatial processing in FXTAS and pre-symptomatic premutation carriers, and suggest FC alterations of cerebellar-cortical networks during sensorimotor behavior may represent a “prodromal” feature associated with FXTAS degeneration.

Aging with Autism Departs Greatly from Typical Aging

Autism has been largely portrayed as a psychiatric and childhood disorder. However, autism is a lifelong neurological condition that evolves over time through highly heterogeneous trajectories. These trends have not been studied in relation to normative aging trajectories, so we know very little about aging with autism. One aspect that seems to develop differently is the sense of movement, inclusive of sensory kinesthetic-reafference emerging from continuously sensed self-generated motions. These include involuntary micro-motions eluding observation, yet routinely obtainable in fMRI studies to rid images of motor artifacts. Open-access repositories offer thousands of imaging records, covering 5-65 years of age for both neurotypical and autistic individuals to ascertain the trajectories of involuntary motions. Here we introduce new computational techniques that automatically stratify different age groups in autism according to probability distance in different representational spaces. Further, we show that autistic cross-sectional population trajectories in probability space fundamentally differ from those of neurotypical controls and that after 40 years of age, there is an inflection point in autism, signaling a monotonically increasing difference away from age-matched normative involuntary motion signatures. Our work offers new age-appropriate stochastic analyses amenable to redefine basic research and provide dynamic diagnoses as the person's nervous systems age.

Precision Sensorimotor Control in Aging FMR1 Gene Premutation Carriers

BACKGROUND

Individuals with premutation alleles of the FMR1 gene are at risk of developing fragile X-associated tremor/ataxia syndrome (FXTAS), a neurodegenerative condition affecting sensorimotor function. Information on quantitative symptom traits associated with aging in premutation carriers is needed to clarify neurodegenerative processes contributing to FXTAS.

MATERIALS AND METHODS

26 FMR1 premutation carriers ages 44-77 years and 31 age-matched healthy controls completed rapid (2 s) and sustained (8 s) visually guided precision gripping tasks. Individuals pressed at multiple force levels to determine the impact of increasing the difficulty of sensorimotor actions on precision behavior. During initial pressing, reaction time, the rate at which individuals increased their force, the duration of pressing, and force accuracy were measured. During sustained gripping, the complexity of the force time series, force variability, and mean force were examined. During relaxation, the rate at which individuals decreased their force was measured. We also examined the relationships between visuomotor behavior and cytosine-guanine-guanine (CGG) repeat length and clinically rated FXTAS symptoms.

RESULTS

Relative to controls, premutation carriers showed reduced rates of initial force generation during rapid motor actions and longer durations of their initial pressing with their dominant hand. During sustained force, premutation carriers demonstrated reduced force complexity, though this effect was specific to younger premutation carries during dominant hand pressing and was more severe for younger relative to older premutation carriers at low and medium force levels. Increased reaction time and lower sustained force complexity each were associated with greater CGG repeat length for premutation carriers. Increased reaction time and increased sustained force variability were associated with more severe clinically rated FXTAS symptoms.

CONCLUSION

Overall our findings suggest multiple sensorimotor processes are disrupted in aging premutation carriers, including initial force control guided by feedforward mechanisms and sustained sensorimotor behaviors guided by sensory feedback control processes. Results indicating that sensorimotor issues in aging premutation carriers relate to both greater CGG repeat length and clinically rated FXTAS symptoms suggest that quantitative tests of precision sensorimotor ability may serve as key targets for monitoring FXTAS risk and progression.

Functional motor control deficits in older FMR1 premutation carriers

Individuals with fragile X mental retardation 1 (FMR1) gene premutations are at increased risk for fragile X-associated tremor/ataxia syndrome (FXTAS) during aging. However, it is unknown whether older FMR1 premutation carriers, with or without FXTAS, exhibit functional motor control deficits compared with healthy individuals. The purpose of this study, therefore, was to determine whether older FMR1 premutation carriers exhibit impaired ability to perform functional motor tasks. Eight FMR1 premutation carriers (age: 58.88 ± 8.36 years) and eight age- and sex-matched healthy individuals (60.13 ± 9.25 years) performed (1) a steady isometric force control task with the index finger at 20% of their maximum voluntary contraction (MVC) and; (2) a single-step task. During the finger abduction task, firing rate of multiple motor units of the first dorsal interosseous (FDI) muscle was recorded. Compared with healthy controls, FMR1 premutation carriers exhibited (1) greater force variability (coefficient of variation of force) during isometric force (1.48 ± 1.02 vs. 0.63 ± 0.37%; P = 0.04); (2) reduced firing rate of multiple motor units during steady force, and; (3) reduced velocity of their weight transfer during stepping (156.62 ± 26.24 vs. 191.86 ± 18.83 cm/s; P = 0.01). These findings suggest that older FMR1 premutation carriers exhibit functional motor control deficits that reflect either subclinical issues associated with premutations independent of FXTAS, or prodromal markers of the development of FXTAS.