Deleterious coding variation associated with autism is consistent across populations, as exemplified by admixed Latin American populations

medRxiv · 2025-01-06 · 3 citations

Abstract The past decade has seen remarkable progress in identifying genes that, when impacted by deleterious coding variation, confer high risk for autism spectrum disorder (ASD), intellectual disability, and other developmental disorders. However, most underlying gene discovery efforts have focused on individuals of European ancestry, limiting insights into genetic risks across diverse populations. To help address this, the Genomics of Autism in Latin American Ancestries Consortium (GALA) was formed, presenting here the largest sequencing study of ASD in Latin American individuals (n>15,000). We identified 35 genome-wide significant (FDR < 0.05) ASD risk genes, with substantial overlap with findings from European cohorts, and highly constrained genes showing consistent signal across populations. The results provide support for emerging (e.g., MARK2 , YWHAG , PACS1 , RERE, SPEN, GSE1, GLS, TNPO3, ANKRD17 ) and established ASD genes, and for the utility of genetic testing approaches for deleterious variants in diverse populations, while also demonstrating the ongoing need for more inclusive genetic research and testing. We conclude that the biology of ASD is universal and not impacted to any detectable degree by ancestry. Autism Sequencing Consortium (ASC) Branko Aleksic, Mykyta Artomov, Mafalda Barbosa, Elisa Benetti, Catalina Betancur, Monica Biscaldi-Schafer, Anders D. Børglum, Harrison Brand, Alfredo Brusco, Joseph D. Buxbaum, Gabriele Campos, Simona Cardaropoli, Diana Carli, Angel Carracedo, Marcus C. Y. Chan, Andreas G. Chiocchetti, Brian H. Y. Chung, Brett Collins, Ryan L. Collins, Edwin H. Cook, Hilary Coon, Claudia I. S. Costa, Michael L. Cuccaro, David J. Cutler, Mark J. Daly, Silvia De Rubeis, Bernie Devlin, Ryan N. Doan, Enrico Domenici, Shan Dong, Chiara Fallerini, Magdalena Fernandez, Montserrat Fernández-Prieto, Giovanni Battista Ferrero, Eugenio Ferro, Jennifer Foss Feig, Christine M. Freitag, Jack M. Fu, Liliana Galeano, J. Jay Gargus, Sherif Gerges, Elisa Giorgio, Ana Cristina Girardi, Stephen Guter, Emily Hansen-Kiss, Erina Hara, Danielle Halpern, Gail E. Herman, Luis C. Hernandez, Irva Hertz-Picciotto, David M. Hougaard, Christina M. Hultman, Suma Jacob, Miia Kaartinen, Lambertus Klei, Alexander Kolevzon, Itaru Kushima, Maria C. Lattig, So Lun Lee, Terho Lehtimäki, Lindsay Liang, Carla Lintas, Alicia Ljungdahl, Andrea del Pilar Lopez, Caterina Lo Rizzo, Yunin Ludena, Patricia Maciel, Behrang Mahjani, Nell Maltman, Marianna Manara, Dara S. Manoach, Dalia Marquez, Gal Meiri, Idan Menashe, Judith Miller, Nancy Minshew, Matthew Mosconi, Marina Natividad Avila, Rachel Nguyen, Norio Ozaki, Aarno Palotie, Mara Parellada, Maria Rita Passos-Bueno, Lisa Pavinato, Katherine P. Peña, Minshi Peng, Margaret Pericak-Vance, Antonio M. Persico, Isaac N. Pessah, Thariana Pichardo, Kaija Puura, Abraham Reichenberg, Alessandra Renieri, Kathryn Roeder, Catherine Sancimino, Stephan J. Sanders, Sven Sandin, F. Kyle Satterstrom, Stephen W. Scherer, Sabine Schlitt, Rebecca J. Schmidt, Lauren Schmitt, Katja Schneider-Momm, Paige M. Siper, Laura Sloofman, Moyra Smith, Renee Soufer, Christine R. Stevens, Pål Suren, James S. Sutcliffe, John A. Sweeney, Michael E. Talkowski, Flora Tassone, Karoline Teufel, Elisabetta Trabetti, Slavica Trajkova, Maria del Pilar Trelles, Brie Wamsley, Jaqueline Y. T. Wang, Lauren A. Weiss, Mullin H. C. Yu, Ryan Yuen, Jessica Zweifach.

Longitudinal Analysis of Neuroradiological Biomarkers for Fragile X‐Associated Tremor/Ataxia Syndrome and Implications for Clinical Trials

Annals of Neurology · 2025-06-03 · 6 citations

OBJECTIVE: The objective of this study was to show the capacity of structural brain magnetic resonance imaging (MRI) measures to serve as monitoring biomarkers for Fragile X-Associated Tremor/Ataxia Syndrome (FXTAS). METHODS: From 2 longitudinal studies of male FMR1 premutation carriers, 2 brain MRI scans were selected from each participant, collected within a period of 2 years (12 healthy controls, 17 carriers without FXTAS, and 51 carriers with FXTAS; all men, ages 40 to 80 years), along with clinical measurements and FMR1 cytosine-guanine-guanine (CGG) repeat numbers. Candidate MRI biomarkers included whole brain white matter hyperintensity (WMH) and cerebellar, brainstem, and whole brain volumes. RESULTS: In the FXTAS group, mixed-effects models demonstrated significant volume loss across an average interval of 1.32 years for the whole brain, cerebellum and brain stem volumes, and significant increases in WMH, with large magnitude effects for whole brain and WMH volumes. All MRI measures showed deterioration with advancing FXTAS stage, with the strongest pattern shown in WMH volume. CGG repeat number showed significant nonlinear associations with all 4 brain MRI metrics, with mid-range CGG repeat carriers evidencing the worst brain atrophy and WMHs. INTERPRETATION: Structural brain MRI measurements, especially those capturing white matter deterioration, are correlated with FMR1 premutation size of CGG repeat length and sensitive to FXTAS disease progression across a relatively short interval of less than 2 years, making them potentially suitable as surrogate end points for clinical trials. ANN NEUROL 2025;98:471-481.

Premutation Females with preFXTAS

International Journal of Molecular Sciences · 2025-03-20 · 8 citations

Fragile-X-associated tremor/ataxia syndrome (FXTAS) is a progressive neurodegenerative disorder associated with the FMR1 gene premutation, characterized by the presence of 55 to 200 CGG triplet repeat expansions. Although the initial symptoms of FXTAS typically manifest in males around the age of 60 with motor symptoms and cognitive deficits, the presentation and progression in females differ. Women, in fact, exhibit a higher prevalence of neuropsychiatric symptoms, with an earlier onset compared to the motor symptoms observed in men. The following article reports on ten cases of women with a diagnosis of FMR1 gene premutation, originating from two medical centers. All the women in the study exhibited neuropsychiatric symptoms and subtle neurological signs as common features. Symptoms typically observed in the male population, such as tremors and cerebellar ataxia, were either absent or significantly reduced in the female cohort. Conversely, there was a higher prevalence of neuropsychiatric symptoms among the women. Neurocognitive impairment was only minimally evident, with mild executive dysfunction and memory complaints noted in a subset of cases. For this reason, we propose the terminology preFXTAS or prodromic FXTAS to define a clinical presentation in women characterized by early manifestations of FXTAS that do not entirely fulfill the established diagnostic criteria but exhibit MRI evidence of white matter alterations suggesting the initiation of the disease process. The study underscores the importance of establishing new diagnostic criteria for FXTAS and, at the same time, developing new biomarkers and interview checklists/assessment scales dedicated to females.

Novel p.Arg534del Mutation and MTHFR C667T Polymorphism in Fragile X Syndrome (FXS) With Autism Spectrum Phenotype: A Case Report

Case Reports in Genetics · 2025-01-01

Fragile X syndrome (FXS) presents with autism spectrum disorder (ASD), intellectual disability, developmental delay, seizures, hypotonia during infancy, joint laxity, behavioral issues, and characteristic facial features. The predominant mechanism is due to CGG trinucleotide repeat expansion of more than 200 repeats in the 5′UTR (untranslated region) of FMR1 (Fragile X Messenger Ribonucleoprotein 1) causing promoter methylation and transcriptional silencing. However, not all patients presenting with the characteristic phenotype and point/frameshift mutations with deletions in FMR1 have been described in the literature. It is believed that < 1% of cases are caused by point mutations. Genetic and functional testing of point mutations in FXS has yielded insights on KH domain RNA‐binding properties of FMRP (Fragile X Messenger Ribonucleoprotein Protein) and nuclear export of the protein. Here, we report a c.1599_1601del p.Arg534del novel mutation in FMR1 with homozygous C677T MTHFR polymorphism in a 12‐year‐old boy. He presents with unique phenotype of FXS with ASD, developmental delay, nonverbal learning disorder (NVLD), overall IQ in the 5 th percentile with above average verbal IQ (66 th percentile), difficulties with quantitative reasoning, dyspraxia, below average visual‐spatial skills (2 nd percentile), difficulty with social pragmatics and social understanding, and executive dysfunction. He has a strong aptitude for music and exceptional aural skills. Identification of novel variants has helped in understanding functional aspects of FMRP. In addition, it aids families in genetic counseling and in administering therapies for children with FXS who present with atypical features.

Reduced Sensorimotor, Working Memory, and Episodic Memory Abilities in Aging Female FMR1 Premutation Carriers with and Without Fragile X-Associated Tremor/Ataxia Syndrome (FXTAS)

Genes · 2025-11-04 · 1 citations

Background/Objectives: Fragile X-associated tremor/ataxia syndrome (FXTAS) is characterized by tremor, gait ataxia, and cerebellar white matter degeneration, along with possible cognitive and cerebral changes. Although diagnostic criteria were originally developed in males, emerging evidence suggests that FXTAS may present differently in females. The present study examined sensorimotor and memory features of aging in female premutation carriers with (FXTAS+) and without FXTAS (FXTAS−). Methods: We studied 51 female premutation carriers (FXTAS+ = 16, FXTAS− = 35) and 24 age-matched female controls. Participants ranged in age from 47–80 years. All participants completed genetic testing, clinical evaluations, T2-weighted MRIs, and quantitative assessments of sensorimotor (precision grip force task) and memory (reading span; visual paired associates task) functions. Results: During precision grip testing, FXTAS+ carriers showed higher sustained force regularity than FXTAS− carriers (p = 0.03, d = 1.0) and controls (p = 0.004, d = 1.1) at low gain levels only. FXTAS+ participants were slower than controls on motor reaction time (p = 0.009, d = 0.82). Initial force output was higher in FXTAS+ than FXTAS− carriers (p = 0.03, d = 1.0) and controls (p = 0.03, d = 1.0) but at low gain only. FXTAS+ carriers exhibited poorer working memory than FXTAS− carriers (p = 0.03, d = 0.91) and controls (p = 0.02, d = 1.0). During a long-term memory task, FXTAS+ participants were less accurate than FXTAS− carriers (p = 0.04, d = 0.86) and controls (p = 0.004, d = 1.1) and showed increased reaction times relative to FXTAS− carriers (p = 0.03, d = −0.82) and controls (p = 0.01, d = −1.2). Conclusions: Together, these findings indicate that FXTAS+ females exhibit distinct motor and cognitive impairments, underscoring the value of quantitative behavioral measures for detecting and tracking neurodegenerative progression in female premutation carriers.

In Utero Alcohol and Unsuitable Home Environmental Exposure Combined with FMR1 Full Mutation Allele Cause Severe Fragile X Syndrome Phenotypes

International Journal of Molecular Sciences · 2025-03-21 · 2 citations

We investigated the molecular and clinical profile of five boys carrying the fragile X messenger ribonucleoprotein 1 (FMR1) mutation and who suffered from the effects of prenatal alcohol exposure. Fragile X syndrome (FXS) testing was performed using PCR and Southern Blot analysis, and fragile X messenger ribonucleoprotein protein (FMRP) expression levels were measured by Western blot analysis. Clinical evaluation included cognitive functions, adaptive skills, autism phenotype, and severity of behavior measures. Fetal Alcohol Spectrum Disorder (FASD) was also assessed. Five adopted male siblings were investigated, four of which (cases 1, 2, 3, and 4) were diagnosed with FXS, FASD, and ASD, and one, the fraternal triplet (case 5), was diagnosed with FASD and ASD and no FXS. The molecular profile of case 1 and 2 showed the presence of a hypermethylated full mutation (FM) and the resulting absence of FMRP. Cases 3 and 4 (identical twins) were FM-size mosaics (for the presence of an FM and a deleted allele), resulting in 16% and 50% FMRP expression levels, respectively. FMRP expression level was normal in case 5 (fraternal twin). Severe behavioral problems were observed in all cases, including aggression, tantrum, self-harming, anxiety, and defiant behavior, due to different mutations of the FMR1 gene, in addition to biological exposure, home environmental factors, and potentially to additional background gene effects.

Depression Symptom Trajectories in Mothers With the <scp><i>FMR1</i></scp> Premutation Vary by <scp>CGG</scp> Repeat Length: A Longitudinal Study of 73 Women Spanning 20–75 Years of Age

American Journal of Medical Genetics Part B Neuropsychiatric Genetics · 2025-05-26 · 4 citations

Women with the FMR1 premutation (FXpm) are at heightened genetic vulnerability for depression, with risk compounded by the stressors of parenting a disabled child. Although risk factors persist as FXpm women age, depression in FXpm mothers during midlife and old age is poorly characterized. This study used an accelerated longitudinal design to capture the trajectory of depressive symptoms in 73 FXpm mothers across 20-75 years of age. The FXpm mothers had children with fragile X syndrome or FXpm and contributed 2-11 longitudinal assessments, for a total of 294 observations. Mothers with mid-range CGG expansions (91-110 CGG repeats) exhibited the highest overall symptoms, with a marked increase in depression during early midlife, followed by late midlife trajectories that varied by history of premature menopause. Symptoms of mothers with high CGGs (111-200) peaked during early and late adulthood rather than midlife. At low CGGs (55-90) symptoms were low and stable across age. Parenting stress was associated with increased symptoms during early adulthood, but this effect dwindled with age. Findings illuminate evolving patterns of depression vulnerability across adulthood that are shaped by specific environmental and genetic factors, offering insights for personalized medicine to enhance the health of aging FXpm mothers.

Swallowing and choking difficulties as potential markers of FXTAS progression in FMR1 premutation carriers

Scientific Reports · 2025-11-26

Fragile X-associated tremor/ataxia syndrome (FXTAS) affects motor and coordination pathways and is linked to swallowing and choking difficulties, which can lead to aspiration pneumonia, a leading cause of death in late-stage FXTAS. Despite their severity, these issues are under-investigated. This study examined their association with FXTAS stages and potential as markers of disease progression in FMR1 premutation (PM) carriers. A secondary analysis of Genotype-Phenotype cohort data (2017-2025, MIND Institute, UC Davis) examined swallowing/choking problems, FXTAS stage, neuroimaging, and psychological distress (Symptom Checklist-90-Revised; SCL-90-R). Associations between independent and dependent variables were tested using Generalized Estimating Equation (GEE) regression due to their correlated data. The study included 169 PM carriers (mean age 65 ± 10.9 years; 54% male), with approximately 35% reporting swallowing/choking difficulties. After adjusting for age and sex, individuals in the severe stage of FXTAS (stage 4-5) had a significantly higher risk of swallowing/choking problems compared to those without FXTAS (adjusted odds ratio [aOR] = 4.17; 95%CI = 1.28-13.58). PM carriers with swallowing/choking problems showed a significantly increased association with magnetic resonance imaging (MRI) findings of moderate to severe abnormalities in several brain regions, including cerebral atrophy (aOR = 2.69, p = 0.027), cerebellar atrophy (aOR = 3.34, p = 0.013), cerebellar white matter hyperintensity (aOR = 3.33, p = 0.012), and pons white matter hyperintensity (aOR = 3.93, p = 0.035). Swallowing/choking problems are common in FXTAS, particularly in later stages, and may represent an important clinical marker of disease progression. These patients should be referred to speech-language pathologists for evaluation and treatment. Such interventions could reduce morbidity-mortality associated with these problems.

Electroretinographic Findings in Fragile X, Premutation, and Controls: A Study of Biomarker Correlations

International Journal of Molecular Sciences · 2025-07-16 · 1 citations

The study’s aim was to evaluate electroretinographic (ERG) alterations in Fragile X syndrome (FXS), FMR1 premutation carriers, and controls, and to explore correlations with peripheral blood FMRP expression levels and behavioral outcomes. ERG recordings were obtained using a handheld device across three stimulus protocols in 43 premutation carriers, 39 individuals with FXS, and 23 controls. Peripheral blood FMRP expression levels were quantified using TR-FRET (Time-Resolved Fluorescence Resonance Energy Transfer). Correlations were assessed with cognitive and behavioral measures including IQ (Intelligence Quotient), ABCFX (Aberrant Behavior Checklist for Fragile X Syndrome), SNAP-IV (Swanson, Nolan, and Pelham Teacher and Parent Rating Scale), SEQ (Sensory Experiences Questionnaire), ADAMS (Anxiety, Depression, and Mood Scale), and the Vineland III Adaptive Behavior Scale standard score. Significant group differences were observed in multiple ERG parameters, particularly in 2 Hz b-wave amplitude (p = 0.0081), 2 Hz b-wave time to peak (p = 0.0164), 28.3 Hz flash combined amplitude (p = 0.0139), 3.4 Hz red/blue flash b-wave amplitude (p = 0.0026), and PhNR amplitude (p = 0.0026), indicating both outer and inner retinal dysfunction in FXS and premutation groups. Despite high test–retest reliability for ERG (ICC range = 0.71–0.92) and FMRP (ICC = 0.70), no correlation was found between ERG metrics and FMRP or behavioral measures. However, FMRP levels strongly correlated with IQ (ρ = 0.69, p &lt; 0.0001) and inversely with behavioral impairment [ABCFX (ρ = −0.47, p = 0.0041), SNAP-IV (ρ = −0.48, p = 0.0039), SEQ (ρ = −0.43, p = 0.0146), and the Vineland III standard score (ρ = 0.56, p = 0.0019)]. ERG reveals distinct retinal functional abnormalities in FMR1-related conditions but does not correlate with peripheral FMRP expression levels, highlighting the need for multimodal biomarkers integrating radiological, physiological, behavioral, and molecular measures.

Specific EEG resting state biomarkers in FXS and ASD

Research Square · 2024-01-15