FXN methylation predicts expression and clinical outcome in Friedreich ataxia.

OBJECTIVE: Friedreich ataxia (FA) is the most common ataxia and results from an expanded GAA repeat in the first intron of FXN. This leads to epigenetic modifications and reduced frataxin. We investigated the relationships between genetic, epigenetic, and clinical parameters in a large case-control study of FA. METHODS: Clinical data and samples were obtained from individuals with FA during annual visits to our dedicated FA clinic. GAA expansions were evaluated by polymerase chain reaction (PCR) and restriction endonuclease digest. DNA methylation was measured using bisulfite-based EpiTYPER MassARRAY (Sequenom, San Diego, CA). FXN expression was determined using real-time reverse transcriptase PCR. Significant correlations between the different parameters were examined using the nonparametric Spearman rank correlation coefficient, as well as univariate and multivariate regression modeling. RESULTS: Characteristic DNA methylation was identified upstream and downstream of the expansion, and validated in an independent FA cohort. Univariate and multivariate analyses showed significant inverse correlations between upstream methylation and FXN expression, and variation in downstream methylation and age of onset. FXN expression also inversely correlated with the Friedreich Ataxia Rating Scale score, an indicator of disease severity. INTERPRETATION: These novel findings provide compelling evidence for the link between the GAA expansion, the DNA methylation profile, FXN expression, and clinical outcome in FA. Epigenetic profiling of FXN could be used to gain greater insight into disease onset and progression, but also as a biomarker to learn more about specific treatment responses and pharmacological mechanism(s). This work also highlights the potential for developing therapies aimed at increasing frataxin levels to treat this debilitating disease.

Natural history of Huntington disease.

IMPORTANCE: Understanding the natural history of Huntington disease will inform patients and clinicians on the disease course and researchers on the design of clinical trials. OBJECTIVE: To determine the longitudinal change in clinical features among individuals with Huntington disease compared with controls. DESIGN, SETTING, AND PARTICIPANTS: Prospective, longitudinal cohort study at 44 research sites in Australia (n = 2), Canada (n =4), and the United States (n = 38). Three hundred thirty-four individuals with clinically manifest Huntington disease who had at least 3 years of annually accrued longitudinal data and 142 controls consisting of caregivers and spouses who had no genetic risk of Huntington disease. MAIN OUTCOMES AND MEASURES: Change in movement, cognition, behavior, and function as measured by the Unified Huntington's Disease Rating Scale, the Mini-Mental State Examination, and vital signs. RESULTS: Total motor score worsened by 3.0 points (95% CI, 2.5-3.4) per year and chorea worsened by 0.3 point per year (95% CI, 0.1-0.5). Cognition declined by 0.7 point (95% CI, 0.6-0.8) per year on the Mini-Mental State Examination. Behavior, as measured by the product of frequency and severity score on the Unified Huntington's Disease Rating Scale, worsened by 0.6 point per year (95% CI, 0.0-1.2). Total functional capacity declined by 0.6 point per year (95% CI, 0.5-0.7). Compared with controls, baseline body mass index was lower in those with Huntington disease (25.8 vs 28.8; P < .001), and average pulse was higher (74.2 vs 69.6 beats/min; P < .001). CONCLUSIONS AND RELEVANCE: Over 3 years, the cardinal features of Huntington disease all declined in a monotonic manner. These data quantify the natural history of the disease and may inform the design of trials aimed at reducing its burden. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00313495.

Depressed mood and suicidality in individuals exposed to tetrabenazine in a large Huntington disease observational study.

BACKGROUND: Tetrabenazine, a treatment for chorea in Huntington disease, carries a boxed warning due to safety, especially related to suicidality. OBJECTIVE: To compare the frequency of depressed mood and suicidality among a closely monitored cohort of individuals with Huntington disease who were exposed and not exposed to tetrabenazine. METHODS: A longitudinal prospective study involving 1360 individuals with HD evaluated at 48 research centers in Australia, Canada, and the United States was examined for frequency of depressed mood that triggered a risk assessment, suicidal thoughts, suicide attempts, and completed suicide among individuals with prior, new, and no exposure to tetrabenazine.. Seventy-seven individuals were on tetrabenazine at study enrollment (prior exposure), 64 individuals were exposed to tetrabenazine during the study's course (new exposure), and 1219 individuals had no exposure to tetrabenazine. RESULTS: The hazard ratio for depressed mood among those with prior exposure to tetrabenazine compared to no exposure was 0.9 (95% CI, 0.5-1.6) and for those with new exposure compared to no exposure was 1.2 (95% CI, 0.8-1.9). One individual (1.3%) with prior exposure, one individual (1.6%) with new exposure, and 35 individuals (2.9%) with no exposure to tetrabenazine reported suicidal thoughts. The hazard ratio for suicidal ideation among those with prior exposure to tetrabenazine compared to no exposure was 0.5 (95% CI, 0.1-3.8) and for those with new exposure to tetrabenazine compared to no exposure was 0.6 (95% CI, 0.1-4.4). Among individuals with prior or new exposure to tetrabenazine, no suicide attempts or suicides occurred. Among those with no exposure to tetrabenazine 17 suicide attempts (1.4%) and four suicides (0.3%) occurred. CONCLUSIONS: In a large observational study with close clinical supervision, tetrabenazine treatment was not associated with an increased risk of depressed mood, suicidal ideation, suicide attempts, or suicide.