S. H. Subramony

Autosomal dominant cerebellar ataxia (SCA6) associated with small polyglutamine expansions in the α(1A)-voltage-dependent calcium channel

A polymorphic CAG repeat was identified in the human α1A voltage-dependent calcium channel subunit. To test the hypothesis that expansion of this CAG repeat could be the cause of an inherited progressive ataxia, we genotyped a large number of unrelated controls and ataxia patients. Eight unrelated patients with late onset ataxia had alleles with larger repeat numbers (21‐27) compared to the number of repeats (4‐16) in 475 non‐ataxia individuals. Analysis of the repeat length in families of the affected individuals revealed that the expansion segregated with the phenotype in every patient. We identified six isoforms of the human α1A calcium channel subunit. The CAG repeat is within the open reading frame and is predicted to encode glutamine in three of the isoforms. We conclude that a small polyglutamine expansion in the human α1A calcium channel is most likely the cause of a newly classified autosomal dominant spinocerebellar ataxia, SCA6.

International Cooperative Ataxia Rating Scale for pharmacological assessment of the cerebellar syndrome

Despite the involvement of cerebellar ataxia in a large variety of conditions and its frequent association with other neurological symptoms, the quantification of the specific core of the cerebellar syndrome is possible and useful in Neurology. Recent studies have shown that cerebellar ataxia might be sensitive to various types of pharmacological agents, but the scales used for assessment were all different. With the long-term goal of double-blind controlled trials-multicentric and international-an ad hoc Committee of the World Federation of Neurology has worked to propose a one-hundred-point semi-quantitative International Cooperative Ataxia Rating Scale (ICARS). The scale proposed involves a compartimentalized quantification of postural and stance disorders, limb ataxia, dysarthria and oculomotor disorders, in order that a subscore concerning these symptoms may be separately studied. The weight of each symptomatologic compartment has been carefully designed. The members of the Committee agreed upon precise definitions of the tests, to minimize interobserver variations. The validation of this scale is in progress.

Mutations in Kir2.1 Cause the Developmental and Episodic Electrical Phenotypes of Andersen's Syndrome

Andersens syndrome is characterized by periodic paralysis, cardiac arrhythmias, and dysmorphic features. We have mapped an Andersens locus to chromosome 17q23 near the inward rectifying potassium channel gene KCNJ2. A missense mutation in KCNJ2 (encoding D71V) was identified in the linked family. Eight additional mutations were identified in unrelated patients. Expression of two of these mutations in Xenopus oocytes revealed loss of function and a dominant negative effect in Kir2.1 current as assayed by voltage-clamp. We conclude that mutations in Kir2.1 cause Andersens syndrome. These findings suggest that Kir2.1 plays an important role in developmental signaling in addition to its previously recognized function in controlling cell excitability in skeletal muscle and heart.

RAN proteins and RNA foci from antisense transcripts in C9ORF72 ALS and frontotemporal dementia

Significance A GGGGCC expansion mutation located in intron 1 of chromosome 9 ORF 72 (C9ORF72) was recently described as a common cause of familial amyotrophic lateral sclerosis/frontotemporal dementia (ALS/FTD). We show that this single mutation results in the accumulation of sense and antisense RNA foci plus six expansion proteins expressed by repeat-associated non-ATG (RAN) translation. RNAs accumulate in nuclear foci and the RAN proteins form cytoplasmic aggregates in neurons that often cluster in affected brain regions. These results indicate that bidirectional transcription and RAN translation are fundamental pathologic features of C9ORF72 ALS/FTD. Additionally these data have broad implications that change our understanding of how microsatellite expansion mutations are expressed in patient cells and how they cause disease. The finding that a GGGGCC (G4C2) hexanucleotide repeat expansion in the chromosome 9 ORF 72 (C9ORF72) gene is a common cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) links ALS/FTD to a large group of unstable microsatellite diseases. Previously, we showed that microsatellite expansion mutations can be bidirectionally transcribed and that these mutations express unexpected proteins by a unique mechanism, repeat-associated non-ATG (RAN) translation. In this study, we show that C9ORF72 antisense transcripts are elevated in the brains of C9ORF72 expansion-positive [C9(+)] patients, and antisense GGCCCC (G2C4) repeat-expansion RNAs accumulate in nuclear foci in brain. Additionally, sense and antisense foci accumulate in blood and are potential biomarkers of the disease. Furthermore, we show that RAN translation occurs from both sense and antisense expansion transcripts, resulting in the expression of six RAN proteins (antisense: Pro-Arg, Pro-Ala, Gly-Pro; and sense: Gly-Ala, Gly-Arg, Gly-Pro). These proteins accumulate in cytoplasmic aggregates in affected brain regions, including the frontal and motor cortex, hippocampus, and spinal cord neurons, with some brain regions showing dramatic RAN protein accumulation and clustering. The finding that unique antisense G2C4 RNA foci and three unique antisense RAN proteins accumulate in patient tissues indicates that bidirectional transcription of expanded alleles is a fundamental pathologic feature of C9ORF72 ALS/FTD. Additionally, these findings suggest the need to test therapeutic strategies that target both sense and antisense RNAs and RAN proteins in C9ORF72 ALS/FTD, and to more broadly consider the role of antisense expression and RAN translation across microsatellite expansion diseases.

Subcutaneous IGF-1 is not beneficial in 2-year ALS trial

Background: Previous human clinical trials of insulin-like growth factor type I (IGF-1) in amyotrophic lateral sclerosis (ALS) have been inconsistent. This phase III, randomized, double-blind, placebo-controlled study was undertaken to address whether IGF-1 benefited patients with ALS. Methods: A total of 330 patients from 20 medical centers were randomized to receive 0.05 mg/kg body weight of human recombinant IGF-1 given subcutaneously twice daily or placebo for 2 years. The primary outcome measure was change in their manual muscle testing score. Secondary outcome measures included tracheostomy-free survival and rate of change in the revised ALS functional rating scale. Intention to treat analysis was used. Results: There was no difference between treatment groups in the primary or secondary outcome measures after the 2-year treatment period. Conclusions: Insulin-like growth factor type I does not provide benefit for patients with amyotrophic lateral sclerosis. GLOSSARY: ALS = amyotrophic lateral sclerosis; ALSFRS-r = revised ALS functional rating scale; AUC = area under the curve; DVT = deep venous thromboses; IGF-1 = insulin-like growth factor type I; MMT = manual muscle testing; PE = pulmonary embolisms.

Measuring Friedreich ataxia: Interrater reliability of a neurologic rating scale

Measuring the severity of neurologic dysfunction in patients with inherited ataxias, including Friedreich ataxia (FA), is difficult because of the variable rate of progression, the variable age at onset and the variety of neural systems that may be affected. The authors discuss the problems related to rating scales in the ataxias, report a neurologic rating scale for FA, and demonstrate acceptable interrater reliability of the instrument.

Measuring Friedreich ataxia Complementary features of examination and performance measures

Objective: To examine the potential validity of performance measures and examination-based scales in Friedreich ataxia (FA) by examining their correlation with disease characteristics. Methods: The authors assessed the properties of a candidate clinical outcome measure, the Friedreich Ataxia Rating Scale (FARS), and simple performance measures (9-hole peg test, the timed 25-foot walk, PATA test, and low-contrast letter acuity) in 155 patients with FA from six institutions, and correlated the scores with disease duration, functional disability, activity of daily living scores, age, and shorter GAA repeat length to assess whether these measures capture the severity of neurologic dysfunction in FA. Results: Scores for the FARS and performance measures correlated significantly with functional disability, activities of daily living scores, and disease duration, showing that these measures meet essential criteria for construct validity for measuring the progressive nature of FA. In addition, the FARS and transformed performance measures scores were predicted by age and shorter GAA repeat length in linear regression models accounting for sex and testing site. Correlations between performance measures were moderate in magnitude, suggesting that each test captures separate yet related dimensions of neurologic function in FA and that a composite measure might better predict disease status. Composite measures created using cohort means and standard deviations predicted disease status better than or equal to single performance measures or examination-based measures. Conclusions: The Friedreich Ataxia Rating Scale, performance measures, and performance measure composites provide valid assessments of disease progression in Friedreich ataxia.

New NBIA subtype Genetic, clinical, pathologic, and radiographic features of MPAN

Objective: To assess the frequency of mutations in C19orf12 in the greater neurodegeneration with brain iron accumulation (NBIA) population and further characterize the associated phenotype. Methods: Samples from 161 individuals with idiopathic NBIA were screened, and C19orf12 mutations were identified in 23 subjects. Direct examinations were completed on 8 of these individuals, and medical records were reviewed on all 23. Histochemical and immunohistochemical studies were performed on brain tissue from one deceased subject. Results: A variety of mutations were detected in this cohort, in addition to the Eastern European founder mutation described previously. The characteristic clinical features of mitochondrial membrane protein-associated neurodegeneration (MPAN) across all age groups include cognitive decline progressing to dementia, prominent neuropsychiatric abnormalities, and a motor neuronopathy. A distinctive pattern of brain iron accumulation is universal. Neuropathologic studies revealed neuronal loss, widespread iron deposits, and eosinophilic spheroidal structures in the basal ganglia. Lewy neurites were present in the globus pallidus, and Lewy bodies and neurites were widespread in other areas of the corpus striatum and midbrain structures. Conclusions: MPAN is caused by mutations in C19orf12 leading to NBIA and prominent, widespread Lewy body pathology. The clinical phenotype is recognizable and distinctive, and joins pantothenate kinase–associated neurodegeneration and PLA2G6-associated neurodegeneration as one of the major forms of NBIA.

CINRG randomized controlled trial of creatine and glutamine in Duchenne muscular dystrophy

We tested the efficacy and safety of glutamine (0.6gm/kg/day) and creatine (5gm/day) in 50 ambulant boys with Duchenne muscular dystrophy in a 6‐month, double‐blind, placebo‐controlled clinical trial. Drug efficacy was tested by measuring muscle strength manually (34 muscle groups) and quantitatively (10 muscle groups). Timed functional tests, functional parameters, and pulmonary function tests were secondary outcome measures. Although there was no statistically significant effect of either therapy based on manual and quantitative measurements of muscle strength, a disease‐modifying effect of creatine in older Duchenne muscular dystrophy and creatine and glutamine in younger Duchenne muscular dystrophy cannot be excluded. Creatine and glutamine were well tolerated. Ann Neurol 2005;58:151–155

Measuring the rate of progression in Friedreich ataxia: Implications for clinical trial design

Friedreich ataxia is an autosomal recessive neurodegenerative disorder characterized by ataxia of all four limbs, dysarthria, and arreflexia. A variety of measures are currently used to quantify disease progression, including the Friedreich Ataxia Rating Scale, examiner‐rated functional disability scales, self‐reported activities of daily living and performance measures such as the timed 25‐foot walk, 9‐hole pegboard test, PATA speech test, and low‐contrast letter acuity vision charts. This study examines the rate of disease progression over one and two years in a cohort of 236 Friedreich ataxia patients using these scales and performance measure composites. The Friedreich Ataxia Rating Scale and performance‐measure composites captured disease progression, with a greater sensitivity to change over 2 years than over 1 year. The measures differed in their sensitivity to change and in possible bias. These results help to establish norms for progression in FRDA that can be useful in measuring the long‐term success of therapeutic agents and defining sample‐size calculations for double‐blind clinical trials.