SCN1A-deficient excitatory neuronal networks display mutation-specific phenotypes.

Dravet syndrome is a severe epileptic encephalopathy, characterized by (febrile) seizures, behavioural problems and developmental delay. Eighty per cent of patients with Dravet syndrome have a mutation in SCN1A, encoding Nav1.1. Milder clinical phenotypes, such as GEFS+ (generalized epilepsy with febrile seizures plus), can also arise from SCN1A mutations. Predicting the clinical phenotypic outcome based on the type of mutation remains challenging, even when the same mutation is inherited within one family. This clinical and genetic heterogeneity adds to the difficulties of predicting disease progression and tailoring the prescription of anti-seizure medication. Understanding the neuropathology of different SCN1A mutations may help to predict the expected clinical phenotypes and inform the selection of best-fit treatments. Initially, the loss of Na+-current in inhibitory neurons was recognized specifically to result in disinhibition and consequently seizure generation. However, the extent to which excitatory neurons contribute to the pathophysiology is currently debated and might depend on the patient clinical phenotype or the specific SCN1A mutation. To examine the genotype-phenotype correlations of SCN1A mutations in relation to excitatory neurons, we investigated a panel of patient-derived excitatory neuronal networks differentiated on multi-electrode arrays. We included patients with different clinical phenotypes, harbouring various SCN1A mutations, along with a family in which the same mutation led to febrile seizures, GEFS+ or Dravet syndrome. We hitherto describe a previously unidentified functional excitatory neuronal network phenotype in the context of epilepsy, which corresponds to seizurogenic network prediction patterns elicited by proconvulsive compounds. We found that excitatory neuronal networks were affected differently, depending on the type of SCN1A mutation, but did not segregate according to clinical severity. Specifically, loss-of-function mutations could be distinguished from missense mutations, and mutations in the pore domain could be distinguished from mutations in the voltage sensing domain. Furthermore, all patients showed aggravated neuronal network responses at febrile temperatures compared with controls. Finally, retrospective drug screening revealed that anti-seizure medication affected GEFS+ patient- but not Dravet patient-derived neuronal networks in a patient-specific and clinically relevant manner. In conclusion, our results indicate a mutation-specific excitatory neuronal network phenotype, which recapitulates the foremost clinically relevant features, providing future opportunities for precision therapies.

Human KCNQ5 de novo mutations underlie epilepsy and intellectual disability.

We identified six novel de novo human KCNQ5 variants in children with motor/language delay, intellectual disability (ID), and/or epilepsy by whole exome sequencing. These variants, comprising two nonsense and four missense alterations, were functionally characterized by electrophysiology in HEK293/CHO cells, together with four previously reported KCNQ5 missense variants (Lehman A, Thouta S, Mancini GM, Naidu S, van Slegtenhorst M, McWalter K, Person R, Mwenifumbo J, Salvarinova R; CAUSES Study; EPGEN Study; Guella I, McKenzie MB, Datta A, Connolly MB, Kalkhoran SM, Poburko D, Friedman JM, Farrer MJ, Demos M, Desai S, Claydon T. Am J Hum Genet 101: 65-74, 2017). Surprisingly, all eight missense variants resulted in gain of function (GOF) due to hyperpolarized voltage dependence of activation or slowed deactivation kinetics, whereas the two nonsense variants were confirmed to be loss of function (LOF). One severe GOF allele (P369T) was tested and found to extend a dominant GOF effect to heteromeric KCNQ5/3 channels. Clinical presentations were associated with altered KCNQ5 channel gating: milder presentations with LOF or smaller GOF shifts in voltage dependence [change in voltage at half-maximal conduction (ΔV50) = ∼-15 mV] and severe presentations with larger GOF shifts in voltage dependence (ΔV50 = ∼-30 mV). To examine LOF pathogenicity, two Kcnq5 LOF mouse lines were created with CRISPR/Cas9. Both lines exhibited handling- and thermal-induced seizures and abnormal cortical EEGs consistent with epileptiform activity. Our study thus provides evidence for in vivo KCNQ5 LOF pathogenicity and strengthens the contribution of both LOF and GOF mutations to global pediatric neurological impairment, including ID/epilepsy.NEW & NOTEWORTHY Six novel de novo human KCNQ5 variants were identified from children with neurodevelopmental delay, intellectual disability, and/or epilepsy. Expression of these variants along with four previously reported KCNQ5 variants from a similar cohort revealed GOF potassium channels, negatively shifted in V50 of activation and/or delayed deactivation kinetics. GOF is extended to KCNQ5/3 heteromeric channels, making these the predominant channels affected in heterozygous de novo patients. Kcnq5 LOF mice exhibited seizures, consistent with in vivo pathogenicity.

People with epilepsy and intellectual disability: More than a sum of two conditions.

BACKGROUND: Around 25% of people with Intellectual Disability (PwID) have comorbid epilepsy with seizures in up to two-thirds being drug-resistant. Little is known of the general characteristics and prescribing practices to this population. AIM: Describe and compare characteristics of two cohorts of PwID and epilepsy in two different countries to inform clinical practice better. METHOD: An explorative, retrospective, case-note review in a specialist ID community service in England and in an expert center for PwID and epilepsy in the Netherlands was conducted. Information on ID severity, medical/behavioral/psychiatric/neurodevelopmental/genetic comorbidities, psychotropic, and antiepileptic drugs (AEDs) for each cohort was collected. FINDINGS: The English cohort consisted of 167 people (98 males; age range 18-73 years; mild/moderate ID- 35%) and the Dutch cohort of 189 people (111 males; age range 18-85 years; mild/moderate ID - 51%). The two cohorts were comparable in their baseline characteristics. The Dutch had higher rates of physical comorbidity, but less mental or behavioral disorders and were more likely to be on anti-psychotic medication. The mean dosages between three most common AEDs prescribed were similar. The most frequently prescribed drug in both centers is valproate. Three-quarters of the Dutch were on three or more AEDs compared to a third in the English cohort. CONCLUSIONS: Structured description of the characteristics, differences, and commonalities of PwID, treatment, and services of both countries is presented. This is the first real-world study to reveal unique characteristics of managing epilepsy for a complex ID population. In particular, it highlights the considerable comorbid psychiatric burden and psychotropic prescribing.

Efficacy and tolerability of brivaracetam in patients with intellectual disability and epilepsy.

Patients with intellectual disability (ID) are often excluded from clinical trials, and little is known about the best approach to treat their epilepsy. Brivaracetam (BRV) is a new antiepileptic drug (AED) for adjunctive treatment in patients with focal-onset seizures with or without secondary generalization. We analyzed the efficacy and tolerability of BRV in patients with ID and epilepsy who either had or had not previously received treatment with levetiracetam (LEV). Data on efficacy and tolerability were retrospectively collected. After the initial start of BRV in our tertiary epilepsy center, we analyzed medical records at 0, 3, 6 and 12 months of follow-up. 116 patients were included (mean age = 34.9 years, 44% female). All had complete data of 3-month follow-up, 76 of 6-month follow-up, and 39 patients of 1-year follow-up. Median starting dose of BRV was 50.0 mg/day and the mean number of concomitant AEDs was 2.6. Seizure reduction and no side effects were reported in more than half of all patients. The most reported side effects were somnolence, dizziness and aggression. Retention rates for BRV were 84.4%, 75.5% and 58.1% after 3, 6 and 12 months, respectively. Seizure reduction and side effects did not differ significantly between the groups with or without previous LEV treatment. We demonstrate that BRV is effective and well tolerated in patients with epilepsy and ID, even in those where previous LEV treatment failed.

Mood, anxiety, and perceived quality of life in adults with epilepsy and intellectual disability.

OBJECTIVE: Depression and anxiety symptoms are common among patients with epilepsy, but are relatively under-researched in patients with both epilepsy and intellectual disability (ID). The aim was to investigate whether epilepsy and ID characteristics are associated with mood, anxiety, and quality of life. MATERIALS AND METHODS: Adult patients with epilepsy and ID who rely on tertiary epilepsy care were included (N = 189). Mood, anxiety, and quality of life were assessed by standardized questionnaires. Epilepsy and ID characteristics were retrieved from patient charts or determined by psychometric instruments. RESULTS: Elevated levels of depressive and anxiety symptoms were present in 21.7% and 12.7%, respectively. Anxiety was significantly associated with a focal epilepsy type and ID domain discrepancy (substantial difference between two domains of adaptive behavior), but was negatively related to seizure frequency and drug load of mood-stabilizing antiepileptic drugs. Depressive symptoms were not significantly related to epilepsy characteristics, but a severe ID and ID domain discrepancy was associated with more depressive symptoms. Quality of life was significantly worse in those with multiple seizure types and ID domain discrepancy. CONCLUSION: Whereas anxiety and quality of life are associated with individual epilepsy characteristics, this could not be confirmed for depressive symptoms in patients with epilepsy and ID, despite its high prevalence.

Diagnostic exome sequencing in 100 consecutive patients with both epilepsy and intellectual disability.

OBJECTIVE: Epilepsy is highly prevalent among patients with intellectual disability (ID), and seizure control is often difficult. Identification of the underlying etiology in this patient group is important for daily clinical care. We assessed the diagnostic yield of whole exome sequencing (WES). In addition, we evaluated which clinical characteristics influence the likelihood of identifying a genetic cause and we assessed the potential impact of the genetic diagnosis on (antiepileptic) treatment strategy. METHODS: One hundred patients with both unexplained epilepsy and (borderline) ID (intelligence quotient ≤ 85) were included. All patients were evaluated by a clinical geneticist, a (pediatric) neurologist, and/or a specialist ID physician. WES analysis was performed in two steps. In step 1, analysis was restricted to the latest versions of ID and/or epilepsy gene panels. In step 2, exome analysis was extended to all genes (so-called full exome analysis). The results were classified according to the American College of Medical Genetics and Genomics guidelines. RESULTS: In 58 patients, the diagnostic WES analysis reported one or more variant(s). In 25 of the 100 patients, these were classified as (likely) pathogenic, in 24 patients as variants of uncertain significance, and in the remaining patients the variant was most likely not related to the phenotype. In 10 of 25 patients (40%) with a (likely) pathogenic variant, the genetic diagnosis might have an impact on the treatment strategy in the future. SIGNIFICANCE: This study illustrates the clinical diagnostic relevance of WES for patients with both epilepsy and ID. It also demonstrates that implementing WES diagnostics might have impact on the (antiepileptic) treatment strategy in this population. Confirmation of variants of uncertain significance in (candidate) genes may further increase the yield.

Characterization of glycosylphosphatidylinositol biosynthesis defects by clinical features, flow cytometry, and automated image analysis.

BACKGROUND: Glycosylphosphatidylinositol biosynthesis defects (GPIBDs) cause a group of phenotypically overlapping recessive syndromes with intellectual disability, for which pathogenic mutations have been described in 16 genes of the corresponding molecular pathway. An elevated serum activity of alkaline phosphatase (AP), a GPI-linked enzyme, has been used to assign GPIBDs to the phenotypic series of hyperphosphatasia with mental retardation syndrome (HPMRS) and to distinguish them from another subset of GPIBDs, termed multiple congenital anomalies hypotonia seizures syndrome (MCAHS). However, the increasing number of individuals with a GPIBD shows that hyperphosphatasia is a variable feature that is not ideal for a clinical classification. METHODS: We studied the discriminatory power of multiple GPI-linked substrates that were assessed by flow cytometry in blood cells and fibroblasts of 39 and 14 individuals with a GPIBD, respectively. On the phenotypic level, we evaluated the frequency of occurrence of clinical symptoms and analyzed the performance of computer-assisted image analysis of the facial gestalt in 91 individuals. RESULTS: We found that certain malformations such as Morbus Hirschsprung and diaphragmatic defects are more likely to be associated with particular gene defects (PIGV, PGAP3, PIGN). However, especially at the severe end of the clinical spectrum of HPMRS, there is a high phenotypic overlap with MCAHS. Elevation of AP has also been documented in some of the individuals with MCAHS, namely those with PIGA mutations. Although the impairment of GPI-linked substrates is supposed to play the key role in the pathophysiology of GPIBDs, we could not observe gene-specific profiles for flow cytometric markers or a correlation between their cell surface levels and the severity of the phenotype. In contrast, it was facial recognition software that achieved the highest accuracy in predicting the disease-causing gene in a GPIBD. CONCLUSIONS: Due to the overlapping clinical spectrum of both HPMRS and MCAHS in the majority of affected individuals, the elevation of AP and the reduced surface levels of GPI-linked markers in both groups, a common classification as GPIBDs is recommended. The effectiveness of computer-assisted gestalt analysis for the correct gene inference in a GPIBD and probably beyond is remarkable and illustrates how the information contained in human faces is pivotal in the delineation of genetic entities.

Defining the phenotypic spectrum of SLC6A1 mutations.

OBJECTIVE: Pathogenic SLC6A1 variants were recently described in patients with myoclonic atonic epilepsy (MAE) and intellectual disability (ID). We set out to define the phenotypic spectrum in a larger cohort of SCL6A1-mutated patients. METHODS: We collected 24 SLC6A1 probands and 6 affected family members. Four previously published cases were included for further electroclinical description. In total, we reviewed the electroclinical data of 34 subjects. RESULTS: Cognitive development was impaired in 33/34 (97%) subjects; 28/34 had mild to moderate ID, with language impairment being the most common feature. Epilepsy was diagnosed in 31/34 cases with mean onset at 3.7 years. Cognitive assessment before epilepsy onset was available in 24/31 subjects and was normal in 25% (6/24), and consistent with mild ID in 46% (11/24) or moderate ID in 17% (4/24). Two patients had speech delay only, and 1 had severe ID. After epilepsy onset, cognition deteriorated in 46% (11/24) of cases. The most common seizure types were absence, myoclonic, and atonic seizures. Sixteen cases fulfilled the diagnostic criteria for MAE. Seven further patients had different forms of generalized epilepsy and 2 had focal epilepsy. Twenty of 31 patients became seizure-free, with valproic acid being the most effective drug. There was no clear-cut correlation between seizure control and cognitive outcome. Electroencephalography (EEG) findings were available in 27/31 patients showing irregular bursts of diffuse 2.5-3.5 Hz spikes/polyspikes-and-slow waves in 25/31. Two patients developed an EEG pattern resembling electrical status epilepticus during sleep. Ataxia was observed in 7/34 cases. We describe 7 truncating and 18 missense variants, including 4 recurrent variants (Gly232Val, Ala288Val, Val342Met, and Gly362Arg). SIGNIFICANCE: Most patients carrying pathogenic SLC6A1 variants have an MAE phenotype with language delay and mild/moderate ID before epilepsy onset. However, ID alone or associated with focal epilepsy can also be observed.

Accuracy of WISC-III and WAIS-IV short forms in patients with neurological disorders.

The assessment of intellectual abilities is intensive, time-consuming, and might be considered burdensome for patients. We examined psychometric qualities of short forms (SFs) of the Wechsler Intelligence Scales for Children (WISC-third edition) and for adults (WAIS-fourth edition), in children (n = 986; Mage = 10.9) and adults (n = 324; Mage = 40.9) with neurological disorders. SF estimates were compared with Full Scale IQ (FSIQ), obtained by a complete administration, for the entire sample and for the subgroups FSIQ < 80 and FSIQ ≥ 80. The FSIQ was correctly identified within ± 7 points in 86% of children and 87% of adults. There were, however, some differences regarding the optimal SF subtest combination between subgroups. Although clinical inferences should not be made, SFs may be useful in research settings to obtain a global estimate of intelligence, and in clinical settings to screen periodically for possible intellectual deterioration.

Tau Rather than TDP-43 Proteins are Potential Cerebrospinal Fluid Biomarkers for Frontotemporal Lobar Degeneration Subtypes: A Pilot Study.

BACKGROUND: Frontotemporal dementia (FTD) is a heterogeneous disease both at the clinical, genetic, and pathobiological level. The underlying pathological spectrum (termed FTLD, frontotemporal lobar degeneration) is in most cases defined by accumulation of either tau (FTLD-tau) or TDP-43 proteins (FTLD-TDP). Biomarkers to differentiate these subtypes are not yet available, whereas these are essential requirements to study the natural course of disease and for homogeneous inclusion of patients in clinical studies. OBJECTIVE: To study if a combination of total (t-) and phosphorylated (p-)tau, and t-TDP-43 and p-TDP-43 proteins in cerebrospinal fluid (CSF) is suitable to discriminate FTLD-tau and FTLD-TDP subtypes. METHODS: We developed immunoassays for the quantification of t-TDP-43 and p-TDP-43 proteins and used commercially available assays for the quantification of t-tau and p-tau proteins. We quantified these proteins in ventricular CSF samples from neuropathologically defined FTLD-tau and FTLD-TDP cases to study the reflection of underlying brain pathology in CSF composition, and in lumbar CSF samples from FTLD-tau and FTLD-TDP patients to study the diagnostic potential of CSF biomarkers. RESULTS: In ventricular CSF, t-TDP-43 and t-tau levels, when combined into one model, were significantly different between neuropathologically-defined FTLD-tau and FTLD-TDP cases. In a pilot study using lumbar CSF, the p-tau/t-tau ratio, but not t-TDP-43 levels, were significantly different between FTLD-TDP and FTLD-tau patients. CONCLUSION: We conclude that with current available methods, CSF tau, rather than TDP-43 proteins, may have diagnostic value in the differentiation of FTLD patients with either tau or TDP-43 pathology.

Evaluation of perampanel in patients with intellectual disability and epilepsy.

INTRODUCTION: Initial registration studies of perampanel (PMP), an AMPA receptor antagonist, have now been followed up by 'clinical' studies that confirmed its efficacy and safety in patients with refractory epilepsy. Publications on the use of PMP among patients with intellectual disability (ID) are still limited. This study extends our knowledge with respect to the relevance of PMP for patients with both ID and epilepsy, and furthermore specifies the behavioral side effects of PMP in this specific population. METHODS: Retrospective evaluation of medical records at 3, 6 and 12months of follow-up after the initial start of PMP. RESULTS: 62 patients were included. 21 patients (33.9%) were female. All patients had complete data of 6months follow-up and we were able to review 42 patients with a 1-year follow-up. Level of ID varied from borderline to profound, and mild ID was most common (43.5%). The mean maximum daily dosage of PMP was 5.6mg (range 1-12mg). Retention rates for PMP were 87.1% and 67.7% after three and six months. A trend indicated a longer mean retention time in patients with a more severe ID (borderline-mild-moderate ID: 205days, severe-profound ID: 275days). Seizure reduction was achieved in 53.2%. 36 patients (58.1%) experienced adverse effects, 80.6% of those within 3months. 45.2% of the patients experienced somatic adverse effects. Most common were fatigue & sleep problems, motor problems & unsteadiness, and gastrointestinal problems. Behavioral adverse effects were present in 40.3%. Most common were aggression, agitated behavior, disruptive behavior, and mood symptoms. Reasons for discontinuation of PMP were lack of efficacy in 14.8%, intolerable adverse effects in 44.4%, and a combination of both in 40.7%. Altogether, 24.2% (15/62) of the patients achieved seizure reduction without experiencing adverse effects, though none reached seizure freedom. CONCLUSIONS: The use of PMP might lead to an effective seizure reduction without adverse effects in a minority of patients with both epilepsy and ID. Pre-existing behavioral problems or polypharmacy do not predict the occurrence of additional behavioral adverse effects, implying that these patients need not be excluded from the introduction of PMP when clinically indicated. Patients should, ideally, be monitored at a multidisciplinary clinic.

A systematic review of neuropsychiatric comorbidities in patients with both epilepsy and intellectual disability.

Epilepsy is a neurological condition that is particularly common in people with intellectual disability (ID). The care for people with both epilepsy and ID is often complicated by the presence of neuropsychiatric disorders, defined as psychiatric symptoms, psychiatric disorders, and behavioral problems. The aim of this study was to investigate associations between epilepsy or epilepsy-related factors and neuropsychiatric comorbidities in patients with ID and between ID and neuropsychiatric comorbidities in patients with epilepsy. We performed a systematic review of the literature, published between January 1995 and January 2015 and retrieved from PubMed/Medline, PsycINFO, and ERIC and assessed the risk of bias using the SIGN-50 methodology. Forty-two studies were identified, fifteen of which were assessed as having a low or acceptable risk-of-bias evaluation. Neuropsychiatric comorbidities were examined in relation to epilepsy in nine studies; in relation to epilepsy-related factors, such as seizure activity, seizure type, and medication in four studies; and in relation to the presence and degree of ID in five studies. We conclude that the presence of epilepsy only was not a clear determinant of neuropsychiatric comorbidity in patients with ID, although a tendency towards negative mood symptoms was identified. Epilepsy-related factors indicating a more severe form of epilepsy were associated with neuropsychiatric comorbidity as was the presence of ID as compared to those without ID in patients with epilepsy, although this should be validated in future research. A large proportion of the studies in this area is associated with a substantial risk of bias. There is a need for high quality studies using standardized methods to enable clear conclusions to be drawn that might assist in improving the quality of care for this population.

Euthanasia and physician-assisted suicide in amyotrophic lateral sclerosis: a prospective study.

The objective of this study is to determine if quality of care, symptoms of depression, disease characteristics and quality of life of patients with amyotrophic lateral sclerosis (ALS) are related to requesting euthanasia or physician-assisted suicide (EAS) and dying due to EAS. Therefore, 102 ALS patients filled out structured questionnaires every 3 months until death and the results were correlated with EAS. Thirty-one percent of the patients requested EAS, 69% of whom eventually died as a result of EAS (22% of all patients). Ten percent died during continuous deep sedation; only one of them had explicitly requested death to be hastened. Of the patients who requested EAS, 86% considered the health care to be good or excellent, 16% felt depressed, 45% experienced loss of dignity and 42% feared choking. These percentages do not differ from the number of patients who did not explicitly request EAS. The frequency of consultations of professional caregivers and availability of appliances was similar in both groups. Our findings do not support continuous deep sedation being used as a substitute for EAS. In this prospective study, no evidence was found for a relation between EAS and the quality and quantity of care received, quality of life and symptoms of depression in patients with ALS. Our study does not support the notion that unmet palliative care needs are related to EAS.

Mutations in BICD2, which encodes a golgin and important motor adaptor, cause congenital autosomal-dominant spinal muscular atrophy.

Spinal muscular atrophy (SMA) is a heterogeneous group of neuromuscular disorders caused by degeneration of lower motor neurons. Although functional loss of SMN1 is associated with autosomal-recessive childhood SMA, the genetic cause for most families affected by dominantly inherited SMA is unknown. Here, we identified pathogenic variants in bicaudal D homolog 2 (Drosophila) (BICD2) in three families afflicted with autosomal-dominant SMA. Affected individuals displayed congenital slowly progressive muscle weakness mainly of the lower limbs and congenital contractures. In a large Dutch family, linkage analysis identified a 9q22.3 locus in which exome sequencing uncovered c.320C>T (p.Ser107Leu) in BICD2. Sequencing of 23 additional families affected by dominant SMA led to the identification of pathogenic variants in one family from Canada (c.2108C>T [p.Thr703Met]) and one from the Netherlands (c.563A>C [p.Asn188Thr]). BICD2 is a golgin and motor-adaptor protein involved in Golgi dynamics and vesicular and mRNA transport. Transient transfection of HeLa cells with all three mutant BICD2 cDNAs caused massive Golgi fragmentation. This observation was even more prominent in primary fibroblasts from an individual harboring c.2108C>T (p.Thr703Met) (affecting the C-terminal coiled-coil domain) and slightly less evident in individuals with c.563A>C (p.Asn188Thr) (affecting the N-terminal coiled-coil domain). Furthermore, BICD2 levels were reduced in affected individuals and trapped within the fragmented Golgi. Previous studies have shown that Drosophila mutant BicD causes reduced larvae locomotion by impaired clathrin-mediated synaptic endocytosis in neuromuscular junctions. These data emphasize the relevance of BICD2 in synaptic-vesicle recycling and support the conclusion that BICD2 mutations cause congenital slowly progressive dominant SMA.

Autoantibodies to cytosolic 5'-nucleotidase 1A in inclusion body myositis.

OBJECTIVE: Sporadic inclusion body myositis (sIBM) is an inflammatory myopathy characterized by both degenerative and autoimmune features. In contrast to other inflammatory myopathies, myositis-specific autoantibodies had not been found in sIBM patients until recently. We used human skeletal muscle extracts as a source of antigens to detect autoantibodies in sIBM and to characterize the corresponding antigen. METHODS: Autoantibodies to skeletal muscle antigens were detected by immunoblotting. The target antigen was immunoaffinity-purified from skeletal muscle extracts and characterized by mass spectrometry. A cDNA encoding this protein was cloned and expressed in vitro, and its recognition by patient sera was analyzed in an immunoprecipitation assay. Epitopes were mapped using microarrays of overlapping peptides. RESULTS: An Mr 44,000 polypeptide (Mup44) was frequently targeted by sIBM autoantibodies. The target protein was purified, and subsequent mass spectrometry analysis revealed that Mup44 is the cytosolic 5'-nucleotidase 1A (cN1A). By immunoprecipitation of recombinant cN1A, high concentrations of anti-Mup44 autoantibodies were detected in 33% of sIBM patient sera, whereas their prevalence in dermatomyositis, polymyositis, and other neuromuscular disorders appeared to be rare (4.2%, 4.5%, and 3.2%, respectively). Low concentrations of anti-Mup44 antibodies were found in myositis as well as other neuromuscular disorders, but not in healthy controls. Three major autoepitope regions of cN1A were mapped by using microarrays containing a set of overlapping peptides covering the complete cN1A amino acid sequence. INTERPRETATION: Anti-Mup44 autoantibodies, which are targeted to cN1A, represent the first serological biomarker for sIBM and may facilitate the diagnosis of this type of myositis.

Rapidly deteriorating course in Dutch hereditary spastic paraplegia type 11 patients.

Although SPG11 is the most common complicated hereditary spastic paraplegia, our knowledge of the long-term prognosis and life expectancy is limited. We therefore studied the disease course of all patients with a proven SPG11 mutation as tested in our laboratory, the single Dutch laboratory providing SPG11 mutation analysis, between 1 January 2009 and 1 January 2011. We identified nine different SPG11 mutations, four of which are novel, in nine index patients. Eighteen SPG11 patients from these nine families were studied by means of a retrospective chart analysis and additional interview/examination. Ages at onset were between 4 months and 14 years; 39% started with learning difficulties rather than gait impairment. Brain magnetic resonance imaging showed a thin corpus callosum and typical periventricular white matter changes in the frontal horn region (known as the 'ears-of the lynx'-sign) in all. Most patients became wheelchair bound after a disease duration of 1 to 2 decades. End-stage disease consisted of loss of spontaneous speech, severe dysphagia, spastic tetraplegia with peripheral nerve involvement and contractures. Several patients died of complications between ages 30 and 48 years, 3-4 decades after onset of gait impairment. Other relevant features during the disease were urinary and fecal incontinence, obesity and psychosis. Our study of 18 Dutch SPG11-patients shows the potential serious long-term consequences of SPG11 including a possibly restricted life span.

The C9ORF72 expansion mutation is a common cause of ALS+/-FTD in Europe and has a single founder.

A massive hexanucleotide repeat expansion mutation (HREM) in C9ORF72 has recently been linked to amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Here we describe the frequency, origin and stability of this mutation in ALS+/-FTD from five European cohorts (total n=1347). Single-nucleotide polymorphisms defining the risk haplotype in linked kindreds were genotyped in cases (n=434) and controls (n=856). Haplotypes were analysed using PLINK and aged using DMLE+. In a London clinic cohort, the HREM was the most common mutation in familial ALS+/-FTD: C9ORF72 29/112 (26%), SOD1 27/112 (24%), TARDBP 1/112 (1%) and FUS 4/112 (4%) and detected in 13/216 (6%) of unselected sporadic ALS cases but was rare in controls (3/856, 0.3%). HREM prevalence was high for familial ALS+/-FTD throughout Europe: Belgium 19/22 (86%), Sweden 30/41 (73%), the Netherlands 10/27 (37%) and Italy 4/20 (20%). The HREM did not affect the age at onset or survival of ALS patients. Haplotype analysis identified a common founder in all 137 HREM carriers that arose around 6300 years ago. The haplotype from which the HREM arose is intrinsically unstable with an increased number of repeats (average 8, compared with 2 for controls, P<10(-8)). We conclude that the HREM has a single founder and is the most common mutation in familial and sporadic ALS in Europe.

Genetic overlap between apparently sporadic motor neuron diseases.

Progressive muscular atrophy (PMA) and amyotrophic lateral sclerosis (ALS) are devastating motor neuron diseases (MNDs), which result in muscle weakness and/or spasticity. We compared mutation frequencies in genes known to be associated with MNDs between patients with apparently sporadic PMA and ALS. A total of 261 patients with adult-onset sporadic PMA, patients with sporadic ALS, and control subjects of Dutch descent were obtained at national referral centers for neuromuscular diseases in The Netherlands. Sanger sequencing was used to screen these subjects for mutations in the coding regions of superoxide dismutase-1 (SOD1), angiogenin (ANG), fused in sarcoma/translated in liposarcoma (FUS/TLS), TAR DNA-binding protein 43 (TARDBP), and multivesicular body protein 2B (CHMP2B). In our cohort of PMA patients we identified two SOD1 mutations (p.D90A, p.I113T), one ANG mutation (p.K17I), one FUS/TLS mutation (p.R521H), one TARDBP mutation (p.N352S), and one novel CHMP2B mutation (p.R69Q). The mutation frequency of these genes was similar in sporadic PMA (2.7%) and ALS (2.0%) patients, and therefore, our findings demonstrate a genetic overlap between apparently sporadic PMA and ALS.