SCN4A pore mutation pathogenetically contributes to autosomal dominant essential tremor and may increase susceptibility to epilepsy.

Essential tremor (ET) is the most prevalent movement disorder, affecting millions of people in the USA. Although a positive family history is one of the most important risk factors for ET, the genetic causes of ET remain unknown. In an attempt to identify genetic causes for ET, we performed whole-exome sequencing analyses in a large Spanish family with ET, in which two patients also developed epilepsy. To further assess pathogenicity, site-directed mutagenesis, mouse and human brain expression analyses, and patch clamp techniques were performed. A disease-segregating mutation (p.Gly1537Ser) in the SCN4A gene was identified. Posterior functional analyses demonstrated that more rapid kinetics at near-threshold potentials altered ion selectivity and facilitated the conductance of both potassium and ammonium ions, which could contribute to tremor and increase susceptibility to epilepsy, respectively. In this report, for the first time, we associated the genetic variability of SCN4A with the development of essential tremor, which adds ET to the growing list of neurological channelopathies.

Inflammatory profile in LRRK2-associated prodromal and clinical PD.

BACKGROUND: There is evidence for a relevant role of inflammation in the pathogenesis of Parkinson's disease (PD). Mutations in the LRRK2 gene represent the most frequent genetic cause for autosomal dominant PD. LRRK2 is highly expressed in macrophages and microglia suggesting an involvement in inflammatory pathways. The objectives are to test (1) whether idiopathic PD and LRRK2-associated PD share common inflammatory pathways or present distinct profiles and (2) whether non-manifesting LRRK2 mutation carriers present with similar aspects of inflammatory profiles as seen in PD-affected patients. METHODS: We assessed serum profiles of 23 immune-associated markers and the brain-derived neurotrophic factor in 534 individuals from the MJFF LRRK2 consortium. RESULTS: A large proportion of inflammatory markers were gender-dependent. Both PD-affected cohorts showed increased levels of the pro-inflammatory marker fatty-acid-binding protein. Additionally, idiopathic PD but not LRRK2-associated PD patients showed increased levels of the pro-inflammatory marker interleukin-12-p40 as well as the anti-inflammatory species interleukin-10, brain-derived neurotrophic factor, and stem cell factor. Non-manifesting LRRK2 mutation carriers including those with prodromal characteristics of PD presented with control-like inflammatory profiles. CONCLUSIONS: Concomitant inflammation seems to be associated with idiopathic and LRRK2-associated PD. Identifying PD patients in whom inflammatory processes play a major role in their pathophysiology might offer a new therapeutic window at least for a subgroup of patients. Since non-manifesting LRRK2 mutation carriers with symptoms of the prodromal phase of PD did not show inflammatory profiles, activation of the immune system seems not an early event in the disease cascade.

DAT imaging and clinical biomarkers in relatives at genetic risk for LRRK2 R1441G Parkinson's disease.

BACKGROUND: The objective of this study was to study motor and nonmotor symptoms and striatal dopaminergic denervation, as well as the relationship between them, in a cohort of asymptomatic relatives of patients with Parkinson's disease (PD) with the R1441G-leucine-rich repeat kinase 2 mutation. METHODS: Asymptomatic relatives of patients with PD and this mutation were tested for the presence of the mutation and evaluated for striatal, putamenal, and caudate dopaminergic transporters using (123)I-2ß-carbomethoxy-3ß-(4-iodophenyl)-N-(3-fluoropropyl)-nortropane single-photon emission computed tomography binding ratios. Clinical and neuropsychological evaluations including timed motor tests, a smell identification test, and global cognition, attention, executive, visuospatial, and memory functions as well as depression, constipation, and rapid eye movement sleep behavior disorder were also assessed. RESULTS: Twenty-seven carriers and 19 noncarriers were studied. Compared with noncarriers, mutation carriers had significantly lower (123)I-2ß-carbomethoxy-3ß-(4-iodophenyl)-N-(3-fluoropropyl)-nortropan mean striatal (P = 0.03), mean putamenal (P = 0.01), and lowest putamenal (P = 0.01) binding ratios. Multiple linear regression analysis showed that the carrier status and the execution of timed tests significantly predicted striatal (123)I-2ß-carbomethoxy-3ß-(4-iodophenyl)-N-(3-fluoropropyl)-nortropane binding. The proportion of variation accounted for by the regression model of these variables was 69% for the putamen and 53% for the caudate nucleus. CONCLUSIONS: Asymptomatic carriers of the R1441G-leucine-rich repeat kinase 2 mutation have evidence of dopaminergic nigrostriatal denervation, mainly in the putamen, which is associated with a decline in the execution of complex motor tests. These tests could be early indicators of the ongoing dopaminergic deficit in this group at risk of PD.

Congenital Spinal Malformation and Stroke: Aneurysmal Dilatations and Bilateral Rotational Vertebral Artery Occlusion.

A 30-year-old woman suffered from acute vertebrobasilar stroke. Cranial tomography (CT) scans showed multiple vertebral abnormalities suggestive of congenital spine malformation, and angiographic CT revealed aneurysmal dilatations (ADs) at segment V2 of both vertebral arteries (VAs). Dynamic neuroimaging tests including angiography and angio-CT were performed and showed occlusion of both VAs at the point of the ADs with contralateral rotation of the neck. The presence of a bony structure causing the artery compression was excluded and embolic phenomena originating at the AD was proposed as the likely source of stroke. Even if infrequent, the presence of craniocervical anomalies should be considered in vertebrobasilar stroke of indeterminate etiology.

Neurogenetic disorders in the Basque population.

In the molecular era, the study of neurogenetic disorders in relict populations provides an opportunity to discover new genes by linkage studies and to establish clearer genotype-phenotype correlations in large cohorts of individuals carrying the same mutation. The Basque people are one of the most ancient populations living in Europe and represent an excellent resource for this type of analysis in certain genetic conditions. Our objective was to describe neurogenetic disorders reported in the Basque population due to the presence of ancestral mutations or an accumulation of cases or both. We conducted a search in PubMed with the terms: Basque, neurogenetic disorders, genetic risk, and neurological disorders. We identified nine autosomal and two recessive disorders in the Basque population attributable to ancestral mutations (such as in PNRP, PARK8, FTDP-TDP43, LGMD2A, VCP, c9ORF72, and CMT4A), highly prevalent (DM1) or involving unique mutations (PARK1 or MAPT). Other genes were reported for their role as protective/risk factors in complex diseases such as multiple sclerosis, Alzheimer's disease, and Parkinson's disease. At the present time, when powerful sequencing techniques are identifying large numbers of genetic variants associated with unique phenotypes, the scrutiny of these findings in genetically homogeneous populations can help analyze genotype-phenotype correlations.

GIGYF2 mutation in late-onset Parkinson's disease with cognitive impairment.

Although in the last two decades there has been considerable progress in understanding the genetic basis of Parkinson's disease (PD), the majority of PD is sporadic and its genetic causes are largely unknown. In an attempt to identify novel genetic causes of PD, whole-exome sequencing and subsequent analyses were performed in a family featuring late-onset PD with cognitive impairment. A novel genetic variant (p.Arg610Gly) in the GIGYF2 gene, previously known to be associated with PD, was identified as potential disease-causing mutation. The GIGYF2 p.Arg610Gly mutation situated in the GYF domain of the encoding protein was predicted to be pathogenic and to disrupt the GYF's ligand-binding abilities. Although further research is still required, this finding may shed light on the GIGYF2-associated mechanisms that lead to PD and suggests insulin dysregulation as a disease-specific mechanism for both PD and cognitive dysfunction.

Pathogenic Parkinson's disease mutations across the functional domains of LRRK2 alter the autophagic/lysosomal response to starvation.

LRRK2 is one of the most important genetic contributors to Parkinson's disease (PD). Point mutations in this gene cause an autosomal dominant form of PD, but to date no cellular phenotype has been consistently linked with mutations in each of the functional domains (ROC, COR and Kinase) of the protein product of this gene. In this study, primary fibroblasts from individuals carrying pathogenic mutations in the three central domains of LRRK2 were assessed for alterations in the autophagy/lysosomal pathway using a combination of biochemical and cellular approaches. Mutations in all three domains resulted in alterations in markers for autophagy/lysosomal function compared to wild type cells. These data highlight the autophagy and lysosomal pathways as read outs for pathogenic LRRK2 function and as a marker for disease, and provide insight into the mechanisms linking LRRK2 function and mutations.

Exome sequencing identifies GCDH (glutaryl-CoA dehydrogenase) mutations as a cause of a progressive form of early-onset generalized dystonia.

Dystonias are a clinically and genetically heterogeneous group of movement disorders characterized by involuntary, sustained muscular contractions affecting one or more sites of the body, and abnormal postures. In this study, we describe an autosomal recessive family that presents with a progressive and early-onset form of generalized dystonia. The nuclear family consists of two healthy parents and two affected daughters. To elucidate the genetic causes underlying disease, whole-exome sequencing analysis was performed in one affected sibling, followed by validation, biochemical analyses and MRI brain imaging. A homozygous, disease-segregating mutation (p.Val400Met) was identified in the glutaryl-CoA dehydrogenase (GCDH) gene at chromosome 19p13. The mutation, in an amino acid that is highly conserved among species, was absent in large number of neurologically normal individuals. Biochemical analyses demonstrated increased 3-hydroxy glutaric acid present in urine samples from both patients. MRI imaging revealed a T2 and flair hyperintense signal in lenticular nuclei with bilateral and symmetrical distribution. We conclude that both GCDH activity and GCDH mutation analysis should be considered in the differential diagnosis of progressive forms of early-onset generalized dystonia and that mitochondrial fatty acid metabolism is one important pathway in the development of dystonia. As lysine restriction and L: -carnitine supplementation are important treatments for GCDH deficiency, identification of this deficiency in patients with progressive forms of early-onset generalized dystonia has potential treatment implications.

Neuropsychological features of asymptomatic c.709-1G>A progranulin mutation carriers.

Mutations in the progranulin (PGRN) gene have been identified as a cause of frontotemporal dementia (FTD). However, little is known about the neuropsychological abilities of asymptomatic carriers of these mutations. The aim of the study was to assess cognitive functioning in asymptomatic c.709-1G>A PGRN mutation carriers. We hypothesized that poorer neuropsychological performance could be present before the development of clinically significant FTD symptoms. Thirty-two asymptomatic first-degree relatives of FTD patients carrying the c.709-1G>A mutation served as study participants, including 13 PGRN mutation carriers (A-PGRN+) and 19 non-carriers (PGRN-). A neuropsychological battery was administered. We found that the A-PGRN+ participants obtained significantly poorer scores than PGRN- individuals on tests of attention (Trail-Making Test Part A), mental flexibility (Trail-Making Test Part B), and language (Boston Naming Test). Poorer performance on these tests in asymptomatic PGRN mutation carriers may reflect a prodromal phase preceding the onset of clinically significant symptoms of FTD.

Analysis of Fine Motor Skills in Essential Tremor: Combining Neuroimaging and Handwriting Biomarkers for Early Management.

Essential tremor (ET) is a highly prevalent neurological disorder characterized by action-induced tremors involving the hand, voice, head, and/or face. Importantly, hand tremor is present in nearly all forms of ET, resulting in impaired fine motor skills and diminished quality of life. To advance early diagnostic approaches for ET, automated handwriting tasks and magnetic resonance imaging (MRI) offer an opportunity to develop early essential clinical biomarkers. In this study, we present a novel approach for the early clinical diagnosis and monitoring of ET based on integrating handwriting and neuroimaging analysis. We demonstrate how the analysis of fine motor skills, as measured by an automated Archimedes' spiral task, is correlated with neuroimaging biomarkers for ET. Together, we present a novel modeling approach that can serve as a complementary and promising support tool for the clinical diagnosis of ET and a large range of tremors.

Neuropathology of Parkinson's disease with the R1441G mutation in LRRK2.

We report the neuropathological findings in a patient with Parkinson's disease (PD) associated with Basque R1441G-LRRK2/dardarin mutation. The patient was a man with disease onset at 68 years of age, with unilateral rest tremor; the Parkinsonism was well controlled with medication for 15 years. He died at the age of 86, after 18 years of evolution. The neuropathological examination disclosed mild neuronal loss in the substantia nigra pars compacta without alpha-synuclein, tau, LRRK2, or ubiquitin cytoplasmic inclusions. Lewy bodies and Lewy neurites were absent. This is the first neuropathological study of PD associated with brain with the R1441G mutation in LRRK2.

Cloning of the gene containing mutations that cause PARK8-linked Parkinson's disease.

Parkinson's disease (PD; OMIM #168600) is the second most common neurodegenerative disorder in the Western world and presents as a progressive movement disorder. The hallmark pathological features of PD are loss of dopaminergic neurons from the substantia nigra and neuronal intracellular Lewy body inclusions. Parkinsonism is typically sporadic in nature; however, several rare familial forms are linked to genetic loci, and the identification of causal mutations has provided insight into the disease process. PARK8, identified in 2002 by Funayama and colleagues, appears to be a common cause of familial PD. We describe here the cloning of a novel gene that contains missense mutations segregating with PARK8-linked PD in five families from England and Spain. Because of the tremor observed in PD and because a number of the families are of Basque descent, we have named this protein dardarin, derived from the Basque word dardara, meaning tremor.

Tremor dominant parkinsonism: Clinical description and LRRK2 mutation screening.

Tremor dominant parkinsonism (TDP) is characterized by initial prominent resting and action tremor, mild parkinsonism, unpredictable response to medication, and a better prognosis than idiopathic Parkinson's disease (PD). We report on clinical features and longitudinal course of 26 patients suffering from TDP. Mean disease duration was 6.5 +/- 3 years, 61.5% of patients had a positive family history of tremor, 73% did not need drug treatment, performance of 123I-Ioflupane SPECT showed reduced striatal tracer uptake in 65.4% of patients, and odor identification testing was pathologic in all the patients tested (n = 22). Co-occurrence of action and resting tremor were the most annoying and disabling symptoms in all the patients, whereas rigidity and/or bradykinesia were clinically irrelevant in most of them. We also sequenced the full coding region of the Leucine-rich repeat kinase 2 gene (LRRK2) in all patients. We found a novel Val2390Met mutation that was not found in 864 chromosomes. Our results suggest a broader clinical heterogeneity related to LRRK2 mutations and points towards TDP as a subtype within the spectrum of PD, in which disabling tremor but otherwise mild parkinsonian signs and a better prognosis are the main characteristics.

Genetic Mutation Analysis of Parkinson's Disease Patients Using Multigene Next-Generation Sequencing Panels.

BACKGROUND: Parkinson's disease (PD) is the second most common neurodegenerative disorder, affecting millions of people. Genome-wide association studies (GWAS) have found >25 genetic risk factors and at least 15 loci directly associated with PD. Recent advances in new next-generation DNA sequencing technologies, such as the semiconductor-based Ion Torrent platform, make multigene sequencing cheaper, faster, and more reliable. OBJECTIVES: Our objective was to test the power of this next-generation sequencing technology to analyze large samples by screening the majority of the most relevant PD-related genes known for single and compound mutations. METHODS: To archive a rapid, robust, and cost-effective genetic analysis of a PD cohort, we designed a multiplex, polymerase chain reaction (PCR)-based primer panel to amplify and sequence coding exons of 15 PD-associated genes (SNCA, LRRK2, PARK2, PINK1, PARK7, GIGYF2, ATP13A2, UCHL1, PLA2G6, FBXO7, EIF4G1, VPS35, ACMSD, APOE, and GBA). We conducted parallel sequencing using the Ion Torrent Personal Genome Machine(®) system to detect mutations in 92 blood DNA samples from PD patients. RESULTS: After bioinformatics analysis and filtering, 95.13 % coverage of the targeted region was obtained at >40-fold mean coverage. The results revealed 44 previously documented variants in these 15 genes, with five revealed as pathogenic. We also discovered six novel variants, five of which had an in silico prediction of being pathogenic. CONCLUSIONS: Benchtop next-generation sequencing is a powerful method for genetic screening for PD. Our results indicated that it yielded a high frequency of discovery (66 %; n = 92) of variants in carriers from an enriched Spanish PD sample.

[Gait analysis in Parkinson's disease and response to dopaminergic treatment]. / Análisis de la marcha en la enfermedad de Parkinson y su respuesta al tratamiento dopaminérgico.

BACKGROUND AND OBJECTIVE: The objective of this study was to analyze the gait abnormalities in patients with idiopathic Parkinson's disease (PD), and their response to dopaminergic treatment. PATIENTS AND METHOD: 15 patients and 15 healthy age-matched subjects were included for comparison between pathologic and "normal" gait, and 24 PD patients were included to assess the effects of treatment. Gait analysis was achieved with a new 3D-photogrammetry system. RESULTS: Patients had significative lower velocity, stride length, step length and hip and knee ranges when compared with control subjects. There were no differences in cadence, step width and relative times of gait-cycle. There were no differences in the patients' gait variables after administration of a dopaminergic medication. CONCLUSIONS: Gait analysis allows quantification of gait disturbances in patients with PD and the potential effects of treatment. The results of this study suggest a certain degree of "levodopa-resistance" in gait in these patients.

Trimetazidine induces parkinsonism, gait disorders and tremor.

OBJECTIVE: To study the adverse effects of trimetazidine on motor functions. DESIGN: A retrospective study was carried out using electronic records to identify all patients seen between January 1990 and August 2003. SETTING: A neurological out-patient clinic. PARTICIPANTS: Of the 10 258 patients who attended the clinic, 130 received trimetazidine. Treatment with this drug was discontinued in 128 patients. Of the 130 patients treated with trimetazidine, 29 also had other drugs capable of inducing parkinsonism withdrawn from their treatment. MAIN OUTCOME MEASURES: Identification of an improvement in motor function after drug withdrawal. RESULTS: In 56 of the 130 patients who were treated with trimetazidine (43%), an adverse effect on motor function was detected that had been induced or aggravated by one of the withdrawn drugs. Indeed, drug-induced parkinsonism was detected in 20 of these patients. Of these, ten were being treated with trimetazidine only, while the remaining ten were simultaneously receiving other drugs potentially capable of inducing parkinsonism. Treatment with trimetazidine worsened previously diagnosed Parkinson's disease in 12 patients, and gait disorders coupled with disequilibrium was observed in 15 patients. Trimetazidine induced tremor in nine patients. CONCLUSION: Trimetazidine can induce parkinsonism, gait disorder and tremor. These adverse effects have not been previously described for this drug.

SORT1 Mutation Resulting in Sortilin Deficiency and p75(NTR) Upregulation in a Family With Essential Tremor.

*These authors contributed equally to this work.Essential tremor (ET) is the most prevalent movement disorder affecting millions of people in the United States. Although a positive family history is one of the most important risk factors for ET, the genetic causes of ET remain unknown. In this study, whole exome sequencing and subsequent approaches were performed in a family with an autosomal dominant form of early-onset ET. Functional analyses including mutagenesis, cell culture, gene expression, enzyme-linked immunosorbent, and apoptosis assays were also performed. A disease-segregating mutation (p.Gly171Ala), absent in normal population, was identified in the SORT1 gene. The p.Gly171Ala mutation was shown not only to impair the expression of its encoding protein sortilin but also the mRNA levels of its binding partner p75 neurotrophin receptor that is known to be implicated in brain injury, neuronal apoptosis, and neurotransmission.