Spatial Discrimination Threshold Abnormalities are not Detected in a Pilot Study of DYT6 Dystonia Mutation Carriers

Background: Spatial discrimination thresholds (SDTs) assess somatosensory integration, and provide a window into better understanding the pathophysiology of dystonia. They are abnormal in some focal dystonias, but normal in DYT1 dystonia. It is unknown whether SDTs are altered in DYT6 gene mutation carriers (C). Methods: SDTs were assessed in 17 DYT6 C (including eight manifesting carriers), 15 DYT1 C (including seven manifesting carriers) and 34 controls, using a standardized grating orientation task. Subjects were asked to recognize the orientation of Johnson–Van Boven–Philips (JVP) dome gratings on either index fingertip until 40% or more answers were incorrect. SDTs between indexes were calculated and averaged, with a final SDT assigned to each subject, and tertiles for control SDTs were constructed. Results: SDTs of DYT6 C or DYT1 C were comparable to those of controls, and not more likely to be in the worst tertile (p = 0.8 for DYT6 C vs. controls and p = 1.0 for DYT1 C vs. controls). This was independent of gene expression. Discussion: DYT6 carriers do not have impaired SDTs with the JVP dome paradigm. The normal SDT pattern thus suggests shared sensory physiologic patterns with DYT1 dystonia

Digitized Spiral Drawing: A Possible Biomarker for Early Parkinson’s Disease

Introduction Pre-clinical markers of Parkinson’s Disease (PD) are needed, and to be relevant in pre-clinical disease, they should be quantifiably abnormal in early disease as well. Handwriting is impaired early in PD and can be evaluated using computerized analysis of drawn spirals, capturing kinematic, dynamic, and spatial abnormalities and calculating indices that quantify motor performance and disability. Digitized spiral drawing correlates with motor scores and may be more sensitive in detecting early changes than subjective ratings. However, whether changes in spiral drawing are abnormal compared with controls and whether changes are detected in early PD are unknown. Methods 138 PD subjects (50 with early PD) and 150 controls drew spirals on a digitizing tablet, generating x, y, z (pressure) data-coordinates and time. Derived indices corresponded to overall spiral execution (severity), shape and kinematic irregularity (second order smoothness, first order zero-crossing), tightness, mean speed and variability of spiral width. Linear mixed effect adjusted models comparing these indices and cross-validation were performed. Receiver operating characteristic analysis was applied to examine discriminative validity of combined indices. Results All indices were significantly different between PD cases and controls, except for zero-crossing. A model using all indices had high discriminative validity (sensitivity = 0.86, specificity = 0.81). Discriminative validity was maintained in patients with early PD. Conclusion Spiral analysis accurately discriminates subjects with PD and early PD from controls supporting a role as a promising quantitative biomarker. Further assessment is needed to determine whether spiral changes are PD specific compared with other disorders and if present in pre-clinical PD

Mutations in the Na+/K+-ATPase α3 Gene ATP1A3 Are Associated with Rapid-Onset Dystonia Parkinsonism

AbstractRapid-onset dystonia-parkinsonism (RDP, DYT12) is a distinctive autosomal-dominant movement disorder with variable expressivity and reduced penetrance characterized by abrupt onset of dystonia, usually accompanied by signs of parkinsonism. The sudden onset of symptoms over hours to a few weeks, often associated with physical or emotional stress, suggests a trigger initiating a nervous system insult resulting in permanent neurologic disability. We report the finding of six missense mutations in the gene for the Na+/K+-ATPase α3 subunit (ATP1A3) in seven unrelated families with RDP. Functional studies and structural analysis of the protein suggest that these mutations impair enzyme activity or stability. This finding implicates the Na+/K+ pump, a crucial protein responsible for the electrochemical gradient across the cell membrane, in dystonia and parkinsonism

GBA mutations are associated with Rapid eye movement sleep behavior disorder

Rapid eye movement sleep behavior disorder and GBA mutations are both associated with Parkinson’s disease. The GBA gene was sequenced in idiopathic rapid eye movement sleep behavior disorder patients (n = 265), and compared to controls (n = 2240). Rapid eye movement sleep behavior disorder questionnaire was performed in an independent Parkinson’s disease cohort (n = 120). GBA mutations carriers had an OR of 6.24 (10.2% in patients vs. 1.8% in controls, P < 0.0001) for rapid eye movement sleep behavior disorder, and among Parkinson’s disease patients, the OR for mutation carriers to have probable rapid eye movement sleep behavior disorder was 3.13 (P = 0.039). These results demonstrate that rapid eye movement sleep behavior disorder is associated with GBA mutations, and that combining genetic and prodromal data may assist in identifying individuals susceptible to Parkinson’s disease

A Genome-Wide Scan of Ashkenazi Jewish Crohn's Disease Suggests Novel Susceptibility Loci

Crohn's disease (CD) is a complex disorder resulting from the interaction of intestinal microbiota with the host immune system in genetically susceptible individuals. The largest meta-analysis of genome-wide association to date identified 71 CD–susceptibility loci in individuals of European ancestry. An important epidemiological feature of CD is that it is 2–4 times more prevalent among individuals of Ashkenazi Jewish (AJ) descent compared to non-Jewish Europeans (NJ). To explore genetic variation associated with CD in AJs, we conducted a genome-wide association study (GWAS) by combining raw genotype data across 10 AJ cohorts consisting of 907 cases and 2,345 controls in the discovery stage, followed up by a replication study in 971 cases and 2,124 controls. We confirmed genome-wide significant associations of 9 known CD loci in AJs and replicated 3 additional loci with strong signal (p<5×10−6). Novel signals detected among AJs were mapped to chromosomes 5q21.1 (rs7705924, combined p = 2×10−8; combined odds ratio OR = 1.48), 2p15 (rs6545946, p = 7×10−9; OR = 1.16), 8q21.11 (rs12677663, p = 2×10−8; OR = 1.15), 10q26.3 (rs10734105, p = 3×10−8; OR = 1.27), and 11q12.1 (rs11229030, p = 8×10−9; OR = 1.15), implicating biologically plausible candidate genes, including RPL7, CPAMD8, PRG2, and PRG3. In all, the 16 replicated and newly discovered loci, in addition to the three coding NOD2 variants, accounted for 11.2% of the total genetic variance for CD risk in the AJ population. This study demonstrates the complementary value of genetic studies in the Ashkenazim

Intragenic Cis and Trans Modification of Genetic Susceptibility in DYT1 Torsion Dystonia

A GAG deletion in the DYT1 gene is a major cause of early-onset dystonia, but clinical disease expression occurs in only 30% of mutation carriers. To gain insight into genetic factors that may influence penetrance, we evaluated three DYT1 single-nucleotide polymorphisms, including D216H, a coding-sequence variation that moderates the effects of the DYT1 GAG deletion in cellular models. We tested DYT1 GAG-deletion carriers with (n=119) and without (n=113) clinical signs of dystonia and control individuals (n=197) and found the frequency of the 216H allele to be increased in GAG-deletion carriers without dystonia and to be decreased in carriers with dystonia, compared with the control individuals. Analysis of haplotypes demonstrated a highly protective effect of the H allele in trans with the GAG deletion; there was also suggestive evidence that the D216 allele in cis is required for the disease to be penetrant. Our findings establish, for the first time, a clinically relevant gene modifier of DYT1

DYT1 dystonia increases risk taking in humans

It has been difficult to link synaptic modification to overt behavioral changes. Rodent models of DYT1 dystonia, a motor disorder caused by a single gene mutation, demonstrate increased long-term potentiation and decreased long-term depression in corticostriatal synapses. Computationally, such asymmetric learning predicts risk taking in probabilistic tasks. Here we demonstrate abnormal risk taking in DYT1 dystonia patients, which is correlated with disease severity, thereby supporting striatal plasticity in shaping choice behavior in humans

Mutations in THAP1 (DYT6) in early-onset dystonia: a genetic screening study

Summary Background Mutations in THAP1 were recently identifi ed as the cause of DYT6 primary dystonia; a founder mutation was detected in Amish-Mennonite families, and a diff erent mutation was identifi ed in another family of European descent. To assess more broadly the role of this gene, we screened for mutations in families that included one family member who had early-onset, non-focal primary dystonia