Thalamic structural connectivity profiles in blepharospam/Meige's syndrome

BACKGROUND

Blepharospasm is a debilitating focal dystonia characterized by involuntary eyelid spasms that can be accompanied by oromandibular muscle involvement (Meige's syndrome). Frequently observed abnormality in functional neuroimaging hints at an important position of the thalamus, that relays involved cortico-basal ganglia-cortical and cortico-cerebello-cortical circuits, within the abnormal network in blepharospasm.

OBJECTIVE

To characterize abnormal cortico-thalamic structural/streamline connectivity (SC) patterns in the disease, as well as their potential co-occurrence with abnormal subcortico-thalamo-cortical projections using diffusion tractography.

METHODS

Diffusion imaging was obtained in 17 patients with blepharospasm (5 with mild lower facial involvement) and 17 healthy controls. Probabilistic tractography was used for quantification of SC between six cortical regions and thalamus, and voxel-level thalamic SC mapping as well as evaluation of the thalamic SC distributions' topography by center-of-gravity analysis was performed. Post-hoc, correlations of SC with clinical parameters were evaluated. Further, white matter integrity was investigated within representative segments of the dentato-thalamo-cortical and pallido-thalamo-cortical tract.

RESULTS

Connectivity mapping showed significant reduction of right (pre)motor- and left occipital-thalamic SC, as well as a topographic shift of the left occipital-thalamic SC distribution in patients. Significant positive correlation of occipital-thalamic SC with disease severity was found. Post-hoc analysis revealed significantly reduced mean fractional anisotropy in patients within the dentato-thalamo-cortical trajectory connecting to right (pre)motor and left occipital cortex.

CONCLUSION

Abnormal occipital/motor SC provides evidence for dysfunction of the thalamus-relayed visual and motor network as a key aspect in the disease. Concurrent impairment of microstructural integrity within the dentato-thalamic trajectories targeting those cortices hints at cerebellar contribution.

Monogenic variants in dystonia: an exome-wide sequencing study

BACKGROUND

Dystonia is a clinically and genetically heterogeneous condition that occurs in isolation (isolated dystonia), in combination with other movement disorders (combined dystonia), or in the context of multisymptomatic phenotypes (isolated or combined dystonia with other neurological involvement). However, our understanding of its aetiology is still incomplete. We aimed to elucidate the monogenic causes for the major clinical categories of dystonia.

METHODS

For this exome-wide sequencing study, study participants were identified at 33 movement-disorder and neuropaediatric specialty centres in Austria, Czech Republic, France, Germany, Poland, Slovakia, and Switzerland. Each individual with dystonia was diagnosed in accordance with the dystonia consensus definition. Index cases were eligible for this study if they had no previous genetic diagnosis and no indication of an acquired cause of their illness. The second criterion was not applied to a subset of participants with a working clinical diagnosis of dystonic cerebral palsy. Genomic DNA was extracted from blood of participants and whole-exome sequenced. To find causative variants in known disorder-associated genes, all variants were filtered, and unreported variants were classified according to American College of Medical Genetics and Genomics guidelines. All considered variants were reviewed in expert round-table sessions to validate their clinical significance. Variants that survived filtering and interpretation procedures were defined as diagnostic variants. In the cases that went undiagnosed, candidate dystonia-causing genes were prioritised in a stepwise workflow.

FINDINGS

We sequenced the exomes of 764 individuals with dystonia and 346 healthy parents who were recruited between June 1, 2015, and July 31, 2019. We identified causative or probable causative variants in 135 (19%) of 728 families, involving 78 distinct monogenic disorders. We observed a larger proportion of individuals with diagnostic variants in those with dystonia (either isolated or combined) with coexisting non-movement disorder-related neurological symptoms (100 [45%] of 222; excepting cases with evidence of perinatal brain injury) than in those with combined (19 [19%] of 98) or isolated (16 [4%] of 388) dystonia. Across all categories of dystonia, 104 (65%) of the 160 detected variants affected genes which are associated with neurodevelopmental disorders. We found diagnostic variants in 11 genes not previously linked to dystonia, and propose a predictive clinical score that could guide the implementation of exome sequencing in routine diagnostics. In cases without perinatal sentinel events, genomic alterations contributed substantively to the diagnosis of dystonic cerebral palsy. In 15 families, we delineated 12 candidate genes. These include IMPDH2, encoding a key purine biosynthetic enzyme, for which robust evidence existed for its involvement in a neurodevelopmental disorder with dystonia. We identified six variants in IMPDH2, collected from four independent cohorts, that were predicted to be deleterious de-novo variants and expected to result in deregulation of purine metabolism.

INTERPRETATION

In this study, we have determined the role of monogenic variants across the range of dystonic disorders, providing guidance for the introduction of personalised care strategies and fostering follow-up pathophysiological explorations.

FUNDING

Else Kröner-Fresenius-Stiftung, Technische Universität München, Helmholtz Zentrum München, Medizinische Universität Innsbruck, Charles University in Prague, Czech Ministry of Education, the Slovak Grant and Development Agency, the Slovak Research and Grant Agency.

Structure-function abnormalities in cortical sensory projections in embouchure dystonia

BACKGROUND

Embouchure dystonia (ED) is a task-specific focal dystonia in professional brass players leading to abnormal orofacial muscle posturing/spasms during performance. Previous studies have outlined abnormal cortical sensorimotor function during sensory/motor tasks and in the resting state as well as abnormal cortical sensorimotor structure. Yet, potentially underlying white-matter tract abnormalities in this network disease are unknown.

OBJECTIVE

To delineate structure-function abnormalities within cerebral sensorimotor trajectories in ED.

METHOD

Probabilistic tractography and seed-based functional connectivity analysis were performed in 16/16 ED patients/healthy brass players within a simple literature-informed network model of cortical sensorimotor processing encompassing supplementary motor, superior parietal, primary somatosensory and motor cortex as well as the putamen. Post-hoc grey matter volumetry was performed within cortices of abnormal trajectories.

RESULTS

ED patients showed average axial diffusivity reduction within projections between the primary somatosensory cortex and putamen, with converse increases within projections between supplementary motor and superior parietal cortex in both hemispheres. Increase in the mode of anisotropy in patients was accompanying the latter left-hemispheric projection, as well as in the supplementary motor area's projection to the left primary motor cortex. Patient's left primary somatosensory functional connectivity with the putamen was abnormally reduced and significantly associated with the axial diffusivity reduction. Left primary somatosensory grey matter volume was increased in patients.

CONCLUSION

Correlates of abnormal tract integrity within primary somatosensory cortico-subcortical projections and higher-order sensorimotor projections support the key role of dysfunctional sensory information propagation in ED pathophysiology. Differential directionality of cortico-cortical and cortico-subcortical abnormalities hints at non-uniform sensory system changes.

Altered sensory system activity and connectivity patterns in adductor spasmodic dysphonia

Adductor-type spasmodic dysphonia (ADSD) manifests in effortful speech temporarily relievable by botulinum neurotoxin type A (BoNT-A). Previously, abnormal structure, phonation-related and resting-state sensorimotor abnormalities as well as peripheral tactile thresholds in ADSD were described. This study aimed at assessing abnormal central tactile processing patterns, their spatial relation with dysfunctional resting-state connectivity, and their BoNT-A responsiveness. Functional MRI in 14/12 ADSD patients before/under BoNT-A effect and 15 controls was performed (i) during automatized tactile stimulus application to face/hand, and (ii) at rest. Between-group differential stimulation-induced activation and resting-state connectivity (regional homogeneity, connectivity strength within selected sensory(motor) networks), as well as within-patient BoNT-A effects on these differences were investigated. Contralateral-to-stimulation overactivity in ADSD before BoNT-A involved primary and secondary somatosensory representations, along with abnormalities in higher-order parietal, insular, temporal or premotor cortices. Dysphonic impairment in ADSD positively associated with left-hemispheric temporal activity. Connectivity was increased within right premotor (sensorimotor network), left primary auditory cortex (auditory network), and regionally reduced at the temporoparietal junction. Activation/connectivity before/after BoNT-A within-patients did not significantly differ. Abnormal ADSD central somatosensory processing supports its significance as common pathophysiologic focal dystonia trait. Abnormal temporal cortex tactile processing and resting-state connectivity might hint at abnormal cross-modal sensory interactions.

Abnormalities in grey matter structure in embouchure dystonia

INTRODUCTION

Embouchure dystonia (ED) is a debilitating movement disorder in professional brass players leading to involuntary muscle contractions/spasms during play. To date, activity changes in sensorimotor cortices during motor tasks and tactile processing, as well as connectivity changes at rest in sensorimotor and auditory brain networks have been described in the disease.

OBJECTIVE

To characterize differences in grey matter volume and asymmetry between brass musicians suffering from ED, healthy brass musicians and healthy nonmusicians.

METHODS

High-resolution structural magnetic resonance imaging was obtained from 24 brass musicians with ED, 23 healthy brass musicians and 24 healthy nonmusicians. Whole-brain voxel-wise morphometry and asymmetry analyses, as well as region-of-interest-based volumetry analysis were performed on the subjects' images and compared between groups. Further, correlations with clinical parameters were investigated.

RESULTS

ED patients showed increased grey matter volume in the primary sensorimotor cortex in relation to both healthy brass players and nonmusicians. Both healthy and diseased musicians showed increased thalamic symmetry in relation to nonmusicians; diseased brass musicians additionally showed increased basal ganglia symmetry compared to nonmusicians. There was an inverse correlation of disease duration with both mean putaminal volume and the extent of basal ganglia asymmetry.

CONCLUSION

This work provides first evidence for structural abnormalities in task-specific orofacial (musician's) dystonia. Somatotopy-related structural primary sensorimotor cortex changes underlying previously observed functional abnormalities underscore the role of maladaptive plasticity in the disease. The study further shows subcortical brain (a)symmetry changes in healthy brass players and hints at a possible role of such changes in focal dystonia.

Impaired white matter integrity between premotor cortex and basal ganglia in writer's cramp

INTRODUCTION

Writer's cramp (WC) as a focal hand dystonia is characterized by abnormal postures of the hand during writing. Impaired inhibition and maladaptive plasticity in circuits linking the basal ganglia and sensorimotor cortices have been described. In particular, a dysfunction of lateral premotor cortices has been associated with impaired motor control in WC. We applied diffusion tensor imaging to identify changes in white matter connectivity between premotor regions and important cortical and subcortical structures.

METHODS

Whole brain white matter tracts were reconstructed in 18 right-handed WC patients and 18 matched controls, using probabilistic fiber tracking. We restricted our analyses to left-hemispheric fibers between the middle frontal gyrus (MFG) and basal ganglia, thalamus, primary motor, and sensory cortex. Diffusion parameters (fractional anisotropy and linear anisotropy) were compared between both groups.

RESULTS

A significant reduction in fractional anisotropy values was shown for patients (mean ± SD: 0.37 ± 0.02) vs. controls (0.39 ± 0.03) regarding fibers between the left-sided MFG and the putamen (p < 0.05). The same applied for linear anisotropy values in this connection (p < 0.05).

CONCLUSIONS

Our results suggest an impaired structural connectivity between the left-hemispheric MFG and putamen with a loss of equally aligned fibers in WC patients. This could reflect a structural basis for functional findings interpreted as altered inhibition and plasticity, both within the premotor cortex and the basal ganglia, that at last lead to the clinical symptoms of WC.

Altered functional connectivity in blepharospasm/orofacial dystonia

INTRODUCTION

Blepharospasm is characterized by involuntary eyelid spasms. It can be associated with perioral dystonia (Meige's syndrome or orofacial dystonia). We aimed at studying resting-state functional brain connectivity in these patients and its potential modulation by therapeutic botulinum toxin injections.

METHODS

We performed resting-state functional MRI and a region of interest-based analysis of functional connectivity in 13 patients with blepharospasm/Meige's syndrome in comparison to 13 healthy controls. Patients were studied before and 4 weeks after botulinum toxin treatment. Simultaneous facial electromyography was applied to control for involuntary facial movements.

RESULTS

Before botulinum toxin treatment, patients showed reduced functional connectivity between caudate and primary sensorimotor, somatosensory association and visual cortices as well as between putamen and parietal association cortex. Cerebellar areas displayed decreased functional connectivity to somatosensory and visual association cortices. On the cortical level, connectivity was reduced between the cingulate cortex and the primary sensorimotor/premotor and parietal association cortex, between premotor areas and the primary somatosensory cortices, and between the postcentral gyrus and temporoparietal, secondary somatosensory, cingular, and cerebellar regions. Botulinum toxin treatment modulated functional connectivity, especially between cerebellum and visual cortices.

CONCLUSIONS

Patients with blepharospasm/Meige's syndrome show altered functional connectivity at rest in widespread brain regions including basal ganglia, cerebellar, primary/secondary sensorimotor, and visual areas. Functionally, this may reflect a predisposition for defective movement inhibition and sensorimotor integration. Botulinum toxin treatment could modulate brain connectivity in blepharospasm by altering visual and sensory input.

Network-specific resting-state connectivity changes in the premotor-parietal axis in writer's cramp

Background

Writer's cramp is a task-specific dystonia impairing writing and sometimes other fine motor tasks. Neuroimaging studies using manifold designs have shown varying results regarding the nature of changes in the disease.

Objective

To clarify and extend the knowledge of underlying changes by investigating functional connectivity (FC) in intrinsic connectivity networks with putative sensorimotor function at rest in an increased number of study subjects.

Methods

Resting-state functional magnetic resonance imaging with independent component analysis was performed in 26/27 writer's cramp patients/healthy controls, and FC within and between resting state networks with putative sensorimotor function was compared. Additionally, voxel-based morphometry was carried out on the subjects' structural images.

Results

Patients displayed increased left- and reduced right-hemispheric primary sensorimotor FC in the premotor-parietal network. Mostly bilaterally altered dorsal/ventral premotor FC, as well as altered parietal FC were observed within multiple sensorimotor networks and showed differing network-dependent directionality. Beyond within-network FC changes and reduced right cerebellar grey matter volume in the structural analysis, the positive between-network FC of the cerebellar network and the basal ganglia network was reduced.

Conclusions

Abnormal resting-state FC in multiple networks with putative sensorimotor function may act as basis of preexisting observations made during task-related neuroimaging. Further, altered connectivity between the cerebellar and basal ganglia network underlines the important role of these structures in the disease.

•

Investigation of FC changes in various sensorimotor ICNs at rest in writer's cramp.

•

We saw multiple, network-specific FC changes in primary/higher sensorimotor cortices.

•

This may act as basis of the varying nature of sensorimotor changes during task-fMRI.

•

Further, findings supporting disrupted cerebellar-basal ganglia interaction were made.

•

An additional morphometric analysis demonstrated structural cerebellar abnormality.

Microstructural white matter abnormalities in patients with COL6A3 mutations (DYT27 dystonia)

INTRODUCTION

Recently, mutations in the collagen gene COL6A3 have been reported in patients with autosomal-recessive, isolated dystonia (DYT27). Zebrafish models of COL6A3 mutations showed deficits in axonal targeting mechanisms. Therefore, COL6A3 mutations have been considered to contribute to irregular sensorimotor circuit formation. To test this hypothesis, we examined structural abnormalities in cerebral fiber tracts of dystonia patients with COL6A3 mutations using diffusion tensor imaging.

METHODS

We performed a voxel-wise statistical analysis to compare fractional anisotropy within whole-brain white matter in four of the previously reported dystonia patients with COL6A3 mutations and 12 healthy controls. Region of interests-based probabilistic tractography was performed as a post-hoc-analysis.

RESULTS

Dystonia patients with COL6A3 mutations showed significantly decreased fractional anisotropy bilaterally in midbrain, pons, cerebellar peduncles, thalamus, internal capsule and in frontal and parietal subcortical regions compared to healthy controls. Tractography revealed a decreased fractional anisotropy in patients with COL6A3-associated dystonia between bilateral dentate nucleus and thalamus.

CONCLUSION

Diffusion tensor imaging demonstrates an altered white matter structure especially in various parts of the cerebello-thalamo-cortical network in dystonia patients with COL6A3 mutations. This suggests that COL6A3 mutations could contribute to abnormal circuit formation as potential basis of dystonia.

Clinical exome sequencing in early-onset generalized dystonia and large-scale resequencing follow-up

BACKGROUND

Dystonia is clinically and genetically heterogeneous. Despite being a first-line testing tool for heterogeneous inherited disorders, whole-exome sequencing has not yet been evaluated in dystonia diagnostics. We set up a pilot study to address the yield of whole-exome sequencing for early-onset generalized dystonia, a disease subtype enriched for monogenic causation.

METHODS

Clinical whole-exome sequencing coupled with bioinformatics analysis and detailed phenotyping of mutation carriers was performed on 16 consecutive cases with genetically undefined early-onset generalized dystonia. Candidate pathogenic variants were validated and tested for cosegregation. The whole-exome approach was complemented by analyzing 2 mutated yet unestablished causative genes in another 590 dystonia cases.

RESULTS

Whole-exome sequencing detected clinically relevant mutations of known dystonia-related genes in 6 generalized dystonia cases (37.5%), among whom 3 had novel variants. Reflecting locus heterogeneity, identified unique variants were distributed over 5 genes (GCH1, THAP1, TOR1A, ANO3, ADCY5), of which only 1 (ANO3) was mutated recurrently. Three genes (GCH1, THAP1, TOR1A) were associated with isolated generalized dystonia, whereas 2 (ANO3, ADCY5) gave rise to combined dystonia-myoclonus phenotypes. Follow-up screening of ANO3 and ADCY5 revealed a set of distinct variants of interest, the pathogenicity of which was supported by bioinformatics testing and cosegregation work.

CONCLUSIONS

Our study identified whole-exome sequencing as an effective strategy for molecular diagnosis of early-onset generalized dystonia and offers insights into the heterogeneous genetic architecture of this condition. Furthermore, it provides confirmatory evidence for a dystonia-relevant role of ANO3 and ADCY5, both of which likely associate with a broader spectrum of dystonic expressions than previously thought. © 2016 International Parkinson and Movement Disorder Society.

Large-scale TUBB4A mutational screening in isolated dystonia and controls

INTRODUCTION

Mutations in TUBB4A have recently been implicated in two seemingly different disease entities, namely DYT4-isolated dystonia and hypomyelination with atrophy of the basal ganglia and cerebellum (H-ABC), a disorder characterized by considerable clinical variability. While several follow-up studies confirmed the importance of TUBB4A mutations in the development of H-ABC, their contribution to isolated dystonia remains uncertain.

METHODS

We screened the TUBB4A coding regions in a large population of 709 isolated dystonia patients of German/Austrian ancestry as well as in 376 ancestry-matched control subjects by means of Sanger sequencing and high-resolution melting. In addition, we assessed the overall frequency of rare non-synonymous TUBB4A genetic variation in the huge exome dataset released by the Exome Aggregation Consortium (ExAC).

RESULTS

We were unable to identify any possibly pathogenic sequence alteration in either patients or controls. According to ExAC, the overall prevalence of rare missense and loss-of-function alleles in the TUBB4A gene can be estimated at ∼1:706.

CONCLUSIONS

In accordance with previous work, our data indicate that TUBB4A coding mutations do not play a critical role in the broad population of isolated dystonia patients. Rather, isolated dystonia as seen in DYT4 might be an exceptional feature occurring in the heterogeneous phenotypic spectrum due to TUBB4A mutations.

DYT16 revisited: exome sequencing identifies PRKRA mutations in a European dystonia family

Recessive DYT16 dystonia associated with mutations in PRKRA has until now been reported only in seven Brazilian patients. The aim of this study was to elucidate the genetic cause underlying disease in a Polish family with autosomal-recessive, early-onset generalized dystonia and slight parkinsonism, and to explore further the role of PRKRA in a dystonia series of European ancestry. We employed whole-exome sequencing in two affected siblings of the Polish family and filtered for rare homozygous and compound heterozygous variants shared by both exomes. Validation of the identified variants as well as homozygosity screening and copy number variation analysis was carried out in the two affected individuals and their healthy siblings. PRKRA was analyzed in 339 German patients with various forms of dystonia and 376 population-based controls by direct sequencing or high-resolution melting. The previously described homozygous p.Pro222Leu mutation in PRKRA was found to segregate with the disease in the studied family, contained in a 1.2 Mb homozygous region identical by state with all Brazilian patients in chromosome 2q31.2. The clinical presentation with young-onset, progressive generalized dystonia and mild parkinsonism resembled the phenotype of the original DYT16 cases. PRKRA mutational screening in additional dystonia samples revealed three novel heterozygous changes (p.Thr34Ser, p.Asn102Ser, c.-14A>G), each in a single subject with focal/segmental dystonia. Our study provides the first independent replication of the DYT16 locus at 2q31.2 and strongly confirms the causal contribution of the PRKRA gene to DYT16. Our data suggest worldwide involvement of PRKRA in dystonia.

Analysis of immune-related loci identifies 48 new susceptibility variants for multiple sclerosis

Using the ImmunoChip custom genotyping array, we analyzed 14,498 subjects with multiple sclerosis and 24,091 healthy controls for 161,311 autosomal variants and identified 135 potentially associated regions (P < 1.0 × 10(-4)). In a replication phase, we combined these data with previous genome-wide association study (GWAS) data from an independent 14,802 subjects with multiple sclerosis and 26,703 healthy controls. In these 80,094 individuals of European ancestry, we identified 48 new susceptibility variants (P < 5.0 × 10(-8)), 3 of which we found after conditioning on previously identified variants. Thus, there are now 110 established multiple sclerosis risk variants at 103 discrete loci outside of the major histocompatibility complex. With high-resolution Bayesian fine mapping, we identified five regions where one variant accounted for more than 50% of the posterior probability of association. This study enhances the catalog of multiple sclerosis risk variants and illustrates the value of fine mapping in the resolution of GWAS signals.

Rare sequence variants in ANO3 and GNAL in a primary torsion dystonia series and controls

BACKGROUND

Rare autosomal-dominant mutations in ANO3 and GNAL have been recently shown to represent novel genetic factors underlying primary torsion dystonia (PTD) with predominantly craniocervical involvement.

METHODS

We used high-resolution melting to screen all exons of ANO3 and GNAL for rare sequence variants in a population of 342 German individuals with mainly sporadic PTD and 376 general population controls.

RESULTS

We identified 2 novel missense variants in ANO3 (p.Ile833Val and p.Gly973Arg) and 1 novel missense variant in GNAL (p.Val146Met) in three different nonfamilial cases. Variant carriers presented with adult-onset dystonia involving the neck and/or face. In controls, 3 rare ANO3 missense variants (p.Tyr235Cys, p.Asn256Ser, and p.Pro893Leu) but no rare nonsynonymous GNAL variants were present.

CONCLUSIONS

GNAL variants seem to be a rare cause of PTD in our mainly sporadic German sample. Low frequency missense variants in ANO3 occur in both cases and controls, warranting further assessment of this gene in PTD pathogenesis.

White-matter lesions drive deep gray-matter atrophy in early multiple sclerosis: support from structural MRI

BACKGROUND

In MS, the relationship between lesions within cerebral white matter (WM) and atrophy within deep gray matter (GM) is unclear.

OBJECTIVE

To investigate the spatial relationship between WM lesions and deep GM atrophy.

METHODS

We performed a cross-sectional structural magnetic resonance imaging (MRI) study (3 Tesla) in 249 patients with clinically-isolated syndrome or relapsing-remitting MS (Expanded Disability Status Scale score: median, 1.0; range, 0-4) and in 49 healthy controls. Preprocessing of T1-weighted and fluid-attenuated T2-weighted images resulted in normalized GM images and WM lesion probability maps. We performed two voxel-wise analyses: 1. We localized GM atrophy and confirmed that it is most pronounced within deep GM; 2. We searched for a spatial relationship between WM lesions and deep GM atrophy; to this end we analyzed WM lesion probability maps by voxel-wise multiple regression, including four variables derived from maxima of regional deep GM atrophy (caudate and pulvinar, each left and right).

RESULTS

Atrophy of each deep GM region was explained by ipsilateral WM lesion probability, in the area most densely connected to the respective deep GM region.

CONCLUSION

We demonstrated that WM lesions and deep GM atrophy are spatially related. Our results are best compatible with the hypothesis that WM lesions contribute to deep GM atrophy through axonal pathology.

Genetic variants in the immunoglobulin heavy chain locus are associated with the IgG index in multiple sclerosis

OBJECTIVE

Intrathecal synthesis of immunoglobulin gamma (IgG) synthesis is frequently observed in patients with multiple sclerosis (MS). Whereas the extent of intrathecal IgG synthesis varies largely between patients, it remains rather constant in the individual patient over time. The aim of this study was to identify common genetic variants associated with the IgG index as a marker of intrathecal IgG synthesis in MS.

METHODS

We performed a genome-wide association study of the IgG index in a discovery series of 229 patients. For confirmation we performed a replication in 2 independent series comprising 256 and 153 patients, respectively. The impact of associated single nucleotide polymorphisms (SNPs) on MS susceptibility was analyzed in an additional 1,854 cases and 5,175 controls.

RESULTS

Significant association between the IgG index and 5 SNPs was detected in the discovery and confirmed in both replication series reaching combined p values of p = 6.5 × 10(-11) to p = 7.5 × 10(-16) . All identified SNPs are clustered around the immunoglobulin heavy chain (IGHC) locus on chromosome 14q32.33 and are in linkage disequilibrium (r(2) range, 0.71-0.95). The best associated SNP is located in an intronic region of the immunoglobulin gamma3 heavy chain gene. Additional sequencing identified the GM21* haplotype to be associated with a high IgG index. Further evaluation of the IGHC SNPs revealed no association with susceptibility to MS in our data set.

INTERPRETATION

The extent of intrathecal IgG in MS is influenced by the IGHC locus. No association with susceptibility to MS was found. Therefore GM haplotypes might affect intrathecal IgG synthesis independently of the underlying disease.

Co-occurrence of two cases of progressive multifocal leukoencephalopathy in a natalizumab "infusion group"

We observed two cases of progressive multifocal leukoencephalopathy (PML) that occurred in the same "infusion group". The group consisted of four patients with relapsing-remitting multiple sclerosis (RRMS) who had been treated with natalizumab (NAT) in the same medical practice for more than four years at the same times and in the same room, raising concerns about viral transmission between members of the infusion group. DNA amplification and sequence comparison of the non-coding control region (NCCR) of JC virus (JCV) present in cerebrospinal fluid (CSF) samples from PML patients #1 and #2 revealed that the amplified JCV sequences differed from the JCV archetype. The NCRR of the viral DNA was unique to each patient, arguing against the possibility of viral transmission between patients. Statistical considerations predict that similar co-occurrences of PML are likely to happen in the future.

IRAG determines nitric oxide- and atrial natriuretic peptide-mediated smooth muscle relaxation

AIMS

Nitric oxide (NO) and atrial natriuretic peptide (ANP) signalling via cGMP controls smooth muscle tone. One important signalling pathway of cGMP-dependent protein kinase type I (cGKI) is mediated by IRAG (IP(3) receptor associated cGKI substrate) which is highly expressed in smooth muscle tissues. To elucidate the role of IRAG for NO- and ANP-mediated smooth muscle tone regulation, cGKI localization, and for its possible function in blood pressure adjustment, we generated IRAG-knockout mice by targeted deletion of exon 3.

METHODS AND RESULTS

IRAG deletion prevented stable interaction of IP(3) receptor type I (IP(3)RI) with cGKIbeta determined by cGMP affinity chromatography. Confocal microscopy in vascular smooth muscle cells (VSMCs) showed that localization of cGKIbeta and cGKIalpha did not change in absence of IRAG. NO-, ANP-, and cGMP-dependent relaxation of hormone-contracted aortic vessels and colon was significantly affected in IRAG-knockout mice. The suppression of cGMP-induced relaxation was not rescued by selective expression of cGKIbeta in smooth muscle from cGKIbeta-transgenic mice. NO-, ANP-, and cGMP-mediated inhibition of the hormone-induced increase in intracellular calcium concentration measured by Fura2 was suppressed in IRAG-deficient VSMC. Telemetric measurements revealed that IRAG-deficient animals exhibited normal basal tone, but were resistant to blood pressure reduction induced by lipopolysaccharide-treatment.

CONCLUSION

These findings indicate that signalling of cGKIbeta via IRAG is an essential functional part for regulation of smooth muscle tone and of intracellular calcium by NO (exogenously applicated or endogenously synthesized) and by ANP. IRAG signalling does not modulate basal tone but might be important for blood pressure regulation under pathophysiological conditions.

Addition of dacarbazine or cisplatin to interferon-alpha/interleukin-2 in metastatic melanoma: toxicity and immunological effects

The combination of chemotherapy and immunotherapy seems to improve response rate in metastatic melanoma. We investigated the effects on toxicity and immunological effects of a single dose of dacarbacin (DTIC; 850 mg/m2) or cisplatin (CDDP; 100 mg/m2) added to subsequent immunotherapy with interferon-alpha (IFN-alpha) and interleukin-2 (IL-2). Twelve patients, who did not respond to IFN-alpha/IL-2 alone were studied. Six received DTIC and IFN-alpha/IL-2, and six received CDDP and IFN-alpha/IL-2. DTIC did not add significant toxicity except for nausea. Significant thrombocytopenia was observed in two patients after CDDP. Although CDDP led to grade 3 nephrotoxicity in two patients, the IL-2-induced fluid retention was less severe than with IFN-alpha/IL-2 alone. Pharmacokinetics of IL-2 were not altered by DTIC, but higher IL-2 serum levels were found in patients with grade 3 nephrotoxicity after CDDP. The IL-2-related induction of secondary mediators (interferon-gamma, tumour necrosis factor-alpha, soluble CD25) was not impaired by chemotherapy and the induction of neopterin was significantly higher after addition of CDDP. One partial response was observed after addition of DTIC to IFN-alpha/IL-2, and one after addition of CDDP. The addition of a single dose of DTIC or CDDP to IFN-alpha/IL-2 is fairly well tolerated and does not abolish induction of secondary mediators. Randomized trials are necessary to test the clinical efficacy.

Comparison between simvastatin and bezafibrate in effect on plasma lipoproteins and apolipoproteins in primary hypercholesterolaemia

The ability of simvastatin, a competitive inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase, to lower lipid levels in 16 patients with primary hypercholesterolaemia was compared with that of bezafibrate in a 16-week, double-blind, parallel, placebo-controlled trial that was continued in an open crossover fashion. Simvastatin was better than bezafibrate at lowering total and low-density lipoprotein (LDL)-cholesterol and apolipoprotein B concentrations (30.4% [p less than 0.001], 37.3% [p less than 0.001], and 37.8% [p less than 0.001] vs 17.0%, 19.6%, and 24.0%, respectively). Both drugs increased the high-density lipoprotein (HDL)-cholesterol and apolipoprotein A-I, but this change was significant only with bezafibrate (p less than 0.05). Bezafibrate and simvastatin reduced triglycerides by 25.6% (p less than 0.001) and 13.7% (p less than 0.05), respectively. Very low-density lipoprotein (VLDL)-cholesterol was significantly reduced only by bezafibrate (44.3%, p less than 0.001). Both drugs were tolerated well and no serious side-effects were noted. The results show that simvastatin was more effective than bezafibrate in lowering total-cholesterol, LDL-cholesterol, and apolipoprotein B, while bezafibrate was better at lowering triglycerides and VLDL-cholesterol and at raising HDL-cholesterol and apolipoprotein A-I.

Mutual potentiation of antinociceptive effects of morphine and clonidine on motor and sensory responses in rat spinal cord

Clonidine and morphine depress nociceptive reflex responses when given alone; when given in combination, the effect of each is potentiated by the other. The present study was designed to test if activity in ascending axons evoked by electrical stimulation of afferent C-fibers in the sural nerve of the rat also exhibits potentiation of the depressant effects of clonidine and morphine when both drugs are administered in combination by intrathecal (i.t.) injection to the lumbar spinal cord. For comparison, experiments were also carried out on the tail-flick response in rats. The results show that clonidine produced a dose-dependent inhibition of the tail-flick response (Ed50 20 micrograms); a combination of ineffective doses of clonidine (0.3 microgram) and morphine (2 micrograms) significantly inhibited the tail-flick response; clonidine (35 micrograms) reduced spontaneous, C-fiber-evoked and, due to co-activation, A delta-fibre-evoked activity in ascending axons; and clonidine at a threshold (0.3 microgram) or higher (3 micrograms) dose administered together with morphine at a dose (2 micrograms) that caused only a moderate inhibition produced a supra-additive effect in significantly depressing spontaneous. A delta- and C-fiber-evoked ascending activity. The dose-response curve of depression by morphine alone of C-fiber-evoked activity (ED50 8 micrograms) is significantly shifted by clonidine to the left (ED50 0.9 microgram). Naloxone (0.2 mg/kg) injected intravenously did not affect the inhibition of ascending activity caused by clonidine at the highest dose (35 micrograms), but it reduced the depressant effect of combined i.t. administration of clonidine and morphine. The potentiation of the antinociceptive effects of clonidine and morphine given in combination are possibly due to actions of the two drugs at different sites between the nociceptive afferents and the neurons sending their axons to the brain.