The serotonergic and the endocannabinoid system are involved in the etiology of depression. Depressive patients exhibit low serotonergic activity and decreased level of the endocannabinoids anandamide (AEA) and 2-arachidonylglycerol (2AG). Since the cannabinoid (CB) 1 receptor is activated by endogenous ligands such as AEA and 2AG, whose concentration are controlled by the fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase, respectively, we investigated the effects on serotonergic utilization. In this study, we investigated the impact of the rs1049353 single-nucleotide polymorphism (SNP) of the cannabinoid receptor 1 (CNR1) gene, which codes the endocannabinoid CB1 receptor, and the rs324420 SNP of the FAAH gene on the serotonergic and endocannabinoid system in 59 healthy volunteers. Serotonergic activity was measured by loudness dependence of auditory-evoked potentials (LDAEP). Plasma concentrations of AEA, 2AG and its inactive isomer 1AG were determined by mass spectrometry. Genotyping of two SNPs (rs1049353, rs344420) was conducted by polymerase chain reaction (PCR) and differential enzymatic analysis with the PCR restriction fragment length polymorphism method. Genotype distributions by serotonergic activity or endocannabinoid concentration showed no differences. However, after detailed consideration of the CNR1-A-allele-carriers, a reduced AEA (A-allele-carrier M = 0.66, SD = 0.24; GG genotype M = 0.72, SD = 0.24) and 2AG (A-allele-carriers M = 0.70, SD = 0.33; GG genotype M = 1.03, SD = 0.83) plasma concentration and an association between the serotonergic activity and the concentrations of AEA and 2AG has been observed. Our results suggest that carriers of the CNR1-A allele may be more susceptible to developing depression.

We report upon PanelDesign, a framework to support the design of diagnostic next generation DNA sequencing panels with epidemiological information. Two publicly available resources, namely Genomics England PanelApp and Orphadata, were combined into a single data set to allow genes in a given NGS panel to be ranked according to the frequency of the associated diseases, thereby highlighting potential core genes as defined by the Eurogenetest/ESHG guidelines for diagnostic next generation DNA sequencing. In addition, PanelDesign can be used to evaluate the contribution of different genes to a given disease following ACMG (American College of Medical Genetics) technical standards.

ZusammenfassungDie meisten Kapitel in diesem Buch belegen, dass genetische Gesichtspunkte im Alltag der klinischen Neurologie zunehmend an Bedeutung gewinnen. Aus dem Blickwinkel des Neurologen könnte Humangenetik vereinfacht in Molekularbiologie, Zytogenetik und medizinische Genetik untergliedert werden. Problemstellungen und spezifische Vorgehensweisen in der medizinischen Genetik sind jedoch nur direkt interagierenden Klinikern besser bekannt. Aktuelle Ergebnisse der neurogenetischen Forschung wirken sich unmittelbar auf das diagnostische Vorgehen aus. Beispielsweise können Mutationen in unabhängigen Genen auf verschiedenen Chromosomen klinisch nicht differenzierbare, hereditäre motorisch-sensible Neuropathieformen hervorrufen. Andererseits führen verschiedene Mutationen in ein und demselben Gen, welches für eine Untereinheit eines Kalziumkanals kodiert, zu klinisch offenbar separierten Krankheitsentitäten (hemiplegische Migräne vs. episodische Ataxie vs. SCA6). Humangenetische Forschung weist demnach wesentliche Überschneidungen mit der syndromorientierten klinischen Forschung auf, wobei sich die beiden Arbeitsrichtungen – zunehmend verzahnt – eines identischen Methodenspektrums bedienen. Klinische Genetik versteht sich im Kanon der Medizin als Querschnittsfach mit sehr vielfältigen Bezügen. Die Humangenetik insgesamt fördert aus ihrem biologischen Grundlagencharakter heraus konzeptionell die Medizin des gesamten Menschen. Diese Zusammenhänge werden an einigen ausgewählten Erkrankungen des Zentralnervensystems mit dem gemeinsamen Phänomen der Neurodegeneration bzw. an den hereditären Neuropathien dargestellt.

Eosinophilic granulomatosis with polyangiitis (EGPA) is a rare inflammatory disease of unknown cause. 30% of patients have anti-neutrophil cytoplasmic antibodies (ANCA) specific for myeloperoxidase (MPO). Here, we describe a genome-wide association study in 676 EGPA cases and 6809 controls, that identifies 4 EGPA-associated loci through conventional case-control analysis, and 4 additional associations through a conditional false discovery rate approach. Many variants are also associated with asthma and six are associated with eosinophil count in the general population. Through Mendelian randomisation, we show that a primary tendency to eosinophilia contributes to EGPA susceptibility. Stratification by ANCA reveals that EGPA comprises two genetically and clinically distinct syndromes. MPO+ ANCA EGPA is an eosinophilic autoimmune disease sharing certain clinical features and an HLA-DQ association with MPO+ ANCA-associated vasculitis, while ANCA-negative EGPA may instead have a mucosal/barrier dysfunction origin. Four candidate genes are targets of therapies in development, supporting their exploration in EGPA.

The nodal cascade influences the development of bodily asymmetries in humans and other vertebrates. The gene PCSK6 has shown a regulatory function during left-right axis formation and is therefore thought to influence bodily left-right asymmetries. However, it is not clear if variation in this gene is also associated with structural asymmetries in the brain. We genotyped an intronic 33bp PCSK6 variable number tandem repeat (VNTR) polymorphism that has been associated with handedness in a cohort of healthy adults. We acquired T1-weighted structural MRI images of 320 participants and defined cortical surface and thickness for each HCP region. The results demonstrate a significant association between PCSK6 VNTR genotypes and gray matter asymmetry in the superior temporal sulcus, which is involved in voice perception. Heterozygous individuals who carry a short (≤ 6 repeats) and a long (≥ 9 repeats) PCSK6 VNTR allele show stronger rightward asymmetry. Further associations were evident in the dorsolateral prefrontal cortex. Here, individuals homozygous for short alleles show a more pronounced asymmetry. This shows that PCSK6, a gene that has been implicated in the ontogenesis of bodily asymmetries by regulating the nodal cascade, is also relevant for structural asymmetries in the human brain.

The aryl hydrocarbon receptor (AhR) contributes to immune regulation in autoimmune diseases such as multiple sclerosis (MS). Analysis of selected polymorphisms in AhR pathway genes in 805 MS patients and 1023 controls revealed a modest association of a CYP1B1 polymorphism with secondary progressive MS that became more pronounced in combination with other SNPs in the pathway, suggesting interactive effects. Additionally, first evidence for an interaction with smoking was found, but due to small sample sizes statistical significance was only nominal. Confirmation of these results in independent cohorts is recommended, since targeting the AhR constitutes a therapeutic option for autoimmune diseases.

ZusammenfassungDie neu überarbeiteten Leitlinien Chorea/Morbus Huntington geben auf S2k Niveau einen Überblick über den Stand der Forschung zum Erkrankungsverlauf sowie zu neuen Ansätzen der symptomatischen und verlaufsmodifizierenden Therapie bei der Huntington-Krankheit. Im Gegensatz zu vielen anderen Leitlinien bevorzugen die Autoren aus den deutschsprachigen Ländern als Erstlinienbehandlung der Chorea Tiaprid. Aufgrund von Nebenwirkungen, welche unter Tetrabenazin auftreten können – wie etwa Depression oder Akathisie, ist es gängige Praxis, Tetrabenazin erst in zweiter Linie einzusetzen. Die Leitlinien nehmen Stellung zu rechtlichen Fragen der Präimplantationsdiagnostik (PID) und der pränatalen Diagnostik (PD) in Deutschland, Österreich und der Schweiz sowie zu den Unterschieden zwischen dem prädiktiven und dem differenzialdiagnostischen Einsatz der molekulargenetischen Diagnostik. In den Leitlinien wird darüber hinaus sehr ausführlich zu den möglichen Differenzialdiagnosen bei einer Chorea ungeklärter Ätiologie Stellung genommen.

The corpus callosum is the brain's largest commissural fiber tract and is crucial for interhemispheric integration of neural information. Despite the high relevance of the corpus callosum for several cognitive systems, the molecular determinants of callosal microstructure are largely unknown. Recently, it was shown that genetic variations in the myelin-related proteolipid 1 gene PLP1 and the axon guidance related contactin 1 gene CNTN1 were associated with differences in interhemispheric integration at the behavioral level. Here, we used an innovative new diffusion neuroimaging technique called neurite orientation dispersion and density imaging (NODDI) to quantify axonal morphology in subsections of the corpus callosum and link them to genetic variation in PLP1 and CNTN1. In a cohort of 263 healthy human adults, we found that polymorphisms in both PLP1 and CNTN1 were significantly associated with callosal microstructure. Importantly, we found a double dissociation between gene function and neuroimaging variables. Our results suggest that genetic variation in the myelin-related gene PLP1 impacts white matter microstructure in the corpus callosum, possibly by affecting myelin structure. In contrast, genetic variation in the axon guidance related gene CNTN1 impacts axon density in the corpus callosum. These findings suggest that PLP1 and CNTN1 gene variations modulate specific aspects of callosal microstructure that are in line with their gene function.

Myopathies comprise a heterogeneous group of disorders characterized by variable phenotypes. The increasing use of next-generation sequencing allows identification of the causative genes in a much higher percentage of patients with hereditary muscle disorders and also illustrates a considerable degree of overlap with other clinical entities, including connective tissue disorders. Here, we present a 14-year-old German patient who was initially suspected to suffer from myopathy based on his clinical, radiological, and muscle biopsy findings. Exome sequencing revealed a novel homozygous nonsense mutation in the SLC39A13 gene, causative for spondylocheiro dysplastic Ehlers Danlos syndrome (SCD-EDS), suggesting a connective tissue disorder. Including our patient, only 9 affected individuals from 4 families have been described for SCD-EDS so far. The previously reported patients did not show obvious evidence of myopathy, suggesting a broader clinical presentation than originally suspected. We summarize herein the current knowledge on clinical features as well as pathophysiological pathways for this rare connective tissue disease and discuss the high degree of clinical overlap between myopathic and connective tissue disorders.

BACKGROUND:Spinocerebellar ataxia (SCA) subtypes are often caused by expansions in non-coding regions of genes like SCA8, SCA10, SCA12 and SCA36. Other ataxias are known to be associated with repeat expansions such as fragile X-associated tremor ataxia syndrome (FXTAS) or expansions in the C9orf72 gene. When no mutation has been identified in the aforementioned genes next-generation sequencing (NGS)-based diagnostics may also be applied. In order to define an optimal diagnostic strategy, more information about the frequency and phenotypic characteristics of rare repeat expansion disorders associated with ataxia should be at hand.METHODS:We analyzed a consecutive cohort of 440 German unrelated patients with symptoms of cerebellar ataxia, dysarthria and other unspecific symptoms who were referred to our center for SCA diagnostics. They showed alleles in the normal range for the most common SCA subtypes SCA1-3, SCA6, SCA7 and SCA17. These patients were screened for expansions causing SCA8, SCA10, SCA12, SCA36 and FXTAS as well as for the pathogenic hexanucleotide repeat in the C9orf72 gene.RESULTS:Expanded repeats for SCA10, SCA12 or SCA36 were not identified in the analyzed patients. Five patients showed expanded SCA8 CTA/CTG alleles with 92-129 repeats. One 51-year-old male with unclear dementia symptoms was diagnosed with a large GGGGCC repeat expansion in C9orf72. The analysis of the fragile X mental retardation 1 gene (FMR1) revealed one patient with a premutation (>50 CGG repeats) and seven patients with alleles in the grey zone (41 to 54 CGG repeats).CONCLUSIONS:Altogether five patients showed 92 or more SCA8 CTA/CTG combined repeats. Our results support the assumption that smaller FMR1 gene expansions could be associated with the risk of developing neurological signs. The results do not support genetic testing for C9orf72 expansion in ataxia patients.

Introduction: Mutations in the BICD2 gene are causative for an autosomal dominant form of spinal muscular atrophy (SMALED2). Further, BICD2 mutations have been implicated in hereditary spastic paraplegia (HSP), but only very few such patients have been described. In this report we aimed to investigate the frequency of BICD2 mutations in patients with HSP and hereditary motor and sensory neuropathy (HMSN) who were negative for the most common known genetic causes. Methods: The cohorts comprised 171 HSP and 189 HMSN patients. Mutational analysis was performed with high-resolution melting analysis followed by Sanger sequencing. Results: In both cohorts, we found no known or likely pathogenic mutations in the BICD2 gene. Discussion:BICD2 mutations appear rather unlikely to cause a phenotype of HMSN and are a very rare cause of the HSP phenotype. Muscle Nerve 59:484-486, 2019

The Ccdc66-deficient (Ccdc66 -/-) mouse model exhibits slow progressive retinal degeneration. It is unclear whether CCDC66 protein also plays a role in the wildtype (WT; Ccdc66 +/+) mouse brain and whether the lack of Ccdc66 gene expression in the Ccdc66 -/- mouse brain may result in morphological and behavioral alterations. CCDC66 protein expression in different brain regions of the adult WT mouse and in whole brain during postnatal development was quantified by SDS-PAGE and Western blot. Ccdc66 reporter gene expression was visualized by X-gal staining. Selected brain regions were further analyzed by light and electron microscopy. In order to correlate anatomical with behavioral data, an olfactory habituation/dishabituation test was performed. CCDC66 protein was expressed throughout the early postnatal development in the WT mouse brain. In adult mice, the main olfactory bulb exhibited high CCDC66 protein levels comparable to the expression in the retina. Additionally, the Ccdc66 -/- mouse brain showed robust Ccdc66 reporter gene expression especially in adult olfactory bulb glomeruli, the olfactory nerve layer and the olfactory epithelium. Degeneration was detected in the Ccdc66 -/- olfactory bulb glomeruli at advanced age. This degeneration was also reflected in behavioral alterations; compared to the WT, Ccdc66 -/- mice spent significantly less time sniffing at the initial presentation of unknown, neutral odors and barely responded to social odors. Ccdc66 -/- mice develop substantial olfactory nerve fiber degeneration and alteration of olfaction-related behavior at advanced age. Thus, the Ccdc66 -/- mouse model for retinal degeneration adds the possibility to study mechanisms of central nervous system degeneration.

Anti-neutrophil cytoplasmic autoantibodies (ANCA) targeting proteinase 3 (PR3) and myeloperoxidase expressed by innate immune cells (neutrophils and monocytes) are salient diagnostic and pathogenic features of small vessel vasculitis, comprising granulomatosis with polyangiitis (GPA), microscopic polyangiitis, and eosinophilic GPA. Genetic studies suggest that ANCA-associated vasculitides (AAV) constitute separate diseases, which share common immunological and pathological features, but are otherwise heterogeneous. The successful therapeutic use of anti-CD20 antibodies emphasizes the prominent role of ANCA and possibly other autoantibodies in the pathogenesis of AAV. However, to elucidate causal effects in AAV, a better understanding of the complex interplay leading to the emergence of B lymphocytes that produce pathogenic ANCA remains a challenge. Different scenarios seem possible; e.g., the break of tolerance induced by a shift from non-pathogenic toward pathogenic autoantigen epitopes in inflamed tissue. This review gives a brief overview on current knowledge about genetic and epigenetic factors, barrier dysfunction and chronic non-resolving inflammation, necro-inflammatory auto-amplification of cellular death and inflammation, altered autoantigen presentation, alternative complement pathway activation, alterations within peripheral and inflamed tissue-residing T- and B-cell populations, ectopic lymphoid tissue neoformation, the characterization of PR3-specific T-cells, properties of ANCA, links between autoimmune disease and infection-triggered pathology, and animal models in AAV.

Myelination of axons in the central nervous system is critical for human cognition and behavior. The predominant protein in myelin is proteolipid proteinmaking PLP1, the gene that encodes for proteolipid protein, one of the primary candidate genes for white matter structure in the human brain. Here, we investigated the relation of genetic variation within PLP1 and white matter microstructure as assessed with myelin water fraction imaging, a neuroimaging technique that has the advantage over conventional diffusion tensor imaging in that it allows for a more direct assessment of myelin content. We observed significant asymmetries in myelin water fraction that were strongest and rightward in the parietal lobe. Importantly, these parietal myelin water fraction asymmetries were associated with genetic variation in PLP1. These findings support the assumption that genetic variation in PLP1 affects white matter myelination in the healthy human brain.

Eosinophilic granulomatosis with polyangiitis (EGPA: formerly Churg-Strauss syndrome) is a rare inflammatory disease of unknown cause. 30% of patients have anti-neutrophil cytoplasm antibodies (ANCA) specific for myeloperoxidase (MPO). We performed a genome-wide association study (GWAS) of EGPA, testing 7.5 million genetic variants in 684 cases and 6,838 controls. Case-control analyses were performed for EGPA as a whole, and stratified by ANCA. To increase power, we used a conditional false discovery rate method to leverage findings from GWASs of related phenotypes. In total, 11 variants were associated with EGPA, two specifically with ANCA-negative EGPA, and one ( HLA-DQ ) with MPO+ANCA EGPA. Many variants were associated with asthma, eosinophilic and immune-mediated diseases and, strikingly, nine were associated with eosinophil count in the general population. Through Mendelian randomisation, we show that a primary tendency to eosinophilia underlies EGPA susceptibility. We demonstrate that EGPA comprises two genetically and clinically distinct syndromes, with ANCA-negative EGPA genetically more similar to asthma. MPO+ ANCA EGPA is an eosinophilic autoimmune disease sharing certain clinical features and an MHC association with MPO+ ANCA-associated vasculitis, while ANCA-negative EGPA may instead have a mucosal/barrier dysfunction origin. Five identified candidate genes are targets of therapies in development, supporting their exploration in EGPA.

Molecular neurobiological factors determining corpus callosum physiology and anatomy have been suggested to be one of the major factors determining functional hemispheric asymmetries. Recently, it was shown that allelic variations in two myelin-related genes, the proteolipid protein 1 gene PLP1 and the contactin 1 gene CNTN1, are associated with differences in interhemispheric integration. Here, we investigated whether three single nucleotide polymorphisms that were associated with interhemispheric integration via the corpus callosum in a previous study also are relevant for functional hemispheric asymmetries. To this end, we tested more than 900 healthy adults with the forced attention dichotic listening task, a paradigm to assess language lateralization and its modulation by cognitive control processes. Moreover, we used the line bisection task, a paradigm to assess functional hemispheric asymmetries in spatial attention. We found that a polymorphism in PLP1, but not CNTN1, was associated with performance differences in both tasks. Both functional hemispheric asymmetries and their modulation by cognitive control processes were affected. These findings suggest that both left and right hemisphere dominant cognitive functions can be modulated by allelic variation in genes affecting corpus callosum structure. Moreover, higher order cognitive processes may be relevant parameters when investigating the molecular basis of hemispheric asymmetries.

Cognitive control processes play an essential role not only in controlling actions but also in guiding attentional selection processes. Interestingly, these processes are strongly affected by organizational principles of the cerebral cortex and related functional asymmetries, but the neurobiological foundations are elusive. We ask whether neurobiological mechanisms that affect functional cerebral asymmetries will also modulate effects of top-down control processes on functional cerebral asymmetries. To this end, we examined potential effects of the imprinted gene leucine-rich repeat transmembrane neuronal 1 (LRRTM1) on attentional biasing processes in a forced attention dichotic listening task in 983 healthy adult participants of Caucasian descent using the "iDichotic smartphone app." The results show that functional cerebral asymmetries in the language domain are associated with the rs6733871 LRRTM1 polymorphism when cognitive control and top-down attentional mechanisms modulate processes in bottom-up attentional selection processes that are dependent on functional cerebral asymmetries. There is no evidence for an effect of LRRTM1 on functional cerebral asymmetries in the language domain unrelated to cognitive control processes. The results suggest that cognitive control processes are an important factor to consider when being interested in the molecular genetic basis of functional cerebral architecture.