@article{EgenolfAltenschildescheKressetal.2021, author = {Egenolf, Nadine and Altenschildesche, Caren Meyer zu and Kreß, Luisa and Eggermann, Katja and Namer, Barbara and Gross, Franziska and Klitsch, Alexander and Malzacher, Tobias and Kampik, Daniel and Malik, Rayaz A. and Kurth, Ingo and Sommer, Claudia and {\"U}{\c{c}}eyler, Nurcan}, title = {Diagnosing small fiber neuropathy in clinical practice: a deep phenotyping study}, series = {Therapeutic Advances in Neurological Disorders}, volume = {14}, journal = {Therapeutic Advances in Neurological Disorders}, issn = {1756-2864}, doi = {10.1177/17562864211004318}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-232019}, year = {2021}, abstract = {Background and aims: Small fiber neuropathy (SFN) is increasingly suspected in patients with pain of uncertain origin, and making the diagnosis remains a challenge lacking a diagnostic gold standard. Methods: In this case-control study, we prospectively recruited 86 patients with a medical history and clinical phenotype suggestive of SFN. Patients underwent neurological examination, quantitative sensory testing (QST), and distal and proximal skin punch biopsy, and were tested for pain-associated gene loci. Fifty-five of these patients additionally underwent pain-related evoked potentials (PREP), corneal confocal microscopy (CCM), and a quantitative sudomotor axon reflex test (QSART). Results: Abnormal distal intraepidermal nerve fiber density (IENFD) (60/86, 70\%) and neurological examination (53/86, 62\%) most frequently reflected small fiber disease. Adding CCM and/or PREP further increased the number of patients with small fiber impairment to 47/55 (85\%). Genetic testing revealed potentially pathogenic gene variants in 14/86 (16\%) index patients. QST, QSART, and proximal IENFD were of lower impact. Conclusion: We propose to diagnose SFN primarily based on the results of neurological examination and distal IENFD, with more detailed phenotyping in specialized centers.}, language = {en} } @article{KuzkinaBargarSchmittetal.2021, author = {Kuzkina, Anastasia and Bargar, Connor and Schmitt, Daniela and R{\"o}ßle, Jonas and Wang, Wen and Schubert, Anna-Lena and Tatsuoka, Curtis and Gunzler, Steven A. and Zou, Wen-Quan and Volkmann, Jens and Sommer, Claudia and Doppler, Kathrin and Chen, Shu G.}, title = {Diagnostic value of skin RT-QuIC in Parkinson's disease: a two-laboratory study}, series = {NPJ Parkinson's Disease}, volume = {7}, journal = {NPJ Parkinson's Disease}, number = {1}, doi = {10.1038/s41531-021-00242-2}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-260451}, year = {2021}, abstract = {Skin alpha-synuclein deposition is considered a potential biomarker for Parkinson's disease (PD). Real-time quaking-induced conversion (RT-QuIC) is a novel, ultrasensitive, and efficient seeding assay that enables the detection of minute amounts of alpha-synuclein aggregates. We aimed to determine the diagnostic accuracy, reliability, and reproducibility of alpha-synuclein RT-QuIC assay of skin biopsy for diagnosing PD and to explore its correlation with clinical markers of PD in a two-center inter-laboratory comparison study. Patients with clinically diagnosed PD (n = 34), as well as control subjects (n = 30), underwent skin punch biopsy at multiple sites (neck, lower back, thigh, and lower leg). The skin biopsy samples (198 in total) were divided in half to be analyzed by RT-QuIC assay in two independent laboratories. The a-synuclein RT-QuIC assay of multiple skin biopsies supported the clinical diagnosis of PD with a diagnostic accuracy of 88.9\% and showed a high degree of inter-rater agreement between the two laboratories (92.2\%). Higher alpha-synuclein seeding activity in RT-QuIC was shown in patients with longer disease duration and more advanced disease stage and correlated with the presence of REM sleep behavior disorder, cognitive impairment, and constipation. The alpha-synuclein RT-QuIC assay of minimally invasive skin punch biopsy is a reliable and reproducible biomarker for Parkinson's disease. Moreover, alpha-synuclein RT-QuIC seeding activity in the skin may serve as a potential indicator of progression as it correlates with the disease stage and certain non-motor symptoms.}, language = {en} } @article{PiroEckesKasaragodetal.2021, author = {Piro, Inken and Eckes, Anna-Lena and Kasaragod, Vikram Babu and Sommer, Claudia and Harvey, Robert J. and Schaefer, Natascha and Villmann, Carmen}, title = {Novel Functional Properties of Missense Mutations in the Glycine Receptor β Subunit in Startle Disease}, series = {Frontiers in Molecular Neuroscience}, volume = {14}, journal = {Frontiers in Molecular Neuroscience}, issn = {1662-5099}, doi = {10.3389/fnmol.2021.745275}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-246676}, year = {2021}, abstract = {Startle disease is a rare disorder associated with mutations in GLRA1 and GLRB, encoding glycine receptor (GlyR) α1 and β subunits, which enable fast synaptic inhibitory transmission in the spinal cord and brainstem. The GlyR β subunit is important for synaptic localization via interactions with gephyrin and contributes to agonist binding and ion channel conductance. Here, we have studied three GLRB missense mutations, Y252S, S321F, and A455P, identified in startle disease patients. For Y252S in M1 a disrupted stacking interaction with surrounding aromatic residues in M3 and M4 is suggested which is accompanied by an increased EC\(_{50}\) value. By contrast, S321F in M3 might stabilize stacking interactions with aromatic residues in M1 and M4. No significant differences in glycine potency or efficacy were observed for S321F. The A455P variant was not predicted to impact on subunit folding but surprisingly displayed increased maximal currents which were not accompanied by enhanced surface expression, suggesting that A455P is a gain-of-function mutation. All three GlyR β variants are trafficked effectively with the α1 subunit through intracellular compartments and inserted into the cellular membrane. In vivo, the GlyR β subunit is transported together with α1 and the scaffolding protein gephyrin to synaptic sites. The interaction of these proteins was studied using eGFP-gephyrin, forming cytosolic aggregates in non-neuronal cells. eGFP-gephyrin and β subunit co-expression resulted in the recruitment of both wild-type and mutant GlyR β subunits to gephyrin aggregates. However, a significantly lower number of GlyR β aggregates was observed for Y252S, while for mutants S321F and A455P, the area and the perimeter of GlyR β subunit aggregates was increased in comparison to wild-type β. Transfection of hippocampal neurons confirmed differences in GlyR-gephyrin clustering with Y252S and A455P, leading to a significant reduction in GlyR β-positive synapses. Although none of the mutations studied is directly located within the gephyrin-binding motif in the GlyR β M3-M4 loop, we suggest that structural changes within the GlyR β subunit result in differences in GlyR β-gephyrin interactions. Hence, we conclude that loss- or gain-of-function, or alterations in synaptic GlyR clustering may underlie disease pathology in startle disease patients carrying GLRB mutations.}, language = {en} } @article{SommerCarrollKoikeetal.2021, author = {Sommer, Claudia and Carroll, Antonia S. and Koike, Haruki and Katsuno, Masahisa and Ort, Nora and Sobue, Gen and Vucic, Steve and Spies, Judith M. and Doppler, Kathrin and Kiernan, Matthew C.}, title = {Nerve biopsy in acquired neuropathies}, series = {Journal of the Peripheral Nervous System}, volume = {26}, journal = {Journal of the Peripheral Nervous System}, number = {S2}, doi = {10.1111/jns.12464}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-259555}, pages = {S21-S41}, year = {2021}, abstract = {A diagnosis of neuropathy can typically be determined through clinical assessment and focused investigation. With technological advances, including significant progress in genomics, the role of nerve biopsy has receded over recent years. However, making a specific and, in some cases, tissue-based diagnosis is essential across a wide array of potentially treatable acquired peripheral neuropathies. When laboratory investigations do not suggest a definitive diagnosis, nerve biopsy remains the final step to ascertain the etiology of the disease. The present review highlights the utility of nerve biopsy in confirming a diagnosis, while further illustrating the importance of a tissue-based diagnosis in relation to treatment strategies, particularly when linked to long-term immunosuppressive therapies,}, language = {en} } @article{BrumbergKuzkinaLapaetal.2021, author = {Brumberg, Joachim and Kuzkina, Anastasia and Lapa, Constantin and Mammadova, Sona and Buck, Andreas and Volkmann, Jens and Sommer, Claudia and Isaias, Ioannis U. and Doppler, Kathrin}, title = {Dermal and cardiac autonomic fiber involvement in Parkinson's disease and multiple system atrophy}, series = {Neurobiology of Disease}, volume = {153}, journal = {Neurobiology of Disease}, doi = {10.1016/j.nbd.2021.105332}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-260061}, pages = {105332}, year = {2021}, abstract = {Pathological aggregates of alpha-synuclein in peripheral dermal nerve fibers can be detected in patients with idiopathic Parkinson's disease and multiple system atrophy. This study combines skin biopsy staining for p-alpha-synuclein depositions and radionuclide imaging of the heart with [\(^{123}\)I]-metaiodobenzylguanidine to explore peripheral denervation in both diseases. To this purpose, 42 patients with a clinical diagnosis of Parkinson's disease or multiple system atrophy were enrolled. All patients underwent a standardized clinical workup including neurological evaluation, neurography, and blood samples. Skin biopsies were obtained from the distal and proximal leg, back, and neck for immunofluorescence double labeling with anti-p-alpha-synuclein and anti-PGP9.5. All patients underwent myocardial [\(^{123}\)I]-metaiodobenzylguanidine scintigraphy. Dermal p-alpha-synuclein was observed in 47.6\% of Parkinson's disease patients and was mainly found in autonomic structures. 81.0\% of multiple system atrophy patients had deposits with most of cases in somatosensory fibers. The [\(^{123}\)I]-metaiodobenzylguanidine heart-to-mediastinum ratio was lower in Parkinson's disease than in multiple system atrophy patients (1.94 +/- 0.63 vs. 2.91 +/- 0.96; p < 0.0001). Irrespective of the diagnosis, uptake was lower in patients with than without p-alpha-synuclein in autonomic structures (1.42 +/- 0.51 vs. 2.74 +/- 0.83; p < 0.0001). Rare cases of Parkinson's disease with p-alpha-synuclein in somatosensory fibers and multiple system atrophy patients with deposits in autonomic structures or both fiber types presented with clinically overlapping features. In conclusion, this study suggests that alpha-synuclein contributes to peripheral neurodegeneration and mediates the impairment of cardiac sympathetic neurons in patients with synucleinopathies. Furthermore, it indicates that Parkinson's disease and multiple system atrophy share pathophysiologic mechanisms of peripheral nervous system dysfunction with a clinical overlap.}, language = {en} }