RFC1 and FGF14 Repeat Expansions in Serbian Patients with Cerebellar Ataxia.

BACKGROUND: The newly discovered intronic repeat expansions in the genes encoding replication factor C subunit 1 (RFC1) and fibroblast growth factor 14 (FGF14) frequently cause late-onset cerebellar ataxia. OBJECTIVES: To investigate the presence of RFC1 and FGF14 pathogenic repeat expansions in Serbian patients with adult-onset cerebellar ataxia. METHODS: The study included 167 unrelated patients with sporadic or familial cerebellar ataxia. The RFC1 repeat expansion analysis was performed by duplex PCR and Sanger sequencing, while the FGF14 repeat expansion was tested for by long-range PCR, repeat-primed PCR, and Sanger sequencing. RESULTS: We identified pathogenic repeat expansions in RFC1 in seven patients (7/167; 4.2%) with late-onset sporadic ataxia with neuropathy and chronic cough. Two patients also had bilateral vestibulopathy. Repeat expansions in FGF14 were found in nine unrelated patients (9/167; 5.4%) with ataxia, less than half of whom presented with neuropathy and two-thirds with global brain atrophy. Tremor and episodic features were the most frequent additional characteristics in carriers of uninterrupted FGF14 repeat expansions. Among the 122 sporadic cases, 12 (9.8%) carried an expansion in either RFC1 or FGF14, comparable to 4/45 (8.9%) among the patients with a positive family history. CONCLUSIONS: Pathogenic repeat expansions in RFC1 and FGF14 are relatively frequent causes of adult-onset cerebellar ataxia, especially among sporadic patients, indicating that family history should not be considered when prioritizing ataxia patients for testing of RFC1 or FGF14 repeat expansions.

Genotype-phenotype correlation in PRKN-associated Parkinson's disease.

Bi-allelic pathogenic variants in PRKN are the most common cause of autosomal recessive Parkinson's disease (PD). 647 patients with PRKN-PD were included in this international study. The pathogenic variants present were characterised and investigated for their effect on phenotype. Clinical features and progression of PRKN-PD was also assessed. Among 133 variants in index cases (n = 582), there were 58 (43.6%) structural variants, 34 (25.6%) missense, 20 (15%) frameshift, 10 splice site (7.5%%), 9 (6.8%) nonsense and 2 (1.5%) indels. The most frequent variant overall was an exon 3 deletion (n = 145, 12.3%), followed by the p.R275W substitution (n = 117, 10%). Exon3, RING0 protein domain and the ubiquitin-like protein domain were mutational hotspots with 31%, 35.4% and 31.7% of index cases presenting mutations in these regions respectively. The presence of a frameshift or structural variant was associated with a 3.4 ± 1.6 years or a 4.7 ± 1.6 years earlier age at onset of PRKN-PD respectively (p < 0.05). Furthermore, variants located in the N-terminus of the protein, a region enriched with frameshift variants, were associated with an earlier age at onset. The phenotype of PRKN-PD was characterised by slow motor progression, preserved cognition, an excellent motor response to levodopa therapy and later development of motor complications compared to early-onset PD. Non-motor symptoms were however common in PRKN-PD. Our findings on the relationship between the type of variant in PRKN and the phenotype of the disease may have implications for both genetic counselling and the design of precision clinical trials.

α-Synuclein Pathology in PRKN-Linked Parkinson's Disease: New Insights from a Blood-Based Seed Amplification Assay.

Pathogenic variants in PRKN cause early-onset Parkinson's disease (PD), while the role of alpha-synuclein in PRKN-PD remains uncertain. One study performed a blood-based alpha-synuclein seed amplification assay (SAA) in PRKN-PD, not detecting seed amplification in 17 PRKN-PD patients. By applying a methodologically different SAA focusing on neuron-derived extracellular vesicles, we demonstrated alpha-synuclein seed amplification in 8 of 13 PRKN-PD patients, challenging the view of PRKN-PD as a non-synucleinopathy. Moreover, we performed blinded replication of the neuron-derived extracellular vesicles-dependent SAA in idiopathic PD patients and healthy controls. In conclusion, blood-based neuron-derived extracellular vesicles-dependent SAA represents a promising biomarker to elucidate the underpinnings of (monogenic) PD. ANN NEUROL 2024;95:1173-1177.

POLG2-Linked Mitochondrial Disease: Functional Insights from New Mutation Carriers and Review of the Literature.

Different pathogenic variants in the DNA polymerase-gamma2 (POLG2) gene cause a rare, clinically heterogeneous mitochondrial disease. We detected a novel POLG2 variant (c.1270 T > C, p.Ser424Pro) in a family with adult-onset cerebellar ataxia and progressive ophthalmoplegia. We demonstrated altered mitochondrial integrity in patients' fibroblast cultures but no changes of the mitochondrial DNA were found when compared to controls. We consider this novel, segregating POLG2 variant as disease-causing in this family. Moreover, we systematically screened the literature for POLG2-linked phenotypes and re-evaluated all mutations published to date for pathogenicity according to current knowledge. Thereby, we identified twelve published, likely disease-causing variants in 19 patients only. The core features included progressive ophthalmoplegia and cerebellar ataxia; parkinsonism, neuropathy, cognitive decline, and seizures were also repeatedly found in adult-onset heterozygous POLG2-related disease. A severe phenotype relates to biallelic pathogenic variants in POLG2, i.e., newborn-onset liver failure, referred to as mitochondrial depletion syndrome. Our work underlines the broad clinical spectrum of POLG2-related disease and highlights the importance of functional characterization of variants of uncertain significance to enable meaningful genetic counseling.

Estimates of protection levels against SARS-CoV-2 infection and severe COVID-19 in Germany before the 2022/2023 winter season: the IMMUNEBRIDGE project.

PURPOSE: Despite the need to generate valid and reliable estimates of protection levels against SARS-CoV-2 infection and severe course of COVID-19 for the German population in summer 2022, there was a lack of systematically collected population-based data allowing for the assessment of the protection level in real time. METHODS: In the IMMUNEBRIDGE project, we harmonised data and biosamples for nine population-/hospital-based studies (total number of participants n = 33,637) to provide estimates for protection levels against SARS-CoV-2 infection and severe COVID-19 between June and November 2022. Based on evidence synthesis, we formed a combined endpoint of protection levels based on the number of self-reported infections/vaccinations in combination with nucleocapsid/spike antibody responses ("confirmed exposures"). Four confirmed exposures represented the highest protection level, and no exposure represented the lowest. RESULTS: Most participants were seropositive against the spike antigen; 37% of the participants ≥ 79 years had less than four confirmed exposures (highest level of protection) and 5% less than three. In the subgroup of participants with comorbidities, 46-56% had less than four confirmed exposures. We found major heterogeneity across federal states, with 4-28% of participants having less than three confirmed exposures. CONCLUSION: Using serological analyses, literature synthesis and infection dynamics during the survey period, we observed moderate to high levels of protection against severe COVID-19, whereas the protection against SARS-CoV-2 infection was low across all age groups. We found relevant protection gaps in the oldest age group and amongst individuals with comorbidities, indicating a need for additional protective measures in these groups.

Characterization of the pathogenic α-Synuclein Variant V15A in Parkinson´s disease.

Despite being a major component of Lewy bodies and Lewy neurites, pathogenic variants in the gene encoding alpha-Synuclein (α-Syn) are rare. To date, only four missense variants in the SNCA gene, encoding α-Syn have unequivocally been shown to be disease-causing. We here describe a Parkinson´s disease patient with early cognitive decline carrying an as yet not fully characterized variant in SNCA (NM_001146055: c.44T > C, p.V15A). We used different cellular models, including stably transfected neuroblastoma (SH-SY5Y) cell cultures, induced pluripotent stem cell (iPSC)-derived neuronal cultures, and generated a Drosophila model to elucidate the impact of the p.V15A variant on α-Syn function and aggregation properties compared to other known pathogenic variants. We demonstrate that p.V15A increased the aggregation potential of α-Syn and the levels of apoptotic markers, and impaired the mitochondrial network. Moreover, p.V15A affects the flying ability and survival of mutant flies. Thus, we provide supporting evidence for the pathogenicity of the p.V15A variant, suggesting its inclusion in genetic testing approaches.

Depressive symptoms in Parkinson's disease are insufficiently but more often treated than in other chronic conditions.

Depressive symptoms in Parkinson's disease (PD) are multifactorial and are partly linked to the underlying dopaminergic deficit. However, at least a subset of PD patients may exhibit an unspecific depressive reaction to chronic illness. Here, we compared the prevalence and severity of depressive symptoms in PD patients and disease controls (DC). PD patients reported depressive symptoms at similar frequencies as DC but were on antidepressants, especially Mirtazapine, more frequently. Still, in both groups, a high proportion of patients with clinically significant depressive symptoms was not receiving medication. Diagnosis and treatment of depressive symptoms both in PD and DC should be improved.

Transition to endemic: 2-year SARS-CoV-2 surveillance follow-up of the ELISA cohort.

The 2-year SARS-CoV-2 surveillance follow-up of the ELISA cohort shows the successful transition from COVID-19 pandemic to endemic, confirms occupational risk factors in healthcare and identifies household risk factors in a high-incidence period https://bit.ly/43x8q6i.

Embracing Monogenic Parkinson's Disease: The MJFF Global Genetic PD Cohort.

BACKGROUND: As gene-targeted therapies are increasingly being developed for Parkinson's disease (PD), identifying and characterizing carriers of specific genetic pathogenic variants is imperative. Only a small fraction of the estimated number of subjects with monogenic PD worldwide are currently represented in the literature and availability of clinical data and clinical trial-ready cohorts is limited. OBJECTIVE: The objectives are to (1) establish an international cohort of affected and unaffected individuals with PD-linked variants; (2) provide harmonized and quality-controlled clinical characterization data for each included individual; and (3) further promote collaboration of researchers in the field of monogenic PD. METHODS: We conducted a worldwide, systematic online survey to collect individual-level data on individuals with PD-linked variants in SNCA, LRRK2, VPS35, PRKN, PINK1, DJ-1, as well as selected pathogenic and risk variants in GBA and corresponding demographic, clinical, and genetic data. All registered cases underwent thorough quality checks, and pathogenicity scoring of the variants and genotype-phenotype relationships were analyzed. RESULTS: We collected 3888 variant carriers for our analyses, reported by 92 centers (42 countries) worldwide. Of the included individuals, 3185 had a diagnosis of PD (ie, 1306 LRRK2, 115 SNCA, 23 VPS35, 429 PRKN, 75 PINK1, 13 DJ-1, and 1224 GBA) and 703 were unaffected (ie, 328 LRRK2, 32 SNCA, 3 VPS35, 1 PRKN, 1 PINK1, and 338 GBA). In total, we identified 269 different pathogenic variants; 1322 individuals in our cohort (34%) were indicated as not previously published. CONCLUSIONS: Within the MJFF Global Genetic PD Study Group, we (1) established the largest international cohort of affected and unaffected individuals carrying PD-linked variants; (2) provide harmonized and quality-controlled clinical and genetic data for each included individual; (3) promote collaboration in the field of genetic PD with a view toward clinical and genetic stratification of patients for gene-targeted clinical trials. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Participant perspective on the recall-by-genotype research approach: a mixed-method embedded study with participants of the CHRIS study.

Recall-by-genotype (RbG) research recruits participants previously involved in genetic research based on their genotype. RbG enables the further study of a particular variant of interest, but in recalling participants, it risks disclosing potentially unwanted or distressing genetic information. Any RbG strategy must therefore be done in a manner that addresses the potential ethical and social issues. As part of an RbG pilot on the penetrance of Parkinson's disease variants, we conducted an empirical mixed-method study with 51 participants of the Cooperative Health Research in South Tyrol (CHRIS) study to understand participant views on RbG research approach. Participants were disclosed the disease under investigation but not the individual variant carrier status. Results showed that participants filtered the information received through personal experience and enacted mechanisms to address the concerns raised by invitation by resorting to personal resources and the support provided by experts. While the non-disclosure of the Parkin variant carrier status was deemed acceptable, disclosing the disease under study was important for participants. Participant preferences for disclosure of the disease under investigation and the carrier status varied according to how the knowledge of individual carrier status was perceived to impact the participant's life. This study provided insights into participant response to the RbG research approach, which are relevant for RbG policy development. A suitable communication strategy and granular options addressing preferences for invitation in the original informed consent are critical for an ethically informed RbG policy.

In Vivo Investigation of Glucose Metabolism in Idiopathic and PRKN-Related Parkinson's Disease.

BACKGROUND: Alterations in mitochondrial dysfunction have been implicated in the pathogenesis of Parkinson's disease (PD). Mitochondrial energy production is linked to glucose metabolism, and diabetes is associated with PD. However, studies investigating glucose metabolism in vivo in genetically stratified PD patients and controls have yet to be performed. OBJECTIVES: The objectives of this study were to explore glucose production, gluconeogenesis, and the contribution of gluconeogenesis to glucose production in idiopathic and PRKN PD compared with healthy controls with state-of-the-art biochemical methods. METHODS: We applied a dried-blood sampling/gas chromatography/mass spectrometry approach to monitor fluxes in the Cori cycle in vivo. RESULTS: The contribution of gluconeogenesis to total glucose production is increased in idiopathic PD patients (n = 33), but not in biallelic PRKN mutation carriers (n = 5) compared with healthy controls (n = 13). CONCLUSIONS: We provide first-time in vivo evidence for alterations in glucose metabolism in idiopathic PD, in keeping with the epidemiological evidence for an association between PD and diabetes. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Mitochondrial DNA heteroplasmy distinguishes disease manifestation in PINK1/PRKN-linked Parkinson's disease.

Biallelic mutations in PINK1/PRKN cause recessive Parkinson's disease. Given the established role of PINK1/Parkin in regulating mitochondrial dynamics, we explored mitochondrial DNA integrity and inflammation as disease modifiers in carriers of mutations in these genes. Mitochondrial DNA integrity was investigated in a large collection of biallelic (n = 84) and monoallelic (n = 170) carriers of PINK1/PRKN mutations, idiopathic Parkinson's disease patients (n = 67) and controls (n = 90). In addition, we studied global gene expression and serum cytokine levels in a subset. Affected and unaffected PINK1/PRKN monoallelic mutation carriers can be distinguished by heteroplasmic mitochondrial DNA variant load (area under the curve = 0.83, CI 0.74-0.93). Biallelic PINK1/PRKN mutation carriers harbour more heteroplasmic mitochondrial DNA variants in blood (P = 0.0006, Z = 3.63) compared to monoallelic mutation carriers. This enrichment was confirmed in induced pluripotent stem cell-derived (controls, n = 3; biallelic PRKN mutation carriers, n = 4) and post-mortem (control, n = 1; biallelic PRKN mutation carrier, n = 1) midbrain neurons. Last, the heteroplasmic mitochondrial DNA variant load correlated with IL6 levels in PINK1/PRKN mutation carriers (r = 0.57, P = 0.0074). PINK1/PRKN mutations predispose individuals to mitochondrial DNA variant accumulation in a dose- and disease-dependent manner.

[Quality assurance follow-up survey of the ELISA cohort study on the prevalence of COVID-19: The view of study participants - What is well received?] / Nachbefragung zur Qualitätssicherung der ELISA-Kohortenstudie zur COVID-19-Prävalenz: Die Sicht von Studienteilnehmerinnen und Studienteilnehmern ­ Was kommt gut an?

INTRODUCTION: With the outbreak of the Corona pandemic, the LübEcker longitudinal study on infections with SARS-CoV-2 (ELISA study) was conducted in the Lübeck area to provide information on the prevalence, unreported cases and symptoms of COVID-19. The aim of the present study is to evaluate defined structure and process indictors of the study conduct of the ELISA study by subjects. METHODS: After defining and operationalizing participant-oriented quality indicators, 3,710 participants were surveyed online via LimeSurvey. Indicators defined were access to the study, time requirements, reporting of findings, ratings of the study apps used, communication, study center, tolerability of sample collection, and willingness to re-participate. In addition, comments on push and pull factors of study participation could be made. The evaluation was both quantitative and qualitative. RESULTS: 45% of the follow-up respondents (n=1,684) answered the questions on the defined structural and process indicators. In the quantitative part of the survey, tolerability of venous blood sampling was rated as significantly better than that of nasopharyngeal smears. 91% of the follow-up respondents welcomed the offer to view their findings in the personal results portal. Overall, the indicators were mostly rated positively. According to the qualitative data, the study participants found the win-win situation of the test opportunity to contribute to research, the local relevance of the study, the small incentives, and the low-threshold nature of the study registration to be positive aspects of the study. According to the quantitative data, participants suggested improving the usability of the digital applications in terms of more user-friendly identification solutions, reminder functions, announcements of software updates and avoidance of double entries. DISCUSSION: The defined structure and process indicators appear to be suitable for assessing the quality of study implementation from the subjects' point of view and indicate a good quality of study implementation under pandemic conditions. The lowest participation rate (75%) was measured at the fifth test time of strongly declining COVID-19 infections during the summer holidays in Schleswig-Holstein. Obviously, the benefit and meaningfulness of further study participation as well as competing factors were weighted differently by the subjects at this point. The follow-up survey suggests a variety of options for motivating participants to maintain a high level of participation. Possible limitations are that a non-response bias cannot be excluded for the follow-up survey and that no suitable standardised questionnaire was available. CONCLUSION: The present study provides recommendations for the planning of future cohort studies. It makes sense to continuously evaluate the motives for participation or non-participation and to explicitly consider them in the course of the study. Therefore, the definition of general quality indicators for the practical implementation of studies seems desirable. Positive experiences of the participants in connection with study participation are important, such as good time management, short response times, technical support offers and additional services such as a study homepage with frequently asked questions (FAQs), timely individual notifications of results and transparent, generally understandable information about study results during the study. Digital solutions are well received, but can still be improved for specific studies.

Protocol of the Luebeck longitudinal investigation of SARS-CoV-2 infection (ELISA) study - a prospective population-based cohort study.

BACKGROUND: Considering the insufficiently controlled spread of new SARS-CoV-2 variants, partially low vaccination rates, and increased risk of a post-COVID syndrome, well-functioning, targeted intervention measures at local and national levels are urgently needed to contain the SARS-CoV-2 pandemic. Surveillance concepts (cross-sectional, cohorts, clusters) need to be carefully selected to monitor and assess incidence and prevalence at the population level. A critical methodological gap for identifying specific risks/dynamics for SARS-Cov-2 transmission and post-COVID-19-syndrome includes repetitive testing for past or present infection of a defined cohort with simultaneous assessment of symptoms, behavior, risk, and protective factors, as well as quality of life. METHODS: The ELISA-Study is a longitudinal, prospective surveillance study with a cohort approach launched in Luebeck in April 2020. The first part comprised regular PCR testing, antibody measurements, and a recurrent App-based questionnaire for a population-based cohort of 3000 inhabitants of Luebeck. The follow-up study protocol includes self-testing for antibodies and PCR testing for a subset of the participants, focusing on studying immunity after vaccination and/or infection and post-COVID-19 symptoms. DISCUSSION: The ELISA cohort and our follow-up study protocol will enable us to study the effects of a sharp increase of SARS-CoV-2 infections on seroprevalence of Anti-SARS-CoV-2 antibodies, post-COVID-19-symptoms, and possible medical, occupational, and behavioral risk factors. We will be able to monitor the pandemic continuously and discover potential sequelae of an infection long-term. Further examinations can be readily set up on an ad-hoc basis in the future. Our study protocol can be adapted to other regions and settings and is transferable to other infectious diseases. TRIAL REGISTRATION: DRKS.de, German Clinical Trials Register (DRKS), Identifier: DRKS00023418 , Registered on 28 October 2020.

Head impulse testing in bilateral vestibulopathy in patients with genetically defined CANVAS.

BACKGROUND: To investigate the association between disease duration and the severity of bilateral vestibulopathy in individuals with complete or incomplete CANVAS (Cerebellar Ataxia with Neuropathy and Vestibular Areflexia Syndrome) and biallelic RFC1 repeat expansions. METHODS: Retrospective analysis of clinical data and the vestibulo-ocular reflex quantified by the video head impulse test in 20 patients with confirmed biallelic RFC1 repeat expansions. RESULTS: Vestibulo-ocular reflex gain at first admittance 6.9 ± 5.0 years after disease onset was 0.16 [0.15-0.31] (median [interquartile range]). Cross-sectional analysis revealed that gain reduction was associated with disease duration. Follow-up measurements were available for ten individuals: eight of them exhibited a progressive decrease of the vestibulo-ocular reflex gain over time. At the first visit, six of all patients (30%) did not show clinical signs of cerebellar ataxia. CONCLUSIONS: Our data suggest a pathological horizontal head impulse test, which can easily be obtained in many outpatient clinics, as a sign of bilateral vestibulopathy in genetically confirmed CANVAS that can precede clinically accessible cerebellar ataxia at least in a subset of patients. The presumably continuous decline over time possibly reflects the neurodegenerative character of the disease. Thus, genetic testing for RFC1 mutations in (isolated) bilateral vestibulopathy might allow disease detection before the onset of cerebellar signs. Further studies including a wider spectrum of vestibular function tests are warranted in a prospective design.

One-year surveillance of SARS-CoV-2 transmission of the ELISA cohort: A model for population-based monitoring of infection risk.

With newly rising coronavirus disease 2019 (COVID-19) cases, important data gaps remain on (i) long-term dynamics of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection rates in fixed cohorts (ii) identification of risk factors, and (iii) establishment of effective surveillance strategies. By polymerase chain reaction and antibody testing of 1% of the local population and >90,000 app-based datasets, the present study surveilled a catchment area of 300,000 inhabitants from March 2020 to February 2021. Cohort (56% female; mean age, 45.6 years) retention was 75 to 98%. Increased risk for seropositivity was detected in several high-exposure groups, especially nurses. Unreported infections dropped from 92 to 29% during the study. "Contact to COVID-19-affected" was the strongest risk factor, whereas public transportation, having children in school, or tourism did not affect infection rates. With the first SARS-CoV-2 cohort study, we provide a transferable model for effective surveillance, enabling monitoring of reinfection rates and increased preparedness for future pandemics.

Eosinophils Suppress the Migration of T Cells Into the Brain of Plasmodium berghei-Infected Ifnar1-/- Mice and Protect Them From Experimental Cerebral Malaria.

Cerebral malaria is a potentially lethal disease, which is caused by excessive inflammatory responses to Plasmodium parasites. Here we use a newly developed transgenic Plasmodium berghei ANKA (PbAAma1OVA) parasite that can be used to study parasite-specific T cell responses. Our present study demonstrates that Ifnar1-/- mice, which lack type I interferon receptor-dependent signaling, are protected from experimental cerebral malaria (ECM) when infected with this novel parasite. Although CD8+ T cell responses generated in the spleen are essential for the development of ECM, we measured comparable parasite-specific cytotoxic T cell responses in ECM-protected Ifnar1-/- mice and wild type mice suffering from ECM. Importantly, CD8+ T cells were increased in the spleens of ECM-protected Ifnar1-/- mice and the blood-brain-barrier remained intact. This was associated with elevated splenic levels of CCL5, a T cell and eosinophil chemotactic chemokine, which was mainly produced by eosinophils, and an increase in eosinophil numbers. Depletion of eosinophils enhanced CD8+ T cell infiltration into the brain and increased ECM induction in PbAAma1OVA-infected Ifnar1-/- mice. However, eosinophil-depletion did not reduce the CD8+ T cell population in the spleen or reduce splenic CCL5 concentrations. Our study demonstrates that eosinophils impact CD8+ T cell migration and proliferation during PbAAma1OVA-infection in Ifnar1-/- mice and thereby are contributing to the protection from ECM.