Genetic Analysis of Patients With Early-Onset Parkinson’s Disease in Eastern China

Rethinking 'rare' PINK1 Parkinson's disease: A meta-analysis of geographical prevalence, phenotypic diversity, and α-synuclein pathology

PTEN-induced kinase 1 (PINK1)-related Parkinson's disease (PD) is traditionally considered a rare autosomal recessive form of early-onset PD (EOPD), lacking classical Lewy body pathology. However, this characterization underestimates and oversimplifies PINK1-PD, largely due to a lack of extensive studies in diverse ethnic populations. This review and meta-analysis explores considerable variations in PINK1 variant rates and the wide heterogeneity influenced by patient- and variant-specific factors, delineating a more precise disease profile. Our findings reveal that PINK1-PD is more common than previously thought, with geographic 'hotspots' where up to 9% of EOPD cases are linked to PINK1 variants, including the pathogenic p.Leu347Pro variant affecting 1 in 1300 West Polynesians. Homozygous PINK1-PD typically manifests around age 35, predominantly affecting the lower limbs, with an excellent response to levodopa. Heterozygous PINK1-PD presents an 'intermediate' phenotype, with a later onset age (around 43 years) than homozygous PINK1-PD but earlier than idiopathic PD (typically after age 65). The severity of the phenotype is influenced by variant zygosity and pathogenicity, interacting with genetic and environmental factors to push some individuals beyond the disease threshold. Notably, females with PINK1-PD have earlier onset age than males, particularly in homozygous cases and when variants occur in the first half of PINK1's kinase domain. Contrary to traditional views, α-synuclein pathology is present in 87.5% of PINK1-PD postmortem cases across ages and variants. We challenge conventional views on PINK1-PD, highlighting distinct phenotypes influenced by zygosity, sex, and a role for α-synuclein pathology, urging for increased recognition and research of this not-so-rare disease.

Challenging Diagnosis of Fahr's Disease Mimicking Parkinson's Disease: A Case Report

Patients presenting with parkinsonism symptoms such as severe bradykinesia and significant hypophonia, along with an atypical clinical course, should be evaluated for secondary parkinsonism syndromes and other causes of parkinsonism. One of these causes is known as Fahr's disease, which is often overlooked by neurologists and other physicians.

Genetic architecture of a single cohort of 230 Indian Parkinson's Disease patients

INTRODUCTION

Indian Parkinson's Disease (PD) patients are severely underrepresented in terms of genetic studies and little is known about the frequency of variants and their impact on motor and nonmotor symptoms (NMS).

METHODS

This retrospective cross-sectional study was conducted in PD patients undergoing treatment at a tertiary care hospital from India. Patients were advised genetic testing if they had (i) age at onset (AAO) of motor symptoms at or before 50 years (EOPD), (ii) positive family history of PD, parkinsonism or dystonia. All patients underwent whole exome sequencing and potentially pathogenic variants were identified.

RESULTS

Clinical and genetic data were available for 230 (163 males, 70.4 %) patients. Thirty-five pathogenic and likely pathogenic variants in various PD genes were identified in 47 patients resulting in a yield of 20.4 %. In the remaining, 82 patients had either variants of uncertain significance or had variants in genes not associated with parkinsonism and 101 patients did not have any non-benign variants. Patients with genetically mediated PD had a lower AAO and statistically greater frequency of dystonia (36.2 %), postural instability (29.8 %) and mood disorder (29.8 %) and a higher Hoehn and Yahr score (2.9). Among the 47 patients, 11 patients had PARK-PRKN, six patients had PARK-PLA2G6, and 22 patients had PARK-GBA1.

CONCLUSION

Around one-fifth of early-onset PD can have an underlying monogenetic cause. PARK-GBA1, PARK-PRKN and PARK-PLA2G6 are the commoner causes of genetically mediated PD in India. Patients with genetic cause had an earlier age at onset, and more frequent dystonia, postural instability and dyskinesia.

Resequencing the complete SNCA locus in Indian patients with Parkinson's disease

The genetic loci implicated in familial Parkinson's disease (PD) have limited generalizability to the Indian PD population. We tested mutations and the frequency of known mutations in the SNCA gene in a PD cohort from India. We selected 298 PD cases and 301 age-matched controls for targeted resequencing (before QC), along with 363 PD genomes of Indian ancestry and 1029 publicly available whole genomes from India as healthy controls (IndiGenomes), to determine the frequency of monogenic SNCA mutations. The raw sequence reads were analyzed using an in-house analysis pipeline, allowing the detection of small variants and structural variants using Manta. The in-depth analysis of the SNCA locus did not identify missense or structural variants, including previously identified SNCA mutations, in the Indian population. The familial forms of SNCA gene variants do not play a major role in the Indian PD population and this warrants further research in the under-represented population.

Iron toxicity, ferroptosis and microbiota in Parkinson's disease: Implications for novel targets

Parkinson's Disease (PD) is a progressive neurodegenerative disease characterized by loss of dopaminergic neurons in substantia nigra pars compacta (SNpc). Iron (Fe)-dependent programmed cell death known as ferroptosis, plays a crucial role in the etiology and progression of PD. Since SNpc is particularly vulnerable to Fe toxicity, a central role for ferroptosis in the etiology and progression of PD is envisioned. Ferroptosis, characterized by reactive oxygen species (ROS)-dependent accumulation of lipid peroxides, is tightly regulated by a variety of intracellular metabolic processes. Moreover, the recently characterized bi-directional interactions between ferroptosis and the gut microbiota, not only provides another window into the mechanistic underpinnings of PD but could also suggest novel interventions in this devastating disease. Here, following a brief discussion of PD, we focus on how our expanding knowledge of Fe-induced ferroptosis and its interaction with the gut microbiota may contribute to the pathophysiology of PD and how this knowledge may be exploited to provide novel interventions in PD.

The Genetic Drivers of Juvenile, Young, and Early-Onset Parkinson's Disease in India

BACKGROUND

Recent studies have advanced our understanding of the genetic drivers of Parkinson's disease (PD). Rare variants in more than 20 genes are considered causal for PD, and the latest PD genome-wide association study (GWAS) identified 90 independent risk loci. However, there remains a gap in our understanding of PD genetics outside of the European populations in which the vast majority of these studies were focused.

OBJECTIVE

The aim was to identify genetic risk factors for PD in a South Asian population.

METHODS

A total of 674 PD subjects predominantly with age of onset (AoO) ≤50 years (encompassing juvenile, young, or early-onset PD) were recruited from 10 specialty movement disorder centers across India over a 2-year period; 1376 control subjects were selected from the reference population GenomeAsia, Phase 2. We performed various case-only and case-control genetic analyses for PD diagnosis and AoO.

RESULTS

A genome-wide significant signal for PD diagnosis was identified in the SNCA region, strongly colocalizing with SNCA region signal from European PD GWAS. PD cases with pathogenic mutations in PD genes exhibited, on average, lower PD polygenic risk scores than PD cases lacking any PD gene mutations. Gene burden studies of rare, predicted deleterious variants identified BSN, encoding the presynaptic protein Bassoon that has been previously associated with neurodegenerative disease.

CONCLUSIONS

This study constitutes the largest genetic investigation of PD in a South Asian population to date. Future work should seek to expand sample numbers in this population to enable improved statistical power to detect PD genes in this understudied group. © 2023 Denali Therapeutics and The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Genetic Testing of Movements Disorders: A Review of Clinical Utility

Currently, pathogenic variants in more than 500 different genes are known to cause various movement disorders. The increasing accessibility and reducing cost of genetic testing has resulted in increasing clinical use of genetic testing for the diagnosis of movement disorders. However, the optimal use case(s) for genetic testing at a patient level remain ill-defined. Here, we review the utility of genetic testing in patients with movement disorders and also highlight current challenges and limitations that need to be considered when making decisions about genetic testing in clinical practice.

Highlights

The utility of genetic testing extends across multiple clinical and non-clinical domains. Here we review different aspects of the utility of genetic testing for movement disorders and the numerous associated challenges and limitations. These factors should be weighed on a case-by-case basis when requesting genetic tests in clinical practice.

Abnormal intra- and inter-network functional connectivity of brain networks in early-onset Parkinson's disease and late-onset Parkinson's disease

Objective

The purpose of this study is to look into the altered functional connectivity of brain networks in Early-Onset Parkinson's Disease (EOPD) and Late-Onset Parkinson's Disease (LOPD), as well as their relationship to clinical symptoms.

Methods

A total of 50 patients with Parkinson' disease (28 EOPD and 22 LOPD) and 49 healthy controls (25 Young Controls and 24 Old Controls) were admitted to our study. Employing independent component analysis, we constructed the brain networks of EOPD and Young Controls, LOPD and Old Controls, respectively, and obtained the functional connectivity alterations in brain networks.

Results

Cerebellar network (CN), Sensorimotor Network (SMN), Executive Control Network (ECN), and Default Mode Network (DMN) were selected as networks of interest. Compared with their corresponding health controls, EOPD showed increased functional connectivity within the SMN and ECN and no abnormalities of inter-network functional connectivity were found, LOPD demonstrated increased functional connectivity within the ECN while decreased functional connectivity within the CN. Furthermore, in LOPD, functional connectivity between the SMN and DMN was increased. The functional connectivity of the post-central gyrus within the SMN in EOPD was inversely correlated with the Unified Parkinson's Disease Rating Scale Part III scores. Age, age of onset, and MMSE scores are significantly different between EOPD and LOPD (p < 0.05).

Conclusion

There is abnormal functional connectivity of networks in EOPD and LOPD, which could be the manifestation of the associated pathological damage or compensation.

Case Report: A case of PLA2G6 gene-related early-onset Parkinson's disease and review of literature

Background

Early onset Parkinson's disease (EOPD) is a neurodegenerative disease associated with the action ofto genetic factors. A mutated phospholipase A2 type VI gene (PLA2G6) is considered to be one of pathogenic genes involved in EOPD development. Although EOPD caused by a mutated PLA2G6 has been recorded in major databases, not all mutant genotypes have been reported. Here, we report a case of PLA2G6-related EOPD caused by a novel compound heterozygous mutation.

Case presentation

The case was an of 26-year-old young male with a 2-year course of disease. The onset of the disease was insidious and developed gradually. The patient presented with unsteady walking, bradykinesia, unresponsiveness, and decreased facial expression. Auxiliary examination showed a compound heterozygous mutation of the PLA2G6gene with c.991G > T and c.1427 + 1G > A. Mild atrophy of the cerebrum and cerebellum was detected on brain MRI. The patient was diagnosed with EOPD. We administered treatment with Madopar, which was effective. After a two-year disease course, we observed progression to stage 5 according to the Hoehn-Yahr Scale (without medicine in the off-stage). An MDS-UPDRS III score of 62 was obtained, with characteristics of severe disease and rapid progress. The diagnosis was an EOPD phenotype caused by a combination of mutations at the c.991G > T and c.1427 + 1G > A sites of the PLA2G6gene.

Conclusion

After active treatment, the disease was set under control, with no significant progression during the three-month follow-up period. Dyskinesia did not recur after reducing the Madopar dose. The freezing sign was slightly decreased and the wearing-off was delayed to 2 h.