Novel ATP13A2 and PINK1 variants identified in Chinese patients with Parkinson’s disease by whole-exome sequencing

Advances in animal models of Parkinson's disease

Parkinson's disease is a complex neurodegenerative disease characterized by progressive movement impairments. Predominant symptoms encompass resting tremor, bradykinesia, limb rigidity, and postural instability. In addition, it also includes a series of non-motor symptoms such as sleep disorders, hyposmia, gastrointestinal dysfunction, autonomic dysfunction and cognitive impairment. Pathologically, the disease manifests through dopaminergic neuronal loss and the presence of Lewy bodies. At present, no significant breakthrough has been achieved in clinical Parkinson's disease treatment. Exploring treatment modalities necessitate the establishment of scientifically sound animal models. In recent years, researchers have focused on replicating the symptoms of human Parkinson's disease, resulting in the establishment of various experimental animal models primarily through drugs and transgenic methods to mimic relevant pathologies and identify more effective treatments. This review examines traditional neurotoxin and transgenic animal models as well as α-synuclein pre-formed fibrils models, non-human primate models and non-mammalian specie models. Additionally, it introduces emerging models, including models based on optogenetics, induced pluripotent stem cells, and gene editing, aiming to provide a reference for the utilization of experimental animal models and clinical research for researchers in this field.

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.

A genetic analysis of Chinese patients with early-onset Parkinson' s disease

Genetic factors play an important role in early-onset Parkinson's disease (EOPD). The genetic spectrum of patients with EOPD varies widely among different ethnicities, with extensive investigations having been performed in Caucasian populations; however, research in Chinese populations remains limited. In this study, we performed multiplex ligation-dependent probe amplification assay and whole-exome sequencing in 15 unrelated Chinese EOPD patients with age of onset before 40 years. Among them, a patient carried compound heterozygous exon duplications in Parkin (exon 3 duplication and exon 4 duplication) (6.67%) and two patients carried the homozygous pathogenic variant (p.D331Y) in PLA2G6 (13.33%). Three novel variants in EIF4G1 (p.P1043S, p.R1505Q, and p.P266A) were identified and classified as uncertain significance. Additionally, a risk variant in GBA (p.L483P) was detected in one patient (6.67%). PLA2G6 (13.33%) was the most common causative gene among our EOPD patients. Furthermore, detailed clinical features were presented. Our results broaden the genetic spectrum and clinical phenotypic spectrum of EOPD patients.

ATP13A2 protects dopaminergic neurons in Parkinson's disease: from biology to pathology

As a late endosomal/lysosomal transport protein of the P5-type, ATP13A2 is capable of removing the abnormal accumulation of α-synuclein, which maintains the homeostasis of metal ions and polyamines in the central nervous system. Furthermore, ATP13A2 regulates the normal function of several organelles such as lysosomes, endoplasmic reticulum (ER) and mitochondria, and maintains the normal physiological activity of neural cells. Especially, ATP13A2 protects dopaminergic (DA) neurons against environmental or genetically induced Parkinson's disease (PD). As we all know, PD is a neurodegenerative disease characterized by the loss of DA neurons in the substantia nigra pars compacta. An increasing number of studies have reported that the loss-of-function of ATP13A2 affects normal physiological processes of various organelles, leading to abnormalities and the death of DA neurons. Previous studies in our laboratory have also shown that ATP13A2 deletion intensifies the neuroinflammatory response induced by astrocytes, thus inducing DA neuronal injury. In addition to elucidating the normal structure and function of ATP13A2, this review summarized the pathological mechanisms of ATP13A2 mutations leading to PD in existing literature studies, deepening the understanding of ATP13A2 in the pathological process of PD and other related neurodegenerative diseases. This review provides inspiration for investigators to explore the essential regulatory role of ATP13A2 in PD in the future.

Novel compound heterozygous of PARKIN causes early-onset Parkinson's disease

Genetics has an essential role in the development of early-onset Parkinson's disease (EOPD). Consequently, genetic screening is of great significance for the diagnosis and treatment of EOPD. In this study, we reported two EOPD with compound heterozygous in PARKIN detected by whole-exome sequencing (WES) and ligation-dependent probe amplification (MLPA). Two unrelated EOPD patients and their parents were enrolled in this study. Genetic analysis was performed through WES and verified by direct Sanger sequencing. In addition, MLPA was used to detect exon dosage. Detailed clinical manifestations and several scale assessments were collected for genotype and phenotype analysis. Compound heterozygous mutations in PARKIN were identified in both patients. c.735-1G > A and Ex2del were detected in Case A, while G284R (c.850 G > C) and Ex2del were found in Case B. These variants were confirmed to originate from their normal parents. The c.735-1G > A is a novel PARKIN variant, which was predicted to result from disappearing of the acceptor splice site by NetGene2. The G284R is a previously reported pathological mutation and the Ex2del is a hot variant of PARKIN found in the Asian population. The phenotypes of both patients are quite different, the main manifestation of case A is rigidity onset, while the case B starts with tremor and foot dystonia. In the present study, we reported a novel compound heterozygous form of PARKIN consisting of splice variant c. 735-1G > A and Ex2del. Moreover, we also found that tiny differences in genotypes of PARKIN may lead to obvious clinical phenotypic differences.

ATP13A2 Gene Variants in Patients with Parkinson's Disease in Xinjiang

OBJECTIVE

To analyze the ATP13A2 gene variants in the Han and Uyghur populations residing in Xinjiang and to determine their correlation with the risk of Parkinson's disease (PD).

METHODS

Four ATP13A2 SNVs-rs56367069 (Arg294Gln), rs151117874 (Thr12Met), rs147277743 (Ala746Thr), and rs2076603-were analyzed in 218 patients (75 Uyghurs and 143 Hans) with sporadic PD and 234 healthy controls (90 Uyghurs and 144 Hans) by Sanger DNA sequencing.

RESULTS

Only one Han patient harbored the AG genotype of the rs147277743 SNV, indicating a frequency of 0.46% in the Han population. In addition, this SNV was not associated with PD risk. The rs2076603 SNV was correlated with PD development, and the A allele in particular was significantly different across ethnicity and age. The rs56367069 and rs151117874 SNVs were not detected in the entire cohort.

CONCLUSION

ATP13A2 rs2076603 SNV is associated with PD susceptibility, and the A allele is a PD protective factor in the Han population.