Association of Parkinson’s disease with six single nucleotide polymorphisms located in four PARK genes in the northern Han Chinese population

Advancements in Genetic and Biochemical Insights: Unraveling the Etiopathogenesis of Neurodegeneration in Parkinson's Disease

Parkinson's disease (PD) is the second most prevalent neurodegenerative movement disorder worldwide, which is primarily characterized by motor impairments. Even though multiple hypotheses have been proposed over the decades that explain the pathogenesis of PD, presently, there are no cures or promising preventive therapies for PD. This could be attributed to the intricate pathophysiology of PD and the poorly understood molecular mechanism. To address these challenges comprehensively, a thorough disease model is imperative for a nuanced understanding of PD's underlying pathogenic mechanisms. This review offers a detailed analysis of the current state of knowledge regarding the molecular mechanisms underlying the pathogenesis of PD, with a particular emphasis on the roles played by gene-based factors in the disease's development and progression. This study includes an extensive discussion of the proteins and mutations of primary genes that are linked to PD, including α-synuclein, GBA1, LRRK2, VPS35, PINK1, DJ-1, and Parkin. Further, this review explores plausible mechanisms for DAergic neural loss, non-motor and non-dopaminergic pathologies, and the risk factors associated with PD. The present study will encourage the related research fields to understand better and analyze the current status of the biochemical mechanisms of PD, which might contribute to the design and development of efficacious and safe treatment strategies for PD in future endeavors.

Biomarkers in Neurodegenerative Diseases: Proteomics Spotlight on ALS and Parkinson’s Disease

Neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS) and Parkinson’s disease (PD) are both characterized by pathogenic protein aggregates that correlate with the progressive degeneration of neurons and the loss of behavioral functions. Both diseases lack biomarkers for diagnosis and treatment efficacy. Proteomics is an unbiased quantitative tool capable of the high throughput quantitation of thousands of proteins from minimal sample volumes. We review recent proteomic studies in human tissues, plasma, cerebrospinal fluid (CSF), and exosomes in ALS and PD that identify proteins with potential utility as biomarkers. Further, we review disease-related post-translational modifications in key proteins TDP43 in ALS and α-synuclein in PD studies, which may serve as biomarkers. We compare relative and absolute quantitative proteomic approaches in key biomarker studies in ALS and PD and discuss recent technological advancements which may identify suitable biomarkers for the early-diagnosis treatment efficacy of these diseases.

A Comprehensive Analysis of Population Differences in LRRK2 Variant Distribution in Parkinson's Disease

Background:LRRK2 variants have been demonstrated to have distinct distributions in different populations. However, researchers have thus far chosen to focus on relatively few variants, such as R1628P, G2019S, and G2385R. We therefore investigated the relationship between common LRRK2 variants and PD risk in various populations.

Methods: Using a set of strict inclusion criteria, six databases were searched, resulting in the selection of 94 articles covering 49,299 cases and 47,319 controls for final pooled analysis and frequency analysis. Subgroup analysis were done for Africans, European/West Asians, Hispanics, East Asians, and mixed populations. Statistical analysis was carried out using the Mantel-Haenszel approach to determine the relationship between common LRRK2 variants and PD risk, with the significance level set at p < 0.05.

Results: In the absence of obvious heterogeneities and publication biases among the included studies, we concluded that A419V, R1441C/G/H, R1628P, G2019S, and G2385R were associated with increased PD risk (p: 0.001, 0.0004, < 0.00001, < 0.00001, and < 0.00001, respectively), while R1398H was associated with decreased risk (p: < 0.00001). In East Asian populations, A419V, R1628P, and G2385R increased risk (p: 0.001, < 0.00001, < 0.00001), while R1398H had the opposite effect (p: 0.0005). G2019S increased PD risk in both European/West Asian and mixed populations (p: < 0.00001, < 0.00001), while R1441C/G/H increased risk in European/West Asian populations only (p: 0.0004).

Conclusions: We demonstrated that LRRK2 variant distribution is different among various populations, which should inform decisions regarding the development of future genetic screening strategies.

The Role of LRRK2 in Neurodegeneration of Parkinson Disease

The leucine-rich repeat kinase 2 (LRRK2) gene and α-synuclein gene (SNCA) are the key influencing factors of Parkinson’s disease (PD). It is reported that dysfunction of LRRK2 may influence the accumulation of α-synuclein and its pathology to alter cellular functions and signaling pathways by the kinase activation of LRRK2. The accumulation of α-synuclein is one of the main stimulants of microglial activation. Microglia are macrophages that reside in the brain, and acti-vation of microglia is believed to contribute to neuroinflammation and neuronal death in PD. Therefore, clarifying the com-plex relationship among LRRK2, α-synuclein and microglials could offer targeted clinical therapies for PD. Here, we provide an updated review focused on the discussion of the evidence supporting some of the key mechanisms that are important for LRRK2-dependent neurodegeneration in PD

The Association between LRRK2 G2385R and Phenotype of Parkinson's Disease in Asian Population: A Meta-Analysis of Comparative Studies

Numerous studies have investigated the relationship between the LRRK2 G2385R variant and clinical characteristics in Parkinson's disease (PD), but the results have been inconsistent. This study investigated whether the LRRK2 G2385R variant was associated with a unique clinical phenotype of PD in the Asian population, using a meta-analysis. The PubMed, Web of Science, EMBASE, CNKI, and WANFANG databases were searched until September 2017. The strict selection criteria and exclusion criteria were determined, and mean differences (MD) or odds ratios (OR) with 95% confidence intervals (CI) were used to assess the strength of associations. Statistical analyses and graphics were performed using Review Manager 5.3. Sixteen related case-control studies were included in the meta-analysis. The LRRK2 G2385R carriers significantly more often presented a family history (OR: 1.98; 95% CI: 1.16−3.39; P=0.01) and had a longer disease duration (MD = 0.47, 95% CI: 0.01−0.93, P=0.04) and a higher MMSE score (MD = 1.02, 95% CI: 0.43–1.62 P=0.0007) than LRRK2 G2385R noncarriers. There were no significant differences in sex distribution, age at onset, initial symptoms, motor symptoms, depression, levodopa-equivalent dose, and related complications between LRRK2 G2385R-carrier and LRRK2 G2385R-noncarrier PD patients. Our results suggested that most of the clinical characteristics of PD patients with LRRK2 G2385R mutations are similar to those of LRRK2 G2385R noncarriers among Asian PD patients, except for the more common family history, relatively longer disease duration, and higher MMSE scores in the former group.

Relationship between LRRK2 R1628P polymorphism and Parkinson's disease in Asian populations

Although the leucine-rich repeat kinase 2 (LRRK2) R1628P polymorphism has been associated with the risk of Parkinson's disease (PD) in Taiwan, China, and Singapore, there are conflicting findings regarding this relationship. Thus, the aim of the present meta-analysis was to evaluate the associations between the LRRK2 R1628P polymorphism (rs33949390) and PD in Asian populations. A search for eligible studies was performed in PubMed, Embase, SinoMed, and the China Knowledge Resource Integrated Database, and pooled odds ratios and 95% confidence intervals were used to evaluate the strength of the association between the R1628P polymorphism and PD. This meta-analysis assessed 19 studies from 14 papers that involved a total of 9,927 PD patients and 8,602 controls and found that the R1628P polymorphism was significantly associated with the risk of PD in Asian populations. Moreover, stratification analyses indicated that the R1628P polymorphism was significantly associated with an increased risk of PD among Chinese as well as non-Chinese Asian populations and an increased risk of PD in Chinese patients from China, Taiwan, and Singapore. In a stratified analysis conducted according to age, significant associations were found for both late-onset PD and early-onset PD. The present data indicate that the R1628P polymorphism of the LRRK2 gene contributes to PD susceptibility in Asian, especially Chinese, populations.

Genetic Analysis of LRRK2 R1628P in Parkinson's Disease in Asian Populations

Although the etiology of Parkinson's disease (PD) remains unclear, there is increasing evidence of genetic factors contributing to the onset of PD. Various mutations and risk variants of the gene LRRK2 have been reported, but the association between LRRK2 R1628P and PD is still inconsistent. Thus, we conducted a meta-analysis to determine the potential relationship between R1628P and PD. Our study sample was an aggregate of 17 publications, which in total consisted of 9,275 PD patients and 8,114 controls. All of these articles are of high quality according to NOS, and there was no obvious reporting bias or heterogeneity. In a general Asian population, the pooled OR of the risk genotype contrasts was 1.83 (95% CI: 1.57, 2.13). When stratified by ethnicity, the pooled ORs were 1.84 (95% CI: 1.56, 2.18) in a Chinese population and 1.79 (95% CI: 1.27, 2.52) in a non-Chinese population. Our study suggests that LRRK2 R1628P appears to be a risk factor for PD in Asian populations, both Chinese and non-Chinese.

Association of LRRK2 R1628P variant with Parkinson's disease in Ethnic Han-Chinese and subgroup population

Recent studies have linked certain single nucleotide polymorphisms in the leucine-rich repeat kinase 2 (LRRK2) gene with Parkinson’s disease (PD). The R1628P variant of LRRK2 may be a specific risk factor for PD in ethnic Han-Chinese populations. This study is to elucidate the epidemiological feature of R1628P in ethnic Han-Chinese population with PD. A comprehensive meta-analysis was performed to evaluate the precise association between R1628P variant and the risk for PD in ethnic Han-Chinese and subgroups stratified by gender, onset age, or family history. The analysis assessing the role of R1628P on the risk of PD in ethnic Han-Chinese supported a significant association, and the odds ratio was 1.86. We further estimate the specific prevalence in relevant ethnic Han-Chinese subgroups. After stratifying the eligible data by gender, onset age, or family history, significant associations were found in all male, female, early-onset, late-onset, familial and sporadic subgroups, and the odds ratio were 1.90, 1.94, 2.12, 1.75, 6.71 and 1.81 respectively. In conclusion, our meta-analysis suggests that R1628P variant of LRRK2 has a significant association with the risk of PD in ethnic Han-Chinese and subgroup population.

The association between the LRRK2 R1628P variant and the risk of Parkinson's disease in Asian: a meta-analysis

Many published case-control studies have investigated the association between Leucine-rich repeat kinase 2(LRRK2) R1628P and the susceptibility of Parkinson's disease (PD). However, controversial results were obtained. Herein we performed this meta-analysis to assess the association between the LRRK2 R1628P variants and the risk of PD. Up to January of 2016, 5 databases were searched to identify case-control studies involving LRRK2 R1628P variants and PD risk. A total of 5736 PD patients and 4786 controls in 14 case-control studies were included in this meta-analysis. And STATA 12.0 statistics software was used to calculate available data from each study. The pooled odds ratios (OR) and 95% confidence interval (CI) were calculated to assess the genetic association between LRRK2 R1628P polymorphism and the risk of PD. The results indicated that LRRK2 R1628P variants were increased risk of PD when all studies were pooled (C vs. G OR=1.983, 95% CI 1.640-2.399; GC+CC vs. GG OR=1.971, 95% CI 1.625-2.391). Moreover, in the subgroup analysis by ethnicity, increased risks were identified among Chinese (GC+CC vs. GG, OR=1.96, 95% CI 1.60-2.41) as well as in non-Chinese Asian races (GC+CC vs. GG, OR=2.03, 95% CI 1.13-3.65). Therefore, our results suggest that the C allele, GC and CC genotype of LRRK2 R1628P variants contribute to the susceptibility of PD in Asian.

High-Resolution Melting Analysis as a Developed Method for Genotyping the PD Susceptibility Loci in LRRK2 Gene

BACKGROUND

Single-nucleotide polymorphisms (SNPs) have been reported as a highly relevant point for the mechanisms of Parkinson's disease (PD). The invention of saturating dye makes it possible to identify heteroduplex DNA without redistribution during melting, which allows using high-resolution melting (HRM) to detect SNPs. However, the HRM analysis for detection of those SNPs associated with PD was rarely applied.

METHODS

Two SNPs, G2385R and R1628P, located in leucine-rich repeat kinase 2 (LRRK2) gene were individually and multiplexedly genotyped using HRM analysis. The sequence variant observed in unexpected HRM curves was confirmed by DNA sequencing.

RESULTS

HRM analysis identified successfully all genotypes both on R1628P and G2385R loci. The unexpected HRM curves appeared in R1628P amplicon generated from combinations of R1628P and rs11176013 loci. A multiplexed HRM assay that genotyped R1628P, rs11176013, and G2385R loci was efficiently established.

CONCLUSIONS

The present HRM assay is a reliable and rapid method for genotyping R1628P and G2385R loci in LRRK2 gene, and multiplex HRM analysis results in high throughput and has the potential to facilitate a wide range of genotyping studies on PD susceptibility genes.