LRRK2 G2385R and R1628P mutations are associated with an increased risk of Parkinson's disease in the Malaysian population

Parkinson's Disease is Predominantly a Genetic Disease

The discovery of a pathogenic variant in the alpha-synuclein (SNCA) gene in the Contursi kindred in 1997 indisputably confirmed a genetic cause in a subset of Parkinson's disease (PD) patients. Currently, pathogenic variants in one of the seven established PD genes or the strongest known risk factor gene, GBA1, are identified in ∼15% of PD patients unselected for age at onset and family history. In this Debate article, we highlight multiple avenues of research that suggest an important - and in some cases even predominant - role for genetics in PD aetiology, including familial clustering, high rates of monogenic PD in selected populations, and complete penetrance with certain forms. At first sight, the steep increase in PD prevalence exceeding that of other neurodegenerative diseases may argue against a predominant genetic etiology. Notably, the principal genetic contribution in PD is conferred by pathogenic variants in LRRK2 and GBA1 and, in both cases, characterized by an overall late age of onset and age-related penetrance. In addition, polygenic risk plays a considerable role in PD. However, it is likely that, in the majority of PD patients, a complex interplay of aging, genetic, environmental, and epigenetic factors leads to disease development.

An overview of the worldwide distribution of LRRK2 mutations in Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder with significant genetic influence. The LRRK2 gene is a major genetic contributor, particularly the Gly2019Ser mutation. This focused review investigates the global distribution of LRRK2 mutations, with emphasis on Gly2019Ser and other pathogenic variants. Prevalence rates of Gly2019Ser are highest in North Africa and the Ashkenazi-Jewish population, indicating a potential common ancestor and founder effect. Other LRRK2 mutations, including Asn1437His, Arg1441Gly/Cys/His, Tyr1699Cys and Ile2020Thr, exhibit varying global prevalences. Understanding these distributions enhances our knowledge of PD genetics and aids personalized medicine. Further research is crucial to unravel clinical implications and develop targeted therapies for LRRK2 mutation carriers.

Understanding the involvement of innate immunity and the Nrf2-NLRP3 axis on mitochondrial health in Parkinson's disease

Parkinson's disease (PD), a multifactorial movement disorder, is interlinked with numerous molecular pathways, including neuroinflammation, which is a critical factor in the development and progression of PD. Microglia play a central role in driving neuroinflammation through activation and overexpression of the M1 phenotype, which has a significant impact on mitochondria. Multiple regulators converge together, and among these, the NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasomes have been implicated in transmitting inflammatory and deleterious components to the mitochondria. Nuclear factor erythroid 2-related factor 2 (Nrf2) regulates the NLRP3 inflammasome and acts as the saviour of the mitochondria. Together, the NLRP3-Nrf2 axis functions in regulating mitochondrial function in the case of PD. It regulates fundamental processes such as oxidative stress, mitochondrial respiratory function, and mitochondrial dynamics. In this review, we discuss the contributions that a variety of miRNAs make to the regulation of the NLRP3 inflammasome and Nrf2, which can be used to target this important axis and contribute to the preservation of mitochondrial integrity. This axis may prove to be a crucial target for extending the lives of Parkinson's patients by deferring neuroinflammatory damage to mitochondria.

Genetic variations in GBA1 and LRRK2 genes: Biochemical and clinical consequences in Parkinson disease

Variants in the GBA1 and LRRK2 genes are the most common genetic risk factors associated with Parkinson disease (PD). Both genes are associated with lysosomal and autophagic pathways, with the GBA1 gene encoding for the lysosomal enzyme, glucocerebrosidase (GCase) and the LRRK2 gene encoding for the leucine-rich repeat kinase 2 enzyme. GBA1-associated PD is characterized by earlier age at onset and more severe non-motor symptoms compared to sporadic PD. Mutations in the GBA1 gene can be stratified into severe, mild and risk variants depending on the clinical presentation of disease. Both a loss- and gain- of function hypothesis has been proposed for GBA1 variants and the functional consequences associated with each variant is often linked to mutation severity. On the other hand, LRRK2-associated PD is similar to sporadic PD, but with a more benign disease course. Mutations in the LRRK2 gene occur in several structural domains and affect phosphorylation of GTPases. Biochemical studies suggest a possible convergence of GBA1 and LRRK2 pathways, with double mutant carriers showing a milder phenotype compared to GBA1-associated PD. This review compares GBA1 and LRRK2-associated PD, and highlights possible genotype-phenotype associations for GBA1 and LRRK2 separately, based on biochemical consequences of single variants.

Structural Insights and Development of LRRK2 Inhibitors for Parkinson’s Disease in the Last Decade

Parkinson’s disease (PD) is the second most prevalent neurodegenerative disease, characterized by the specific loss of dopaminergic neurons in the midbrain. The pathophysiology of PD is likely caused by a variety of environmental and hereditary factors. Many single-gene mutations have been linked to this disease, but a significant number of studies indicate that mutations in the gene encoding leucine-rich repeat kinase 2 (LRRK2) are a potential therapeutic target for both sporadic and familial forms of PD. Consequently, the identification of potential LRRK2 inhibitors has been the focus of drug discovery. Various investigations have been conducted in academic and industrial organizations to investigate the mechanism of LRRK2 in PD and further develop its inhibitors. This review summarizes the role of LRRK2 in PD and its structural details, especially the kinase domain. Furthermore, we reviewed in vitro and in vivo findings of selected inhibitors reported to date against wild-type and mutant versions of the LRRK2 kinase domain as well as the current trends researchers are employing in the development of LRRK2 inhibitors.

A 10-Year Community-Based Study of Leucine-Rich Repeat Kinase 2 G2385R Carriers' Conversion to Parkinson's Disease

BACKGROUND

The G2385R variant of leucine-rich repeat kinase 2 (LRRK2) is mainly associated with Parkinson's disease(PD) in Asian populations.

OBJECTIVE

The aim of this study was to investigate the PD conversion rate and clinical characteristics of LRRK2 G2385R nonmanifesting carriers.

METHODS

All participants were from the community-based longitudinal cohort of Shanghai Ruijin Hospital. The G2385R carriers and noncarriers were screened by Sanger sequencing and received face-to-face interviews at baseline and follow-up assessments. The Kaplan-Meier method was used to compare the conversion rate of PD. Cox regression models were used to estimate the risk of G2385R variant for PD.

RESULTS

In the combined cohort, 26 (7.9%) people developed PD in 329 carriers versus 9 (2.6%) in 345 noncarriers (P = 0.0016). Cox regression model confirmed that the G2385R variant was a strong risk factor for PD in a Chinese population older than 50 years (hazard ratio, 3.314; 95% confidence interval, 1.551-7.078; P = 0.002). No difference was found in clinical symptoms between carriers and noncarriers.

CONCLUSIONS

We confirmed an increased conversion of PD in leucine-rich repeat kinase 2 G2385R carriers during a 10-year follow-up. © 2022 International Parkinson and Movement Disorder Society.

Association study of MCCC1/LAMP3 and DGKQ variants with Parkinson's disease in patients of Malay ancestry

BACKGROUND

Genome-wide association studies (GWAS) have shown that variants in the 3-methylcrotonyl-CoA carboxylase (MCCC1)/lysosome-associated membrane protein 3 (LAMP3) loci (rs10513789, rs12637471, rs12493050) reduce the risk of Parkinson's disease (PD) in Caucasians, Chinese and Ashkenazi-Jews while the rs11248060 variant in the diacylglycerol kinase theta (DGKQ) gene increases the risk of PD in Caucasian and Han Chinese cohorts. However, their roles in Malays are unknown. Therefore, this study aims to investigate the association of these variants with the risk of PD in individuals of Malay ancestry.

METHODS

A total of 1114 subjects comprising of 536 PD patients and 578 healthy controls of Malay ancestry were recruited and genotyped using Taqman® allelic discrimination assays.

RESULTS

The G allele of rs10513789 (OR = 0.83, p = 0.001) and A allele of rs12637471 (OR = 0.79, p = 0.007) in the MCCC1/LAMP3 locus were associated with a protective effect against developing PD in the Malay population. A recessive model of penetrance showed a protective effect of the GG genotype for rs10513789 and the AA genotype for rs12637471. No association with PD was found with the other MCCC1/LAMP3 rs12493050 variant or with the DGKQ (rs11248060) variant. No significant associations were found between the four variants with the age at PD diagnosis.

CONCLUSION

MCCC1/LAMP3 variants rs10513789 and rs12637471 protect against PD in the Malay population.

MicroRNA Dysregulation in Parkinson's Disease: A Narrative Review

Parkinson’s disease (PD) is a severely debilitating neurodegenerative disease, affecting the motor system, leading to resting tremor, cogwheel rigidity, bradykinesia, walking and gait difficulties, and postural instability. The severe loss of dopaminergic neurons in the substantia nigra pars compacta causes striatal dopamine deficiency and the presence of Lewy bodies indicates a pathological hallmark of PD. Although the current treatment of PD aims to preserve dopaminergic neurons or to replace dopamine depletion in the brain, it is notable that complete recovery from the disease is yet to be achieved. Given the complexity and multisystem effects of PD, the underlying mechanisms of PD pathogenesis are yet to be elucidated. The advancement of medical technologies has given some insights in understanding the mechanism and potential treatment of PD with a special interest in the role of microRNAs (miRNAs) to unravel the pathophysiology of PD. In PD patients, it was found that striatal brain tissue and dopaminergic neurons from the substantia nigra demonstrated dysregulated miRNAs expression profiles. Hence, dysregulation of miRNAs may contribute to the pathogenesis of PD through modulation of PD-associated gene and protein expression. This review will discuss recent findings on PD-associated miRNAs dysregulation, from the regulation of PD-associated genes, dopaminergic neuron survival, α-synuclein-induced inflammation and circulating miRNAs. The next section of this review also provides an update on the potential uses of miRNAs as diagnostic biomarkers and therapeutic tools for PD.

Identification of LRRK2 missense variants in the accelerating medicines partnership Parkinson's disease cohort

Pathogenic missense variants in the leucine-rich repeat kinase 2 (LRRK2) gene have been identified through linkage analysis in familial Parkinson disease (PD). Subsequently, other missense variants with lower effect sizes on PD risk have emerged, as well as non-coding polymorphisms (e.g. rs76904798) enriched in PD cases in genome-wide association studies. Here we leverage recent whole-genome sequences from the Accelerating Medicines Partnership-Parkinson's Disease (AMP-PD) and the Genome Aggregation (gnomAD) databases to characterize novel missense variants in LRRK2 and explore their relationships with known pathogenic and PD-linked missense variants. Using a computational prediction tool that successfully classifies known pathogenic LRRK2 missense variants, we describe an online web-based resource that catalogs characteristics of over 1200 LRRK2 missense variants of unknown significance. Novel high-pathogenicity scoring variants, some identified exclusively in PD cases, tightly cluster within the ROC-COR-Kinase domains. Structure-function predictions support that some of these variants exert gain-of-function effects with respect to LRRK2 kinase activity. In AMP-PD participants, all p.R1441G carriers (N = 89) are also carriers of the more common PD-linked variant p.M1646T. In addition, nearly all carriers of the PD-linked p.N2081D missense variant are also carriers of the LRRK2 PD-risk variant rs76904798. These results provide a compendium of LRRK2 missense variants and how they associate with one another. While the pathogenic p.G2019S variant is by far the most frequent high-pathogenicity scoring variant, our results suggest that ultra-rare missense variants may have an important cumulative impact in increasing the number of individuals with LRRK2-linked PD.

Accelerated telomere shortening independent of LRRK2 variants in Chinese patients with Parkinson's disease

Oxidative stress and inflammation play vital roles in Parkinson's disease (PD) development. Thus, telomere length is expected to be shortened in this disease, but current data are inconclusive. We performed a case-control study of 261 patients with PD and 270 sex and age-matched healthy controls treated at the Peking Union Medical College Hospital. We found leucocyte telomere length (LTL) was significantly shortened in PD as compared with controls [1.02 (0.84-1.39) vs. 1.48 (1.08-1.94), P<0.001] and shorter LTL was associated with a dramatically increased risk of PD (lowest vs. highest quartile odds ratio (OR) =9.54, 95% CI: 5.33-17.06, P<0.001). We also investigated the roles of six LRRK2 variants in the susceptibility to PD. R1441C/G/H, G2019S, and I2020T variations were not detected in our study. No significant differences were found in the presence of variants R1398H (15.4% vs. 17.0%, P=0.619) and R1628P (2.3% vs. 0.7%, P=0.159) in PD and controls, while the G2385R variant was found to be a risk factor associated with increased PD susceptibility (OR=2.14, 95% CI: 1.12-4.10, P=0.021). No significant association was found between different LRRK2 variants and telomere length. These findings suggest that shorter LTL might be associated with PD in a manner independent of LRRK2 variants.

Clinical Phenotype of LRRK2 R1441C in 2 Chinese Sisters

Pathogenic and risk variants in the LRRK2 gene are among the main genetic contributors to Parkinson's disease (PD) worldwide, and LRRK2-targeted therapies for patients with PARK-LRRK2are now entering clinical trials. However, in contrast to the LRRK2 G2019S mutation commonly found in Caucasians, North-African Arabs, and Ashkenazi Jews, relatively little is known about other causative LRRK2 mutations, and data on genotype-phenotype correlations are largely lacking. This report is from an ongoing multicentre study in which next-generation sequencing-based PD gene panel testing has so far been conducted on 499 PD patients of various ethnicities from Malaysia. We describe 2 sisters of Chinese ancestry with PD who carry the R1441C mutation in LRRK2 (which in Asians has been reported in only 2 Chinese patients previously), and highlight interesting clinical observations made over a decade of close follow-up. We further explored the feasibility of using a brief, expert-administered rating scale (the Clinical Impression of Severity Index; CISI-PD) to capture data on global disease severity in a large (n = 820) unselected cohort of PD patients, including severely disabled individuals typically excluded from research studies. All patients in this study were managed and evaluated by the same PD neurologist, and these data were used to make broad comparisons between the monogenic PD cases versus the overall "real world" PD cohort. This report contributes to the scarce literature on R1441C PARK-LRRK2, offering insights into natural history and epidemiological aspects, and provides support for the application of a simple and reliable clinical tool that can improve the inclusion of under-represented patient groups in PD research.

LRRK2 Mutations and Asian Disease-Associated Variants in the First Parkinson's Disease Cohort from Kazakhstan

BACKGROUND

LRRK2 mutations have emerged as the most prevalent and potentially treatable determinants of Parkinson's disease (PD). Peculiar geographic distribution of these mutations has triggered an interest in genotyping PD cohorts of different ethnic backgrounds for LRRK.

OBJECTIVE

Here, we report on the results of LRRK2 screening in the first Central Asian PD cohort.

METHODS

246 PD patients were consecutively recruited by movement disorder specialists from four medical centers in Kazakhstan, and clinicodemographic data and genomic DNA from blood were systematically obtained and shipped to the Institute of Neurology University College London together with DNAs from 200 healthy controls. The cohort was genotyped for five LRRK2 mutations (p.Gly2019Ser, p.Arg1441His, p.Tyr1699Cys, p.Ile2020Thr, and p.Asn1437His) and three East Asian disease-associated variants (p.Gly2385Arg, p.Ala419Val, and p.Arg1628Pro) via Kompetitive allele-specific polymerase chain reaction assay analysis.

RESULTS

None of the study subjects carried LRRK2 mutations, whereas the following Asian variants were found with insignificant odds ratios (OR): p.Gly2385Arg (1.2%, minor allele frequency (MAF) 0.007, OR 1.25, p=0.8), p.Ala419Val (3.7%, MAF 0.02, OR 1.5, p=0.8), p.Ala419Val (3.7%, MAF 0.02, OR 1.5.

CONCLUSIONS

We showed that East Asian LRRK variants could be found in Central Asian populations but their pathogenicity remains to be elucidated in larger PD cohorts.

LRRK2 N551K and R1398H variants are protective in Malays and Chinese in Malaysia: A case-control association study for Parkinson's disease

BACKGROUND

The LRRK2 gene is associated with Parkinson's disease (PD) as a number of mutations within the gene have been shown to be susceptibility factors. Studies on various global populations have determined that mutations such as G2019S, G2385R, and R1628P in LRRK2 increase the risk of developing PD while the N551K-R1398H haplotype is associated with conferring protection against developing PD. Here we report a study looking at the N551K and R1398H variants for the first time in the Malaysian population.

METHODS

Cases (523) which conformed to the United Kingdom PD Brain Bank Criteria for PD were recruited through trained neurologists and age- and ethnically matched controls (491) were individuals free of any neurological disorder. The N551K and R1398H mutations were genotyped using the Taqman SNP genotyping assay.

RESULTS

A significant protective association for N551K was found in those of Malay ancestry, with a protective trend seen for R1398H. A meta-analysis of Chinese individuals in this cohort with other published cohorts of Chinese ancestry indicated a significant protective role for N551K and R1398H.

CONCLUSION

This study reports that the N551K-R1398H haplotype is also relevant to the Malaysian population, with a significant protective effect found in those of Malay and Chinese ancestries.

Advances in the Research of Risk Factors and Prodromal Biomarkers of Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disease in the world. With the advent of an aging population and improving life expectancy worldwide, the number of PD patients is expected to increase, which may lead to an urgent need for effective preventive and diagnostic strategies for PD. Although there is increasing research regarding the pathogenesis of PD, there is limited knowledge regarding the prevention of PD. Moreover, the diagnosis of PD depends on clinical criteria, which require the occurrence of bradykinesia and at least one symptom of rest tremor or rigidity. However, converging evidence from clinical, genetic, neuropathological, and imaging studies suggests the initiation of PD-specific pathology prior to the initial presentation of these classical motor clinical features by years or decades. This latent stage of neurodegeneration in PD is a particularly important stage for effective neuroprotective therapies, which might retard the progression or prevent the onset of PD. Therefore, the exploration of risk factors and premotor biomarkers is not only crucial to the early diagnosis of PD but is also helpful in the development of effective neuroprotection and health care strategies for appropriate populations at risk for PD. In this review, we searched and summarized ∼249 researches and 31 reviews focusing on the risk factors and prodromal biomarkers of PD and published in MEDLINE.

Understanding the role of genetic variability in LRRK2 in Indian population

BACKGROUND

Genetic variability in LRRK2 has been unequivocally established as a major risk factor for familial and sporadic forms of PD in ethnically diverse populations.

OBJECTIVES

To resolve the role of LRRK2 in the Indian population.

METHODS

We performed targeted resequencing of the LRRK2 locus in 288 cases and 298 controls and resolved the haplotypic structure of LRRK2 in a combined cohort of 800 cases and 402 controls in the Indian population. We assessed the frequency of novel missense variants in the white and East Asian population by leveraging exome sequencing and densely genotype data, respectively. We did computational modeling and biochemical approach to infer the potential role of novel variants impacting the LRRK2 protein function. Finally, we assessed the phosphorylation activity of identified novel coding variants in the LRRK2 gene.

RESULTS

We identified four novel missense variants with frequency ranging from 0.0008% to 0.002% specific for the Indian population, encompassing armadillo and kinase domains of the LRRK2 protein. A common genetic variability within LRRK2 may contribute to increased risk, but it was nonsignificant after correcting for multiple testing, because of small cohort size. The computational modeling showed destabilizing effect on the LRRK2 function. In comparison to the wild-type, the kinase domain variant showed 4-fold increase in the kinase activity.

CONCLUSIONS

Our study, for the first time, identified novel missense variants for LRRK2, specific for the Indian population, and showed that a novel missense variant in the kinase domain modifies kinase activity in vitro. © 2018 International Parkinson and Movement Disorder Society.

The role of monogenic genes in idiopathic Parkinson's disease

In the past two decades, mutations in multiple genes have been linked to autosomal dominant or recessive forms of monogenic Parkinson's disease (PD). Collectively, these monogenic (often familial) cases account for less than 5% of all PD, the majority being apparently sporadic cases. More recently, large-scale genome-wide association studies have identified over 40 loci that increase risk of PD. Importantly, there is overlap between monogenic and sporadic PD genes, particularly for the loci that contain the genes SNCA and LRRK2, which are mutated in monogenic dominant PD. There have also been reports of idiopathic PD cases with heterozygous variants in autosomal recessive genes suggesting that these mutations may increase risk of PD. These observations suggest that monogenic and idiopathic PD may have shared pathogenic mechanisms. Here, we focus mainly on the role of monogenic PD genes that represent pleomorphic risk loci for idiopathic PD. We also discuss the functional mechanisms that may play a role in increasing risk of disease in both monogenic and idiopathic forms.

The genetic architecture of mitochondrial dysfunction in Parkinson's disease

Mitochondrial impairment is a well-established pathological pathway implicated in Parkinson's disease (PD). Defects of the complex I of the mitochondrial respiratory chain have been found in post-mortem brains from sporadic PD patients. Furthermore, several disease-related genes are linked to mitochondrial pathways, such as PRKN, PINK1, DJ-1 and HTRA2 and are associated with mitochondrial impairment. This phenotype can be caused by the dysfunction of mitochondrial quality control machinery at different levels: molecular, organellar or cellular. Mitochondrial unfolded protein response represents the molecular level and implicates various chaperones and proteases. If the molecular level of quality control is not sufficient, the organellar level is required and involves mitophagy and mitochondrial-derived vesicles to sequester whole dysfunctional organelle or parts of it. Only when the impairment is too severe, does it lead to cell death via apoptosis, which defines the cellular level of quality control. Here, we review how currently known PD-linked genetic variants interfere with different levels of mitochondrial quality control. We discuss the graded risk concept of the most recently identified PARK loci (PARK 17-23) and some susceptibility variants in GBA, LRRK2 and SNCA. Finally, the emerging concept of rare genetic variants in candidates genes for PD, such as HSPA9, TRAP1 and RHOT1, complete the picture of the complex genetic architecture of PD that will direct future precision medicine approaches.

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.

Leucine-Rich Repeat Kinase (LRRK2) Genetics and Parkinson's Disease

The discovery of LRRK2 mutations as a cause of Parkinson's disease (PD), including the sporadic late-onset form, established the decisive role of genetics in the field of PD research. Among LRRK2 mutations, the G2019S, mostly lying in a haplotype originating from a common Middle Eastern ancestor, has been identified in different populations worldwide. The G2385R and R1628P variants represent validated risk factors for PD in Asian populations. Here, we describe in detail the origin, the present worldwide epidemiology, and the penetrance of LRRK2 mutations. Furthermore, this chapter aims to characterize other definitely/probably pathogenic mutations and risk variants of LRRK2. Finally, we provide some general guidelines for a LRRK2 genetic testing and counseling. In summary, LRRK2 discovery revolutionized the understanding of PD etiology and laid the foundation for a promising future of genetics in PD research.

Reprogramming of a human induced pluripotent stem cell (iPSC) line from a Parkinson's disease patient with a R1628P variant in the LRRK2 gene

Peripheral blood mononuclear cells (PBMCs) were collected from a clinically diagnosed 59-year old male Parkinson's disease (PD) patient with R1628P variant in the LRRK2 gene. The PMBCs were reprogrammed with the human OSKM transcription factors using the Sendai-virus reprogramming system. The transgene-free iPSC showed pluripotency confirmed by immunofluorescent staining for pluripotency markers and differentiated into the 3 germ layers in vivo. The iPSC line also showed normal karyotype. This cellular model will provide a good resource for further pathophysiological studies of PD.

PARK16 is associated with PD in the Malaysian population

PARK16 was identified as a risk factor for Parkinson's disease in a Japanese cohort; however, subsequent studies in the other populations including the Chinese, European, Caucasian, and Chilean have shown a protective role instead. To investigate this locus in our Malaysian cohort, 1,144 individuals were screened for five SNPs in the PARK16 locus and logistic regression analysis showed that the A allele of the rs947211 SNP reduced the risk of developing PD via a recessive model (Odds ratio 0.57, P-value 0.0003). Pooled analysis with other Asian studies showed that A allele of the rs947211 SNP decreased the risk of developing PD via a recessive model (Odds ratio 0.71, P-value 0.0001). In addition, when meta-analysis was performed with other Asian population, three SNPs (rs823128, rs823156, and rs11240572) reduced risk of developing PD via a dominant model. © 2016 Wiley Periodicals, Inc.