LRRK2 Gly2385Arg mutation and clinical features in a Chinese population with early-onset Parkinson’s disease compared to late-onset patients

The frequency of LRRK2 Gly2385Arg mutation in Hong Kong Chinese with early-onset (age 50 years) and controls. The mutation prevalence were 8.8, 8.3, and 0% for early-onset, late-onset, and controls, respectively. The mean age of onset among LRRK2 G2385R carriers was 42.7 years old for early-onset compared to 74.3 for late-onset patients. LRRK2 G2385R mutation appears to be as prevalent among early-onset as late-onset patients.     

The LRRK2 Arg1628Pro variant is a risk factor for Parkinson’s disease in the Chinese population

The c.G4883C variant in the leucine-rich repeat kinase 2 (LRRK2) gene (protein effect: Arg1628Pro) has been recently proposed as a second risk factor for sporadic Parkinson’s disease in the Han Chinese population (after the Gly2385Arg variant). In this paper, we analyze the Arg1628Pro variant and the associated haplotype in a large sample of 1,337 Han subjects (834 patients and 543 controls) ascertained from a single referral center in Taiwan. In our sample, the Arg1628Pro allele was more frequent among patients (3.8%) than among controls (1.8%; p = 0.004, OR 2.13, 95% CI 1.29–3.52). Sixty heterozygous and two homozygous carriers of the Arg1628Pro variant were identified among the patients, of which only one was also a carrier of the LRRK2 Gly2385Arg variant. We also show that carriers of the Arg1628Pro variant share a common, extended haplotype, suggesting a founder effect. Parkinson’s disease onset age was similar in patients who carried the Arg1628Pro variant and in those who did not carry it. Our data support the contention that the Arg1628Pro variant is a second risk factor for Parkinson’s disease in the Han Chinese population. Adding the estimated effects of Arg1628Pro (population attributable risk [PAR] ~4%) and Gly2385Arg variants (PAR ~6%) yields a total PAR of ~10%.     

Association between the missense alcohol dehydrogenase rs1229984T variant with the risk for Parkinson’s disease in women

Journal of Neurology - Several meta-analyses including retrospective case–control studies have shown that the risk of developing Parkinson’s disease (PD) correlates inversely with...     

LRRK2 G2385R variant carriers of female Parkinson’s disease are more susceptible to motor fluctuation

The relation between the LRRK2 mutation and its effect on Parkinson’s disease (PD) has always caught a lot attention. Recent studies found that the G2385R polymorphism of LRRK2 may increase the risk of PD in Asian populations. Here we tried to clarify the relationship between the LRRK2 G2385R variant and the clinical profiles including motor complication in Chinese PD patients. We identified the LRRK2 variant in the Chinese Han population in northern China and evaluated the relationship between the G2385R variant and clinical profiles through comparison between 36 carriers and 139 non-carriers. We found that G2385R carriers scored significantly higher in motor fluctuation and dyskinesia than non-carriers. Logistic regression analysis showed that the G2385R variant was an independent risk factor for motor fluctuation in females (odds ratio = 12.538, 95 % CI 2.216–70.942, P = 0.004), and a Chi-squared test showed that the frequency of dyskinesia tended to be higher in the carrier group compared to the non-carrier group (16 vs. 4.4 %, P = 0.050, OR = 4.127, 95 % CI 1.074–15.864). These findings indicate that the variant was closely related to the occurrence of motor complication. Additionally, the G2385R variant was significantly related to the early-onset of PD in female carriers (20.0 vs. 1.5 %, odds ratio = 16.25, 95 % CI 1.557–169.618, P = 0.020). Our study found that the G2385R variant was significantly associated with motor complications and that this variant was an independent risk factor for motor fluctuation in females. These findings provide the necessary preliminary data to better understand the unique profile of PD G2385R variant carriers.     

Mitochondrial DNA polymorphisms and the risk of Parkinson’s disease in Taiwan

Summary A critical role of mitochondrial dysfunction has been implicated in the pathogenesis of Parkinson’s disease (PD). The association of mitochondrial DNA (mtDNA) polymorphisms 9055G/A, 10398G/A and 13708G/A with PD has been controversial. In this study we analyzed whether these three genetic polymorphisms are associated with PD in a cohort of 416 PD cases and 372 ethnically matched controls. The allele frequency distribution of any of these three analyzed polymorphisms was not significantly different between the cases and the controls. None of the six haplotypes derived influences risk of PD. Notably, after stratification by age, individuals over 70 years of age carrying the haplotype 9055G-10398A-13708G demonstrated a significant decrease in risk of developing PD (OR = 0.44, 95% CI = 0.24–0.80, p = 0.008). These results suggest that the mtDNA haplotype 9055G-10398A-13708G plays a role in PD susceptibility among Taiwanese people older than 70 years of age.     

Dopamine D3 receptor Ser9Gly variant is associated with impulse control disorders in Parkinson’s disease patients

IntroductionImpulse control disorders (ICD) are reported to occur at variable frequencies in different ethnic groups. Genetic vulnerability is suspected to underlie the individual risk for ICD. We investigated whether the allelic variants of dopamine (DRD3), glutamate (GRIN2B) and serotonin (HTR2A) receptors are linked to ICD in Indian Parkinson’s disease (PD) patients.MethodsWe conducted a prospective, case-control study which included PD patients (70 with ICD, 100 without ICD categorized after direct psychiatric interview of patient and caregiver) and 285 healthy controls. Single nucleotide polymorphism (SNP) variants of DRD3 p.S9G (rs6280), GRIN2B c.2664C>T (rs1806201) and HTR2A c.102T>C (rs6313) were genotyped.ResultsMultivariate regression analysis revealed that DRD3 p.Ser9Gly (rs6280) heterozygous variant CT (OR = 2.22, 95% CI: 1.03–4.86, p = 0.041), higher daily Levodopa equivalent doses (LED) of drugs (for 100 mg LED, OR = 1.14, 95% CI: 1.01–1.29, p = 0.041), current dopamine agonist but not Levodopa use (OR = 2.16, 95% CI: 1.03–4.55, p = 0.042) and age of onset of motor symptoms under 50 years (OR 2.09, 95% CI: 1.05–4.18, p = 0.035) were independently associated with ICD.ConclusionDRD3 p.Ser9Gly (rs6280) CT genotype is associated with ICD in Indian PD patients and this association is novel. Enhanced D3 receptor affinity due to gain-of-function conferred by the glycine residues could impair reward-risk assessment in the mesolimbic system and contribute to development of impulsive behaviour, in carriers of this genotype.     

Tremor in Parkinson’s disease is not associated with the DRD3 Ser9Gly polymorphism

A common subset of genetic risk factors for Parkinson’s disease (PD) and essential tremor (ET) has been postulated. Recently, an association between the dopamine D₃ receptor (DRD3) Ser9Gly polymorphism and ET has been reported. We studied whether PD tremor is influenced by Ser9Gly in a genetic association study based on the gene bank of the German Competence Network on Parkinson’s disease. The study included analyses of motor predominance (mixed, hypokinetic, and tremor), and tremor type (resting, postural, and action). We did not identify any effect of DRD3 Ser9Gly on tremor in PD, even when regarding various symptom combinations to avoid missing a weak effect on the phenotype. Additional studies incorporating symptoms at disease onset, and grading of tremor response to dopaminergic therapy, are warranted.     

The association between the LRRK2 G2385R variant and the risk of Parkinson’s disease: a meta-analysis based on 23 case–control studies

Clinical diagnosis of Parkinson’s disease (PD) is essential but misdiagnosis of PD-like diseases is quite common. LRRK2 G2385R variants have been extensively examined for the association to the risk of Parkinson’s disease. However, results from different studies are inconsistent. The purpose of this meta-analysis was to assess the association between the LRRK2 G2385R variants and the risk of PD. A systematic literature search was performed for 6 databases up to January of 2014 to identify case–control studies involving LRRK2 G2385R variants and the risk of PD. A total of 12,915 cases and 12,451 controls in 23 case–control studies were included in this meta-analysis. The results indicated that the variant A allele carriers (GA + AA) increased risk of PD when compared with the homozygote GG (GA + AA vs. GG: OR = 2.4, 95 % CI = 1.97 to 2.92, P < 0.00001). In the subgroup analysis by ethnicity, increased risks were identified among Chinese (OR = 2.69, 95 % CI = 2.1–3.45, P < 0.00001) as well as in non-Chinese (OR = 2.17, 95 % CI 1.75–2.69, P < 0.00001). In the subgroup analysis by age of onset, significant associations were found in both later-onset PD (LOPD) and early-onset PD (EOPD) cases. And there was no significant difference of the allele frequency between patients with LOPD and EOPD (OR = 1.18, 95 % CI = 0.77–1.80, P = 0.45). Our results suggest that the LRRK2 G2385R variants contribute to the susceptibility of PD especially in Chinese PD. Meanwhile, it is possible that age is not the risk factor to facilitate G2385R gene mutation.     

Lack of association between LRRK2 G2385R and cognitive dysfunction in Korean patients with Parkinson’s disease

Aside from the glucocerebrosidase gene, the genetic risk factors for cognitive decline in Parkinson’s disease (PD) are controversial. We investigated whether the G2385R polymorphism in leucine-rich repeat kinase 2 gene (LRRK2), a risk variant for the development of PD in East Asians, is associated with cognitive dysfunction in PD. We recruited 299 PD patients, consisting of 23 carriers and 276 non-carriers of LRRK2 G2385R, from 14 centers. Global cognitive function was assessed using the Mini-Mental State Examination (MMSE) or the Montreal Cognitive Assessment (MoCA). PD with cognitive dysfunction was defined as an MMSE Z score that, adjusting for age at study entry and years of education, was below -1.0 standard deviations.In multivariate analysis, PD duration, age at study entry and depression were significant risk factors for cognitive dysfunction as assessed by MMSE performance or the MoCA. In linear regression analysis of the association between MMSE Z scores and PD duration, there was no significant difference associated with the LRRK2 G2385R genotype. The interaction terms between PD duration and the LRRK2 G2385R genotype were not significant for the MMSE Z score but were significant for the MoCA. In conclusion, the LRRK2 G2385R genotype may not be associated with cognitive dysfunction in PD.     

The role of the Ala746Thr variant in the ATP13A2 gene among Chinese patients with Parkinson’s disease

The association between idiopathic Parkinson’s disease (PD) and the ATP13A2 (PARK9) Ala746Thr variant, associated with Kufor-Rakeb syndrome, is controversial. We investigated this association in 69 patients with early onset PD (EOPD; ≦50 years of age), 192 patients with late onset PD (LOPD; >50 years of age), and 180 healthy controls in the Chinese population in Hong Kong. The presence of the Ala746Thr variant in the ATP13A2 locus was examined in all participants. We detected the heterozygous Ala746Thr variant in one healthy control (0.6%), one patient with EOPD (1.4%, p = 0.50), and one patient with LOPD (0.5%, p = 0.96). We suggest that the ATP13A2 Ala746Thr variant is not a common risk factor for PD in the Chinese population in Hong Kong.     

The personality associated with Parkinson’s disease

Since at least 1913 reports have suggested there are personality traits and behaviors that are found premorbidly in those who go on to develop Parkinson’s disease (PD). This premorbid personality consists of traits such as industriousness, punctuality, inflexibility, cautiousness, and lack of novelty seeking and persists after the onset of the motor illness. The existence of this personality remains controversial but is supported by case-based anecdotes, twin studies, and comparison of patients with PD with medical control patients on standardized instruments. In addition a large number of epidemiologic studies show that people who develop PD have low lifetime risks for cigarette smoking, coffee drinking, and alcohol consumption, again suggesting that there is a behavior pattern that predates PD. Despite the retrospective nature of much of these data, the use of nonstandardized instruments, and diffuse concepts of personality, the great majority of studies show striking similarity in identifying these traits. An integrating hypothesis, involving damage to dopaminergic systems, known to predate the onset of the motor illness, is discussed.     

Genealogical studies in LRRK2-associated Parkinson’s disease in central Norway

The most common mutation related to Parkinson’s disease (PD) is the p.G2019S mutation in the LRRK2 gene. Global population frequencies and crude estimates of haplotype conservation suggest most carriers are related. A total of 671 Norwegian PD patients and 215 of their family members were screened for the LRRK2 p.G2019S mutation. Twenty-one PD cases and 44 family members were positive for the mutation and all could be traced back to 10 different families. A genealogical study employed data from the Norwegian National Family Record Centre, local parish registers and population censuses. A common ancestor couple (living between 1580 and 1650) was found in six families, and two other families were associated by intermarriage. The remaining two families could not be traced back to either of these ancestors, though chromosome 12q12 haplotype analysis showed p.G2019S carriers shared alleles for 15 markers in the LRRK2 region.The study provides support for a common ancestor in Norwegian families with LRRK2 p.G2019S parkinsonism. The mutation was probably introduced to Norway through tradesmen from Europe. The extended pedigree that now links modern day carriers may help in mapping penetrance modifiers.     

A novel ARC gene polymorphism is associated with reduced risk of Alzheimer’s disease

Alzheimer's disease (AD) is the most common neurodegenerative disease, and is clinically characterized by cognitive disturbances and the accumulation of the amyloid β (Aβ) peptides in plaques in the brain. Recent studies have shown the links between AD and the immediate-early gene Arc (activity-regulated cytoskeleton-associated protein), involved in synaptic plasticity and memory consolidation. For example, AD mouse models show a decreased expression of Arc mRNA in the brain. In additional, acute Aβ application to brain slices leads to a widespread ARC protein diffusion, unlike the normal defined localization to synapses. In this study, we investigated genetic variation in human ARC and the risk of developing AD. To this end, we genotyped 713 subjects diagnosed with AD and 841 controls without dementia. ARC was sequenced in a group of healthy individuals, and seven previously known SNPs and three novel SNPs were identified. Two of the newly found SNPs were intronic and one, +2852(G/A), was located in the 3'UTR. Three tag SNPs were selected, including the novel SNP +2852(G/A), to relate to risk of AD, Mini Mental State Examination (MMSE) scores and cerebrospinal fluid (CSF) biomarker levels of total tau (T-tau), hyperphosphorylated tau181 (P-tau(181)) and Aβ(1-42). The AA genotype of the newly found 3'-UTR SNP +2852(A/G), was associated with a decreased risk of AD (p (c)?=?0.005; OR?=?0.74; 95?% CI: 0.61-0.89). No associations of single SNPs or haplotypes with MMSE score or CSF biomarkers were found. Here we report a novel ARC SNP associated with a reduced risk of developing AD. To our knowledge, this is the first study associating a gene variant of ARC with any disease. The location of the SNP within the 3'UTR indicates that dendritic targeting of ARC mRNA could be involved in the molecular mechanisms underlying this protective function. However, further investigation of the importance of this SNP for ARC function, ARC processing and the pathology of AD is needed.