Chin-Hsien Lin

Association of LRRK2 exonic variants with susceptibility to Parkinson's disease: A case-control study

BACKGROUND Background The leucine-rich repeat kinase 2 gene (LRRK2) harbours highly penetrant mutations that are linked to familial parkinsonism. However, the extent of its polymorphic variability in relation to risk of Parkinsons disease (PD) has not been assessed systematically. We therefore assessed the frequency of LRRK2 exonic variants in individuals with and without PD, to investigate the role of the variants in PD susceptibility. METHODS LRRK2 was genotyped in patients with PD and controls from three series (white, Asian, and Arab-Berber) from sites participating in the Genetic Epidemiology of Parkinsons Disease Consortium. Genotyping was done for exonic variants of LRRK2 that were identified through searches of literature and the personal communications of consortium members. Associations with PD were assessed by use of logistic regression models. For variants that had a minor allele frequency of 0·5% or greater, single variant associations were assessed, whereas for rarer variants information was collapsed across variants. FINDINGS 121 exonic LRRK2 variants were assessed in 15 540 individuals: 6995 white patients with PD and 5595 controls, 1376 Asian patients and 962 controls, and 240 Arab-Berber patients and 372 controls. After exclusion of carriers of known pathogenic mutations, new independent risk associations were identified for polymorphic variants in white individuals (M1646T, odds ratio 1·43, 95% CI 1·15-1·78; p=0·0012) and Asian individuals (A419V, 2·27, 1·35-3·83; p=0·0011). A protective haplotype (N551K-R1398H-K1423K) was noted at a frequency greater than 5% in the white and Asian series, with a similar finding in the Arab-Berber series (combined odds ratio 0·82, 0·72-0·94; p=0·0043). Of the two previously reported Asian risk variants, G2385R was associated with disease (1·73, 1·20-2·49; p=0·0026), but no association was noted for R1628P (0·62, 0·36-1·07; p=0·087). In the Arab-Berber series, Y2189C showed potential evidence of risk association with PD (4·48, 1·33-15·09; p=0·012). INTERPRETATION The results for LRRK2 show that several rare and common genetic variants in the same gene can have independent effects on disease risk. LRRK2, and the pathway in which it functions, is important in the cause and pathogenesis of PD in a greater proportion of patients with this disease than previously believed. These results will help discriminate those patients who will benefit most from therapies targeted at LRRK2 pathogenic activity. FUNDING Michael J Fox Foundation and National Institutes of Health.

Minimal Detectable Change of the Timed “Up & Go” Test and the Dynamic Gait Index in People With Parkinson Disease

Background The minimal detectable change (MDC) is the smallest amount of difference in individual scores that represents true change (beyond random measurement error). The MDCs of the Timed “Up & Go” Test (TUG) and the Dynamic Gait Index (DGI) in people with Parkinson disease (PD) are largely unknown, limiting the interpretability of the change scores of both measures. Objective The purpose of this study was to estimate the MDCs of the TUG and the DGI in people with PD. Design This investigation was a prospective cohort study. Methods Seventy-two participants were recruited from special clinics for movement disorders at a university hospital. Their mean age was 67.5 years, and 61% were men. All participants completed the TUG and the DGI assessments twice, about 14 days apart. The MDC was calculated from the standard error of measurement. The percentage MDC (MDC%) was calculated as the MDC divided by the mean of all scores for the sample. Furthermore, the intraclass correlation coefficient was used to examine the reproducibility between testing sessions (test-retest reliability). Results The respective MDC and MDC% of the TUG were 3.5 seconds and 29.8, and those of the DGI were 2.9 points and 13.3. The test-retest reliability values for the TUG and the DGI were high; the intraclass correlation coefficients were .80 and .84, respectively. Limitations The study sample was a convenience sample, and the participants had mild to moderately severe PD. Conclusions The results showed that the TUG and the DGI have generally acceptable random measurement error and test-retest reliability. These findings should help clinicians and researchers determine whether a change in an individual patient with PD is a true change.

LRRK2 G2019S Mutation Induces Dendrite Degeneration through Mislocalization and Phosphorylation of Tau by Recruiting Autoactivated GSK3β

Intraneuronal tau aggregations are distinctive pathological features of Parkinsons disease (PD) with autosomal-dominant mutations in leucine-rich repeat kinase 2 (LRRK2). The most prevalent LRRK2 mutation, G2019S (glycine to serine substitution at amino acid 2019), causes neurite shrinkage through unclear pathogenetic mechanisms. We found that expression of G2019S mutant in Drosophila dendritic arborization neurons induces mislocalization of the axonal protein tau in dendrites and causes dendrite degeneration. G2019S-induced dendrite degeneration is suppressed by reducing the level of tau protein and aggravated by tau coexpression. Additional genetic analyses suggest that G2019S and tau function synergistically to cause microtubule fragmentation, inclusion formation, and dendrite degeneration. Mechanistically, hyperactivated G2019S promotes tau phosphorylation at the T212 site by the Drosophila glycogen synthase kinase 3β homolog Shaggy (Sgg). G2019S increases the recruitment of autoactivated Sgg, thus inducing hyperphosphorylation and mislocalization of tau with resultant dendrite degeneration.

Multiple LRRK2 variants modulate risk of Parkinson disease: a Chinese multicenter study.

We and others found two polymorphic LRRK2 (leucine‐rich repeat kinase 2) variants (rs34778348:G>A; p.G2385R and rs33949390:G>C; p.R1628P) associated with Parkinson disease (PD) among Chinese patients, but the common worldwide rs34637584:G>A; p.G2019S mutation, was absent. Focusing exclusively on Han Chinese, we first sequenced the coding regions in young onset and familial PD patients and identified 59 variants. We then examined these variants in 250 patients and 250 control subjects. Among the 17 polymorphic variants, five demonstrated different frequency in cases versus controls and were considered in a larger sample of 1,363 patients and 1,251 control subjects. The relative risk of an individual with both p.G2385R and p.R1628P is about 1.9, and this is reduced to 1.5–1.6 if the individual also carries rs7133914:G>C; p.R1398H or rs7308720:C>A: p.N551K. The risk of a carrier with p.R1628P is largely negated if the individual also carries p.R1398H or p.N551K. In dopaminergic neuronal lines, p.R1398H had significantly lower kinase activity, whereas p.G2385R and p.R1628P showed higher kinase activity than wild type. We provided the first evidence that multiple LRRK2 variants exert an individual effect and together modulate the risk of PD among Chinese. Hum Mutat 31:561–568, 2010.

Discontinuation of statin therapy associates with Parkinson disease: A population-based study

Objective: To evaluate the effect of discontinuing statin therapy on incidence of Parkinson disease (PD) in statin users. Methods: Participants who were free of PD and initiated statin therapy were recruited between 2001 and 2008. We examined the association between discontinuing use of statins with different lipophilicity and the incidence of PD using the Cox regression model with time-varying statin use. Results: Among the 43,810 statin initiators, the incidence rate for PD was 1.68 and 3.52 per 1,000,000 person-days for lipophilic and hydrophilic statins, respectively. Continuation of lipophilic statins was associated with a decreased risk of PD (hazard ratio [HR] 0.42 [95% confidence interval 0.27–0.64]) as compared with statin discontinuation, which was not modified by comorbidities or medications. There was no association between hydrophilic statins and occurrence of PD. Among lipophilic statins, a significant association was observed for simvastatin (HR 0.23 [0.07–0.73]) and atorvastatin (HR 0.33 [0.17–0.65]), especially in female users (HR 0.11 [0.02–0.80] for simvastatin; HR 0.24 [0.09–0.64] for atorvastatin). As for atorvastatin users, the beneficial effect was seen in the elderly subgroup (HR 0.42 [0.21–0.87]). However, long-term use of statins, either lipophilic or hydrophilic, was not significantly associated with PD in a dose/duration-response relation. Conclusions: Continuation of lipophilic statin therapy was associated with a decreased incidence of PD as compared to discontinuation in statin users, especially in subgroups of women and elderly. Long-term follow-up study is needed to clarify the potential beneficial role of lipophilic statins in PD.

Novel ATP13A2 variant associated with Parkinson disease in Taiwan and Singapore.

Objectives: To assess the association of ATP13A2 gene mutation among patients with early onset Parkinson disease (EOPD, onset < 50 years) in ethnic Chinese population. Methods: Among 771 subjects, we studied 182 patients with EOPD and familial PD and 589 matched controls from two cohorts of Han Chinese in Taiwan and Singapore. The entire ATP13A2 coding region and intron-exon boundaries were sequenced in 71 probands and 70 controls in Taiwanese/ethnic Chinese. An additional 111 index patients with PD in Singapore and 589 controls were later screened to validate possible mutations that were found in the first set of study subjects. Results: We identified one novel missense variant, AL746Thr, in a single heterozygous state in three patients (two were from Taiwan and one was from Singapore) (1.7% in EOPD). The variant was not observed in 589 ethnicity matched controls. The frequency of this variant was significantly higher in PD cases than controls (p = 0.01, relative risk 4.3, 95% CI 1.9–4.3). The clinical phenotype and 18F-dopa PET image of ATP13A2 Ala78Thr carriers are similar to that seen in idiopathic PD. The variant is located between the highly conserved phosphorylation region and the fifth transmembrane domain of the ATP13A2 protein. Conclusions: A rare variant of the ATP13A2 was associated with an increased risk of Parkinson disease among ethnic Chinese in Asia. Further studies are needed to clarify the functional role of this genetic risk factor. GLOSSARY: cDNA = complementary DNA; EOPD = early onset Parkinson disease; ER = endoplasmic reticulum; RT-PCR = reverse-transcriptase PCR; SNP = single nucleotide polymorphism.

Acute disseminated encephalomyelitis: A follow-up study in Taiwan

Background: Acute-disseminated encephalomyelitis (ADEM) is a demyelinating disorder of the central nervous system, whose epidemiology, clinical presentations and functional outcome are incompletely understood in Asian populations. Objective: To assess the clinical presentations, predisposing factors and functional outcome of ADEM in Taiwan. Methods: 50 patients initially diagnosed with ADEM (male, 19; female, 31) were enrolled from 1991 to 2005. Diagnosis of ADEM or multiple sclerosis was established during a follow-up period of 2–120 months. 8 adult patients were noted to have taken the immunomodulatory drug, levamisole, within 3 months before onset of symptoms. The remaining 42 patients (male, 17; female, 25) were categorised by age as children (<16 years, n = 12), young adults (16–49 years, n = 21) and elderly adults (⩾50 years, n = 9). The clinical manifestations, predisposing factors and radiological findings were compared between different age groups and adult patients with or without levamisole use. Functional outcome was compared by a log-rank test. Results: Preceding upper respiratory tract infection was evident in 21 (50%) patients and only one young-adult patient had received Rubella vaccine immunisation. The frequency of fever was higher in children (p = 0.04) and psychiatric symptoms were more prevalent in elderly patients (p = 0.03). Functional recovery was faster in children than in adults (p = 0.002). Initial Expanded Disability Status Scale score (odds ratio (OR) 1.9, p = 0.03) and no fever (OR 0.04, p = 0.06) were associated with poor outcome (modified Rankin scale ⩾2). After a mean (SD) follow-up of 31.8 (9.9) months, 4 (9.5%) patients developed multiple sclerosis (3 (25%) children, 1 (4.7%) young adult, p = 0.03). The neurological disability, radiological and cerebrospinal fluid findings did not differ between patients with and without levamisole use. One elderly adult patient previously receiving levamisole developed multiple sclerosis of relapse-remitting type after a mean follow-up period of 36.9 months. Conclusion: The clinical presentations, functional outcome and risk of developing multiple sclerosis differed between different age groups. Functional recovery was faster in children than in adults. Poor functional outcome was related to initial high Expanded Disability Status Scale score and absence of fever.

LRRK2 mutation in familial Parkinson’s disease in a Taiwanese population: clinical, PET, and functional studies

Pathogenic mutations in leucine-rich repeat kinase 2 (LRRK2) cause autosomal-dominant familial Parkinsons disease (PD). We performed clinical, imaging, and molecular functional studies in one family with the R1441H and six families with the G2385R variants of Lrrk2. To determine the contribution of these variants to familial PD in Taiwanese, we screened 32 Taiwanese or ethnic Chinese patients with familial PD for four pathogenic substitutions (R1441H, I2012T, I2020T, and G2019S) and one susceptibility polymorphism (G2385R). The frequencies of R1441H and G2385R were 3.7% and 22.2%, respectively. G2019S, I2012T, and I2020T were not detected. The clinical phenotypes and [(18)F]-dopa PET findings for subjects with R1441H or G2385R resembled those of patients with idiopathic PD; however, their lymphoblastoid cell lines showed increased apoptosis following exposure to a proteosome inhibitor. Thus, LRRK2 mutations are rare in Taiwanese with familial PD. Further study is needed to identify causative genes or unique biomarkers for familial PD.

Biomarkers of cognitive decline in Parkinson's disease

Cognitive impairment is a frequent and devastating non-motor symptom of Parkinsons disease (PD). Impaired cognition has a major impact on either quality of life or mortality in patients with PD. Notably, the rate of cognitive decline and pattern of early cognitive deficits in PD are highly variable between individuals. Given that the underlying mechanisms of cognitive decline or dementia associated with PD remain unclear, there is currently no mechanism-based treatment available. Identification of biological markers, including neuroimaging, biofluids and common genetic variants, that account for the heterogeneity of PD related cognitive decline could provide important insights into the pathological processes that underlie cognitive impairment in PD. These combined biomarker approaches will enable early diagnosis and provide indicators of cognitive progression in PD patients. This review summarizes recent advances in the development of biomarkers for cognitive impairments in PD.

Preceding pain symptoms and Parkinson's disease: a nationwide population‐based cohort study

Painful sensations are recently reported to be a non‐motor feature of Parkinsons disease (PD). The non‐steroidal anti‐inflammatory drug ibuprofen is a common painkiller and was reported to be associated with a decreased risk of PD. The aim of the present study was to examine the relationship amongst preceding pain symptoms, use of ibuprofen and risk of PD in a nationwide population‐based cohort.