Guey-Jen Lee-Chen

Multicenter Analysis of Glucocerebrosidase Mutations in Parkinson's Disease

BACKGROUND Recent studies indicate an increased frequency of mutations in the gene encoding glucocerebrosidase (GBA), a deficiency of which causes Gauchers disease, among patients with Parkinsons disease. We aimed to ascertain the frequency of GBA mutations in an ethnically diverse group of patients with Parkinsons disease. METHODS Sixteen centers participated in our international, collaborative study: five from the Americas, six from Europe, two from Israel, and three from Asia. Each center genotyped a standard DNA panel to permit comparison of the genotyping results across centers. Genotypes and phenotypic data from a total of 5691 patients with Parkinsons disease (780 Ashkenazi Jews) and 4898 controls (387 Ashkenazi Jews) were analyzed, with multivariate logistic-regression models and the Mantel-Haenszel procedure used to estimate odds ratios across centers. RESULTS All 16 centers could detect two GBA mutations, L444P and N370S. Among Ashkenazi Jewish subjects, either mutation was found in 15% of patients and 3% of controls, and among non-Ashkenazi Jewish subjects, either mutation was found in 3% of patients and less than 1% of controls. GBA was fully sequenced for 1883 non-Ashkenazi Jewish patients, and mutations were identified in 7%, showing that limited mutation screening can miss half the mutant alleles. The odds ratio for any GBA mutation in patients versus controls was 5.43 across centers. As compared with patients who did not carry a GBA mutation, those with a GBA mutation presented earlier with the disease, were more likely to have affected relatives, and were more likely to have atypical clinical manifestations. CONCLUSIONS Data collected from 16 centers demonstrate that there is a strong association between GBA mutations and Parkinsons disease.

Analysis of Lrrk2 R1628P as a risk factor for Parkinson's disease

Common genetic variants that increase the risk for Parkinsons disease may differentiate patient subgroups and influence future individualized therapeutic strategies. Herein we show evidence for leucine‐rich repeat kinase 2 (LRRK2) c.4883G>C (R1628P) as a risk factor in ethnic Chinese populations. A study of 1,986 individuals from 3 independent centers in Taiwan and Singapore demonstrates that Lrrk2 R1628P increases risk for Parkinsons disease (odds ratio, 1.84; 95% confidence interval, 1.20–2.83; p = 0.006). Haplotype analysis suggests an ancestral founder for carriers approximately 2,500 years ago. These findings support the importance of LRRK2 variants in sporadic Parkinsons disease. Ann Neurol 2008

Glucocerebrosidase gene mutation is a risk factor for early onset of Parkinson disease among Taiwanese

Background: Mutations in the glucocerebrosidase (GBA) gene have recently been identified as contributing to the development of Parkinson disease (PD) in Ashkenazi Jews. Methods: To investigate whether this finding can be confirmed in a Taiwanese population, we conducted a case control study in a cohort of 518 PD patients and 339 controls for the three common GBA mutations in Taiwan, L444P, RecNciI and R120W, using PCR restriction enzyme assay and DNA sequencing. Results: Heterozygous GBA mutations were detected in 16 PD patients (3.1%) and four controls (1.2%). Although this difference was not statistically significant (p = 0.0703), the average age at disease onset of the 16 PD patients (50.6 (12.3) years) was significantly younger than that of the total patient group (63.8 (10.5) years; p = 0.0007) and the non-carrier patient group (64.2 (10.2) years; p = 0.0005). After stratification by age, the frequency of mutation carriers was significantly higher for the early onset PD (EOPD, age at onset ⩽50 years) group than for age matched controls (12.9% vs 1.8%; p = 0.0335) and there was a trend towards an increased risk of the mutation carrier with EOPD (odds ratio 8.30; 95% CI 1.45 to 156.53). Clinically, all 16 patients carrying a GBA mutation presented with a typical parkinsonian phenotype and experienced a good or excellent response to levodopa. Conclusions: Mutations of the GBA gene may be associated with the development of EOPD in Taiwan.

Exendin-4 protected against cognitive dysfunction in hyperglycemic mice receiving an Intrahippocampal Lipopolysaccharide injection

Background Chronic hyperglycemia-associated inflammation plays critical roles in disease initiation and the progression of diabetic complications, including Alzheimer’s disease (AD). However, the association of chronic hyperglycemia with acute inflammation of the central nervous system in the progression of AD still needs to be elucidated. In addition, recent evidence suggests that Glucagon-like peptide-1 receptor (GLP-1R) protects against neuronal damage in the brain. Therefore, the neuroprotective effects of the GLP-1R agonist exendin-4 (EX-4) against hyperglycemia/lipopolysaccharides (LPS) damage were also evaluated in this study. Methodology/Principal Findings Ten days after streptozotocin (STZ) or vehicle (sodium citrate) treatment in mice, EX-4 treatment (10 µg/kg/day) was applied to the mice before intrahippocampal CA1 injection of LPS or vehicle (saline) and continued for 28 days. This study examined the molecular alterations in these mice after LPS and EX4 application, respectively. The mouse cognitive function was evaluated during the last 6 days of EX-4 treatment. The results showed that the activation of NF-κB-related inflammatory responses induced cognitive dysfunction in both the hyperglycemic mice and the mice that received acute intrahippocampal LPS injection. Furthermore, acute intrahippocampal LPS injection exacerbated the impairment of spatial learning and memory through a strong decrease in monoaminergic neurons and increases in astrocytes activation and apoptosis in the hyperglycemic mice. However, EX-4 treatment protected against the cognitive dysfunction resulting from hyperglycemia or/and intrahippocampal LPS injection. Conclusions/Significance These findings reveal that both hyperglycemia and intrahippocampal LPS injection induced cognitive dysfunction via activation of NF-κB-related inflammatory responses. However, acute intrahippocampal LPS injection exacerbated the progression of cognitive dysfunction in the hyperglycemic mice via a large increase in astrocytes activation-related responses. Furthermore, EX-4 might be considered as a potential adjuvant entity to protect against neurodegenerative diseases.

SCA8 mRNA expression suggests an antisense regulation of KLHL1 and correlates to SCA8 pathology

An increasing number of inherited neurodegenerative diseases are known to be caused by the expansion of unstable trinucleotide repeat tracts. Spinocerebellar ataxia type 8 (SCA8) has been identified as being partly caused by a CTG expansion in an untranslated, endogenous antisense RNA that overlaps the Kelch-like 1 (KLHL1) gene. Clinically, SCA8 patients show similar features to those with the other SCAs, including limb and truncal ataxia, ataxic dysarthria and horizontal nystagmus, all of which are signs of dysfunction of the cerebellar system. However, allele sizes within the SCA8 proposed pathogenic range have been reported in patients with ataxia of unknown etiology, in individuals from pedigrees with other SCA or Friedreichs ataxia, and in patients with Alzheimers disease, schizophrenia or parkinsonism. These observations suggest that mutation of the SCA8 locus might affect neurons other than the cerebellum. Antisense transcripts are known to regulate complementary sense transcripts and are involved in several biologic functions, such as development, adaptive response, and viral infection. In order to test whether SCA8 affects the KLHL1 expression by antisense RNA in brain cells, we examined the expression pattern of KLHL1 and SCA8 in human tissues and in mouse brain regions. SCA8 expression was colocalized with KLHL1 transcript in many brain regions whose functions are correlated to the clinical symptoms of SCA8 patients. These findings lead to the hypothesis of a possible relevance that SCA8 transcript downregulates KLHL1 expression through an antisense mechanism, which then leads to SCA8 neuropathogenesis.

Mitochondrial Dysfunction and Oxidative Stress Contribute to the Pathogenesis of Spinocerebellar Ataxia Type 12 (SCA12)

Spinal cerebellar ataxia type 12 (SCA12) has been attributed to the elevated expression of ppp2r2b. To better elucidate the pathomechanism of the neuronal disorder and to search for a pharmacological treatment, Drosophila models of SCA12 were generated by overexpression of a human ppp2r2b and its Drosophila homolog tws. Ectopic expression of ppp2r2b or tws caused various pathological features, including neurodegeneration, apoptosis, and shortened life span. More detailed analysis revealed that elevated ppp2r2b and tws induced fission of mitochondria accompanied by increases in cytosolic reactive oxygen species (ROS), cytochrome c, and caspase 3 activity. Transmission electron microscopy revealed that fragmented mitochondria with disrupted cristae were engulfed by autophagosomes in photoreceptor neurons of flies overexpressing tws. Additionally, transgenic flies were more susceptible to oxidative injury induced by paraquat. By contrast, ectopic Drosophila Sod2 expression and antioxidant treatment reduced ROS and caspase 3 activity and extended the life span of the SCA12 fly model. In summary, our study demonstrates that oxidative stress induced by mitochondrial dysfunction plays a causal role in SCA12, and reduction of ROS is a potential therapeutic intervention for this neuropathy.

Apolipoprotein E , angiotensin-converting enzyme and kallikrein gene polymorphisms and the risk of Alzheimer’s disease and vascular dementia

Summary.Lipoproteins and vascular factors may play roles in the development of Alzheimer’s disease (AD) and/or vascular dementia (VaD). In this study, odd ratios (ORs) and 95% confidence intervals (CIs) for apolipoprotein E (APOE), angiotensin-converting enzyme (ACE), and kallikrein (KLK1) polymorphisms were computed to test their association with the disease by a case-control study. The risk of AD was significantly increased for individuals with APOE ɛ4 allele (OR = 3.73, 95% CI = 2.38–5.98). The risk of AD was also significant for people with ACE DD genotype, D allele, or T-D haplotype [OR (95% CI) = 4.29 (1.96–10.23), 1.90 (1.35–2.70), or 2.91 (1.71–5.10), respectively]. The above association between ACE-VaD was also strong (p = 0.0012, 0.0050, 0.0007, respectively). Reporter constructs containing the −240 A or T allele displayed similar transcriptional activity in both HEK-293 and IMR-32 cells. Thus, another putative pathogenic marker that is linked with the Alu D allele might affect the risk of AD and VaD in Taiwan.

Analysis of the PINK1 gene in a cohort of patients with sporadic early-onset parkinsonism in Taiwan

Mutations in the PINK1 gene have been shown to cause autosomal recessive Parkinsons disease (PD) and/or early onset sporadic PD in Italy, Spain, North America, Ireland, and Asia. However, there are limited data on PINK1 mutations in sporadic early onset Asian PD patients. To determine the prevalence of PINK1 mutation in Taiwanese population, we conducted genetic analysis of PINK1 mutation in 73 early onset sporadic PD and 94 normal control subjects. We only identified a novel single heterozygous mutation R 407Q mutation in exon 6 of this gene in one patient at the age onset of 54. Overall, these data indicate that PINK1 mutations are rare in our population. Based on our results, unless common mutational hotspots are identified, routine testing for this mutation at least in our population may not be cost-effective.

Nuclear receptor NR4A2 IVS6 +18insG and brain derived neurotrophic factor (BDNF) V66M polymorphisms and risk of taiwanese Parkinson's disease

Both of environmental and genetic factors confer vulnerability to Parkinsons disease (PD). NR4A2 (Nurr1), a member of the steroid/thyroid hormone nuclear receptor superfamily, is essential for the neurogenesis and differentiation of dopaminergic neurons in the midbrain. Brain derived neurotrophic factor (BDNF) deficiency may play a role in the pathogenesis of PD, as the surviving dopaminergic nigrostriatal neurons have reduced levels of BDNF. This study examines whether BDNF V66M (c.196 G → A) or NR4A2 IVS6 +18insG polymorphism is associated with the risk of Taiwanese PD and the age of onset using a case‐control study. The genotype or allele frequency distribution of both BDNF V66M and NR4A2 IVS6 +18insG polymorphisms was not significantly different between the cases and the controls. Neither BDNF nor NR4A2 polymorphism influences PD onset age. Notably, after stratification by sex, female individuals carrying the NR4A2 2G/2G genotype demonstrated a trend toward significant decrease in risk of developing PD (OR = 0.49, 95% CI = 0.25–0.96, P = 0.039). These results suggest that the NR4A2 IVS6 +18insG polymorphism may play a minor role in PD susceptibility among Taiwanese women.

Dystonia as a presenting sign of spinocerebellar ataxia type 1

We report on a 39‐year‐old man who presented initially with marked blepharospasm, oromandibular dystonia and retrocollis and one year later developed mild ataxia. Our findings suggest that dystonia can be a disabling presenting sign of SCA1 and support the clinical heterogeneity of SCA1, highlighting the importance of considering this entity in patients combining dystonia and cerebellar ataxia.