Lorraine N. Clark

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.

Large-scale meta-analysis of genome-wide association data identifies six new risk loci for Parkinson's disease

We conducted a meta-analysis of Parkinsons disease genome-wide association studies using a common set of 7,893,274 variants across 13,708 cases and 95,282 controls. Twenty-six loci were identified as having genome-wide significant association; these and 6 additional previously reported loci were then tested in an independent set of 5,353 cases and 5,551 controls. Of the 32 tested SNPs, 24 replicated, including 6 newly identified loci. Conditional analyses within loci showed that four loci, including GBA, GAK-DGKQ, SNCA and the HLA region, contain a secondary independent risk variant. In total, we identified and replicated 28 independent risk variants for Parkinsons disease across 24 loci. Although the effect of each individual locus was small, risk profile analysis showed substantial cumulative risk in a comparison of the highest and lowest quintiles of genetic risk (odds ratio (OR) = 3.31, 95% confidence interval (CI) = 2.55–4.30; P = 2 × 10−16). We also show six risk loci associated with proximal gene expression or DNA methylation.

Pharmacological Rescue of Mitochondrial Deficits in iPSC-Derived Neural Cells from Patients with Familial Parkinson’s Disease

Neural cells derived from induced pluripotent stem cells from patients with genetic forms of Parkinson’s disease provide insights into disease pathogenesis. Understanding Mitochondrial Deficits in Parkinson’s Disease Parkinson’s disease (PD) is a common, progressive neurodegenerative disease characterized by loss of dopaminergic neurons in the nigrostriatal pathway of the brain, resulting in motor and cognitive deficits. Rodent and primate models only partially predict disease mechanisms. In a new study, Cooper et al. set out to make a human cellular model of PD. First, the authors obtained fibroblasts from members of families with genetically defined forms of PD and generated induced pluripotent stem cells (iPSCs) from the fibroblasts. They then induced differentiation of these PD patient–derived iPSCs into neural cells including dopaminergic neurons to study how the genetic mutations influenced the responses of neural cells to various cellular stressors. Mitochondrial dysfunction has already been implicated in the pathogenesis of PD, so the authors decided to treat their iPSC-derived neural cells from patients with rare familial forms of PD with chemical stressors and toxins known to disrupt mitochondrial function. The researchers observed a gradual increase in sensitivity to cellular stress as the cell type analyzed became functionally closer to the vulnerable cell types in the PD brain; that is, fibroblasts taken directly from PD patients were less sensitive to the chemical stressors than iPSC-derived neural cells. Several drugs helped iPSC-derived neural cells to resist the damaging effects of the cellular stressors. These studies with human neural cells from iPSCs from patients with familial PD highlight opportunities to characterize disease pathways and to screen for new therapeutic agents. Parkinson’s disease (PD) is a common neurodegenerative disorder caused by genetic and environmental factors that results in degeneration of the nigrostriatal dopaminergic pathway in the brain. We analyzed neural cells generated from induced pluripotent stem cells (iPSCs) derived from PD patients and presymptomatic individuals carrying mutations in the PINK1 (PTEN-induced putative kinase 1) and LRRK2 (leucine-rich repeat kinase 2) genes, and compared them to those of healthy control subjects. We measured several aspects of mitochondrial responses in the iPSC-derived neural cells including production of reactive oxygen species, mitochondrial respiration, proton leakage, and intraneuronal movement of mitochondria. Cellular vulnerability associated with mitochondrial dysfunction in iPSC-derived neural cells from familial PD patients and at-risk individuals could be rescued with coenzyme Q10, rapamycin, or the LRRK2 kinase inhibitor GW5074. Analysis of mitochondrial responses in iPSC-derived neural cells from PD patients carrying different mutations provides insight into convergence of cellular disease mechanisms between different familial forms of PD and highlights the importance of oxidative stress and mitochondrial dysfunction in this neurodegenerative disease.

Placental overgrowth in mice lacking the imprinted gene Ipl

The Ipl (Tssc3) gene lies in an extended imprinted region of distal mouse chromosome 7, which also contains the Igf2 gene. Expression of Ipl is highest in placenta and yolk sac, where its mRNA is derived almost entirely from the maternal allele. Ipl encodes a small cytoplasmic protein with a pleckstrin-homology (PH) domain. We constructed two lines of mice with germ-line deletions of this gene (Iplneo and IplloxP) and another line deleted for the similar but nonimprinted gene Tih1. All three lines were viable. There was consistent overgrowth of the Ipl-null placentas, with expansion of the spongiotrophoblast. These larger placentas did not confer a fetal growth advantage; fetal size was normal in Ipl nulls with the Iplneo allele and was decreased slightly in nulls with the IplloxP allele. When bred into an Igf2 mutant background, the Ipl deletion partially rescued the placental but not fetal growth deficiency. Neither fetal nor placental growth was affected by deletion of Tih1. These results show a nonredundant function for Ipl in restraining placental growth. The data further indicate that Ipl can act, at least in part, independently of insulin-like growth factor-2 signaling. Thus, genomic imprinting regulates multiple pathways to control placental size.

A Multicenter Study of Glucocerebrosidase Mutations in Dementia With Lewy Bodies

IMPORTANCE While mutations in glucocerebrosidase (GBA1) are associated with an increased risk for Parkinson disease (PD), it is important to establish whether such mutations are also a common risk factor for other Lewy body disorders. OBJECTIVE To establish whether GBA1 mutations are a risk factor for dementia with Lewy bodies (DLB). DESIGN We compared genotype data on patients and controls from 11 centers. Data concerning demographics, age at onset, disease duration, and clinical and pathological features were collected when available. We conducted pooled analyses using logistic regression to investigate GBA1 mutation carrier status as predicting DLB or PD with dementia status, using common control subjects as a reference group. Random-effects meta-analyses were conducted to account for additional heterogeneity. SETTING Eleven centers from sites around the world performing genotyping. PARTICIPANTS Seven hundred twenty-one cases met diagnostic criteria for DLB and 151 had PD with dementia. We compared these cases with 1962 controls from the same centers matched for age, sex, and ethnicity. MAIN OUTCOME MEASURES Frequency of GBA1 mutations in cases and controls. RESULTS We found a significant association between GBA1 mutation carrier status and DLB, with an odds ratio of 8.28 (95% CI, 4.78-14.88). The odds ratio for PD with dementia was 6.48 (95% CI, 2.53-15.37). The mean age at diagnosis of DLB was earlier in GBA1 mutation carriers than in noncarriers (63.5 vs 68.9 years; P < .001), with higher disease severity scores. CONCLUSIONS AND RELEVANCE Mutations in GBA1 are a significant risk factor for DLB. GBA1 mutations likely play an even larger role in the genetic etiology of DLB than in PD, providing insight into the role of glucocerebrosidase in Lewy body disease.

Mutations in the glucocerebrosidase gene are associated with early-onset Parkinson disease

Objective: To evaluate the frequency of glucocerebrosidase (GBA) mutations in cases and controls enrolled in the Genetic Epidemiology of Parkinson’s Disease (GEPD) study. Methods: We sequenced all exons of the GBA gene in 278 Parkinson disease (PD) cases and 179 controls enrolled in GEPD, with a wide range of age at onset (AAO), and that included a subset of 178 Jewish cases and 85 Jewish controls. Cases and controls were recruited without knowledge of family history of PD, and cases were oversampled in the AAO < 50 years category. Results: 13.7% of PD cases (38/278) carried GBA mutations, compared with 4.5% of controls (8/179) (odds ratio [OR] 3.4, 95% CI 1.5 to 7.4). The frequency of GBA mutations was 22.2% in 90 cases with AAO ≤ 50 years, compared with 9.7% in 185 cases with AAO > 50 years (OR 2.7, 95% CI 1.3 to 5.3). Adjusting for age at the time of evaluation, sex, family history of PD, and Jewish ancestry, GBA carriers had a 1.7-year-earlier AAO of PD (95% CI 0.5 to 3.3, p < 0.04) than noncarriers. The average AAO of PD was 2.5 years earlier in carriers with an AAO ≤ 50 years compared with noncarriers (95% CI 0.6 to 4.5, p < 0.01) and this was not seen in the AAO > 50 years group. The frequency of GBA mutations was higher in a subset of 178 cases that reported four Jewish grandparents (16.9%) than in cases who did not report Jewish ancestry (8.0%) (p < 0.01). Nine different GBA mutations were identified in PD cases, including 84insGG, E326K, T369M, N370S, D409H, R496H, L444P, RecNciI, and a novel mutation, P175P. Conclusions: This study suggests that the Glucocerebrosidase gene may be a susceptibility gene for Parkinson disease and that Glucocerebrosidase mutations may modify age at onset. GLOSSARY: AAO = age at onset; cDNA = complementary DNA; GBA = glucocerebrosidase; GD = Gaucher disease; GEPD = Genetic Epidemiology of Parkinson’s Disease; MMSE = Mini-Mental State Examination; NA = not applicable; DLB = dementia with Lewy bodies; OR = odds ratio; PD = Parkinson disease; SNP = single nucleotide polymorphism; UPDRS = Unified Parkinson’s Disease Rating Scale.

Meta‐analysis of Parkinson's Disease: Identification of a novel locus, RIT2

Genome‐wide association (GWAS) methods have identified genes contributing to Parkinsons disease (PD); we sought to identify additional genes associated with PD susceptibility.

Frequency of LRRK2 mutations in early-and late-onset Parkinson disease

Objective: To evaluate the frequency of leucine-rich repeat kinase gene (LRRK2) mutations and single nucleotide polymorphisms (SNPs) in early-onset Parkinson disease (EOPD) and late-onset Parkinson disease (LOPD). Methods: We genotyped five previously reported LRRK2 mutations (G2019S, L1114L, I1122V, R1441C, and Y1699C) and 17 coding SNPs for haplotype analysis in 504 cases with PD and 314 controls enrolled in the Genetic Epidemiology of PD Study. Cases and controls were recruited without knowledge of family history of PD and cases were oversampled in the ≤50 age at onset (AAO) category. Results: The LRRK2 G2019S mutation was present in 28 cases with PD (5.6%) and two controls (0.6%) (χ2 = 13.25; p < 0.01; odds ratio 9.18, 95% CI: 2.17 to 38.8). The mutations L1114L, I1122V, R1441C, and Y1699C were not identified. The frequency of the LRRK2 G2019S mutation was 4.9% in 245 cases with AAO ≤50 years vs 6.2% in 259 cases with AAO >50 (p = 0.56). All cases with PD with the G2019S mutation shared the same disease-associated haplotype. The frequency of the LRRK2 G2019S mutation was higher in the subset of 181 cases reporting four Jewish grandparents (9.9%) than in other cases (3.1%) (p < 0.01). Age-specific penetrance to age 80 was 24% and was similar in Jewish and non-Jewish cases. Conclusions: The G2019S mutation is a risk factor in both early- and late-onset Parkinson disease and confirms the previous report of a greater frequency of the G2019S mutation in Jewish than in non-Jewish cases with Parkinson disease.

Cognitive performance of GBA mutation carriers with early-onset PD The CORE-PD study

Objective: To assess the cognitive phenotype of glucocerebrosidase (GBA) mutation carriers with early-onset Parkinson disease (PD). Methods: We administered a neuropsychological battery and the University of Pennsylvania Smell Identification Test (UPSIT) to participants in the CORE-PD study who were tested for mutations in PARKIN, LRRK2, and GBA. Participants included 33 GBA mutation carriers and 60 noncarriers of any genetic mutation. Primary analyses were performed on 26 GBA heterozygous mutation carriers without additional mutations and 39 age- and PD duration–matched noncarriers. Five cognitive domains, psychomotor speed, attention, memory, visuospatial function, and executive function, were created from transformed z scores of individual neuropsychological tests. Clinical diagnoses (normal, mild cognitive impairment [MCI], dementia) were assigned blind to genotype based on neuropsychological performance and functional impairment as assessed by the Clinical Dementia Rating (CDR) score. The association between GBA mutation status and neuropsychological performance, CDR, and clinical diagnoses was assessed. Results: Demographics, UPSIT, and Unified Parkinsons Disease Rating Scale–III performance did not differ between GBA carriers and noncarriers. GBA mutation carriers performed more poorly than noncarriers on the Mini-Mental State Examination (p = 0.035), and on the memory (p = 0.017) and visuospatial (p = 0.028) domains. The most prominent differences were observed in nonverbal memory performance (p < 0.001). Carriers were more likely to receive scores of 0.5 or higher on the CDR (p < 0.001), and a clinical diagnosis of either MCI or dementia (p = 0.004). Conclusion: GBA mutation status may be an independent risk factor for cognitive impairment in patients with PD.

From genotype to phenotype: A clinical, pathological, and biochemical investigation of frontotemporal dementia and parkinsonism (FTDP‐17) caused by the P301L tau mutation

Frontotemporal dementia is a heterogeneous, often inherited disorder that typically presents with the insidious onset of behavioral and personality changes. Two genetic loci have been identified and mutations in tau have been causally implicated in a subset of families linked to one of these loci on chromosome 17q21‐22. In this study, linkage analysis was performed in a large pedigree, the MN family, suggesting chromosome 17q21‐22 linkage. Mutational analysis of the tau coding region identified a C‐to‐T change in exon 10 that resulted in the conversion of proline to a leucine (P301L) that segregated with frontotemporal dementia in this family. The clinical and pathological findings in the MN family emphasize the significant overlap between Picks disease, corticobasal degeneration, and frontotemporal dementia and challenge some of the current dogma surrounding this condition. Pathological studies of two brains from affected members of Family MN obtained at autopsy demonstrate numerous tau‐positive inclusions that were most prominent in the frontal lobes, anterior temporal lobes, and brainstem structures, as well as Pick‐like bodies and associated granulovacuolar degeneration. These Pick‐like bodies were observed in 1 patient with motor neuron disease. Because exon 10 is present only in tau mRNA coding for a protein with four microtubule binding repeats (4R), this mutation should selectively affect 4Rtau isoforms. Indeed, immunoblotting demonstrated that insoluble 4Rtau is selectively aggregated in both gray and white matter of affected individuals. Although there was significant pathological similarity between the 2 cases, the pattern of degenerative changes and tau‐positive inclusions was not identical, suggesting that other genetic or epigenetic factors can significantly modify the regional topology of neurodegeneration in this condition. Ann Neurol 1999;45:704–715