Atypical Parkinsonism associated with white matter pathology has been described in cerebrovascular diseases, mitochondrial cytopathies, osmotic demyelinating disorders, leukoencephalopathies including leukodystrophies, and others. Hereditary diffuse leukoencephalopathy with spheroids (HDLS) is an autosomal dominant disorder with symptomatic onset in midlife and death within a few years after symptom onset. Neuroimaging reveals cerebral white matter lesions that are pathologically characterized by non-inflammatory myelin loss, reactive astrocytosis, and axonal spheroids. Most cases are caused by mutations in the colony-stimulating factor 1 receptor (CSF1R) gene.
We studied neuropathologically verified HDLS patients with CSF1R mutations to assess Parkinsonian features. Ten families were evaluated with 16 affected individuals. During the course of the illness, all patients had at least some degree of bradykinesia. Fifteen patients had postural instability, and seven had rigidity. Two patients initially presented with Parkinsonian gait and asymmetrical bradykinesia. These two patients and two others exhibited bradykinesia, rigidity, postural instability, and tremor (two with resting) early in the course of the illness. Levodopa/carbidopa therapy in these four patients provided no benefit, and the remaining 12 patients were not treated. The mean age of onset for all patients was about 45 years (range, 18-71) and the mean disease duration was approximately six years (range, 3-11).
We also reviewed HDLS patients published prior to the CSF1R discovery for the presence of Parkinsonian features. Out of 50 patients, 37 had gait impairments, 8 rigidity, 7 bradykinesia, and 5 resting tremor. Our report emphasizes the presence of atypical Parkinsonism in HDLS due to CSF1R mutations.
HDLS; CSF1R mutation; Parkinsonism; Autosomal dominant; White matter disorders
Ability to work and independent living capacity are of particular concern for patients with Parkinson’s disease (PD). We utilized a series of PD patients able to work or live independently at baseline, and evaluated potential risk factors for the two separate outcomes of loss of ability to work and loss of ability to live independently.
The series was comprised of 495 PD patients followed prospectively. Ability to work and ability to live independently were based on clinical interview and examination. Cox regression models adjusted for age and disease duration were used to evaluate associations of baseline characteristics with loss of ability to work and loss of ability to live independently.
Higher UPDRS dyskinesia score, UPDRS instability score, UPDRS total score, Hoehn and Yahr stage, and presence of intellectual impairment at baseline were all associated with increased risk of future loss of ability to work and loss of ability to live independently (P≤0.0033). Five years after initial visit, for patients ≤70 years of age with a disease duration ≤4 years at initial visit, 88% were still able to work and 90% to live independently. These estimates worsened as age and disease duration at initial visit increased; for patients >70 years of age with a disease duration >4 years, estimates at 5 years were 43% and 57%, respectively.
The information provided in this study can offer useful information for PD patients in preparing for future loss of ability to perform activities of daily living.
Parkinson disease; work ability; independence
Pigmented orthochromatic leukodystrophy (POLD) and hereditary diffuse leukoencephalopathy with axonal spheroids (HDLS) are rare neurodegenerative disorders characterized by cerebral white matter abnormalities, myelin loss, and axonal swellings. The striking overlap of clinical and pathologic features of these disorders suggested a common pathogenesis; however, no genetic or mechanistic link between POLD and HDLS has been established. Recently, we reported that mutations in the colony-stimulating factor 1 receptor (CSF1R) gene cause HDLS. In this study, we determined whether CSF1R mutations are also a cause of POLD.
We performed sequencing of CSF1R in 2 pathologically confirmed POLD families. For the largest family (FTD368), a detailed case report was provided and brain samples from 2 affected family members previously diagnosed with POLD were re-evaluated to determine whether they had HDLS features. In vitro functional characterization of wild-type and mutant CSF1R was also performed.
We identified CSF1R mutations in both POLD families: in family 5901, we found c.2297T>C (p.M766T), previously reported by us in HDLS family CA1, and in family FTD368, we identified c.2345G>A (p.R782H), recently reported in a biopsy-proven HDLS case. Immunohistochemical examination in family FTD368 showed the typical neuronal and glial findings of HDLS. Functional analyses of CSF1R mutant p.R782H (identified in this study) and p.M875T (previously observed in HDLS), showed a similar loss of CSF1R autophosphorylation of selected tyrosine residues in the kinase domain for both mutations when compared with wild-type CSF1R.
We provide the first genetic and mechanistic evidence that POLD and HDLS are a single clinicopathologic entity.
Genetic variation in the leucine-rich repeat and Ig domain containing 1 gene (LINGO1) was recently associated with an increased risk of developing essential tremor (ET) and Parkinson disease (PD). Herein, we performed a comprehensive study of LINGO1 and its paralog LINGO2 in ET and PD by sequencing both genes in patients (ET, n=95; PD, n=96) and by examining haplotype-tagging single-nucleotide polymorphisms (tSNPs) in a multicenter North American series of patients (ET, n=1,247; PD, n=633) and controls (n=642). The sequencing study identified six novel coding variants in LINGO1 (p.S4C, p.V107M, p.A277T, p.R423R, p.G537A, p.D610D) and three in LINGO2 (p.D135D, p.P217P, p.V565V), however segregation analysis did not support pathogenicity. The association study employed 16 tSNPs at the LINGO1 locus and 21 at the LINGO2 locus. One variant in LINGO1 (rs9652490) displayed evidence of an association with ET (odds ratio (OR)=0.63; P=0.026) and PD (OR=0.54; P=0.016). Additionally, four other tSNPs in LINGO1 and one in LINGO2 were associated with ET and one tSNP in LINGO2 associated with PD (P<0.05). Further analysis identified one tSNP in LINGO1 and two in LINGO2 which influenced age at onset of ET and two tSNPs in LINGO1 which altered age at onset of PD (P<0.05). Our results support a role for LINGO1 and LINGO2 in determining risk for and perhaps age at onset of ET and PD. Further studies are warranted to confirm these findings and to determine the pathogenic mechanisms involved.
Essential tremor; Parkinson disease; LINGO1; LINGO2; Genetic association
Purpose of review
Elucidating the genetic background of Parkinson disease and essential tremor is crucial to understand the pathogenesis and improve diagnostic and therapeutic strategies.
A number of approaches have been applied including familial and association studies, and studies of gene expression profiles to identify genes involved in susceptibility to Parkinson disease. These studies have nominated a number of candidate Parkinson disease genes and novel loci including Omi/HtrA2, GIGYF2, FGF20, PDXK, EIF4G1 and PARK16. A recent notable finding has been the confirmation for the role of heterozygous mutations in glucocerebrosidase (GBA) as risk factors for Parkinson disease. Finally, association studies have nominated genetic variation in the leucine-rich repeat and Ig containing 1 gene (LINGO1) as a risk for both Parkinson disease and essential tremor, providing the first genetic evidence of a link between the two conditions.
Although undoubtedly genes remain to be identified, considerable progress has been achieved in the understanding of the genetic basis of Parkinson disease. This same effort is now required for essential tremor. The use of next-generation high-throughput sequencing and genotyping technologies will help pave the way for future insight leading to advances in diagnosis, prevention and cure.
essential tremor; genetics; LINGO1; PARK16; Parkinson disease
To examine predictive factors associated with onset of depression among individuals diagnosed with Parkinson’s disease (PD).
Depression may precede or follow symptomatic parkinsonism in PD. It is frequently treatable but often overlooked.
The clinical series comprised 685 individuals who were diagnosed with PD and followed by one neurologist (RJU) from 1994 to 2007. The primary outcome was time to depression following the onset of PD. Diagnosis of depression was based on clinical assessment of depressive symptoms from patients (and spouse/family/caregiver) and antidepressant usage. A number of demographic, historical and clinical predictive factors were examined, including gender, age at symptomatic onset, disease duration, onset characteristics, clinical ratings, antiparkinsonian medications, cognitive status, depression history, and familial history of PD and other neurodegenerative disorders.
Seventy-two percent of patients developed depression within ten years of symptomatic PD onset, and the mean time to depression was 7.9 years (median: 5.7 years). Factors associated with depression included longer PD duration, greater impairment in activities of daily living, and positive family history of motor neuron disease (MND).
A high rate of individuals with PD develop depressive symptoms during the course of the disease. Based on first clinic visit characteristics, most factors examined were not helpful in identifying individuals with an increased risk of depression. However, disease duration, functional limitations and family history of MND should lead clinicians to an increased vigilance for identifying depression.
To describe the brain MRI characteristics of hereditary diffuse leukoencephalopathy with spheroids (HDLS) with known mutations in the colony-stimulating factor 1 receptor gene (CSF1R) on chromosome 5.
We reviewed 20 brain MRI scans of 15 patients with autopsy- or biopsy-verified HDLS and CSF1R mutations. We assessed sagittal T1-, axial T1-, T2-, proton density-weighted and axial fluid-attenuated inversion recovery images for distribution of white matter lesions (WMLs), gray matter involvement, and atrophy. We calculated a severity score based on a point system (0−57) for each MRI scan.
Of the patients, 93% (14 of 15) demonstrated localized WMLs with deep and subcortical involvement, whereas one patient revealed generalized WMLs. All WMLs were bilateral but asymmetric and predominantly frontal. Fourteen patients had a rapidly progressive clinical course with an initial MRI mean total severity score of 16.7 points (range 10−33.5). Gray matter pathology and brainstem atrophy were absent, and the corticospinal tracts were involved late in the disease course. There was no enhancement, and there was minimal cerebellar pathology.
Recognition of the typical MRI patterns of HDLS and the use of an MRI severity score might help during the diagnostic evaluation to characterize the natural history and to monitor potential future treatments. Indicators of rapid disease progression were symptomatic disease onset before 45 years, female sex, WMLs extending beyond the frontal regions, a MRI severity score greater than 15 points, and mutation type of deletion.
The study investigates the effects of genetic factors on the pathology of Alzheimer’s disease (AD) and Lewy body (LB) diseases, including Parkinson’s disease and dementia with Lewy bodies. A multicenter autopsy series (762 brain samples) with AD, LB or vascular pathology was examined. We assessed the effects of the tau gene (MAPT) H1 haplotype, the H1-specific SNP rs242557, APOE and the α-synuclein gene (SNCA) 3′UTR SNP rs356165 on the burden of AD and LB pathology. We counted neurofibrillary tangles (NFTs) in four brain regions, senile plaques (SPs) in five and LBs in four. We also documented Braak NFT stage, brain weight and presence of vascular pathology. MAPT H1 associated with lower counts of NFTs in the middle frontal (P<0.001) and inferior parietal (P=0.005) cortices, and also with lower counts of SPs in the motor cortex (P=0.001). Associations of MAPT H1 with increased LB counts in the middle frontal cortex (P=0.011) and inferior parietal cortex (P=0.033) were observed but were not significant after multiple testing adjustment. The APOE ε4 allele was strongly associated with overall Alzheimer type pathology (all P≤0.001). SNCA rs356165 and the MAPT H1-specific SNP rs242557 did not associate with AD or LB pathology. This study shows for the first time that MAPT H1 is associated with reduced Alzheimer type pathology, which could have important implications for the understanding of disease mechanisms and their genetic determinants.
MAPT; SNCA; APOE; Alzheimer pathology; Lewy body
Hereditary diffuse leukoencephalopathy with spheroids (HDLS) is an autosomal dominantly inherited central nervous system white matter disease with variable clinical presentations including personality and behavioral changes, dementia, depression, parkinsonism, seizures, and others1,2. We combined genome-wide linkage analysis with exome sequencing and identified 14 different mutations affecting the tyrosine kinase domain of the colony stimulating factor receptor 1 (encoded by CSF1R) in 14 families affected by HDLS. In one kindred, the de novo occurrence of the mutation was confirmed. Follow-up sequencing analyses identified an additional CSF1R mutation in a patient clinically diagnosed with corticobasal syndrome (CBS). In vitro, CSF-1 stimulation resulted in the rapid autophosphorylation of selected tyrosine-residues in the kinase domain of wild-type but not mutant CSF1R, suggesting that HDLS may result from a partial loss of CSF1R function. Since CSF1R is a critical mediator of microglial proliferation and differentiation in the brain, our findings suggest an important role for microglial dysfunction in HDLS pathogenesis.
Genealogical investigation of a large Norwegian family (F04) with autosomal dominant parkinsonism has identified 18 affected family members over four generations. Genetic studies have revealed a novel pathogenic LRRK2 mutation c.4309 C>A (p.Asn1437His) that co-segregates with disease manifestation (LOD=3.15, θ=0). Affected carriers have an early age at onset (48 ± 7.7 SD years) and are clinically asymmetric and levodopa-responsive. The variant was absent in 623 Norwegian control subjects. Further screening of patients from the same population identified one additional affected carrier (1/692) with familial parkinsonism who shares the same haplotype. The mutation is located within the Roc domain of the protein and enhances GTP-binding and kinase activity, further implicating these activities as the mechanisms that underlie LRRK2-linked parkinsonism.
LRRK2; Parkinson’s disease; genetic; kinase
Mutations in the Glucocerebrosidase gene (GBA) have recently been associated with an increased risk of Parkinson disease (PD). GBA mutations have been observed to be particularly prevalent in the Ashkenazi Jewish population. Interestingly, this population also has a high incidence of the Lrrk2 p.G2019S mutation which is similar in North African Arab-Berber populations. Herein, our sequencing of the GBA gene, in 33 North African Arab-Berber familial parkinsonism probands, identified two novel mutations in three individuals (p.K-26R and p.K186R). Segregation analysis of these two variants did not support a pathogenic role. Genotyping of p.K-26R, p.K186R and the common p.N370S in an ethnically matched series consisting of 395 patients with PD and 372 control subjects did not show a statistically significant association (P>0.05). The p.N370S mutation was only identified in 1 sporadic patient with PD and 3 control subjects indicating that the frequency of this mutation in the North African Arab-Berber population is much lower than that observed in Ashkenazi Jews, and therefore arose in the latter after expansion of the Lrrk2 p.G2019S variant in North Africa.
Parkinson disease; Gaucher disease; genetics
Leucine-rich repeat kinase 2 (LRRK2) has emerged as the most prevalent genetic cause of Parkinson's disease (PD) among Caucasians. Patients carrying an LRRK2 mutation display significant variability of clinical and pathologic phenotypes across and within affected families.
Herein, we review available clinical and pathologic data on patients with an LRRK2 mutation who have come to autopsy.
Thirty-eight patients have been reported who presented clinically with PD; parkinsonism with resistance to levodopa, supranuclear gaze palsy, or autonomic dysfunction; or tremor and dementia. Pathology showed typical PD-type Lewy body disease (LBD) in most patients, whereas in others there was ‘pure’ nigral degeneration (one with TDP-43-positive inclusions), diffuse LBD, or tau-, α-synuclein- or ubiquitin-positive pathology reminiscent of progressive supranuclear gaze palsy, multisystem atrophy, and frontotemporal dementia with ubiquitin-positive inclusions.
Such clinical and pathologic variability suggests Lrrk2 acts upstream from other proteins implicated in neurodegeneration. Specific mutations may be associated with alternative progressive supranuclear gaze palsy-like or ‘pure’ nigral degeneration phenotypes. A different effect on Lrrk2 kinase activity may play a role in such heterogeneity.
Leucine-rich repeat kinase 2gene; Parkinson's disease; Lewy body disease; Progressive supranuclear gaze palsy; Nigral degeneration
Perry syndrome is characterized clinically by autosomal dominantly inherited, rapidly progressive parkinsonism, depression, weight loss and hypoventilation. In the seven families reported previously and the two new families presented herein (the Hawaii family and the Fukuoka-4 Japanese family), the mean disease onset age is 48 years (range: 35-61) and the mean disease duration five years (range: 2-10). Histology and immunohistochemistry show severe neuronal loss in the substantia nigra and locus coeruleus, with TDP-43-positive pathology in neurons (intranuclear and cytoplasmic inclusions, dystrophic neurites, axonal spheroids) and glial cells (glial cytoplasmic inclusions). Compared with other TDP-43-proteinopathies (amyotrophic lateral sclerosis and ubiquitin-positive frontotemporal lobar degeneration), the distribution is unique in Perry syndrome with pallidonigral distribution and sparing of the cortex, hippocampus and motor neurons. The genetic cause of Perry syndrome was recently identified with five mutations in the dynactin gene (DCTN1) segregating with disease in eight families. DCTN1 encodes p150glued, the major subunit of the dynactin protein complex, which plays a crucial role in retrograde axonal and cytoplasmic transport of various cargoes. Evidence suggests the Perry mutations alter the binding of p150glued to microtubules. Further studies will examine reasons for the vulnerability of selected neuronal populations in Perry syndrome, and the link between the genetic defect and TDP-43 pathology.
Perry syndrome; parkinsonism; depression; hypoventilation; dynactin; DCTN1; p150glued; TDP-43
Recently, a variant in LINGO1 (rs9652490) was found to associate with increased risk of essential tremor. We set out to replicate this association in an independent case-control series of essential tremor from North America. In addition, given the clinical and pathological overlap between essential tremor and Parkinson disease, we also evaluate the effect of LINGO1 rs9652490 in two case-control series of Parkinson disease. Our study demonstrates a significant association between LINGO1 rs9652490 and essential tremor (P=0.014) and Parkinson disease (P=0.0003), thus providing the first evidence of a genetic link between both diseases.
LINGO1; Parkinson disease; essential tremor
Dopa-responsive dystonia is a familial childhood-onset disease characterized by fluctuating dystonia, associated with tremor and parkinsonism in some patients. In most families the disease displays autosomal dominant inheritance due to mutations in the GTP cyclohydrolase 1 gene (GCH1). Penetrance and symptom severity display strong female predominance for which gender-specific GCH1 expression has been hypothesized. In this study, GCH1 mRNA expression was measured in cerebellar tissue from 66 healthy human subjects (30 women), and in cerebellar and nigral tissue from 8 individuals. No significant difference was found between men and women with small effect sizes observed. Although the correlation between cerebellar and nigral GCH1 expression remains to be further examined, this exploratory study does not support gender-specific GCH1 expression being the basis for the skewed gender distribution observed in DRD patients.
Dopa-responsive dystonia; DRD; GCH1 expression; gender distribution
Genetic variation in fibroblast growth factor 20 (FGF20) has been associated with risk of Parkinson's disease (PD). Functional evidence suggested the T allele of one SNP, rs12720208 C/T, altered PD risk by increasing FGF20 and α-synuclein protein levels. Herein we report our association study of FGF20 and PD risk in four patient-control series (total: 1,262 patients and 1,881 controls), and measurements of FGF20 and α-synuclein protein levels in brain samples (nine patients). We found no evidence of association between FGF20 variability and PD risk, and no relationship between the rs12720208 genotype, FGF20 and α-synuclein protein levels.
Parkinson's disease; FGF20; α-synuclein; association study; genetics
Fahr disease; brain calcinosis; idiopathic basal ganglia calcification
Autosomal dominant parkinsonism, hypoventilation, depression and severe weight loss (Perry syndrome) is an early-onset rapidly progressive disease. At autopsy, previous studies have found severe neuronal loss in the substantia nigra without Lewy bodies. Transactive response DNA-binding protein of 43 kDa (TDP-43) has recently been identified as a major ubiquitinated constituent of neuronal and glial inclusions in frontotemporal lobar degeneration with ubiquitin-positive inclusions and in amyotrophic lateral sclerosis. This study reports clinical, genetic and neuropathologic investigations of Perry syndrome.
Clinical data and autopsy brain tissue samples were collected from eight patients from four genealogically unrelated kindreds with Perry syndrome. Brain tissue was studied with immunohistochemistry and biochemistry for TDP-43. Patients were screened for mutations in the progranulin (GRN) and TDP-43 (TARDBP) genes.
The mean age at onset was 47 years (range: 40-56), and the mean age at death was 52 years (range: 44-64). In all patients, we identified TDP-43-positive neuronal inclusions, dystrophic neurites and axonal spheroids in a predominantly pallidonigral distribution, and we demonstrated changes in solubility and electrophoretic mobility of TDP-43 in brain tissue. The inclusions were highly pleomorphic and predominated in the extrapyramidal system, sparing the cortex, hippocampus and motor neurons. There were no mutations in GRN or TARDBP.
Perry syndrome displays unique TDP-43 pathology that is selective for the extrapyramidal system and spares the neocortex and motor neurons.
autosomal dominant; axonal dystrophy; neuronal cytoplasmic inclusions; pallidonigral; parkinsonism; Perry syndrome; TARDBP; TDP-43
Attempts at replicating the first genome-wide association study (GWAS) in Parkinson's disease (PD) have not successfully identified genetic risk factors. The present study reevaluates data from the GWAS and focuses on the SNP (rs11155313, located in the Phactr2 gene) with the lowest P-value in the Tier 2 patient-control series of the first PD GWAS. We employed four case-control series to examine the nominated SNP rs11155313 and identified association in US (OR: 1.39, P=0.032), Canadian (OR: 1.41, P=0.014) and Irish (OR: 1.44, P=0.034) patient-control series, but not in the Norwegian series (OR: 1.15, P=0.27). When combining all four series the observed trend was statistically significant (OR: 1.30, P<0.001). This study shows reappraisal of publicly available results of GWAS may help nominate new risk factors for PD.
Genome-wide association; Parkinson's disease; Phactr2
Perry syndrome consists of early-onset parkinsonism, depression, severe weight loss and hypoventilation, in which brain pathology is characterized by TDP-43 immunostaining. Through genome-wide linkage analysis we have identified five disease-segregating dynactin (DCTN1) CAP-Gly domain substitutions in 8 families that diminish microtubule binding and lead to intracytoplasmic inclusions. DCTN1 mutations were previously associated with motor neuron disease but can underlie the selective vulnerability of other neuronal populations in distinct neurodegenerative disorders.
Dynactin; DCTN1; Perry syndrome; parkinsonism; neurodegeneration; TDP-43
Genetic studies have led to major discoveries in the pathogenesis of various neurodegenerative diseases. Ubiquitin-positive familial frontotemporal dementia was recently found to be caused by mutations in the progranulin gene (PGRN), and the major constituent of the inclusions, TDP-43, was subsequently identified. The tau gene (MAPT) causes frontotemporal dementia with parkinsonism linked to chromosome 17. In Parkinson disease, LRRK2 mutations have emerged as a major cause of both familial and sporadic forms, adding to the previously known genes SNCA, PRKN, DJ1 and PINK1. Several genes have been implicated in Alzheimer disease, including the APP gene and the PSEN genes. Recently, variants in the sortilin-related receptor 1 gene, SORL1, were associated with Alzheimer disease.
Alzheimer disease; Dementia; Frontotemporal dementia; Frontotemporal lobar degeneration; Neurodegeneration; Parkinson disease