Major progress in genetic studies of Parkinson's disease (PD) and parkinsonism has been achieved in the last two decades. Objective: We provide a brief review of the current status of PARK and non-PARK loci/genes, and discuss two new genes: eIF4G1 and VPS35.
The literature on PARK and non-PARK loci/genes was reviewed and some novel information on two new genes is provided.
There are 18 PARK loci. The symptomatic carriers of these genes usually present with parkinsonism, although additional clinical features can be seen during the course of the disease. Carriers of non-PARK loci/genes frequently present with a mixed phenotype that includes parkinsonism and additional clinical features. Carriers of the eIF4G1 and VPS35 genes present with a parkinsonian phenotype. The pathology of eIF4G1 is of the α-synuclein type; the pathology of VPS35 is unknown.
The current genetic classification of PD/parkinsonism genes is not ideal. The pathological classification based on the accumulation of particular proteins/inclusions is also misleading since there are kindred with a single mutation but pleomorphic pathology. A better classification of neurodegenerative conditions is needed. It is hoped that the genetic studies will lead to better therapies.
Genetics; Parkinsonism; SNCA; PRKN; LRRK2; GBA; eIF4G1; VPS35
The genetic cause of late-onset focal and segmental dystonia remains unknown in most individuals. Recently, mutations in Thanatos-associated protein domain containing, apoptosis associated protein 1 (THAP1) have been described in DYT6 dystonia and associated with some cases of familial and sporadic late-onset dystonia in Caucasians. We are not aware of any previous descriptions of familial dystonia in African Americans or reports of THAP1 mutations in African Americans. Herein, we characterize an African-American (AA) kindred with late-onset primary dystonia, clinically and genetically. The clinical phenotype included cervical, laryngeal and hand-forearm dystonia. Symptoms were severe and disabling for several family members, whereas others only displayed mild signs. There were no accompanying motor or cognitive signs. In this kindred, age of onset ranged from 45 to 50 years and onset was frequently sudden, with symptoms developing within weeks or months. DYT1 was excluded as the cause of dystonia in this kindred. The entire genomic region of THAP1, including non-coding regions, was sequenced. We identified 13 sequence variants in THAP1, although none co-segregated with dystonia. A novel THAP1 variant (c.-237-3G>T/A) was found in 3/84 AA dystonia patient alleles and 3/212 AA control alleles, but not in 5,870 Caucasian alleles. In summary, although previously unreported, familial primary dystonia does occur in African Americans. Genetic analysis of the entire genomic region of THAP1 revealed a novel variant that was specific for African Americans. Therefore, genetic testing for dystonia and future studies of candidate genes must take genetic background into consideration.
Dystonia; Genetics; African American; DYT6; THAP1; Adult-Onset Dystonias; Dystonia, Hereditary; Focal Dystonia
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
Fahr disease; brain calcinosis; idiopathic basal ganglia calcification
OBJECTIVE: To conduct clinical and molecular genetic analyses of the members of an extended family in Central Indiana with a high prevalence of restless legs syndrome (RLS).
PARTICIPANTS AND METHODS: From February 1, 2006, through August 31, 2008, we collected data from members of this family, which is of English descent. Genealogical methods were used to expand the family tree, and family members were screened with an RLS questionnaire. Telephone interviews and personal examinations were performed at Mayo Clinic and during a field trip to Central Indiana. Blood samples were collected for molecular genetic analysis. A follow-up telephone interview was conducted 1 year later.
RESULTS: The family tree spans 7 generations with 88 living members, 30 of whom meet the criteria for diagnosis of RLS established by the International Restless Legs Syndrome Study Group. Three affected family members also have Parkinson disease or essential tremor. The mode of RLS inheritance is compatible with an autosomal dominant pattern. The affected family members do not exhibit linkage to the 5 known RLS loci or mutations in the RLS susceptibility genes MEIS1 and BTBD9.
CONCLUSION: Of 88 members of this single extended family in Central Indiana, 30 were diagnosed as having RLS. Because our analysis shows that the disease is not linked to any of the known RLS loci or risk-associated genes, we postulate that members of this family may carry a gene mutation in a novel genetic locus.
Of 88 members of a single extended family, 30 were diagnosed as having restless legs syndrome; because this analysis shows that the disease is not linked to any of the known restless legs syndrome loci or risk-associated genes, members of this family may carry a gene mutation in a novel genetic locus.
episodic ataxia type 2; CACNA1A; p.R1346Stop; acetazolamide; cerebellar vermis
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
Mutations within the NOTCH3 gene cause cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). CADASIL mutations appear to be restricted to the first twenty-four exons, resulting in the gain or loss of a cysteine amino acid. The role of other exonic NOTCH3 variation not involving cysteine residues and mutations in exons 25-33 in ischemic stroke remains unresolved.
All 33 exons of NOTCH3 were sequenced in 269 Caucasian probands from the Siblings With Ischemic Stroke Study (SWISS), a 70-center North American affected sibling pair study and 95 healthy Caucasian control subjects. Variants identified by sequencing in the SWISS probands were then tested for association with ischemic stroke using US Caucasian controls collected at the Mayo Clinic (n=654), and further assessed in a Caucasian (n=802) and African American (n=298) patient-control series collected through the Ischemic Stroke Genetics Study (ISGS).
Sequencing of the 269 SWISS probands identified one (0.4%) with small vessel type stroke carrying a known CADASIL mutation (p.R558C; Exon 11). Of the 19 common NOTCH3 variants identified, the only variant significantly associated with ischemic stroke after multiple testing adjustment was p.R1560P (rs78501403; Exon 25) in the combined SWISS and ISGS Caucasian series (Odds Ratio [OR] 0.50, P=0.0022) where presence of the minor allele was protective against ischemic stroke. Although only significant prior to adjustment for multiple testing, p.T101T (rs3815188; Exon 3) was associated with an increased risk of small-vessel stroke (OR: 1.56, P=0.008) and p.P380P (rs61749020; Exon 7) was associated with decreased risk of large-vessel stroke (OR: 0.35, P=0.047) in Caucasians. No significant associations were observed in the small African American series.
Cysteine-affecting NOTCH3 mutations are rare in patients with typical ischemic stroke, however our observation that common NOTCH3 variants may be associated with risk of ischemic stroke warrants further study.
Given the overlap between Parkinson disease and essential tremor, we examined genetic variants in α-synuclein (SNCA) as risk determinants for essential tremor.
Samples from 661 essential tremor subjects and 1,316 control subjects from four participating North American sites were included in this study. Parkinson disease samples (n=427) were compared against controls for two cohorts. Twenty variants were selected for association analysis within the SNCA locus. Individual logistic regression analyses against essential tremor diagnosis and then combined using meta-analysis was run for each variant.
Our results do not show a significant association between variants in the SNCA locus and risk of essential tremor, while the established association of SNCA variants with Parkinson disease risk was observed.
While genetic factors are likely to play a large role in essential tremor pathogenesis our results do not support a role for common SNCA genetic variants in risk for essential tremor.
tremor; essential tremor; association studies in genetics; Parkinson’s disease; parkinsonism; synuclein
An extensive variety of THAP1 sequence variants have been associated with focal, segmental and generalized dystonia with age of onset ranging from 3 to over 60 years. In previous work, we screened 1,114 subjects with mainly adult-onset primary dystonia (Neurology 2010;74:229-238) and identified 6 missense mutations in THAP1. For this report, we screened 750 additional subjects for mutations in coding regions of THAP1 and interrogated all published descriptions of THAP1 phenotypes (gender, age of onset, anatomical distribution of dystonia, family history and site of onset) to explore the possibility of THAP1 genotype-phenotype correlations and facilitate a deeper understanding of THAP1 pathobiology. We identified 5 additional missense mutations in THAP1 (p.A7D, p.K16E, p.S21C, p.R29Q, and p.I80V). Three of these variants are associated with appendicular tremors, which were an isolated or presenting sign in some of the affected subjects. Abductor laryngeal dystonia and mild blepharospasm can be manifestations of THAP1 mutations in some individuals. Overall, mean age of onset for THAP1 dystonia is 16.8 years and the most common sites of onset are the arm and neck, and the most frequently affected anatomical site is the neck. In addition, over half of patients exhibit either cranial or laryngeal involvement. Protein truncating mutations and missense mutations within the THAP domain of THAP1 tend to manifest at an earlier age and exhibit more extensive anatomical distributions than mutations localized to other regions of THAP1.
Dystonia; THAP1; DYT6; Spasmodic dysphonia; Tremor
Aims and objectives
A new pathomechanism of Parkinson’s disease (PD) involving regulation of mitochondrial functions was recently proposed. Parkin complexed with mitochondrial transcription factor A (TFAM) binds mtDNA and promotes mitochondrial biogenesis, which is abolished by PARK2 gene mutations. We have previously shown that mitochondrial haplogroups/clusters and TFAM common variation influenced PD risk. We investigate the role of PARK2 polymorphisms on PD risk and their interactions with mitochondrial haplogroups/clusters as well as with TFAM variability.
104 early-onset PD patients (EOPD, age at onset ≤ 50 years) were screened for PARK2 coding sequence changes including gene dosage alterations. Three selected PARK2 polymorphisms (S167N, V380L, D394N) were genotyped in 326 PD patients and 315 controls using TaqMan allelic discrimination assay.
PARK2 screen revealed two heterozygous changes in two EOPD patients: exon 2 deletion and one novel synonymous variation (c.999C>A, P333P).
In association study no differences in genotype/allele frequencies of S167N, V380L, D394N were found between analyzed groups. Stratification by mitochondrial clusters revealed higher frequency of V380L G/G genotype and allele G in PD patients, within HV cluster (p=0.040; p=0.022, respectively). Moreover, interaction between genotypes G/G V380L of PARK2 and G/G rs2306604 of TFAM, within HV cluster was significant (OR 2.05; CI 1.04 – 4.04; p=0.038).
Our results indicate that co-occurence of G/G V380L PARK2 and G/G rs2306604 TFAM on the prooxidative HV cluster background can contribute to PD risk. We confirm low PARK2 mutation frequency in Polish EOPD patients.
Parkinson’s disease risk factors; PARK2; mitochondrial clusters; mitochondrial transcription factor A (TFAM)
The c.4309A>C mutation in the LRRK2 gene (LRRK2 p.N1437H) has recently been reported as the seventh pathogenic LRRK2 mutation causing monogenic Parkinson's disease (PD). So far, only two families worldwide have been identified with this mutation. By screening DNA from seven brains of PD patients, we found one individual with seemingly sporadic PD and LRRK2 p.N1437H mutation. Clinically, the patient had levodopa-responsive PD with tremor, and developed severe motor fluctuations during a disease duration of 19 years. There was severe and painful ON-dystonia, and severe depression with suicidal thoughts during OFF. In the advanced stage, cognition was slow during motor OFF, but there was no noticeable cognitive decline. There were no signs of autonomic nervous system dysfunction. Bilateral deep brain stimulation of the subthalamic nucleus had unsatisfactory results on motor symptoms. The patient committed suicide. Neuropathological examination revealed marked cell loss and moderate alpha-synuclein positive Lewy body pathology in the brainstem. There was sparse Lewy pathology in the cortex. A striking finding was very pronounced ubiquitin-positive pathology in the brainstem, temporolimbic regions and neocortex. Ubiquitin positivity was most pronounced in the white matter, and was out of proportion to the comparatively weaker alpha-synuclein immunoreactivity. Immunostaining for tau was mildly positive, revealing non-specific changes, but staining for TDP-43 and FUS was entirely negative. The distribution and shape of ubiquitin positive lesions in this patient differed from the few previously described patients with LRRK2 mutations and ubiquitin pathology, and the ubiquitinated protein substrate remains undefined.
Autosomal Dominant Parkinsonism; LRRK2; alpha-Synuclein; Ubiquitin; Deep Brain Stimulation; Suicide
PD; ANG; genetic association; mutation
Previous studies demonstrated decreased levels of DJ-1 and α-synuclein (αSYN) in human cerebrospinal fluid (CSF) in patients with Parkinson’s disease (PD), but neither marker correlated with PD severity, raising the possibility that they may be excellent progression markers during early or preclinical phases of PD. Individuals carrying the leucine-rich repeat kinase 2 (LRRK2) gene mutation are at increased risk for PD, and the phenotype of LRRK2 patients is almost identical to sporadic PD. To determine whether dopaminergic dysfunction in the basal ganglia, as determined by positron emission tomography (PET) scans, correlates with CSF levels of DJ-1 and αSYN during preclinical stages, Luminex assays were used to analyze CSF samples from asymptomatic LRRK2 mutation carriers, along with carriers who presented with a clinical diagnosis of PD. The data revealed no statistically significant relationship between PET scan evidence of loss of striatal dopaminergic function and the CSF biomarkers DJ-1 and αSYN, except for a weak correlation between DJ-1 and MP binding, suggesting that the use of these potential biomarkers on their own to screen LRRK2 gene mutation carriers for PD is not appropriate.
Parkinson’s Disease; LRRK2; gene mutation; biomarker; DJ-1; α-synuclein
Primary dystonia is usually of adult onset, can be familial, and frequently involves the cervical musculature. Our goal was to identify the causal mutation in a family with adult-onset, primary cervical dystonia.
Linkage and haplotype analyses were combined with solution-based whole-exome capture and massively parallel sequencing in a large Caucasian pedigree with adult-onset, primary cervical dystonia to identify a cosegregating mutation. High-throughput screening and Sanger sequencing were completed in 308 Caucasians with familial or sporadic adult-onset cervical dystonia and matching controls for sequence variants in this mutant gene.
Exome sequencing led to the identification of an exonic splicing enhancer mutation in Exon 7 of CIZ1 (c.790A>G, p.S264G) which encodes CIZ1, Cip1-interacting zinc finger protein 1. CIZ1 is a p21Cip1/Waf1-interacting zinc finger protein expressed in brain and involved in DNA synthesis and cell-cycle control. Using a minigene assay, we showed that c.790A>G altered CIZ1 splicing patterns. The p.S264G mutation also altered the nuclear localization of CIZ1. Screening in subjects with adult-onset cervical dystonia identified two additional CIZ1 missense mutations (p.P47S and p.R672M).
Mutations in CIZ1 may cause adult-onset, primary cervical dystonia, possibly by precipitating neurodevelopmental abnormalities that manifest in adults and/or G1/S cell-cycle dysregulation in the mature central nervous system.
Hereditary diffuse leukoencephalopathy with spheroids (HDLS) was originally described in a large Swedish pedigree. Since then, 22 reports describing a total of 13 kindred's and 11 sporadic cases have been published. Inheritance is autosomal dominant, albeit the gene is unknown. Here we report on the clinical findings, genealogical data, brain MRI data, and autopsy/biopsy findings of four probands from three independently ascertained novel families from Norway, Germany and US.
We identified a 39-year-old female and her twin sister, a 52-year-old male and a 47-year-old male with progressive neurological illness characterized by personality changes, cognitive decline and motor impairments, such as gait problems, bradykinesia, tremor and rigidity. Brain MRI showed white matter abnormalities with frontal prominence. Brain biopsy/autopsies were consistent with HDLS.
HDLS is an under-recognized disease and in reporting these cases, we aim to increase the awareness of the disorder. Due to varied and wide phenotypic presentations, which may imitate several neurodegenerative diseases, HDLS can be difficult to diagnose. Definitive diagnosis can be established only by direct brain tissue examination. Familiarity with the clinical presentation and typical neuroimaging findings may be helpful in narrowing the diagnosis.
HDLS; White matter disease; Autosomal dominant; Personality changes; Cognitive problems; Depression; Parkinsonism
Insertion and deletion variants (indels) within poly glycine tracts of fused in sarcoma (FUS) were initially reported as causative of disease in amyotrophic lateral sclerosis (ALS). Subsequent studies identified similar indels in controls and suggested that these indels may confer susceptibility to ALS. We aimed to elucidate the role of previously published and novel exonic indels in FUS in an extensive cohort of 630 ALS patients and 1063 controls. We detected indels in FUS exons 5, 6, 12 and 14 with similar frequencies in patients (0.95%) and controls (0.75%). Exonic indels in poly glycine tracts were also observed with similar frequencies. The largest indel (p.Gly138_Tyr143del) was observed in one control. In one patient, a 3 base pair deletion in exon 14 (p.Gly475del) was identified, however in-vitro studies did not reveal abnormal localization of p.Gly475del mutant FUS. These findings suggest that not all exonic indels in FUS cause disease.
Autosomal Dominant Cerebellar Ataxia (ADCA) Type III is a type of spinocerebellar ataxia (SCA) classically characterized by pure cerebellar ataxia and occasionally by non-cerebellar signs such as pyramidal signs, ophthalmoplegia, and tremor. The onset of symptoms typically occurs in adulthood; however, a minority of patients develop clinical features in adolescence. The incidence of ADCA Type III is unknown. ADCA Type III consists of six subtypes, SCA5, SCA6, SCA11, SCA26, SCA30, and SCA31. The subtype SCA6 is the most common. These subtypes are associated with four causative genes and two loci. The severity of symptoms and age of onset can vary between each SCA subtype and even between families with the same subtype. SCA5 and SCA11 are caused by specific gene mutations such as missense, inframe deletions, and frameshift insertions or deletions. SCA6 is caused by trinucleotide CAG repeat expansions encoding large uninterrupted glutamine tracts. SCA31 is caused by repeat expansions that fall outside of the protein-coding region of the disease gene. Currently, there are no specific gene mutations associated with SCA26 or SCA30, though there is a confirmed locus for each subtype. This disease is mainly diagnosed via genetic testing; however, differential diagnoses include pure cerebellar ataxia and non-cerebellar features in addition to ataxia. Although not fatal, ADCA Type III may cause dysphagia and falls, which reduce the quality of life of the patients and may in turn shorten the lifespan. The therapy for ADCA Type III is supportive and includes occupational and speech modalities. There is no cure for ADCA Type III, but a number of recent studies have highlighted novel therapies, which bring hope for future curative treatments.
SCA5; SCA6; SCA11; SCA26; SCA30; SCA31; SPTBN2; CACNA1A; TTBK2; BEAN
Frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) are part of a disease spectrum associated with TDP-43 pathology. Strong evidence supporting this is the existence of kindreds with family members affected by FTD, ALS or mixed features of FTD and ALS, referred to as FTD-MND. Some of these families have linkage to chromosome 9, with hexanucleotide expansion mutation in a noncoding region of C9ORF72. Discovery of the mutation defines c9FTD/ALS. Prior to discovery of mutations in C9ORF72, it was assumed that TDP-43 pathology in c9FTD/ALS was uniform. In this study, we examined the neuropathology and clinical features of 20 cases of c9FTD/ALS from a brain bank for neurodegenerative disorders. Included are six patients clinically diagnosed with ALS, eight FTD, one FTD-MND and four Alzheimer type dementia. Clinical information was unavailable for one patient. Pathologically, the cases all had TDP-43 pathology, but there were three major pathologic groups: ALS, FTLD-MND and FTLD-TDP. The ALS cases were morphologically similar to typical sporadic ALS with almost no extramotor TDP-43 pathology; all had oligodendroglial cytoplasmic inclusions. The FTLD-MND showed predominantly Mackenzie Type 3 TDP-43 pathology, and all had ALS-like pathology in motor neurons, but more extensive extramotor pathology, with oligodendroglial cytoplasmic inclusions and infrequent hippocampal sclerosis. The FTLD-TDP cases had several features similar to FTLD-TDP due to mutations in the gene for progranulin, including Mackenzie Type 1 TDP-43 pathology with neuronal intranuclear inclusions and hippocampal sclerosis. FTLD-TDP patients were older and some were thought to have Alzheimer type dementia. In addition to the FTD and ALS clinical presentations, the present study shows that c9FTD/ALS can have other presentations, possibly related to age of onset and presence of hippocampal sclerosis. Moreover, there is pathologic heterogeneity not only between ALS and FTLD, but within the FTLD group. Further studies are needed to address the molecular mechanism of clinical and pathological heterogeneity of c9FTD/ALS due to mutations in C9ORF72.
Patients with corticobasal degeneration can present with several different clinical syndromes, making ante-mortem diagnosis a challenge. Corticobasal syndrome is the clinical phenotype originally described for corticobasal degeneration, characterized by asymmetric rigidity and apraxia, cortical sensory deficits, dystonia and myoclonus. Some patients do not develop these features, but instead have clinical features consistent with the Richardson syndrome presentation of progressive supranuclear palsy, characterized by postural instability, early unexplained falls, vertical supranuclear gaze palsy, symmetric motor disability and dysphagia. The aim of this study was to identify differences in corticobasal degeneration presenting with corticobasal syndrome (n = 11) or Richardson syndrome (n = 15) with respect to demographic, clinical and neuropathological features. Corticobasal degeneration cases were also compared with patients with pathologically proven progressive supranuclear palsy with Richardson syndrome (n = 15). Cases with corticobasal degeneration, regardless of presentation, shared histopathological and tau biochemical characteristics, but they had differing densities of tau pathology in neuroanatomical regions that correlated with their clinical presentation. In particular, those with corticobasal syndrome had greater tau pathology in the primary motor and somatosensory cortices and putamen, while those with Richardson syndrome had greater tau pathology in limbic and hindbrain structures. Compared with progressive supranuclear palsy, patients with corticobasal degeneration and Richardson syndrome had less neuronal loss in the subthalamic nucleus, but more severe neuronal loss in the medial substantia nigra and greater atrophy of the anterior corpus callosum. Clinically, they had more cognitive impairment and frontal behavioural dysfunction. The results suggest that Richardson syndrome can be a clinicopathological presentation of corticobasal degeneration. Atrophy of anterior corpus callosum may be a potential neuroimaging marker to differentiate corticobasal degeneration from progressive supranuclear palsy in patients with Richardson syndrome.
pathology; immunocytochemistry; progressive supranuclear palsy; tau protein; corticobasal degeneration
A role for the immune system in the pathogenesis of Parkinson’s Disease (PD) has previously been suggested. A recent genome-wide association (GWA) study identified an association between one single nucleotide polymorphism (SNP) in the human leucocyte antigen (HLA) region (HLA-DRA rs3129882) and PD in a population of American patients with European ancestry. In that study, the minor rs3129882 allele (G) was associated with an increased risk of PD under an additive model. Due to the increased likelihood of obtaining false positive results in GWA studies compared to studies conducted based on a hypothesis-driven approach, repeated validation of findings from GWA studies are necessary. Herein, we evaluated the association between rs3129882 and PD in three different Caucasian patient-control series (combined 1,313 patients and 1,305 controls) from the US, Ireland, and Poland. We observed no association (OR: 0.96, P=0.50) between rs3129882 and PD when analyzing our data under an additive or dominant model. In contrast, when examined under a recessive model, the GG genotype was observed to be protective in the Irish (OR: 0.55, P=0.008), Polish (OR: 0.67, P=0.040) and combined (OR: 0.75, P=0.006) patient-control series. In view of these diverging results, the exact role of genetic variation at the HLA region and susceptibility to PD remains to be resolved.
Association studies; Parkinson’s disease; Human leukocyte antigen; HLA; HLA-DRA; Immune system; Genetics
Sequence variants in coding and non-coding regions of THAP1 have been associated with primary dystonia. In this study, 1446 Caucasian subjects with mainly adult-onset primary dystonia and 1520 controls were genotyped for a variant located in the 5’-untranslated region of THAP1 (c.-237_236GA>TT). Minor allele frequencies were 62/2892 (2.14%) and 55/3040 (1.81%) in subjects with dystonia and controls, respectively (P = 0.202). Subgroup analyses by gender and anatomical distribution also failed to attain statistical significance. In addition, there was no effect of the TT variant on expression levels of THAP1 transcript or protein. Our findings indicate that the c.-237_236GA>TT THAP1 sequence variant does not increase risk for adult-onset primary dystonia in Caucasians.
dystonia; DYT6; high-resolution melting; untranslated region; THAP1
A major recent discovery was the identification of an expansion of a non-coding GGGGCC hexanucleotide repeat in the C9ORF72 gene in patients with frontotemporal dementia and amyotrophic lateral sclerosis. Mutations in two other genes are known to account for familial frontotemporal dementia: microtubule-associated protein tau and progranulin. Although imaging features have been previously reported in subjects with mutations in tau and progranulin, no imaging features have been published in C9ORF72. Furthermore, it remains unknown whether there are differences in atrophy patterns across these mutations, and whether regional differences could help differentiate C9ORF72 from the other two mutations at the single-subject level. We aimed to determine the regional pattern of brain atrophy associated with the C9ORF72 gene mutation, and to determine which regions best differentiate C9ORF72 from subjects with mutations in tau and progranulin, and from sporadic frontotemporal dementia. A total of 76 subjects, including 56 with a clinical diagnosis of behavioural variant frontotemporal dementia and a mutation in one of these genes (19 with C9ORF72 mutations, 25 with tau mutations and 12 with progranulin mutations) and 20 sporadic subjects with behavioural variant frontotemporal dementia (including 50% with amyotrophic lateral sclerosis), with magnetic resonance imaging were included in this study. Voxel-based morphometry was used to assess and compare patterns of grey matter atrophy. Atlas-based parcellation was performed utilizing the automated anatomical labelling atlas and Statistical Parametric Mapping software to compute volumes of 37 regions of interest. Hemispheric asymmetry was calculated. Penalized multinomial logistic regression was utilized to create a prediction model to discriminate among groups using regional volumes and asymmetry score. Principal component analysis assessed for variance within groups. C9ORF72 was associated with symmetric atrophy predominantly involving dorsolateral, medial and orbitofrontal lobes, with additional loss in anterior temporal lobes, parietal lobes, occipital lobes and cerebellum. In contrast, striking anteromedial temporal atrophy was associated with tau mutations and temporoparietal atrophy was associated with progranulin mutations. The sporadic group was associated with frontal and anterior temporal atrophy. A conservative penalized multinomial logistic regression model identified 14 variables that could accurately classify subjects, including frontal, temporal, parietal, occipital and cerebellum volume. The principal component analysis revealed similar degrees of heterogeneity within all disease groups. Patterns of atrophy therefore differed across subjects with C9ORF72, tau and progranulin mutations and sporadic frontotemporal dementia. Our analysis suggested that imaging has the potential to be useful to help differentiate C9ORF72 from these other groups at the single-subject level.
frontotemporal dementia; magnetic resonance imaging; C9ORF72; tau; progranulin
Progressive supranuclear palsy (PSP) is a movement disorder with prominent tau neuropathology. Brain diseases with abnormal tau deposits are called tauopathies, the most common being Alzheimer’s disease. Environmental causes of tauopathies include repetitive head trauma associated with some sports. To identify common genetic variation contributing to risk for tauopathies, we carried out a genome-wide association study of 1,114 PSP cases and 3,247 controls (Stage 1) followed up by a second stage where 1,051 cases and 3,560 controls were genotyped for Stage 1 SNPs that yielded P ≤ 10−3. We found significant novel signals (P < 5 × 10−8) associated with PSP risk at STX6, EIF2AK3, and MOBP. We confirmed two independent variants in MAPT affecting risk for PSP, one of which influences MAPT brain expression. The genes implicated encode proteins for vesicle-membrane fusion at the Golgi-endosomal interface, for the endoplasmic reticulum unfolded protein response, and for a myelin structural component.