Dopamine turnover increases in asymptomatic LRRK2 mutations carriers

Increase in dopamine (DA) turnover was found to occur early in symptomatic Parkinson's disease (PD) and to be functionally related to the dopamine transporter (DAT). The objectives of this study were to examine changes in DA turnover in the asymptomatic PD phase; to compare them with changes in other dopaminergic markers, and to investigate a possible relationship between DAT and DA turnover. Eight subjects from families at increased risk of PD due to LRRK2 mutation were investigated. Positron emission tomography imaging was performed with: ¹⁸F‐fluorodopa to determine the effective DA distribution volume (EDV), the inverse of DA turnover, and the DA uptake rate K_occ, a marker of DA synthesis and storage; ¹¹C‐methylphenidate (MP, a DAT marker) and ¹¹C‐dihydrotetrabenazine (DTBZ, a VMAT2 marker) to estimate the binding potentials BP_{ND_MP} and BP_{ND_DTBZ}. On average, EDV showed the largest reduction from age‐matched control values (42%) followed by BP_{ND _ MP} (23%) and BP_{ND _ DTBZ} (17%), whereas K_occ remained in the normal range for all subjects. No correlation was found between EDV and any other marker. DA turnover was found to be elevated in asymptomatic mutation carriers at increased risk of PD. Such change was determined to be larger than and statistically independent from changes observed with the other markers. These results support a compensatory role of increased DA turnover in presymptomatic disease and indicate that at this stage, in contrast to the symptomatic PD phase, increased turnover is not related to DAT. © 2010 Movement Disorder Society     

Parkinson's disease in Ireland: clinical presentation and genetic heterogeneity in patients with parkin mutations.

Early-onset autosomal recessive parkinsonism is associated with parkin gene mutations. Different parkin mutations occur in many ethnic backgrounds; however, the phenotype may vary. We studied 102 young-onset (age at onset <60 years) Parkinson's disease (PD) patients. From 102 patients, 40 with early-onset PD (<45 years at symptomatic onset) were selected for clinical assessment and parkin gene molecular analysis for duplications/deletions and point mutations. We identified parkin mutations in 7 of 40 early-onset patients; including novel compound heterozygotes and potential splice site changes. The mean age at onset in the 7 parkin mutation-positive patients was 33 +/- 9 years (age range, 18-42 years), marginally lower than that of the 33 parkin-negative early-onset patients, 38 +/- 7 years (age range, 17-45 years). A family history of PD was present in 4 of 7 patients with parkin mutations, compared with 6 of 33 early-onset parkin-negative patients. Overall, parkin mutations were found in 4 of 10 patients with a positive family history and 3 of 30 patients without a family history of PD. Patients with parkin mutations had more dystonia, dyskinesia, and sleep benefit compared with parkin-negative patients. We subsequently identified a single point mutation among the 62 young-onset (age at onset 45 to <60 years). Mutations in the parkin gene may account for approximately 17% of early-onset (age at onset <45 years) parkinsonism in Ireland, in agreement with previous European studies.     

家族性帕金森病患者parkin基因缺失突变的初步研究

目的 探讨中国家族性帕金森病（PD）患者parkin基因第3-7外显子是否存在缺失突变，及其与该病临床特点的关系。方法 采集6例无血缘相关的家族性PD患者外周血液，提取DNA，通过PCR扩增，琼脂糖凝胶电泳鉴定parkin基因第3-7外显子缺失突变，并结合临床资料分析。结果 6例患者中，发现1例有第5外显子缺失，其遗传模式呈常染色体隐性遗传，起病年龄60岁，临床表现为震颤，僵直和运动迟缓，但无异动症，第3、4、6、7外显子未发现缺失突变。结论 中国家族性PD患者中存在parkin基因和5外显子缺失突变改变。     

Mitochondrial complex I and IV activities in leukocytes from patients with parkin mutations.

The parkin protein functions as a RING-type ubiquitin protein ligase. Considering the possibility that impaired ubiquitin-proteosomal system activity may impair antioxidant defenses and enhance oxidative stress, we have investigated the activity of mitochondrial respiratory enzymes in patients with parkin gene mutations. A significant decrease in the leukocyte complex I activity was found both in patients with parkin mutations (62.5%) and idiopathic PD (64.5%) compared with age-matched controls (P < 0.001). Complex IV activity was also decreased significantly in idiopathic PD patients (60%), but no difference was detected between controls and patients with parkin mutations.     

Cognitive impairment in carriers of glucocerebrosidase gene mutation in Parkinson disease patients

AimParkinson disease (PD) is the common neurodegenerative disease with motor and numerous non-motor symptoms, including cognitive impairment. Mutation of glucocerebrosidase (GBA) gene is the most common genetic risk factor of sporadic PD. The aim of this study was to assess clinical features of PD associated with GBA mutation.MethodsOne hundred and thirty-eight PD patients were involved and examined by the movement disorder specialist using several scales including Unified Parkinson Disease Rating Scale (UPDRS) part II and III, Hoehn and Yahr (H&Y) staging, Mini-Mental State Examination (MMSE) and Hamilton Depression Scale (HDS). The exons 8 and 9 of GBA was sequenced and screened for variants.ResultsThe GBA variants were found in 16 (11.6%) PD patients: N370S mutation in 5 (3.6%) and T369M variant in 11 (7.9%). No significant differences between the group of mutation carriers and non-carriers were found in relation to clinical features except for dementia (MMSE score < 26) occurring more often in N370S mutation carriers (60.0% vs 19.6%, p = 0.03).ConclusionThe N370S GBA mutation is the risk factor for cognitive impairment in PD patients.     

Familial Parkinsonism with digenic parkin and PINK1 mutations

To clarify the genetic correlation between parkin and PINK1, we screened for PINK1 mutations in 175 parkinsonism patients with parkin mutations. We detected two sibling pairs and one sporadic patient carrying both parkin and PINK1 mutations. The age at onset of Parkinsonism of patients with the digenic mutations was lower than that of patients with the same parkin mutation alone. In addition, two of three patients carrying both parkin and PINK1 mutations had schizophrenia. These findings indicate that PINK1 mutation might modify parkin mutation‐positive Parkinsonism, and PINK1 mutations might be associated withpsychiatric disorders. © 2008 Movement Disorder Society     

Clinical and pathological characteristics of patients with Leucine‐rich repeat kinase‐2 mutations

Mutations in LRRK2 are the single most common known cause of Parkinson's disease (PD). Two new PD patients with LRRK2 mutation were identified from a cohort with extensive postmortem assessment. One of these patients harbors the R793M mutation and presented with the typical clinical and pathological features of PD. A novel L1165P mutation was identified in a second patient. This patient had the classical and pathological features of PD, but additionally developed severe neuropsychological symptoms and dementia associated with abundant neurofibrillary tangles in the hippocampal formation; features consistent with a secondary diagnosis of tangle‐predominant dementia. α‐Synuclein‐containing pathological inclusions in these patients also were highly phosphorylated at Ser‐129, similar to other patients with idiopathic PD. These two PD patients also were characterized by the presence of occasional cytoplasmic TDP‐43 inclusions in the temporal cortex, a finding that was not observed in three other patients with the G2019S mutation in LRRK2. These findings extend the clinical and pathological features that may be associated with LRRK2 mutations. © 2008 Movement Disorder Society     

Nigrostriatal dysfunction in homozygous and heterozygous parkin gene carriers: An 18F‐dopa PET progression study

Little is known about the rate of progression of striatal dysfunction in subjects with parkin‐linked parkinsonism. Being a heterozygous parkin gene carrier may confer susceptibility to Parkinson's disease (PD). In a previous ¹⁸F‐dopa PET study, we reported that 69% of carriers of a single parkin mutation showed subclinical loss of putamen dopaminergic function. Using serial ¹⁸F‐dopa PET, the present longitudinal study addresses rates of progression of nigrostriatal dysfunction in both compound heterozygous (parkin‐linked parkinsonism) and single heterozygous parkin gene carriers. Three symptomatic patients who were compound heterozygotes for parkin gene mutations and six asymptomatic heterozygous carriers were clinically assessed and had ¹⁸F‐dopa PET at baseline and again after 5 years. The patients with symptomatic parkin showed a mean 0.5% annual reduction in putamen ¹⁸F‐dopa uptake over 5 years while caudate ¹⁸F‐dopa uptake declined by a mean annual rate of 2 %. The asymptomatic heterozygote gene carriers showed a mean 0.56% annual reduction in putamen and 0.62 % annual reduction in caudate ¹⁸F‐dopa uptake. Neurological examination at both baseline and follow‐up showed no evidence of parkinsonism. Loss of nigrostriatal dysfunction in parkin‐linked parkinsonism occurs at a very slow rate compared to the 9–12% annual loss of putamen ¹⁸F‐dopa uptake reported for idiopathic PD. Although subclinical reductions of striatal ¹⁸F‐dopa uptake are common in carriers of a single parkin mutation their slow rate of progression suggests that few if any of these will develop clinical parkinsonism. © 2009 Movement Disorder Society     

Novel compound heterozygous FBXO7 mutations in a family with early onset Parkinson's disease

BackgroundMutations in the F-box protein 7 (FBXO7) gene result in autosomal recessive parkinsonism. This usually manifests as early-onset parkinsonian-pyramidal syndrome but patients exhibit high phenotypic variability. Here we describe the findings of a Yemeni family with two novel FBXO7 mutations.MethodsClinical data and DNA were available for three siblings with early-onset parkinsonism together with their parents and three unaffected siblings. A targeted next generation sequencing panel was used to screen the proband for mutations in 14 genes known to cause a parkinsonian disorder. In addition, SNCA, PARK2, PINK1, and PARK7 were screened for copy number variants.ResultsThe proband carried two novel compound heterozygous FBXO7 mutations: a missense mutation in exon 1 (p.G39R; c.115G > A) and a frameshift mutation in exon 5 (p.L280fs; c.838del). The mutations segregated with disease in the family with the exception of a potentially pre-symptomatic individual whose age was below the age of onset in two of their three affected siblings. P.G39R occurred at a highly conserved amino acid residue and both mutations were predicted to be deleterious in silico. In contrast to most reported families, the phenotype in this pedigree was consistent with clinically typical Parkinson's disease (PD) with a lack of pyramidal signs and good response to dopaminergic therapy.ConclusionsOur study expands the phenotype associated with FBXO7 to include early-onset PD and broadens the list of causative mutations. These data suggest that FBXO7 should be included in clinical genetic testing panels for PD, particularly in patients with early onset or a recessive inheritance pattern.     

Abnormal cortical facilitation and L-dopa-induced dyskinesia in Parkinson's disease

BackgroundAnimal models of Parkinson's Disease (PD) demonstrated increased facilitatory cortico-striatal activity, reflecting overactive glutamatergic neurotransmission and contributing to the pathophysiology of l-dopa induced dyskinesias (LIDs).ObjectiveTo assess different facilitatory intracortical circuits in the primary motor cortex (M1) in patients with PD and LIDs by means of a combination of transcranial magnetic stimulation (TMS) protocols.MethodsWe tested the Input/Output (I/O) curve, intracortical facilitation (ICF) and short-interval intracortical facilitation (SICF) at baseline (T0), ‘OFF’ and ‘ON’ state, in 20 PD patients with LIDs. The same parameters were examined after 2 weeks of chronic intake of 50 mg (T1) and 100 mg/day (T2) of safinamide. Finally, we tested SICF in a further group of patients without LIDs.ResultsAt T0, patients with LIDs showed increased I/O curve steepness, which was partly ameliorated by l-dopa. These patients also had normal ICF, and abnormally increased SICF, which did not change with l-dopa. Safinamide improved the I/O curve both at T1 and T2, it reduced SICF at T1 and normalized this measure at T2. In patients with PD and LIDs, SICF correlated with the severity of dyskinesia. In patients without LIDs, SICF was less prominently abnormal and responsive to l-dopa.ConclusionsPatients with PD and LIDs have abnormal cortical facilitation, possibly suggesting overactive glutamatergic neurotransmission in specific circuits within M1. Although not responsive to l-dopa, this dysfunction is restored by the anti-glutamatergic properties of safinamide 100 mg. The results suggest that the abnormal cortical facilitation in M1 contributes to the pathophysiology of LIDs.     

Glucocerebrosidase gene mutations are associated with Parkinson's disease in southern Italy

Recent studies have reported an association between the glucocerebrosidase (GBA) gene and Parkinson's disease (PD). To elucidate the role of this gene in our population, we screened 395 PD patients and 483 controls from southern Italy for the N370S and the L444P mutations. We found 11 patients (2.8%) carrying a heterozygous mutant GBA allele, whereas only one control subject (0.2%) had a heterozygous substitution (P = 0.0018). These results strongly suggest that Italian carriers of a GBA mutation have an increased risk of developing PD. © 2007 Movement Disorder Society     

Glucocerebrosidase mutations in primary parkinsonism

IntroductionMutations in the lysosomal glucocerebrosidase (GBA) gene increase the risk of Parkinson's Disease (PD). We determined the frequency and relative risk of major GBA mutations in a large series of Italian patients with primary parkinsonism.MethodsWe studied 2766 unrelated consecutive patients with clinical diagnosis of primary degenerative parkinsonism (including 2350 PD), and 1111 controls. The entire cohort was screened for mutations in GBA exons 9 and 10, covering approximately 70% of mutations, including the two most frequent defects, p.N370S and p.L444P.ResultsFour known mutations were identified in heterozygous state: 3 missense mutations (p.N370S, p.L444P, and p.D443N), and the splicing mutation IVS10+1G>T, which results in the in-frame exon-10 skipping. Molecular characterization of 2 additional rare variants, potentially interfering with splicing, suggested a neutral effect. GBA mutations were more frequent in PD (4.5%, RR = 7.2, CI = 3.3–15.3) and in Dementia with Lewy Bodies (DLB) (13.8%, RR = 21.9, CI = 6.8–70.7) than in controls (0.63%). but not in the other forms of parkinsonism such as Progressive Supranuclear Palsy (PSP, 2%), and Corticobasal Degeneration (CBD, 0%). Considering only the PD group, GBA-carriers were younger at onset (52 ± 10 vs. 57 ± 10 years, P < 0.0001) and were more likely to have a positive family history of PD (34% vs. 20%, P < 0.001).ConclusionGBA dysfunction is relevant for synucleinopathies, such as PD and DLB, except for MSA, in which pathology involves oligodendrocytes, and the tauopathies PSP and CBD. The risk of developing DLB is three-fold higher than PD, suggesting a more aggressive phenotype.     

Death certificate data and causes of death in patients with parkinsonism

IntroductionAssessment of variables related to mortality in Parkinson disease (PD) and other parkinsonian syndromes relies, among other sources, on accurate death certificate (DC) documentation. We assessed the documentation of the degenerative disorder on DCs and evaluated comorbidities and causes of death among parkinsonian patients.MethodsDemographic and clinical data were systematically and prospectively collected on deceased patients followed at a tertiary movement disorder clinic. DCs data included the documentation of parkinsonism, causes, and place of death.ResultsAmong 138 cases, 84 (60.9%) male, mean age 77.9 years, mean age of onset 66.7, and mean disease duration 10.9 years. Clinical diagnoses included PD (73.9%), progressive supranuclear palsy (10.9%), multiple system atrophy (7.2%), Lewy body dementia (7.2%) and corticobasal degeneration (0.7%). Psychosis occurred in 60.1% cases, dementia in 48.5%. Most PD patients died due to heterogeneous causes before reaching advanced stages. Non-PD parkinsonian patients died earlier due to causes linked to the advanced neurodegenerative process. PD was documented in 38.4% of DCs with different forms of inconsistencies. That improved, but remained significant when it was signed by a specialist.ConclusionsMore than half of PD cases died while still ambulatory and independent, after a longer disease course and due to causes commonly seen in that age group. Deaths among advanced PD patients occurred due to causes similar to what we found in non-PD cases. These findings can be useful for clinical, prognostic and counseling purposes. Underlying parkinsonian disorders are poorly documented in DCs, undermining its' use as sources of data collection.     

Motor and non-motor features of Parkinson's disease that predict persistent drug-induced Parkinsonism

BackgroundDrug-induced Parkinsonism is common, causes significant morbidity, and can be clinically indistinguishable from idiopathic Parkinson's disease. Additionally, drug-induced Parkinsonism may, in some cases, represent “unmasking” of incipient Parkinson's disease. Clinical features or tests that distinguish degenerative from pharmacologic Parkinsonism are needed.MethodsWe performed a retrospective case-control study of 97 drug-induced Parkinsonism subjects and 97 age-matched patients with Parkinson's disease. We compared the frequency of subjective motor and non-motor complaints, objective motor findings (Unified Parkinson's Disease Rating Scale Part III) and, where available, objective olfactory tests. We also performed a nested case-control study wherein we compared these same features between drug-induced Parkinsonism patients based on whether or not they recovered after changing the offending agent.ResultsNon-motor symptoms including constipation and sexual dysfunction were more common in Parkinson's disease than in drug-induced Parkinsonism. While total motor scores were similar between groups, Postural Instability-Gait Difficulty scores were also higher in Parkinson's disease. Features that were significantly different or showed a trend towards significance in both comparisons included subjective loss of facial expression, dream-enactment behavior, autonomic complaints and Postural Instability-Gait Difficulty scores. Hyposmia was more common in Parkinson's disease and was strongly predictive of persistent drug-induced Parkinsonism after therapy change (odds ratio 30.3, 95% confidence interval: 1.5–500, p = 0.03).ConclusionsA constellation of motor and non-motor features may differentiate unmasked Parkinson's disease from drug-induced Parkinsonism. In particular, olfactory testing may offer a simple and inexpensive method to help predict outcomes in drug-induced Parkinsonism and, potentially, identify a cohort of pre-motor Parkinson's disease.     

It's a double knock-out! The quaking mouse is a spontaneous deletion of parkin and parkin co-regulated gene (PACRG).

Mutations in the parkin gene (PRKN) are the commonest cause of juvenile and early-onset parkinsonism. However, the pathogenic mechanism by which loss of parkin protein results in degeneration of dopaminergic neurons remains elusive. Animal models provide a useful tool for the study of development and disease, and the recent production of transgenic fly and mouse parkin deficient models allows investigation of the molecular role of parkin in dopamine regulation and nigrostriatal function. We have identified the mouse mutant Quaking as a spontaneously occurring PRKN knockout. The quaking mutation is a deletion of approximately 1.17 Mb of mouse chromosome 17, resulting in the deletion of the entire promoter and first five coding exons of PRKN In addition, the recently described Parkin Co-Regulated Gene (PACRG) is completely deleted. Homozygous Quaking mice show a complete loss of PRKN and PACRG mRNA and protein. These mice will constitute a useful additional model for studies of the molecular role of parkin and PACRG in neurodegeneration.     

Cognitive changes in asymptomatic carriers of the Huntington disease mutation gene

Huntington disease (HD) is a neurodegenerative disorder due to an excessive number of CAG repeats in the IT15 gene on chromosome 4. Studies of cognitive function in asymptomatic gene carriers have yielded contradictory results. This study compared cognitive performance in 44 subjects with the HD mutation (group of carriers) who had no clinical signs of HD and 39 at-risk individuals without HD mutation (group of non-carriers). Neuropsychological evaluation focused on global cognitive efficiency, psychomotor speed, attentional, executive and memory functions. Significant differences, with lower performances in the group of gene carriers, were detected for some measures of psychomotor speed, attention and executive functioning (all P  < 0.01). More differences between groups were observed for memory measures, in particular on the California Verbal Memory Test. Complementing these observations, cognitive scores were correlated with age in the group of gene carriers, but not in the group of non-carriers. This suggests that the cognitive changes precede the appearance of the motor and psychiatric symptoms in HD and that tests proved to be sensitive to early HD deficiencies are better suited than global cognitive efficiency scales to observe them.