Krisztina K. Johansen

Mitochondrial impairment in patients with Parkinson disease with the G2019S mutation in LRRK2

Objective: The LRRK2G2019S mutation is the most common identifiable cause for Parkinson disease (PD), but the underlying mechanisms leading to neuronal cell death remain largely unclear. Impaired mitochondrial function and morphology have been described in different in vivo and in vitro model systems of early-onset PD (EOPD) as well as in EOPD patient tissue. The aim of our study was to assess mitochondrial function and morphology in LRRK2G2019S mutant patient tissue to determine whether impaired mitochondrial function and morphology are shared features in early-onset and late-onset PD. Methods: Skin biopsies were taken from 5 patients with PD with the LRRK2G2019S mutation. Assessment of mitochondrial membrane potential and intracellular ATP levels as well as substrate-linked mitochondrial ATP production assays were all carried out on 3 independent cell preparations per patient. Results were compared to 5 age-matched controls. Mitochondrial elongation and interconnectivity was assessed using previously published methods. Results: Both mitochondrial membrane potential and total intracellular ATP levels were decreased in the G2019S mutation carriers. Subsequently undertaken mitochondrial ATP production assays suggested that the observed reduction is at least partially due to impaired mitochondrial function. Mitochondrial elongation and interconnectivity were increased in the LRRK2G2019S patient cohort. Conclusion: Our results provide evidence for impaired mitochondrial function and morphology in LRRK2G2019S mutant patient tissue. Further studies are required to determine whether the impaired mitochondrial function is due to increased LRRK2 kinase activity or other mechanisms such as LRRK2 haploinsufficiency.

Metabolomic Profiling in LRRK2-Related Parkinson's Disease

Background Mutations in LRRK2 gene represent the most common known genetic cause of Parkinsons disease (PD). Methodology/Principal Findings We used metabolomic profiling to identify biomarkers that are associated with idiopathic and LRRK2 PD. We compared plasma metabolomic profiles of patients with PD due to the G2019S LRRK2 mutation, to asymptomatic family members of these patients either with or without G2019S LRRK2 mutations, and to patients with idiopathic PD, as well as non-related control subjects. We found that metabolomic profiles of both idiopathic PD and LRRK2 PD subjects were clearly separated from controls. LRRK2 PD patients had metabolomic profiles distinguishable from those with idiopathic PD, and the profiles could predict whether the PD was secondary to LRRK2 mutations or idiopathic. Metabolomic profiles of LRRK2 PD patients were well separated from their family members, but there was a slight overlap between family members with and without LRRK2 mutations. Both LRRK2 and idiopathic PD patients showed significantly reduced uric acid levels. We also found a significant decrease in levels of hypoxanthine and in the ratios of major metabolites of the purine pathway in plasma of PD patients. Conclusions/Significance These findings show that LRRK2 patients with the G2019S mutation have unique metabolomic profiles that distinguish them from patients with idiopathic PD. Furthermore, asymptomatic LRRK2 carriers can be separated from gene negative family members, which raises the possibility that metabolomic profiles could be useful in predicting which LRRK2 carriers will eventually develop PD. The results also suggest that there are aberrations in the purine pathway in PD which may occur upstream from uric acid.

Novel Pathogenic LRRK2 p.Asn1437His Substitution in Familial Parkinson's Disease

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 A>C (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 of 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.

Amyloid-β and α-synuclein cerebrospinal fluid biomarkers and cognition in early Parkinson's disease

INTRODUCTION Cognitive impairment in early Parkinsons disease (PD) is common and distinct from early Alzheimers disease. Predictors and mechanisms are only partially known, but α-synuclein, amyloid-β and tau dysmetabolism may be involved. Our aim was to study associations between cerebrospinal fluid biomarkers (CSF) and cognition in non-dementia PD compared to normal controls (NC) and non-PD patients with mild cognitive impairment (MCI non-PD). METHODS Patients were classified as having normal, subjective or mild cognitive impairment after cognitive screening. CSF levels of total α-synuclein (t-α-syn), amyloid-β (Aβ) 38, 40 and 42, total tau (T-tau) and phosphorylated tau (P-tau) were measured in 34 NC, 31 early, non-dementia PD and 28 MCI non-PD patients. A well validated neuropsychological test battery was administered. RESULTS In the PD group, 13 had normal cognition, 4 had subjective and 14 mild cognitive impairment. PD patients had significantly lower CSF biomarker levels of t-α-syn, Aβ38, 40 and 42, T-tau and P-tau compared to NC. Compared to MCI non-PD, t-α-syn, Aβ38 and 40, T-tau and P-tau were also lower, while Aβ42 was significantly higher in the PD group. Aβ38 and 40 correlated strongly with t-α-syn levels in PD. Lower Aβ42 was associated with decreased verbal learning, delayed verbal recall and response inhibition in PD. CONCLUSION While Aβ38, 40 and t-α-syn levels are strongly correlated, only lower Aβ42 was associated with reduced cognitive functions in early PD, mainly connected to medial temporal lobe-based cognitive functions.

Cerebrospinal fluid amyloid β and tau in LRRK2 mutation carriers

Objective: The goal of the current investigation was to examine a cohort of symptomatic and asymptomatic LRRK2 mutation carriers, in order to address whether the reported alterations in amyloid β (Aβ) and tau species in the CSF of patients with sporadic Parkinson disease (PD) are a part of PD pathogenesis, the aging process, or a comorbid disease in patients with PD, and to explore the possibility of Aβ and tau as markers of early or presymptomatic PD. Methods: CSF Aβ42, total tau, and phosphorylated tau were measured with Luminex assays in 26 LRRK2 mutation carriers, who were either asymptomatic (n = 18) or had a phenotype resembling sporadic PD (n = 8). All patients also underwent PET scans with 18F-6-fluoro-l-dopa (FD), 11C-(±)-α-dihydrotetrabenazine (DTBZ), and 11C-d-threo-methylphenidate (MP) to measure dopaminergic function in the striatum. The levels of CSF markers were then compared to each PET measurement. Results: Reduced CSF Aβ42 and tau levels correlated with lower striatal dopaminergic function as determined by all 3 PET tracers, with a significant association between Aβ42 and FD uptake. When cases were restricted to carriers of the G2019S mutation, the most common LRRK2 variant in our cohort, significant correlations were also observed for tau. Conclusions: The disposition of Aβ and tau is likely important in both LRRK2-related and sporadic PD, even during early phases of the disease. A better understanding of their production, aggregation, and degradation, including changes in their CSF levels, may provide insights into the pathogenesis of PD and the potential utility of these proteins as biomarkers.

Biomarkers: Parkinson disease with dementia and dementia with Lewy bodies

Dementia is a common feature in Parkinson disease (PD), the time of onset determining how patients are classified. Those patients where dementia develops prior to parkinsonism or during the first year of disease are designated as having dementia with Lewy bodies (DLB). In those where dementia develops over a year after the onset of motor signs, the condition is known as Parkinsons disease with dementia (PDD). While this seems at first sight to be a definitive way to distinguish these conditions, reality is rather different. The overlap between them is considerable, and there is much uncertainty associated with patients who have both motor symptoms and early cognitive impairment. The diagnosis is still based on medical history and clinical evaluation. It is not even certain that they can be accurately distinguished at autopsy. For this reason, the data concerning these entities have been reviewed, to examine various markers employed or measured in clinical, neuropathological, neuroimaging, and biochemical investigations. The concept of PDD and DLB being separate conditions is comparatively new, and the most promising tools with which to separate them at present are cerebrospinal fluid (CSF) markers and positron emission tomography (PET) scanning that indicate increased amyloid-beta burden in DLB compared to PDD. However as yet there are no markers that unequivocally distinguish between PDD and DLB.

Elevated levels of cerebrospinal fluid α-synuclein oligomers in healthy asymptomatic LRRK2 mutation carriers

Mutations in the leucine-rich repeat kinase 2 gene are the most common cause of autosomal dominant Parkinson’s disease (PD). To assess the cerebrospinal fluid (CSF) levels of α-synuclein oligomers in symptomatic and asymptomatic leucine-rich repeat kinase 2 mutation carriers, we used enzyme-linked immunosorbent assays (ELISA) to investigate total and oligomeric forms of α-synuclein in CSF samples. The CSF samples were collected from 33 Norwegian individuals with leucine-rich repeat kinase 2 mutations: 13 patients were clinically diagnosed with PD and 20 patients were healthy, asymptomatic leucine-rich repeat kinase 2 mutation carriers. We also included 35 patients with sporadic PD (sPD) and 42 age-matched healthy controls. Levels of CSF α-synuclein oligomers were significantly elevated in healthy asymptomatic individuals carrying leucine-rich repeat kinase 2 mutations (n = 20; P < 0.0079) and in sPD group (n = 35; P < 0.003) relative to healthy controls. Increased α-synuclein oligomers in asymptomatic leucine-rich repeat kinase 2 mutation carriers showed a sensitivity of 63.0% and a specificity of 74.0%, with an area under the curve of 0.66, and a sensitivity of 65.0% and a specificity of 83.0%, with an area under the curve of 0.74 for sPD cases. An inverse correlation between CSF levels of α- synuclein oligomers and disease severity and duration was observed. Our study suggests that quantification of α-synuclein oligomers in CSF has potential value as a tool for PD diagnosis and presymptomatic screening of high-risk individuals.

Subclinical signs in LRRK2 mutation carriers.

BACKGROUND Several non-motor features have been reported to precede the motor signs of Parkinsons disease (PD) by several years. However, the time of onset of non-motor and motor symptoms is still debated. Healthy individuals carrying a PD-related mutation are candidates for studying the earliest disease signs. OBJECTIVES To describe clinically healthy family members of PD patients carrying a LRRK2 mutation (LRRK2-PD). METHODS A total of 47 family members of LRRK2-PD patients were included in the present study and were screened for the p.G2019S and p.N1437H substitutions in the LRRK2 gene. A standardized case report form was filled out in each case, including general medical evaluation, neurological examination with UPDRS, an olfaction test, mood, sleep and cognitive questionnaires. RESULTS Thirty-two study participants were positive, and 15 were negative for a LRRK2 mutation. Higher UPDRS motor scores, more frequent reports of urinary problems, and fewer hours of sleep were found in mutation carriers compared to non-carriers. The mutation carriers with UPDRS ≥8 were all aged over 50 years, had shorter overall sleeping hours, more frequent urinary and constipation problems, higher mood scores and body mass index. Deterioration of olfaction was not detected in either group. CONCLUSION Healthy LRRK2 mutation carriers presented subclinical parkinsonian motor and non-motor signs in the apparent absence of olfactory loss. Longitudinal studies will determine whether these changes precede alterations detectable by neuroimaging.

Parkinson-related genetics in patients treated with deep brain stimulation.

Johansen KK, Jørgensen JV, White LR, Farrer MJ, Aasly JO. Parkinson‐related genetics in patients treated with deep brain stimulation.
Acta Neurol Scand: 2011: 123: 201–206.
© 2010 John Wiley & Sons A/S.

Olfactory dysfunction in sporadic Parkinson's Disease and LRRK2 carriers

The aim of the study was to examine the sense of smell in LRRK2 mutation carriers and in patients with sporadic PD (sPD).