R1441G Mutation Research Articles

Hybrid enhanced sampling approaches to gain structural insights into leucine-rich repeat kinase 2 (LRRK2) Parkinson's disease mutation.

Parkinson's disease (PD) is a neurodegenerative disease affecting millions worldwide. A commonly mutated gene in PD is leucine-rich repeat kinase 2 (LRRK2), which contains multiple domains, including but not limited to kinase, ATPase, and GTPase. LRRK2 has been found to increase kinase activity and colocalize with microtubules. LRRK2 protein dynamics are affected by its conformation, regulating microtubule interactions and potentially enhancing intracellular trafficking. Despite recent advances in the structural insights of LRRK2, detailed studies on the effects of single-point mutations on the dynamics and conformations of LRRK2 are limited. Consequently, an all-atomistic molecular dynamics simulation is required to understand the allosteric and dynamical effects of single-point disease mutations in LRRK2, but it would be computationally expensive. We thereby employ enhanced molecular dynamics simulations to study single-point mutations in LRRK2, particularly the G2019S, R1441C, R1441G, R1441H, and Y1699C mutations. Our two-phase approach incorporates implementing Gaussian-accelerated molecular dynamics (GaMD) for enhanced sampling, followed by the weighted ensemble (WE) method. GaMD is an enhanced MD approach where a boost potential is added to the total potential energy of the system to accelerate the conformational search, while the WE method readjusts the weight of the simulation trajectories by frequent resampling to obtain the kinetic properties of interest accurately. Investigating the dynamics of such single-point mutations in LRRK2 could explain why specific mutations result in increased kinase activation and dynamicity of LRRK2.

R1441G but not G2019S mutation enhances LRRK2 mediated Rab10 phosphorylation in human peripheral blood neutrophils

Heterozygous gain-of-kinase function variants in LRRK2 (leucine-rich repeat kinase 2) cause 1–2% of all cases of Parkinson’s disease (PD) albeit with incomplete and age-dependent penetrance. All pathogenic LRRK2 mutations reside within the two catalytic domains of LRRK2—either in its kinase domain (e.g. G2019S) with modest effect or its ROC-COR GTPase domain (e.g. R1441G/H) with large effect on LRRK2 kinase activity. We have previously reported assays to interrogate LRRK2 kinase pathway activity in human bio-samples measuring phosphorylation of its endogenous substrate Rab10, that mirrors LRRK2 kinase activation status. Here, we isolated neutrophils from fresh peripheral blood from 101 participants including 42 LRRK2 mutation carriers (21 with the G2019S and 21 with the R1441G mutations), 27 patients with idiopathic PD, and 32 controls. Using a dual approach, LRRK2 dependent Rab10 phosphorylation at Threonine 73 (pRab10Thr73) was measured by quantitative multiplexed immunoblotting for pRab10Thr73/total Rab10 as well as targeted mass-spectrometry for absolute pRab10Thr73 occupancy. We found a significant over fourfold increase in pRab10Thr73 phosphorylation in carriers of the LRRK2 R1441G mutation irrespective of clinical disease status. The effect of the LRRK2 G2019S mutation did not reach statistical significance. Furthermore, we show that LRRK2 phosphorylation at Serine 935 is not a marker for LRRK2 kinase activity in human neutrophils. When analysing pRab10Thr73 phosphorylation in post-mortem brain samples, we observed overall high variability irrespective of clinical and LRRK2 mutation status and attributed this mainly to the adverse effect of the peri- and post-mortem period on the stability of posttranslational modifications such as protein phosphorylation. Overall, in vivo LRRK2 dependent pRab10Thr73 phosphorylation in human peripheral blood neutrophils is a specific, robust and promising biomarker for significant LRRK2 kinase hyperactivation, as with the LRRK2 R1441G mutation. Additional readouts and/or assays may be needed to increase sensitivity to detect modest LRRK2 kinase activation, as with the LRRK2 G2019S mutation. Our assays could be useful for patient stratification and target engagement studies for LRRK2 kinase inhibitors.

A More Homogeneous Phenotype in Parkinson's Disease Related to R1441G Mutation in the LRRK2 Gene.

Parkinson's disease (PD) is characterized by a great clinical heterogeneity. Nevertheless, the biological drivers of this heterogeneity have not been completely elucidated and are likely to be complex, arising from interactions between genetic, epigenetic, and environmental factors. Despite this heterogeneity, the clinical patterns of monogenic forms of PD have usually maintained a good clinical correlation with each mutation once a sufficient number of patients have been studied. Mutations in LRRK2 are the most commonly known genetic cause of autosomal dominant PD known to date. Furthermore, recent genome-wide association studies have revealed variations in LRRK2 as significant risk factors also for the development of sporadic PD. The LRRK2-R1441G mutation is especially frequent in the population of Basque ascent based on a possible founder effect, being responsible for almost 50% of cases of familial PD in our region, with a high penetrance. Curiously, Lewy bodies, considered the neuropathological hallmark of PD, are absent in a significant subset of LRRK2-PD cases. Indeed, these cases appear to be associated with a less aggressive primarily pure motor phenotype. The aim of our research is to examine the clinical phenotype of R1441G-PD patients, more homogeneous when we compare it with sporadic PD patients or with patients carrying other LRRK2 mutations, and reflect on the value of the observed correlation in the genetic forms of PD. The clinical heterogeneity of PD leads us to think that there may be as many different diseases as the number of people affected. Undoubtedly, genetics constitutes a relevant key player, as it may significantly influence the phenotype, with differences according to the mutation within the same gene, and not only in familial PD but also in sporadic forms. Thus, extending our knowledge regarding genetic forms of PD implies an expansion of knowledge regarding sporadic forms, and this may be relevant due to the future therapeutic implications of all forms of PD.

Deciphering the LRRK code: LRRK1 and LRRK2 phosphorylate distinct Rab proteins and are regulated by diverse mechanisms.

Autosomal dominant mutations in LRRK2 that enhance kinase activity cause Parkinson's disease. LRRK2 phosphorylates a subset of Rab GTPases including Rab8A and Rab10 within its effector binding motif. Here, we explore whether LRRK1, a less studied homolog of LRRK2 that regulates growth factor receptor trafficking and osteoclast biology might also phosphorylate Rab proteins. Using mass spectrometry, we found that in LRRK1 knock-out cells, phosphorylation of Rab7A at Ser72 was most impacted. This residue lies at the equivalent site targeted by LRRK2 on Rab8A and Rab10. Accordingly, recombinant LRRK1 efficiently phosphorylated Rab7A at Ser72, but not Rab8A or Rab10. Employing a novel phospho-specific antibody, we found that phorbol ester stimulation of mouse embryonic fibroblasts markedly enhanced phosphorylation of Rab7A at Ser72 via LRRK1. We identify two LRRK1 mutations (K746G and I1412T), equivalent to the LRRK2 R1441G and I2020T Parkinson's mutations, that enhance LRRK1 mediated phosphorylation of Rab7A. We demonstrate that two regulators of LRRK2 namely Rab29 and VPS35[D620N], do not influence LRRK1. Widely used LRRK2 inhibitors do not inhibit LRRK1, but we identify a promiscuous inhibitor termed GZD-824 that inhibits both LRRK1 and LRRK2. The PPM1H Rab phosphatase when overexpressed dephosphorylates Rab7A. Finally, the interaction of Rab7A with its effector RILP is not affected by LRRK1 phosphorylation and we observe that maximal stimulation of the TBK1 or PINK1 pathway does not elevate Rab7A phosphorylation. Altogether, these findings reinforce the idea that the LRRK enzymes have evolved as major regulators of Rab biology with distinct substrate specificity.

Oral P. gingivalis impairs gut permeability and mediates immune responses associated with neurodegeneration in LRRK2 R1441G mice

BackgroundThe R1441G mutation in the leucine-rich repeat kinase 2 (LRRK2) gene results in late-onset Parkinson’s disease (PD). Peripheral inflammation and gut microbiota are closely associated with the pathogenesis of PD. Chronic periodontitis is a common type of peripheral inflammation, which is associated with PD. Porphyromonas gingivalis (Pg), the most common bacterium causing chronic periodontitis, can cause alteration of gut microbiota. It is not known whether Pg-induced dysbiosis plays a role in the pathophysiology of PD.MethodsIn this study, live Pg were orally administrated to animals, three times a week for 1 month. Pg-derived lipopolysaccharide (LPS) was used to stimulate mononuclear cells in vitro. The effects of oral Pg administration on the gut and brain were evaluated through behaviors, morphology, and cytokine expression.ResultsDopaminergic neurons in the substantia nigra were reduced, and activated microglial cells were increased in R1441G mice given oral Pg. In addition, an increase in mRNA expression of tumor necrosis factor (TNF-α) and interleukin-1β (IL-1β) as well as protein level of α-synuclein together with a decrease in zonula occludens-1 (Zo-1) was detected in the colon in Pg-treated R1441G mice. Furthermore, serum interleukin-17A (IL-17A) and brain IL-17 receptor A (IL-17RA) were increased in Pg-treated R1441G mice.ConclusionsThese findings suggest that oral Pg-induced inflammation may play an important role in the pathophysiology of LRRK2-associated PD.

Metabolic alterations in plasma from patients with familial and idiopathic Parkinson's disease.

The research of new biomarkers for Parkinson’s disease is essential for accurate and precocious diagnosis, as well as for the discovery of new potential disease mechanisms and drug targets. The main objective of this work was to identify metabolic changes that might serve as biomarkers for the diagnosis of this neurodegenerative disorder. For this, we profiled the plasma metabolome from mice with neurotoxin-induced Parkinson’s disease as well as from patients with familial or sporadic Parkinson’s disease. By using mass spectrometry technology, we analyzed the complete metabolome from healthy volunteers compared to patients with idiopathic or familial (carrying the G2019S or R1441G mutations in the LRRK2 gene) Parkinson’s disease, as well as, from mice treated with 6-hydroxydopamine to induce Parkinson disease. Both human and murine Parkinson was accompanied by an increase in plasma levels of unconjugated bile acids (cholic acid, deoxycholic acid and lithocholic acid) and purine base intermediary metabolites, in particular hypoxanthine. The comprehensive metabolomic analysis of plasma from Parkinsonian patients underscores the importance of bile acids and purine metabolism in the pathophysiology of this disease. Therefore, plasma measurements of certain metabolites related to these pathways might contribute to the diagnosis of Parkinson’s Disease.

HDAC Inhibition by Valproic Acid Induces Neuroprotection and Improvement of PD-like Behaviors in LRRK2 R1441G Transgenic Mice.

Parkinson’s disease (PD) is one of the late-onset neurodegenerative movement disorder. Major pathological markers of PD include progressive loss of dopaminergic neurons, Lewy body formation, genetic mutations, and environmental factors. Epigenetic regulation of specific gene expression via impaired histone acetylation is associated with neuronal dysfunction in various neurodegenerative diseases. In this study, we hypothesized that histone deacetylase (HDAC) inhibitor, valproic acid (VPA), can improve motor function by enhancing cell survival in PD genetic model mice with LRRK2 R1441G mutation. To address this question, we administered VPA in LRRK2 R1441G transgenic mice to determine whether VPA affects 1) histone acetylation and HDAC expression, 2) dopaminergic neuron survival, 3) inflammatory responses, 4) motor or non-motor symptoms. As results, VPA administration increased histone acetylation level and the number of tyrosine hydroxylase (TH) positive neurons in substantia nigra of LRRK2 R1441G mice. VPA reduced iba-1 positive activated microglia and the mRNA levels of pro-inflammatory marker genes in LRRK2 R1441G mice. In addition, VPA induced the improvement of PD-like motor and non-motor behavior in LRRK2 R1441G mice. These data suggest that the inhibition of HDAC can be further studied as potential future therapeutics for PD.

Mutations in LRRK2 impair NF-κB pathway in iPSC-derived neurons.

BackgroundMutations in leucine-rich repeat kinase 2 (LRRK2) contribute to both familial and idiopathic forms of Parkinson’s disease (PD). Neuroinflammation is a key event in neurodegeneration and aging, and there is mounting evidence of LRRK2 involvement in inflammatory pathways. In a previous study, we described an alteration of the inflammatory response in dermal fibroblasts from PD patients expressing the G2019S and R1441G mutations in LRRK2.MethodsTaking advantage of cellular reprogramming, we generated induced pluripotent stem cell (iPSC) lines and neurons thereafter, harboring LRRK2G2019S and LRRK2R1441G mutations. We used gene silencing and functional reporter assays to characterize the effect of the mutations. We examined the temporal profile of TNFα-induced changes in proteins of the NF-κB pathway and optimized western blot analysis to capture α-synuclein dynamics. The effects of the mutations and interventions were analyzed by two-way ANOVA tests with respect to corresponding controls.ResultsLRRK2 silencing decreased α-synuclein protein levels in mutated neurons and modified NF-κB transcriptional targets, such as PTGS2 (COX-2) and TNFAIP3 (A20). We next tested whether NF-κB and α-synuclein pathways converged and found that TNFα modulated α-synuclein levels, although we could not detect an effect of LRRK2 mutations, partly because of the individual variability. Nevertheless, we confirmed NF-κB dysregulation in mutated neurons, as shown by a protracted recovery of IκBα and a clear impairment in p65 nuclear translocation in the LRRK2 mutants.ConclusionsAltogether, our results show that LRRK2 mutations affect α-synuclein regulation and impair NF-κB canonical signaling in iPSC-derived neurons. TNFα modulated α-synuclein proteostasis but was not modified by the LRRK2 mutations in this paradigm. These results strengthen the link between LRRK2 and the innate immunity system underscoring the involvement of inflammatory pathways in the neurodegenerative process in PD.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-016-0761-x) contains supplementary material, which is available to authorized users.

ID 150 – STN neuron activity in patients carrying the R1441G mutation in the leucine-rich repeat kinase-2 (LRRK2) gene

Objective Mutations in the LRRK2 gene account for higher risk of suffering Parkinson’s disease (PD). To understand the basis of these differences we investigated the neuron activity in the subthalamic nucleus (STN) from patients carrying the R1441G mutation in the LRRK2 gene and without the mutation. Methods Recordings of STN neurons were obtained from intraoperative procedures performed in PD patients; with mutation in the LRRK2 gene ( n = 4, 22 neurons) and without the mutation ( n = 5, 31 neurons). All patients met the CAPSIT criteria for inclusion in the surgical program. Clinical assessment was made using the Unified Parkinson’s disease Rating Scale II, Unified Parkinson’s disease Rating Scale III, and Parkinson’s disease Questionnaire 39 scores. Results Patients with and without R1441G mutation showed equal clinical features as indicated by the used PD rating scales. Parameters of STN neuronal activity were not different among the two groups of patients neither the oscillatory activity. Conclusions Although the number of patients included in this study should be increased results suggest that the R1441G mutation does not determine clinical severity or STN activity. Key message Characteristics of STN neurons in LRRK2–R1441G PD patients are similar to idiopathic PD. Support by UFI11/32 and GV/EJ:IT747-13.

Sleep Disorders in Parkinsonian and Nonparkinsonian LRRK2 Mutation Carriers.

ObjectiveIn idiopathic Parkinson disease (IPD) sleep disorders are common and may antedate the onset of parkinsonism. Based on the clinical similarities between IPD and Parkinson disease associated with LRRK2 gene mutations (LRRK2-PD), we aimed to characterize sleep in parkinsonian and nonmanifesting LRRK2 mutation carriers (NMC).MethodsA comprehensive interview conducted by sleep specialists, validated sleep scales and questionnaires, and video-polysomnography followed by multiple sleep latency test (MSLT) assessed sleep in 18 LRRK2-PD (17 carrying G2019S and one R1441G mutations), 17 NMC (11 G2019S, three R1441G, three R1441C), 14 non-manifesting non-carriers (NMNC) and 19 unrelated IPD.ResultsSleep complaints were frequent in LRRK2-PD patients; 78% reported poor sleep quality, 33% sleep onset insomnia, 56% sleep fragmentation and 39% early awakening. Sleep onset insomnia correlated with depressive symptoms and poor sleep quality. In LRRK2-PD, excessive daytime sleepiness (EDS) was a complaint in 33% patients and short sleep latencies on the MSLT, which are indicative of objective EDS, were found in 71%. Sleep attacks occurred in three LRRK2-PD patients and a narcoleptic phenotype was not observed. REM sleep behavior disorder (RBD) was diagnosed in three LRRK2-PD. EDS and RBD were always reported to start after the onset of parkinsonism in LRRK2-PD. In NMC, EDS was rarely reported and RBD was absent. When compared to IPD, sleep onset insomnia was more significantly frequent, EDS was similar, and RBD was less significantly frequent and less severe in LRRK2-PD. In NMC, RBD was not detected and sleep complaints were much less frequent than in LRRK2-PD. No differences were observed in sleep between NMC and NMNC.ConclusionsSleep complaints are frequent in LRRK2-PDand show a pattern that when compared to IPD is characterized by more frequent sleep onset insomnia, similar EDS and less prominent RBD. Unlike in IPD, RBD and EDS seem to be not markers of the prodromal stage of LRRK2-PD.

Cognitive and behavioral symptoms in Parkinson's disease patients with the G2019S and R1441G mutations of the LRRK2 gene.

To compare the cognitive and psychiatric status of patients with Parkinson's disease related to the G2019S and the R1441G mutations of the LRRK2 gene (LRRK2-PD) and idiopathic Parkinson's disease (iPD) patients. We examined cognition and psychiatric symptoms in 27 patients with LRRK2-PD (12 G2019S and 15 R1441G) and 27 iPD patients. The groups were similar in age, education, disease duration, levodopa equivalent daily dose, and Unified Parkinson's Disease Rating Scale (UPDRS) II-IV; however, the LRRK2-PD showed less impairment on UPDRS-I (2.0±1.7 vs. 4.2±2.8, p=0.003). The LRRK2-PD presented less frequent subjective cognitive complaints (18.5% vs. 63.0%, p=0.002), and mild cognitive impairment or dementia (25.9% vs. 59.2%, p=0.027). They also showed less impairment on scales for general cognition (Mattis dementia rating scale 131.2±10.9 vs. 119±24.0, p=0.022), episodic verbal memory (Rey's auditory verbal learning test, immediate recall 39.2±9.5 vs. 27.6±12.8 p<0.001, delayed recall 7.2±3.7 vs. 4.7±4.0 p=0.022), and the Neuropsychiatric Inventory (9.7±9.2 vs. 20.5±14.3, p=0.004, significant differences for apathy and hallucinations). The LRRK2-PD subjects were less frequently treated with antipsychotic medication (0% vs. 25.9%, p=0.010). There were no significant differences between G2019S and R1441G mutation carriers. Mutations of the LRRK2 gene might cause PD associated with less cognitive and neuropsychiatric impairment as compared to iPD.

Cognitive dysfunction in Parkinson's disease related to the R1441G mutation in LRRK2.

The neuropsychological characteristics of patients with Parkinson's Disease (PD) associated with R1441G mutation in the LRRK2 gene (R1441G-PD) are not well known. The aim of this study was to examine the cognitive status and mood of R1441G-PD patients. Thirty patients with R1441G-PD were compared with thirty idiopathic PD (i-PD) patients who were matched by age, sex, education, disease onset age and duration, using a comprehensive battery of neuropsychological test, and considering the Movement Disorder Society (MDS) criteria for the diagnosis of Mild Cognitive Impairment (PD-MCI) and dementia (PD-Dementia). The mean scores in the depression and anxiety scales were similar in the two groups. Depressive symptoms were detected in 31.8% of R1441G-PD and 25% of i-PD patients and anxiety symptoms were evident in 4.5% and 15%, respectively, but the differences were not significant. The only neuropsychological test on which there was a significantly worse performance in the R1441G-PD group was the Boston naming test but the difference became not significant when Bonferroni's correction was applied. The prevalence of PD-MCI was 30% in both R1441G-PD and i-PD, with no differences in the number and type of domains altered given that executive function, memory and attention were mainly affected. PD-Dementia was diagnosed in 13.3% (n=4) of R1441G-PD and 26.7% (n=8) of i-PD patients (difference was not significant). In conclusion, significant differences were not detected between R1441G-PD and i-PD in cognitive, depression and anxiety scales, or PD-MCI and PD-Dementia prevalence, and the cognitive profile was identical in the two groups.

Gene and MicroRNA Transcriptome Analysis of Parkinson's Related LRRK2 Mouse Models

Mutations in leucine-rich repeat kinase 2 (LRRK2) are the most frequent cause of genetic Parkinson’s disease (PD). The biological function of LRRK2 and how mutations lead to disease remain poorly defined. It has been proposed that LRRK2 could function in gene transcription regulation; however, this issue remains controversial. Here, we investigated in parallel gene and microRNA (miRNA) transcriptome profiles of three different LRRK2 mouse models. Striatal tissue was isolated from adult LRRK2 knockout (KO) mice, as well as mice expressing human LRRK2 wildtype (hLRRK2-WT) or the PD-associated R1441G mutation (hLRRK2-R1441G). We identified a total of 761 genes and 24 miRNAs that were misregulated in the absence of LRRK2 when a false discovery rate of 0.2 was applied. Notably, most changes in gene expression were modest (i.e., <2 fold). By real-time quantitative RT-PCR, we confirmed the variations of selected genes (e.g., adra2, syt2, opalin) and miRNAs (e.g., miR-16, miR-25). Surprisingly, little or no changes in gene expression were observed in mice expressing hLRRK2-WT or hLRRK2-R1441G when compared to non-transgenic controls. Nevertheless, a number of miRNAs were misexpressed in these models. Bioinformatics analysis identified several miRNA-dependent and independent networks dysregulated in LRRK2-deficient mice, including PD-related pathways. These results suggest that brain LRRK2 plays an overall modest role in gene transcription regulation in mammals; however, these effects seem context and RNA type-dependent. Our data thus set the stage for future investigations regarding LRRK2 function in PD development.

Genetic Screening for the LRRK2 R1441C and G2019S Mutations in Parkinsonian Patients from Campania

PARK8 is the most common known mendelian form of Parkinson's Disease (PD). It is due to mutations in the leucine-rich repeat kinase 2 (LRRK2) gene and G2019S is considered the most frequent mutation in the Caucasian population, in particular in the Southern Europe and Mediterranean countries. We assessed the frequency of the G2019S and R1441C/H/G mutations in 513 (311 M and 202 F) unrelated PD patients from Campania, in Southern Italy. Three hundreds and thirty-six patients presented a sporadic disease, and 177 had a familial history of PD or tremor. Three hundreds and eighty cases originated from the province of Naples. We compared our LRRK2 mutation carriers to idiopathic PD patients matched for recruiting center, gender, age and age at onset. Thirteen patients (8 M and 5 F) carried the R1441C mutation and 4 (3 M and 1 F) the G2019S mutation, all in heterozygous state. All carriers originated from the province of Naples. No carriers of the R1441H or R1441G mutations were found. The LRRK2 mutation carriers were clinically similar to idiopathic PD patients. The R1441C and G2019S mutations are not rare causes of PD in Campania, especially in the province of Naples and among the familial cases, where the overall mutation prevalence is 6.8%. The R1441C prevalence was higher than that of G2019S (2.5% vs 0.8%), underlining the importance of the geographical differencies in LRRK2 mutation frequency for molecular screening and genetic counseling of PD patients.

A Direct Interaction between Leucine-rich Repeat Kinase 2 and Specific β-Tubulin Isoforms Regulates Tubulin Acetylation

Mutations in LRRK2, encoding the multifunctional protein leucine-rich repeat kinase 2 (LRRK2), are a common cause of Parkinson disease. LRRK2 has been suggested to influence the cytoskeleton as LRRK2 mutants reduce neurite outgrowth and cause an accumulation of hyperphosphorylated Tau. This might cause alterations in the dynamic instability of microtubules suggested to contribute to the pathogenesis of Parkinson disease. Here, we describe a direct interaction between LRRK2 and β-tubulin. This interaction is conferred by the LRRK2 Roc domain and is disrupted by the familial R1441G mutation and artificial Roc domain mutations that mimic autophosphorylation. LRRK2 selectively interacts with three β-tubulin isoforms: TUBB, TUBB4, and TUBB6, one of which (TUBB4) is mutated in the movement disorder dystonia type 4 (DYT4). Binding specificity is determined by lysine 362 and alanine 364 of β-tubulin. Molecular modeling was used to map the interaction surface to the luminal face of microtubule protofibrils in close proximity to the lysine 40 acetylation site in α-tubulin. This location is predicted to be poorly accessible within mature stabilized microtubules, but exposed in dynamic microtubule populations. Consistent with this finding, endogenous LRRK2 displays a preferential localization to dynamic microtubules within growth cones, rather than adjacent axonal microtubule bundles. This interaction is functionally relevant to microtubule dynamics, as mouse embryonic fibroblasts derived from LRRK2 knock-out mice display increased microtubule acetylation. Taken together, our data shed light on the nature of the LRRK2-tubulin interaction, and indicate that alterations in microtubule stability caused by changes in LRRK2 might contribute to the pathogenesis of Parkinson disease.

Prevalence of cancer in Parkinson's disease related to R1441G and G2019S mutations in LRRK2

An inverse relationship between Parkinson's disease (PD) and cancer has been described. However, the association between cancers and genetic forms of PD, in particular the R1441G mutation in the LRRK2 gene, is not well known. The objective of this work was to analyze cancer prevalence in PD patients with R1441G or G2019S mutations in LRRK2, and in idiopathic PD (iPD). A total of 732 patients with PD (70 and 25 carriers of R1441G or G2019S mutations, respectively), and 177 controls, were linked using a population-based cancer registry of the Spanish province of Gipuzkoa. Cancer prevalence was not significantly higher in PD-G2019S carriers (20%) than in PD-R1441G carriers (14.3%), iPD (13.8%), or controls (12.5%). With the exception of a high prevalence of hematological cancers (crude odds ratio of 7.1) in the R1441G group, specific cancer types were not increased in PD mutation carriers. In both the carrier and iPD groups, cancers were diagnosed after the onset of PD. PD patients had a similar prevalence of cancer to control subjects. There was no increased association between G2019S or R1441G mutations and any type of cancer. Although there was a higher prevalence of hematological cancers in the R1441G group, the low number of such cancers overall makes this finding of uncertain significance. There was a slightly higher but not statistically significant prevalence of non-skin cancers in the G2019S group, suggesting that further study to evaluate the association should be undertaken prior to ascribing an increased cancer risk to this population.

Leucine-rich repeat kinase 2 modulates cyclooxygenase 2 and the inflammatory response in idiopathic and genetic Parkinson's disease

Inflammatory mechanisms are activated in aging and late-onset neurodegenerative diseases, such as Parkinson's disease (PD). Mutations in leucine-rich repeat kinase 2 (LRRK2) contribute to both idiopathic and familial forms of PD. Here, we investigated the involvement of LRRK2 in inflammatory pathways using primary dermal fibroblasts from patients with 2 common mutations in LRRK2 (G2019S and R1441G), idiopathic PD and age-matched healthy individuals. Basal cyclooxygenase (COX)-2 RNA levels were very high in the fibroblasts of all patients. Remarkably, LRRK2 silencing experiments significantly reduced basal COX-2 levels and COX-2 induction after a pro-inflammatory stimulus. Additionally, in samples from patients with the R1441G mutation and with idiopathic PD, we found a prominent cytoplasmic re-distribution of human antigen R, a protein that, among others, stabilizes COX-2 RNA. Furthermore, the response to lipopolysaccharide was defective in these 2 groups, which showed weak induction of pro-inflammatory cytokines and reduced NFκB transcriptional activation. In summary, we describe multiple defects in inflammatory pathways in which LRRK2 appears to be critically involved. Further studies are required to establish the therapeutic implications of inflammatory dysregulation in the pathophysiology of Parkinson's disease.

Non-Motor and Motor Features in LRRK2 Transgenic Mice

BackgroundNon-motor symptoms are increasingly recognized as important features of Parkinson’s disease (PD). LRRK2 mutations are common causes of familial and sporadic PD. Non-motor features have not been yet comprehensively evaluated in LRRK2 transgenic mouse models.ObjectiveUsing a transgenic mouse model overexpressing the R1441G mutation of the human LRRK2 gene, we have investigated the longitudinal correlation between motor and non-motor symptoms and determined if specific non-motor phenotypes precede motor symptoms.MethodologyWe investigated the onset of motor and non-motor phenotypes on the LRRK2R1441G BAC transgenic mice and their littermate controls from 4 to 21 month-old using a battery of behavioral tests. The transgenic mutant mice displayed mild hypokinesia in the open field from 16 months old, with gastrointestinal dysfunctions beginning at 6 months old. Non-motor features such as depression and anxiety-like behaviors, sensorial functions (pain sensitivity and olfaction), and learning and memory abilities in the passive avoidance test were similar in the transgenic animals compared to littermate controls.Conclusions LRRK2R1441G BAC transgenic mice displayed gastrointestinal dysfunction at an early stage but did not have abnormalities in fine behaviors, olfaction, pain sensitivity, mood disorders and learning and memory compared to non-transgenic littermate controls. The observations on olfaction and gastrointestinal dysfunction in this model validate findings in human carriers. These mice did recapitulate mild Parkinsonian motor features at late stages but compensatory mechanisms modulating the progression of PD in these models should be further evaluated.

Olfactory deficits and cardiac 123I‐MIBG in Parkinson's disease related to the LRRK2 R1441G and G2019S mutations

It has been proposed that olfactory tests and metaiodobenzylguanidine cardiac scintigraphy may help diagnose idiopathic Parkinson's disease in the premotor phase. However, it is not clear what value these tests have in all patients with Parkinson's disease and, particularly, in those who carry mutations in LRRK2. The objective was to analyze olfactory dysfunction and the changes in cardiac I-metaiodobenzylguanidine uptake in patients with Parkinson's disease carrying the R1441G and G2019S mutations in LRRK2, and in patients with Parkinson's disease with no known mutations. Patients with Parkinson's disease were screened for R1441G and G2019S LRRK2 gene mutations and classified as LRRK2 mutation carriers or noncarriers. A total of 190 patients with Parkinson's disease (44 LRRK2 mutation carriers) were tested for olfactory dysfunction using the Brief Smell Identification Test. Cardiac (123) I-metaiodobenzylguanidine scintigraphy was performed on 90 patients with Parkinson's disease (27 LRRK2 mutation carriers). Thirty-six percent of patients with LRRK2 mutations have hyposmia, compared to 75% of noncarrier patients with Parkinson's disease (P < .001). Sixty-six percent of LRRK2 mutation carriers have low early metaiodobenzylguanidine uptake, compared to 86% of noncarriers (P = .048). Similarly, the heart/mediastinum ratio in delayed metaiodobenzylguanidine images appeared to differ between these groups of patients with Parkinson's disease, although these results did not reach statistical significance. The data obtained indicate that olfactory and cardiac impairment is less prevalent when Parkinson's disease is associated with mutations in LRRK2, although the underlying mechanisms for this difference remain unclear. Thus, such screening would be less useful to detect the premotor phase in asymptomatic relatives who carry mutations in LRRK2 than in cases not associated with LRRK2.

LRRK2 G2019S mutations may be increased in Puerto Ricans

We read with interest the article by Shino et al. that reported a higher familial aggregation of Parkinson’s Disease (PD) among Hispanics1. In their evaluation of incident PD cases in Northern California, they propose that there is an increased rate of genetic and/or shared environmental factors in this group. We are interested in identifying genetic risk factors among Hispanics in the United States, and performed a pilot study of the LRRK2 G2019S mutation in Hispanic, non-Hispanic, and non-Jewish Caucasian subjects participating in genetics research at Beth Israel Medical Center in New York, who were seen initially as patients or self-referred for genetic studies. Our pilot work suggests that there may be a higher rate of G2019S mutations in Puerto Ricans, and supports that further evaluation of this population is warranted. We analyzed G2019S mutations in 104 individuals who met strict criteria for idiopathic PD2. 19 were of Hispanic descent, and 8 of these were of Puerto Rican background. 85 were non-Hispanic non-Jewish Caucasians. Three cases with the LRRK2 G/A mutation (2.85%) were identified. Two were of Puerto-Rican descent, constituting 25% (2/8) of all Puerto Ricans sampled. Both Puerto Rican cases were women, with onset at ages 53 and 42 years respectively. The latter had an uncle with PD and the former did not have a family history of parkinsonism. They were not known to be related. The third case was a man of Irish/German background, with onset at age 58 and a brother with PD. The frequency of mutations was greater in Puerto Ricans than non-Puerto Ricans, (25.0% vs. 1.0% Fischer’s exact, p=0.01). Mean age at onset and gender did not differ between groups (Table 1). In a logistic regression model adjusting for age at onset of PD, the odds of carrying a G2019S mutation was still greater in the Puerto Rican PD cases compared with non-Puerto Ricans, although the confidence intervals were broad (OR=28.24, 95% CI: 2.16–368.67, p=0.011). While there was a trend, the difference in PD between all Hispanics (11.1%) and non-Hispanic Caucasians (1.16%) was not significant. Table 1 Demographics and Mutation Frequency Puerto Ricans may be of a Spanish, Taino and Black African descent, and genetic admixture is not uncommon.3 The relative admixture in our cases was not known. Spanish colonization and immigration to Puerto Rico as well as Ashkenazi Jewish influence may contribute to the increased rate of G2019S mutations, as this mutation is increased in Spaniards4 as well as in Ashkenazi Jews2. It is of interest that a prior North American screen identified two cases with LRRK2 mutations among twenty Hispanic individuals screened, one with the G2019S mutation and one with the R1441G mutation5. Of note, the Consortium of Risk for Early Onset Parkinson Disease (CORE-PD), a multicenter study of subjects with PD onset younger than 51 years did not report an increased rate of LRRK2 G2019S mutations in Hispanics overall. However, both of their mutation positive cases were Puerto Rican6, and the subtotal of Puerto Rican cases was not indicated. LRRK2 mutations do not appear to be at increased frequency in Mexicans.7 We did not screen for other LRRK2 mutations, including the R1441G mutation, which is increased in Spaniards of Basque origin4. As descendants from the latter group settled in California and the Southwest, it is possible that this other LRRK2 mutation may also account for increased rates in US Hispanics. Further, some of the increased familial aggregation noted in Hispanics may be due to parkin mutations, as these are increased in Hispanics in the US6. The main limitation to our pilot data is the small number of Puerto Ricans sampled. However, our rate of G2019S mutation carriers in non-Jewish Caucasians is similar to that in other such mixed populations that include both sporadic and familial PD and early and late-onset PD. Thus further evaluation for LRRK2 mutations in Hispanic populations in the US should be considered, in both early and late onset cases, as these may constitute an important etiology of PD, particularly among Puerto Ricans.