Micro-and mesoscale aspects of neurodegeneration in engineered human neural networks carrying the LRRK2 G2019S mutation.

Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene have been widely linked to Parkinson's disease, where the G2019S variant has been shown to contribute uniquely to both familial and sporadic forms of the disease. LRRK2-related mutations have been extensively studied, yet the wide variety of cellular and network events related to these mutations remain poorly understood. The advancement and availability of tools for neural engineering now enable modeling of selected pathological aspects of neurodegenerative disease in human neural networks in vitro. Our study revealed distinct pathology associated dynamics in engineered human cortical neural networks carrying the LRRK2 G2019S mutation compared to healthy isogenic control neural networks. The neurons carrying the LRRK2 G2019S mutation self-organized into networks with aberrant morphology and mitochondrial dynamics, affecting emerging structure-function relationships both at the micro-and mesoscale. Taken together, the findings of our study points toward an overall heightened metabolic demand in networks carrying the LRRK2 G2019S mutation, as well as a resilience to change in response to perturbation, compared to healthy isogenic controls.

Role of the Residue Q1919 in Increasing Kinase Activity of G2019S LRRK2 Kinase: A Computational Study.

Mutations in multi-domain leucine-rich repeat kinase 2 (LRRK2) have been an interest to researchers as these mutations are associated with Parkinson's disease. G2019S mutation in LRRK2 kinase domain leads to the formation of additional hydrogen bonds by S2019 which results in stabilization of the active state of the kinase, thereby increasing kinase activity. Two additional hydrogen bonds of S2019 are reported separately. Here, a mechanistic picture of the formation of additional hydrogen bonds of S2019 with Q1919 (also with E1920) is presented using 'active' Roco4 kinase as a homology model and its relationship with the stabilization of the 'active' G2019S LRRK2 kinase. A conformational flipping of residue Q1919 was found which helped to form stable hydrogen bond with S2019 and made 'active' state more stable in G2019S LRRK2. Two different states were found within the 'active' kinase with respect to the conformational change (flipping) in Q1919. Two doubly-mutated systems, G2019S/Q1919A and G2019S/E1920 K, were studied separately to check the effect of Q1919 and E1920. For both cases, the stable S2 state was not formed, leading to a decrease in kinase activity. These results indicate that both the additional hydrogen bonds of S2019 (with Q1919 and E1920) are necessary to stabilize the active G2019S LRRK2.

An overview of the worldwide distribution of LRRK2 mutations in Parkinson's disease.

Parkinson's disease (PD) is a neurodegenerative disorder with significant genetic influence. The LRRK2 gene is a major genetic contributor, particularly the Gly2019Ser mutation. This focused review investigates the global distribution of LRRK2 mutations, with emphasis on Gly2019Ser and other pathogenic variants. Prevalence rates of Gly2019Ser are highest in North Africa and the Ashkenazi-Jewish population, indicating a potential common ancestor and founder effect. Other LRRK2 mutations, including Asn1437His, Arg1441Gly/Cys/His, Tyr1699Cys and Ile2020Thr, exhibit varying global prevalences. Understanding these distributions enhances our knowledge of PD genetics and aids personalized medicine. Further research is crucial to unravel clinical implications and develop targeted therapies for LRRK2 mutation carriers.

Structural Insights and Development of LRRK2 Inhibitors for Parkinson's Disease in the Last Decade.

Parkinson's disease (PD) is the second most prevalent neurodegenerative disease, characterized by the specific loss of dopaminergic neurons in the midbrain. The pathophysiology of PD is likely caused by a variety of environmental and hereditary factors. Many single-gene mutations have been linked to this disease, but a significant number of studies indicate that mutations in the gene encoding leucine-rich repeat kinase 2 (LRRK2) are a potential therapeutic target for both sporadic and familial forms of PD. Consequently, the identification of potential LRRK2 inhibitors has been the focus of drug discovery. Various investigations have been conducted in academic and industrial organizations to investigate the mechanism of LRRK2 in PD and further develop its inhibitors. This review summarizes the role of LRRK2 in PD and its structural details, especially the kinase domain. Furthermore, we reviewed in vitro and in vivo findings of selected inhibitors reported to date against wild-type and mutant versions of the LRRK2 kinase domain as well as the current trends researchers are employing in the development of LRRK2 inhibitors.

Altered Motor Performance, Sleep EEG, and Parkinson's Disease Pathology Induced by Chronic Sleep Deprivation in Lrrk2G2019S Mice.

Parkinson's disease (PD) is a multifaceted disease in which environmental variables combined with genetic predisposition cause dopaminergic (DAergic) neuron loss in the substantia nigra pars compacta. The mutation of leucine-rich repeat kinase 2 (Lrrk2) is the most common autosomal dominant mutation in PD, and it has also been reported in sporadic cases. A growing body of research suggests that circadian rhythm disruption, particularly sleep-wake abnormality, is common during the early phase of PD. Our present study aimed to evaluate the impact of sleep deprivation (SD) on motor ability, sleep performance, and PD pathologies in Lrrk2G2019S transgenic mice. After two months of SD, Lrrk2G2019S mice at 12 months of age showed an exacerbated PD-like phenotype with motor deficits, a reduced striatal DA level, degenerated DAergic neurons, and altered sleep structure and biological rhythm accompanied by the decreased protein expression level of circadian locomotor output cycles kaput Lrrk2 gene in the brain. All these changes persisted and were even more evident in 18-month-old mice after 6 months of follow-up. Moreover, a significant increase in α-synuclein aggregation was found in SD-treated transgenic mice at 18 months of age. Taken together, our findings indicate that sleep abnormalities, as a risk factor, may contribute to the pathogenesis and progression of PD. Early detection of sleep disorders and improvement of sleep quality may help to delay disease progression and provide long-term clinical benefits.

Sensor-based gait analysis in the premotor stage of LRRK2 G2019S-associated Parkinson's disease.

INTRODUCTION: There is a need for biomarkers to monitor the earliest phases of Parkinson's disease (PD), especially in premotor stages. Here, we studied whether there are early gait alterations in carriers of the G2019S mutation of LRRK2 that can be detected by means of an inertial sensor system. METHODS: Twenty-one idiopathic PD patients, 20 LRRK2-G2019S PD, 27 asymptomatic carriers of LRRK2-G2019S mutation (AsG2019S) and 36 controls walked equipped with 16 lightweight inertial sensors in three different experiments: i/normal gait, ii/fast gait and iii/dual-task gait. In the AsG2019S group, DaT-SPECT (123I-ioflupane) with semi-quantitative analysis was carried out. Motor and cognitive performance were evaluated using MDS-UPDRS-III and MoCA scales. We employed neural network techniques to classify individuals based on their walking patterns. RESULTS: PD patients and controls showed differences in speed, stride length and arm swing amplitude, variability and asymmetry in all three tasks (p < 0.01). In the AsG2019S group, the only differences were detected during fast walking, with greater step time on the non-dominant side (p < 0.05), lower step/stride time variability (p < 0.01) and lower step time asymmetry (p < 0.01). DaT uptake showed a significant correlation with step time during fast walking on the non-dominant side (r = -0.52; p < 0.01). The neural network was able to differentiate between AsG2019S and healthy controls with an accuracy rate of 82.5%. CONCLUSION: Our sensor-based analysis did not detect substantial and robust changes in the gait of LRRK2-G2019S asymptomatic mutation carriers. Nonetheless, step or stride time during fast walking, supported by the observed correlation with striatal DaT binding deserves consideration as a potential biomarker in future studies.

Heart rate variability and sympathetic skin response for the assessment of autonomic dysfunction in leucine-rich repeat kinase 2 associated Parkinson's disease.

OBJECTIVES: We aimed to assess and compare autonomic function in Parkinson's disease (PD) associated with the leucine-rich repeat kinase (LRRK2) G2019S mutation (LRRK2-PD) and non-LRRK2 PD, by the study of heart rate variability (HRV) and sympathetic skin responses (SSR). METHODS: In a cross-sectional three-year study, fifty LRRK2-PD and fifty clinically matched non-LRRK2 PD patients were included. Cardiac parasympathetic functions were assessed using heart rate variation to deep breathing (HR-DB), to the Valsalva maneuver (HR-V) and to standing (HR-S) and the sympathetic autonomic system by sympathetic skin responses (SSR). RESULTS: Neurophysiological, parasympathetic and sympathetic dysautonomia were found in 78%, 69% and 37% of all PD patients respectively. Rates of dysautonomia in the LRRK2-PD and non-LRRK2 PD patient subgroups were 76% vs 80% (p = 0.405) for neurophysiological, 62% vs 76% (p = 0.123) for parasympathetic and 38% vs 36% (p = 0.500) for sympathetic dysautonomia. HR-S was the most frequently altered parameter in both groups, and was significantly associated with the tremor-dominant (TD) motor phenotype of PD in the total cohort (p = 0.004) and in LRRK2-PD (p = 0.015). In LRRK2-PD patients, female gender was associated with parasympathetic dysfunction (p = 0.024), and with altered HR-DB (p = 0.022). Early-onset parkinsonism was also significantly associated with preserved neurophysiological autonomic functions (p = 0.044) in LRRK2-PD. In non-LRRK2 PD patients, male gender was associated with early parasympathetic (p = 0.043) and sympathetic dysfunction (p = 0.007). CONCLUSION: Our study showed a roughly similar neurophysiological autonomic profile in non-LRRK2 PD and LRRK2-PD. The latter had some peculiarities with more marked parasympathetic dysfunction and more altered HR-DB in females, more altered HR-S in the TD-motor phenotype, and preserved autonomic functions in early-onset parkinsonism. These preliminary findings would require further investigations on larger genetically homogeneous cohorts to explore the multiple facets of autonomic dysfunction in PD.

Age-related LRRK2 G2019S Mutation Impacts Microglial Dopaminergic Fiber Refinement and Synaptic Pruning Involved in Abnormal Behaviors.

Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene are the most frequent cause of autosomal dominant Parkinson's disease (PD), producing psychiatric and motor symptoms. We conducted this study to explore whether microglial dopaminergic (DAergic) fiber refinement and synaptic pruning are involved in the abnormal behavioral phenotypes of carriers of the LRRK2 G2019S mutation, by employing young and middle-aged PD model mice. The results revealed a characteristic late-onset hyperactivity and a progressive decline in the motor coordination of the LRRK2 G2019S mutation mice. LRRK2 G2019S mutation-induced aberrant microglial morphogenesis, with more branches and junctions per cell, resulted in excessive microglial refinement of dopaminergic (DAergic) fibers. Moreover, aberrant synaptic pruning distinctly impacted the prefrontal cortex (PFC) and dorsal striatum (DS), with significantly higher spine density in the PFC but the opposite effects in the DS region. Furthermore, LRRK2 G2019S mutation remodeled the inflammatory transcription landscape of microglia, rendering certain cerebral areas highly susceptible to microglial immune response. These findings indicate that LRRK2 G2019S mutation induces the production of inflammatory cytokines and mediates abnormal microglial morphogenesis and activity, resulting in abnormal phagocytosis, synaptic pruning and loss of DAergic fibers during aging, and, eventually, PD-related behavioral abnormalities.

Targeting leucine-rich repeat kinase 2 (LRRK2) for the treatment of Parkinson's disease.

Leucine-rich repeat kinase 2 (LRRK2) is a serine-threonine kinase involved in multiple cellular processes and signaling pathways. LRRK2 mutations are associated with autosomal-inherited Parkinson's disease (PD), and evidence suggests that LRRK2 pathogenic variants generally increase kinase activity. Therefore, inhibition of LRRK2 kinase function is a promising therapeutic strategy for PD treatment. The search for drug-like molecules capable of reducing LRRK2 kinase activity in PD led to the design of selective LRRK2 inhibitors predicted to be within the CNS drug-like space. This review highlights the journey that translates chemical tools for interrogating the role of LRRK2 in PD into promising drug candidates, addressing the challenges in discovering selective and brain-penetrant LRRK2 modulators and exploring the structure-activity relationship of distinct LRRK2 inhibitors.

Frequency of the LRRK2 G2019S mutation in South African patients with Parkinson's disease.

G2019S in LRRK2 is the most common mutation associated with Parkinson's disease (PD). Highest frequencies are in North African Arabic (30-41%) and Ashkenazi Jewish (6-30%) populations, mostly due to founder effects. Here, we investigated the frequency of G2019S in 647 unrelated South African PD patients from different ancestral origins. It was found in only 1.2% (8/647) of patients. Notably, none of the 91 individuals of African ancestry had G2019S. It was present in 1.9% (3/154) and 1% (5/493) of early- and late-onset cases, respectively. The frequency of G2019S exhibits ethnic-specific differences and warrants further study in sub-Saharan African populations.

G2019S Variation in LRRK2: An Ideal Model for the Study of Parkinson's Disease?

Parkinson's disease (PD) is the second most common neurodegenerative disorder and has plagued humans for more than 200 years. The etiology and detailed pathogenesis of PD is unclear, but is currently believed to be the result of the interaction between genetic and environmental factors. Studies have found that PD patients with the LRRK2:G2019S variation have the typical clinical manifestations of PD, which may be familial or sporadic, and have age-dependent pathogenic characteristics. Therefore, the LRRK2:G2019S variation may be an ideal model to study the interaction of multiple factors such as genetic, environmental and natural aging factors in PD in the future. This article reviewed the progress of LRRK2:G2019S studies in PD research in order to provide new research ideas and directions for the pathogenesis and treatment of PD.

Cancer outcomes among Parkinson's disease patients with leucine rich repeat kinase 2 mutations, idiopathic Parkinson's disease patients, and nonaffected controls.

BACKGROUND: Increased cancer risk has been reported in Parkinson's disease (PD) patients carrying the leucine rich repeat kinase 2 (LRRK2) G2019S mutation (LRRK2-PD) in comparison with idiopathic PD (IPD). It is unclear whether the elevated risk would be maintained when compared with unaffected controls. METHODS: Cancer outcomes were compared among 257 LRRK2-PD patients, 712 IPD patients, and 218 controls recruited from 7 LRRK2 consortium centers using mixed-effects logistic regression. Data were then pooled with a previous study to examine cancer risk between 401 LRRK2-PD and 1946 IPD patients. RESULTS: Although cancer prevalence was similar among LRRK2-PD patients (32.3%), IPD patients (27.5%), and controls (27.5%; P = 0.33), LRRK2-PD had increased risks of leukemia (odds ratio [OR] = 4.55; 95% confidence interval [CI], 1.46-10.61) and skin cancer (OR = 1.61; 95% CI, 1.09-2.37). In the pooled analysis, LRRK2-PD patients had also elevated risks of leukemia (OR = 9.84; 95% CI, 2.15-44.94) and colon cancer (OR = 2.34; 95% CI, 1.15-4.74) when compared with IPD patients. CONCLUSIONS: The increased risks of leukemia as well as skin and colon cancers among LRRK2-PD patients suggest that LRRK2 mutations heighten risks of certain cancers. © 2019 International Parkinson and Movement Disorder Society.

G2019s LRRK2 promotes mitochondrial fission and increases TNFα-mediated neuroinflammation responses.

Leucine rich-repeat kinase 2 (LRRK2) is involved in the pathogenesis of Parkinson's disease (PD). LRRK2 has kinase and GTPase activities, and mediates several cell functions, including vesicle trafficking, apoptosis, autophagy, mitochondrial dynamics, and neuroinflammation. G2019S (GS) is the most prevalent mutation of LRRK2. The mutation increases kinase activity, suggesting that this activity is crucial for PD pathogenesis. The activation and inhibition of LRRK2 kinase increases and reduces the levels of proinflammatory cytokines, respectively suggesting that the role of LRRK2 in neuroinflammation is critical for the pathology of PD. Previously, we demonstrated that microglial activation by lipopolysaccharide (LPS) increases mitochondrial fission via the activation of LRRK2 kinase, while LRRK2 kinase inhibition diminishes the fission morphology and release of tumor necrosis factor-alpha (TNFα) in BV2 or rat primary microglia and the brains of GS transgenic mice. In this study, the ectopic expression of GS LRRK2 in BV2 cells significantly elevated the expression of Drp1 along the fragmented mitochondria and decreased mitochondria size compared with controls. GS LRRK2-transfected BV2 cells displayed significantly increased TNFα release and neuronal death. Inhibition of LRRK2 kinase alleviated these features. TNFα levels in brains of GS mice were significantly increased compared to those in their littermates. These data further support our previous findings concerning LPS-induced neuroinflammation and mitochondrial fission in microglia via LRRK2 kinase activation.

Neurite Collapse and Altered ER Ca2+ Control in Human Parkinson Disease Patient iPSC-Derived Neurons with LRRK2 G2019S Mutation.

The Parkinson disease (PD) genetic LRRK2 gain-of-function mutations may relate to the ER pathological changes seen in PD patients at postmortem. Human induced pluripotent stem cell (iPSC)-derived neurons with the PD pathogenic LRRK2 G2019S mutation exhibited neurite collapse when challenged with the ER Ca2+ influx sarco/ER Ca2+-ATPase inhibitor thapsigargin (THP). Baseline ER Ca2+ levels measured with the ER Ca2+ indicator CEPIA-ER were lower in LRRK2 G2019S human neurons, including in differentiated midbrain dopamine neurons in vitro. After THP challenge, PD patient-derived neurons displayed increased Ca2+ influx and decreased intracellular Ca2+ buffering upon membrane depolarization. These effects were reversed following LRRK2 mutation correction by antisense oligonucleotides and gene editing. Gene expression analysis in LRRK2 G2019S neurons identified modified levels of key store-operated Ca2+ entry regulators, with no alterations in ER Ca2+ efflux. These results demonstrate PD gene mutation LRRK2 G2019S ER calcium-dependent pathogenic effects in human neurons.

LRRK2 G2019S Parkinson's disease with more benign phenotype than idiopathic.

OBJECTIVES: The LRRK2-G2019S mutation is the most common cause of Parkinson's disease (PD) in North Africa. G2019S-PD has been described as similar to idiopathic with minor clinical differences. The aim of this study was to determine the G2019S-related phenotype and to investigate gender and gene dosage effects on clinical features of G2019S carriers. PATIENTS AND METHODS: The G2019S mutation was screened in 250 Tunisian patients with PD. Twenty-four patients carrying mutations in other PD genes were excluded. Logistic regression models were used to compare clinical features between the studied groups. RESULTS: G2019S carriers (107 cases) and non-carriers (119 cases) were similar in disease duration, levodopa doses, and gender and phenotype distributions. However, carriers had a younger age at examination, higher level of education, and were more likely to report family history of PD and to develop PD at earlier age (P = 0.017). Adjusted for age, sex, disease duration, levodopa-equivalent dose and educational level, MMSE scores remained significantly higher (adjust P = 0.019) and UPDRS-III scores were lower (adjust P = 0.012) in the G2019S carriers than non-carriers. Demographic characteristics of men and women with G2019S mutation were similar, but men had higher level of education, better cognition (adjust P-value for educational level = 0.042) and less tendency towards depression than females (adjust P = 0.046). Furthermore, PD phenotype did not differ between the homozygous and heterozygous G2019S carriers. CONCLUSION: In this study, G2019S carriers had a more benign phenotype than non-carriers. Cognitive impairment and depression were less common in G2019S male carriers compared with females. In addition, we found that LRRK2 gene dosage does not influence the severity of PD.

α-synuclein (SNCA) but not dynamin 3 (DNM3) influences age at onset of leucine-rich repeat kinase 2 (LRRK2) Parkinson's disease in Spain.

OBJECTIVES: A recent study showed that Arab-Berbers GG homozygous at rs2421947(C/G) in the dynamin 3 gene (DNM3) had 12.5 years earlier age at onset of leucine-rich repeat kinase 2 (LRRK2)-associated Parkinson's disease (PD) (L2PD). We explored whether this variant modulates the L2PD age at onset in Spain. METHODS: We genotyped rs2421947 in 329 participants (210 L2PD patients, 119 L2PD nonmanifesting p.G2019S carriers), and marker rs356219 (A/G) in the α-synuclein gene (SNCA). RESULTS: By Kaplan Meier and Cox regression analyses, we did not find an association of the DNM3 polymorphism with L2PD age at onset. However, we found an association of the SNCA marker with up to an 11 years difference in the L2PD median age at onset (58 years for GG carriers vs 69 years for AA). CONCLUSION: Our results indicate that SNCA rs356219 but not dynamin 3 DNM3 rs2421947 modifies the penetrance of the mutation G2019S in the Spanish population by influencing the L2PD age at onset. These findings suggest that different genetic modifiers may influence the L2PD age at onset in different populations. © 2018 International Parkinson and Movement Disorder Society.

Analysis of the LRRK2 p.G2019S mutation in Colombian Parkinson's Disease Patients.

INTRODUCTION: Mutations in the leucine-rich repeat kinase 2 gene (LRRK2 or Dardarin) are considered to be a common cause of autosomal dominant and sporadic Parkinson´s disease, but the prevalence of these mutations varies among populations. OBJECTIVE: to analyzed the frequency of the LRRK2 p.G2019S mutation (c.6055 G>A transition) in a sample of Colombian patients. METHODS: In the present study we have analyzed the frequency of the LRRK2 p.G2019S mutation in 154 patients with familial or sporadic Parkinson Disease, including early and late onset patients, and 162 normal controls. RESULTS: Our results show occurrence of this mutation in two cases (2/154, 1.3%) with classical Parkinson´s signs, and one completely asymptomatic control (1/162, 0.6%). CONCLUSION: The p.G2019S mutation is not an important causal factor of Parkinson Disease in Colombia having similar frequencies to those reported in other Latin American populations.

INTRODUCCIÓN: Mutaciones en el LRRK2 (del inglés gen leucine-rich repeat kinase 2) o Dardarina se consideran una causa común de enfermedad de Parkinson autosómica dominante. Sin embargo, la prevalencia de estas mutaciones varia en diferentes poblaciones. OBJETIVO: analizar la frecuencia de la mutación p.G2019S (transición c.6055 G>A) del gen LRRK2en una muestra de pacientes colombianos. MÉTODOS: En el presente estudio analizamos la frecuencia de la mutación en 154 pacientes con enfermedad de Parkinson familiar o esporádica, y 162 controles normales. RESULTADOS: se determinó la presencia de la mutación en 2 casos de Parkinson (2/154, 1.3%) los cuales presentan los signos clásicos de la enfermedad y en un control completamente asintomático (1/162, 0.6%). CONCLUSIÓN: La mutación p.G2019S no es un factor causal importante de la Enfermedad de Parkinson en la población Colombiana, y muestra frecuencias similares a las reportadas en otras poblaciones latinoamericanas.

Analysis of the LRRK2 p.G2019S mutation in Colombian Parkinson's Disease Patients / Análisis de la mutación p.G2019S del gen LRRK2 en pacientes colombianos con enfermedad de Parkinson

Introduction: Mutations in the leucine-rich repeat kinase 2 gene (LRRK2 or Dardarin) are considered to be a common cause of autosomal dominant and sporadic Parkinson's disease, but the prevalence of these mutations varies among populations. Objective: To analyzed the frequency of the LRRK2 p.G2019S mutation (c.6055G>A transition) in a sample of Colombian patients. Methods: In the present study we have analyzed the frequency of the LRRK2 p.G2019S mutation in 154 patients with familial or sporadic Parkinson Disease, including early and late onset patients, and 162 normal controls. Results: Our results show occurrence of this mutation in two cases (2/154, 1.3%) with classical Parkinson's signs, and one completely asymptomatic control (1/162, 0.6%). Conclusion: The p.G2019S mutation is not an important causal factor of Parkinson Disease in Colombia having similar frequencies to those reported in other Latin American populations.

Introducción: Las mutaciones en el LRRK2 (del inglés gen leucinerich repeat kinase 2) o Dardarina se consideran una causa común de enfermedad de Parkinson autosómica dominante. Sin embargo, la prevalencia de estas mutaciones varia en diferentes poblaciones. Objetivo: Snalizar la frecuencia de la mutación p.G2019S (transición c.6055 G>A) del gen LRRK2en una muestra de pacientes colombianos. Métodos: En el presente estudio analizamos la frecuencia de la mutación en 154 pacientes con enfermedad de Parkinson familiar o esporádica, y 162 controles normales. Resultados: Se determinó la presencia de la mutación en 2 casos de Parkinson (2/154, 1.3%) los cuales presentan los signos clásicos de la enfermedad y en un control completamente asintomático (1/162, 0.6%). Conclusión: La mutación p.G2019S no es un factor causal importante de la Enfermedad de Parkinson en la población Colombiana, y muestra frecuencias similares a las reportadas en otras poblaciones latinoamericanas.

G2019S LRRK2 and aging confer susceptibility to proteasome inhibitor-induced neurotoxicity in nigrostriatal dopaminergic system.

The leucine-rich repeat kinase 2 (LRRK2) mutation G2019S is one of the most common genetic causes in Parkinson's disease (PD). The penetrance of G2019S LRRK2 is incomplete and is age-dependent, therefore, it has been speculated that environmental toxins and aging could contribute to G2019S LRRK2-related PD pathogenesis. To prove this speculation, we performed a longitudinal investigation in mice bearing G2019S LRRK2 mutation. BAC G2019S LRRK2 transgenic (Tg) mice and their wildtype (Wt) littermates were treated with lactacystin, a specific proteasome inhibitor. The susceptibilities of mice to lactacystin-induced nigrostriatal dopaminergic (DAergic) degeneration were evaluated, at 5 and 12 months of age. We found that lactacystin treatment caused a greater decline of striatal DA content in the Tg mice at either 5 or 12 months of age than their age-matched Wt littermates. Moreover, the lactacystin-treated Tg or Wt mice at 12 months of age lose much more nigral tyrosine hydroxylase (TH)-positive neurons than the mice at 5 months of age, indicating an age-associated DAergic neurotoxicity. Additionally, stereotactic injection of lactacystin induced a dramatic increase of activated microglia in substantia nigra of mice at 12 months of age, compared with mice at 5 months of age. In summary, our study suggests that expression of the G2019S mutation in the mouse LRRK2 gene confers an age-associated high susceptibility to proteasome inhibition-induced nigrostriatal DAergic degeneration.

Motor phenotype of LRRK2-associated Parkinson's disease: a Tunisian longitudinal study.

Mutations in the leucine-rich repeat kinase 2 gene (LRRK2) were found to be a significant cause of late-onset autosomal dominant forms of Parkinson's disease (PD). To determine the motor characteristics of LRRK2-related disease, we conducted a longitudinal study of 58 G2019S LRRK2-associated PD patients and compared them with genetically undefined (GU) PD patients. Fifty-eight patients diagnosed with PD-related LRRK2 G2019S mutation were included in the study and compared with 54 sporadic PD patients with negative tests for LRRK2 G2019S, PINK1, SNCA, PRKN, and DJ1 mutations. Patients were assessed at baseline and after a follow-up period of 6 years. The Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS), the Hoehn and Yahr, and the Schwab and England scores were determined. Logistic regression was used to examine associations of G2019S mutation status with motor phenotype and rate of motor decline. The LRRK2-associated PD patients had a mean age of onset of 56.25 ± 12.05 years and in most cases (58.6%) a postural instability gait difficulty (PIGD) phenotype. The mean annual decline in the MDS-UDRS III motor score and the Hoehn and Yahr staging was of 1.3% and 2%, respectively. The PIGD phenotype predicted a more rapid progression of motor impairment. The PD motor phenotype and motor scores were similar in the LRRK2-associated PD group and in the GU PD group, with no significant differences in the progression rate of motor impairment. Motor phenotype seems to be similar in LRRK2-related PD and idiopathic PD.