Conditional expression of Parkinson's disease-related R1441C LRRK2 in midbrain dopaminergic neurons of mice causes nuclear abnormalities without neurodegeneration

Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene cause late-onset, autosomal dominant Parkinson's disease (PD). The clinical and neurochemical features of LRRK2-linked PD are similar to idiopathic disease although neuropathology is somewhat heterogeneous. Dominant mutations in LRRK2 precipitate neurodegeneration through a toxic gain-of-function mechanism which can be modeled in transgenic mice overexpressing human LRRK2 variants. A number of LRRK2 transgenic mouse models have been developed that display abnormalities in dopaminergic neurotransmission and alterations in tau metabolism yet without consistently inducing dopaminergic neurodegeneration. To directly explore the impact of mutant LRRK2 on the nigrostriatal dopaminergic pathway, we developed conditional transgenic mice that selectively express human R1441C LRRK2 in dopaminergic neurons from the endogenous murine ROSA26 promoter. The expression of R1441C LRRK2 does not induce the degeneration of substantia nigra dopaminergic neurons or striatal dopamine deficits in mice up to 2 years of age, and fails to precipitate abnormal protein inclusions containing alpha-synuclein, tau, ubiquitin or autophagy markers (LC3 and p62). Furthermore, mice expressing R1441C LRRK2 exhibit normal motor activity and olfactory function with increasing age. Intriguingly, the expression of R1441C LRRK2 induces age-dependent abnormalities of the nuclear envelope in nigral dopaminergic neurons including reduced nuclear circularity and increased invaginations of the nuclear envelope. In addition, R1441C LRRK2 mice display increased neurite complexity of cultured midbrain dopaminergic neurons. Collectively, these novel R1441C LRRK2 conditional transgenic mice reveal altered dopaminergic neuronal morphology with advancing age, and provide a useful tool for exploring the pathogenic mechanisms underlying the R1441C LRRK2 mutation in PD. (C) 2014 Elsevier Inc All rights reserved.

Exploring the pathological interaction between LRRK2 and alpha-synuclein

Alessandra Musso

Parkinson’s disease (PD) is the most common age-related neurodegenerative movement disorder that affects 1-2% of the general population over the age of 65 and rising to 4-5% over 80 years of age. It is estimated that 6.3 million people worldwide have Parkinson’s disease and 1.2 million in the European Union (EU) alone. As the disease progresses, patients frequently develop a mask-like facial expression, festinating gait and cognitive impairment and the final clinical symptoms are muscle rigidity, bradykinesia, resting tremor and postural instability in addition to non-motor problems that result in a marked reduction in quality of life. The motor symptoms of PD arise from the progressive degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNpc) leading to a deficiency of the neurotransmitter dopamine (DA) in the striatum. While dopamine replacement therapy is initially effective in treating the motor symptoms of PD, there is no known cure or neuroprotective therapy for this debilitating disease. Although the pathology underlying the disease is well defined, it is still unclear why DAergic neurons degenerate and die. PD is generally considered as a sporadic disease of unknown etiology, however in the last two decades it has become clear that heritability plays an important role in the pathogenesis of PD. Of the different genes associated with familial disease, mutations in two genes encoding for α-synuclein and leucine-rich repeat kinase 2 (LRRK2) proteins cause autosomal dominant PD. One of the neuropathological hallmarks of idiopathic and some familial forms of PD are Lewy bodies, which are intracytoplasmic inclusions that are enriched with fibrillar α- synuclein protein. Notably, LRRK2 mutation carriers with PD predominantly develop Lewy body pathology suggesting that LRRK2 may lie upstream of α-synuclein aggregation. These observations and other in vivo studies have suggested a common pathogenic pathway with LRRK2 potentially regulating the aggregation and neuronal toxicity of α-synuclein. However, the relationship between LRRK2 and α-synuclein in the mammalian brain is presently unclear and requires further evaluation, especially within midbrain dopaminergic neurons that degenerate in PD. The aim of this thesis work was to delineate a potential pathogenic interplay between these two PD-related gene products in mediating neurodegeneration in vivo. Understanding how and where the functional pathways of LRRK2 and α-synuclein converge will provide important insight into the common mechanisms underlying neurodegeneration in PD.[...]

EPFL2014

Dopaminergic Neuronal Loss, Reduced Neurite Complexity and Autophagic Abnormalities in Transgenic Mice Expressing G2019S Mutant LRRK2

Liliane Glauser, Ying Liu, Darren Moore, David Ramonet Jimenez, Klodjan Stafa

Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene cause late-onset, autosomal dominant familial Parkinson's disease (PD) and also contribute to idiopathic PD. LRRK2 mutations represent the most common cause of PD with clinical and neurochemical features that are largely indistinguishable from idiopathic disease. Currently, transgenic mice expressing wild-type or disease-causing mutants of LRRK2 have failed to produce overt neurodegeneration, although abnormalities in nigrostriatal dopaminergic neurotransmission have been observed. Here, we describe the development and characterization of transgenic mice expressing human LRRK2 bearing the familial PD mutations, R1441C and G2019S. Our study demonstrates that expression of G2019S mutant LRRK2 induces the degeneration of nigrostriatal pathway dopaminergic neurons in an age-dependent manner. In addition, we observe autophagic and mitochondrial abnormalities in the brains of aged G2019S LRRK2 mice and markedly reduced neurite complexity of cultured dopaminergic neurons. These new LRRK2 transgenic mice will provide important tools for understanding the mechanism(s) through which familial mutations precipitate neuronal degeneration and PD.

Public Library of Science2011

Inhibition of alpha-synuclein fibrillization by dopamine is mediated by interactions with five C-terminal residues and with E83 in the NAC region

Paolo Carloni, Alessandra Chesi, Hilal Lashuel, Adrian Schmid

The interplay between dopamine and alpha-synuclein (AS) plays a central role in Parkinson's disease (PD). PD results primarily from a severe and selective devastation of dopaminergic neurons in substantia nigra pars compacta. The neuropathological hallmark of the disease is the presence of intraneuronal proteinaceous inclusions known as Lewy bodies within the surviving neurons, enriched in filamentous AS. In vitro, dopamine inhibits AS fibril formation, but the molecular determinants of this inhibition remain obscure. Here we use molecular dynamic (MD) simulations to investigate the binding of dopamine and several of its derivatives onto conformers representative of an NMR ensemble of AS structures in aqueous solution. Within the limitations inherent to MD simulations of unstructured proteins, our calculations suggest that the ligands bind to the (125)YEMPS(129) region, consistent with experimental findings. The ligands are further stabilized by long-range electrostatic interactions with glutamate 83 (E83) in the NAC region. These results suggest that by forming these interactions with AS, dopamine may affect AS aggregation and fibrillization properties. To test this hypothesis, we investigated in vitro the effects of dopamine on the aggregation of mutants designed to alter or abolish these interactions. We found that point mutations in the (125)YEMPS(129) region do not affect AS aggregation, which is consistent with the fact that dopamine interacts non-specifically with this region. In contrast, and consistent with our modeling studies, the replacement of glutamate by alanine at position 83 (E83A) abolishes the ability of dopamine to inhibit AS fibrillization.

Public Library of Science2008

Exploring the pathological interaction between LRRK2 and alpha-synuclein

Alessandra Musso

EPFL2014