Article

High LRRK2 Levels Fail to Induce or Exacerbate Neuronal Alpha-Synucleinopathy in Mouse Brain

Department of Neuroscience, Novartis Institutes for BioMedical Research, Novartis Pharma AG, Basel, Switzerland.
PLoS ONE (Impact Factor: 3.23). 05/2012; 7(5):e36581. DOI: 10.1371/journal.pone.0036581
Source: PubMed

ABSTRACT The G2019S mutation in the multidomain protein leucine-rich repeat kinase 2 (LRRK2) is one of the most frequently identified genetic causes of Parkinson's disease (PD). Clinically, LRRK2(G2019S) carriers with PD and idiopathic PD patients have a very similar disease with brainstem and cortical Lewy pathology (α-synucleinopathy) as histopathological hallmarks. Some patients have Tau pathology. Enhanced kinase function of the LRRK2(G2019S) mutant protein is a prime suspect mechanism for carriers to develop PD but observations in LRRK2 knock-out, G2019S knock-in and kinase-dead mutant mice suggest that LRRK2 steady-state abundance of the protein also plays a determining role. One critical question concerning the molecular pathogenesis in LRRK2(G2019S) PD patients is whether α-synuclein (aSN) has a contributory role. To this end we generated mice with high expression of either wildtype or G2019S mutant LRRK2 in brainstem and cortical neurons. High levels of these LRRK2 variants left endogenous aSN and Tau levels unaltered and did not exacerbate or otherwise modify α-synucleinopathy in mice that co-expressed high levels of LRRK2 and aSN in brain neurons. On the contrary, in some lines high LRRK2 levels improved motor skills in the presence and absence of aSN-transgene-induced disease. Therefore, in many neurons high LRRK2 levels are well tolerated and not sufficient to drive or exacerbate neuronal α-synucleinopathy.

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Available from: Derya R Shimshek, Aug 27, 2015
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    • "Recent emerging evidence suggests interactions between LRRK2 and a-synuclein aggregation (Lin et al., 2009; Orenstein et al., 2013), but this remains controversial (Daher et al., 2012; Herzig et al., 2012). Thus, the cortico–striatal circuit may in part be selectively vulnerable in PD because of the concentration of proteins known to underlie aspects of late-onset PD. "
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    ABSTRACT: Mutations in leucine-rich repeat kinase 2 (LRRK2) are found in a significant proportion of late-onset Parkinson's disease (PD) patients. Elucidating the neuroanatomical localization of LRRK2 will further define LRRK2 function and the molecular basis of PD. Here, we utilize recently characterized monoclonal antibodies to evaluate LRRK2 expression in rodent brain regions relevant to PD. In both mice and rats, LRRK2 is highly expressed in the cortex and striatum, particularly in pyramidal neurons of layer V and in medium spiny neurons within striosomes. Overall, rats have a more restricted distribution of LRRK2 compared to mice. Mice, but not rats, show high levels of LRRK2 expression in the substantia nigra pars compacta. Expression of the pathogenic LRRK2-G2019S protein from mouse BAC constructs closely mimics endogenous LRRK2 distribution in the mouse brain. However, LRRK2-G2019S expression derived from human BAC constructs causes LRRK2 to be expressed in additional neuron subtypes in the rat such as striatal cholinergic interneurons and the substantia nigra pars compacta. The distribution of LRRK2 from human BAC constructs more closely resembles descriptions of LRRK2 in humans and non-human primates. Computational analyses of DNA regulatory elements in LRRK2 show a primate-specific promoter sequence that does not exist in lower mammalian species. These non-coding regions may be involved in directing neuronal expression patterns. Together, these studies will aid in understanding the normal function of LRRK2 in the brain and will assist in model selection for future studies. J. Comp. Neurol., 2014. © 2014 Wiley Periodicals, Inc.
    The Journal of Comparative Neurology 08/2014; 522(11). DOI:10.1002/cne.23583 · 3.51 Impact Factor
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    • "These include lines that lack the LRRK2 protein (whole or part), or overexpress human wildtype LRRK2, the LRRK2-G2019S mutation or a LRRK2 kinase-dead mutation. In some cases, neither of these lines showed changes in markers of dopamine neuron health, dopamine levels or dopaminergic drug-evoked behaviors (while displaying pronounced histopathological changes in the kidney and lung where LRRK2 is also highly expressed) [22] [23]. In other cases, such transgenics did display modest alterations in dopamine function/ release and/or related behaviors, but, with one exception [24], none showed dopamine neuron degeneration [25] [26] [27] [28] [29] [30] [31]. "
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    ABSTRACT: It has been 10 years and more since associations between specific genes and Parkinson's disease (PD) were discovered, and it is now assumed that mutations in such PD (risk) genes, probably in interaction with other factors, are a major cause for PD [1–4]. These PD risk genes include alpha-synuclein (SNCA), LRRK2, Parkin, PINK1 and others. Yet after a decade of intense research it is still unclear how most mutations in these genes contribute to the PD pathology. This is likely due to a number of reasons, including that some of these genes seem to encode complex molecules with multiple functions; that mutations may lead to toxic gain-of-function and/or loss-of-function defects; that mutated molecules may need to interact with one another or other influences to be effective; or that some of these molecules or their products may need to migrate from other brain structures or even from the periphery to the dopamine neurons that they are supposed to kill. These factors all complicate the analysis of the mechanisms of action of PD risk genes. LRRK2 Perhaps most is known about the potential mechanisms of action of LRRK2 (e.g., [3,5–11]), which can serve as an example to highlight the many complexities encountered in the search of a function. With the first mutation discovered a decade ago in familial cases of PD [12–14], many mutations have since been described in the LRRK2 gene and several are considered pathogenic [3,5,6,9]. These are missense mutations. The most prevalent of these mutations, G2019S, was found in 1-2% of sporadic PD cases (in a Caucasian population) [15], but in up to 37% of familial PD cases in specific ethnic groups (Ashkenazi Jews, North African Arabs; c.f. [5]). The LRRK2 gene has 51 exons and encodes a large (286 kDa) protein with several predicted functional domains. These include a MAPKKK-like kinase domain and a ROC GTPase domain, as well as COR, leucine-rich repeat (LRR), ankyrin, armadillo and WD40 domains [5–7]. Wildtype LRRK2 binds/affects a variety of proteins, including Parkin, HSP90, moesin, tubulin, as well as presynaptic proteins involved in vesicle trafficking such as NSF, syntaxin 1, actin and others [5,7,16]. The mutations occur throughout LRRK2 [5,6]. Several mutations, including G2019S, are in the kinase domain [5,7,17]; G2019S, for example, abnormally increases kinase activity in in vitro [5,7] and in mouse models [17]. Models To study the function of the wildtype protein or one of these mutations, researchers have used a variety of approaches and expression systems, including targeted deletion (knock-out), or overexpression of wildtype or mutant LRRK2 in bacterial systems, cell lines (e.g., HEK-293, Cos-7, SH-SY5Y), primary neuron cultures or invertebrate models (C. elegans, Drosophila) [3,5,8,9,11], as well as in mouse lines [3,5,18]. Hypotheses as to what could be wrong in these mutants are typically derived from the predicted protein functions (e.g., kinase, GTPase), or from what is now known to be amiss in PD (e.g., loss of dopamine neurons, mitochondrial vulnerability, inflammation, etc.). These studies yielded a plethora of findings on potential LRRK2 (mal)functions, including effects on synaptic vesicle recycling, neurite morphology/outgrowth, autop-hagy, pro-inflammatory factors, susceptibility to oxidative stress, cell death via accumulation of alpha-synuclein, and others [5– 9,17,19]. Yet it is not clear whether or to what extent these mutations make dopamine neurons sick in mammals. For one, in PD their association remains correlative. In animal models, degeneration of dopamine neurons after deletion of LRRK2 (e.g., [20]) or over-expression of LRRK2 or LRRK2-G2019S [21] was reported in some (but not all) Drosophila and other invertebrate models. However, transgenic mice display surprisingly subtle or no effects on the dopamine transmission [3,5,11,18]. Indeed, a lack of significant degeneration of dopamine neurons seems to be a common feature of most mouse models of PD risk genes [3]. For LRRK2, mouse lines with a variety of constructs (knock-out, knock-in, BAC) have been developed [3,5,11,18]. These include lines that lack the LRRK2 protein (whole or part), or overexpress human wildtype LRRK2, the LRRK2-G2019S mutation or a LRRK2 kinase-dead mutation. In some cases, neither of these lines showed changes in markers of dopamine neuron health, dopamine levels or dopaminergic drug-evoked behaviors (while displaying pro-nounced histopathological changes in the kidney and lung where LRRK2 is also highly expressed) [22,23]. In other cases, such transgenics did display modest alterations in dopamine function/ release and/or related behaviors, but, with one exception [24], none showed dopamine neuron degeneration [25–31]. In contrast to these transgenic models, substantial degenera-tion of dopamine neurons could be achieved by virally driven overexpression of pathogenic LRRK2 (G2019S) in dopamine neurons of rodents [32,33]. However, while providing a valuable
    07/2013; 3(2):73-76. DOI:10.1016/j.baga.2013.04.002
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    ABSTRACT: A report suggests that leucine-rich repeat kinase 2 (LRRK2) can be degraded through chaperone-mediated autophagy (CMA) in the lysosome, and several Parkinson's disease-causing LRRK2 mutants impair CMA-mediated selective degradation of cytosolic substrates.
    Nature Neuroscience 04/2013; 16(4):375-7. DOI:10.1038/nn.3361 · 14.98 Impact Factor
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