LRRK 2 R1441G mice are more liable to dopamine depletion and locomotor inactivity

Abstract

ObjectiveMutations in leucine-rich repeat kinase 2 (LRRK2) pose a significant genetic risk in familial and sporadic Parkinson's disease (PD). R1441 mutation (R1441G/C) in its GTPase domain is found in familial PD. How LRRK2 interacts with synaptic proteins, and its role in dopamine (DA) homeostasis and synaptic vesicle recycling remain unclear.MethodsTo explore the pathogenic effects of LRRK2R1441G mutation on nigrostriatal synaptic nerve terminals and locomotor activity, we generated C57BL/6N mice with homozygous LRRK2R1441G knockin (KI) mutation, and examined for early changes in nigrostriatal region, striatal synaptosomal [3H]-DA uptake and locomotor activity after reserpine-induced DA depletion.ResultsUnder normal conditions, mutant mice showed no differences, (1) in amount and morphology of nigrostriatal DA neurons and neurites, (2) tyrosine hydroxylase (TH), DA uptake transporter (DAT), vesicular monoamine transporter-2 (VMAT2) expression in striatum, (3) COX IV, LC3B, Beclin-1 expression in midbrain, (4) LRRK2 expression in total cell lysate from whole brain, (5) α-synuclein, ubiquitin, and tau protein immunostaining in midbrain, (6) locomotor activity, compared to wild-type controls. However, after a single intraperitoneal reserpine dose, striatal synaptosomes from young 3-month-old mutant mice demonstrated significantly lower DA uptake with impaired locomotor activity and significantly slower recovery from the effects of reserpine.InterpretationAlthough no abnormal phenotype was observed in mutant LRRK2R1441G mice, the KI mutation increases vulnerability to reserpine-induced striatal DA depletion and perturbed DA homeostasis resulting in presynaptic dysfunction and locomotor deficits with impaired recovery from reserpine. This subtle nigrostriatal synaptic vulnerability may reflect one of the earliest pathogenic processes in LRRK2-associated PD.

Phos-tag analysis of Rab10 phosphorylation by LRRK2: a powerful assay for assessing kinase function and inhibitors

“…LRRK2[S910A+S935A] cells were genotyped as described above and LRRK2[R1441G] cells were genotyped as described previously [32]. Homozygous LRRK2[S910A+S935A] knockin as well as the WT cells generated from the same littermate were spontaneously immortalized by prolonged passaging in parallel for at least 20 passages before being used for Phos-tag experiments.…”

Progressive dopaminergic alterations and mitochondrial abnormalities in LRRK2 G2019S knock-in mice

“…The overwhelming data from rodent models with near-physiologic levels transgenic expression suggest that mutant LRRK2 impairs dopamine neurotransmission, in the absence of neuronal loss (Li et al, 2009; Li et al, 2010; Melrose et al, 2010; Zhou et al, 2011; Beccano-Kelly et al, 2014b; Liu et al, 2014; Tsika et al, 2014; Walker et al, 2014; Lee et al, 2015) whereas higher levels of expression of LRRK2, via heterologous promoters or viral delivery, leads to dopamine neuronal death in mice and rats (Lee et al, 2010; Dusonchet et al, 2011; Ramonet et al, 2011). Nigro-striatal dopamine alterations were not found in two previously reported gene-targeted LRRK2 mutant models (Tong et al, 2009; Herzig et al, 2011).…”

The effects of gestational and chronic atrazine exposure on motor behaviors and striatal dopamine in male Sprague-Dawley rats

“…In rodents atrazine has been shown to alter locomotor activity (Bardullas et al, 2011; Belloni et al, 2011; Peruzovic et al, 1995; Rodriguez et al, 2013; Ugazio et al, 1991), delay righting reflexes (Belloni et al, 2011), and impair rotarod performance (Bardullas et al, 2011). These tasks have all been shown to measure behaviors that are controlled, in part, by NSDA neurons (Adeosun et al, 2012; Galli et al, 2014; Kravitz et al, 2010; Liu et al, 2014; Verhave et al, 2009; Yin et al, 2009). The walking beam assay assesses the ability of rats to traverse a narrow elevated beam and has proven to be very useful in the assessment of motor coordination (Goldsten, 2003).…”