Abstract
BackgroundMultiple missense mutations in Leucine-rich repeat kinase 2 (LRRK2) are associated with familial forms of late onset Parkinson’s disease (PD), the most common age-related movement disorder. The dysfunction of dopamine transmission contributes to PD-related motor symptoms. Interestingly, LRRK2 is more abundant in the dopaminoceptive striatal spiny projection neurons (SPNs) compared to the dopamine-producing nigrostriatal dopaminergic neurons. Aging is the most important risk factor for PD and other neurodegenerative diseases. However, whether LRRK2 modulates the aging of SPNs remains to be determined.MethodsWe conducted RNA-sequencing (RNA-seq) analyses of striatal tissues isolated from Lrrk2 knockout (Lrrk2−/−) and control (Lrrk2+/+) mice at 2 and 12 months of age. We examined SPN nuclear DNA damage and epigenetic modifications; SPN nuclear, cell body and dendritic morphology; and the locomotion and motor skill learning of Lrrk2+/+ and Lrrk2−/− mice from 2 to 24 months of age. Considering the strength of cell cultures for future mechanistic studies, we also performed preliminary studies in primary cultured SPNs derived from the Lrrk2+/+ and Lrrk2−/− mice as well as the PD-related Lrrk2 G2019S and R1441C mutant mice.ResultsLrrk2-deficiency accelerated nuclear hypertrophy and induced dendritic atrophy, soma hypertrophy and nuclear invagination in SPNs during aging. Additionally, increased nuclear DNA damage and abnormal histone methylations were also observed in aged Lrrk2−/− striatal neurons, together with alterations of molecular pathways involved in regulating neuronal excitability, genome stability and protein homeostasis. Furthermore, both the PD-related Lrrk2 G2019S mutant and LRRK2 kinase inhibitors caused nuclear hypertrophy, while the Lrrk2 R1441C mutant and γ-Aminobutyric acid type A receptor (GABA-AR) inhibitors promoted nuclear invagination in the cultured SPNs. On the other hand, inhibition of neuron excitability prevented the formation of nuclear invagination in the cultured Lrrk2−/− and R1441C SPNs.ConclusionsOur findings support an important physiological function of LRRK2 in maintaining nuclear structure integrity and genomic stability during the normal aging process, suggesting that PD-related LRRK2 mutations may cause the deterioration of neuronal structures through accelerating the aging process.
Highlights
Multiple missense mutations in Leucine-rich repeat kinase 2 (LRRK2) are associated with familial forms of late onset Parkinson’s disease (PD), the most common age-related movement disorder
Since LRRK2 is highly enriched in Striatal spiny projection neuron (SPN) [21], we performed gene expression analysis of the dorsal striatal tissues isolated from Lrrk2+/+ and Lrrk2−/− mice at 2 and 12 months of age
Gene ontology (GO) analysis of genes affected by Lrrk2-deficiency indicate that in the 2-month-old Lrrk2−/− mice, the upregulated genes are mainly involved in potassium ion (K+) transport, cellular response to calcium ion (Ca2+) and action potential pathway (Fig. 1b)
Summary
Multiple missense mutations in Leucine-rich repeat kinase 2 (LRRK2) are associated with familial forms of late onset Parkinson’s disease (PD), the most common age-related movement disorder. The genetic burden of LRRK2 variants appears to correlate with the age at onset of disease [11] and the penetrance of LRRK2 mutations is increased with age [4]. These studies support a potential pathogenic interplay between aging and disease-related genetic mutations in determining the onset and progression of the disease. Despite aging being the most significant risk factor for PD and other neurodegenerative diseases [2, 12, 13], whether LRRK2 regulates normal neuronal aging is unknown
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