Robust kinase- and age-dependent dopaminergic and norepinephrine neurodegeneration in LRRK2 G2019S transgenic mice

Area of Science:

• Neuroscience
• Genetics
• Pathology

Background:

• Mutations in Leucine-Rich Repeat Kinase 2 (LRRK2) are the most frequent genetic cause of Parkinson's disease (PD).
• Existing LRRK2 transgenic or knockin mouse models have not adequately replicated the substantial dopamine neuron degeneration observed in PD patients.

Purpose of the Study:

• To develop novel transgenic mouse models expressing human LRRK2 G2019S (GS) mutations under the control of the tyrosine hydroxylase (TH) promoter.
• To investigate the cell-autonomous and kinase-dependent mechanisms of LRRK2-induced neurodegeneration in dopamine (DA) and norepinephrine (NE) neurons.

Main Methods:

• Generation of TH promoter-controlled tetracycline-sensitive LRRK2 G2019S (GS) and LRRK2 G2019S kinase-dead (GS/DA) transgenic mice.
• Assessment of age- and kinase-dependent neurodegeneration, behavioral deficits, alpha-synuclein pathology, and synaptic ultrastructure using Transmission Electron Microscopy (TEM).

Main Results:

• LRRK2 GS expression induced age- and kinase-dependent, cell-autonomous degeneration of DA and NE neurons.
• DA neuron loss was associated with DA-dependent behavioral deficits and LRRK2 GS kinase-dependent alpha-synuclein pathology.
• TEM revealed reduced synaptic vesicle numbers and increased clathrin-coated vesicles in DA neurons, dependent on LRRK2 GS kinase activity.

Conclusions:

• LRRK2-induced DA and NE neurodegeneration is a kinase-dependent and cell-autonomous process.
• These novel transgenic mice represent a significant advancement for modeling LRRK2-associated Parkinson's disease.
• The models provide a valuable platform for studying the molecular mechanisms underlying DA neuron degeneration in LRRK2-mutant PD.