Objective/Rationale:
Mutations of the gene LRRK2 are identified in both familial and sporadic Parkinson’s disease (PD). How mutation of the LRRK2 gene causes neuronal dysfunction in PD remains to be elucidated. A critical step to understanding LRRK2 pathogenesis is to reproduce the phenotypes of LRRK2 mutation in an intact system such as mammalian animals. This proposal aims to develop a novel model for PD by temporally expressing a mutant human LRRK2 gene selectively in adult rat.
Project Description:
We have created transgenic rats that express a mutant human LRRK2 gene under control of a regulatory promoter. The mutant LRRK2 transgenic rats will be crossed with a tTA transgenic rat line to produce double transgenic offspring that will express the mutant LRRK2 transgene in the absence of the inducer Doxycycline. Expression of the mutant LRRk2 transgene will be suppressed during embryonic and postnatal development, but will be restored in adult rats. Using in-brain microdialysis and stereological cell counting, we will assess the effects of mutant LRRK2 on dopaminergic function and the neuron survival..
Relevance to Diagnosis/Treatment of Parkinson’s Disease:
The results from this in vivo study will advance our understanding of PD pathogenesis and provide theoretic guidance to development of therapeutic strategies for PD treatment. The resulting pre-clinical model will be useful to mechanistic study on PD and to therapeutic test.
Anticipated Outcome:
By end of this project, we expect to characterize the novel pre-clinical model and to determine how mutation of the LRRK2 gene causes dysfunction or death of dopamine neurons in the transgenic rats.
Final Outcome
Mutation of the LRRK2 gene is associated with familial Parkinson’s disease (PD) and toxicity of LRRK2 mutation may be linked to increased kinase activity of LRRK2 protein. Most PD cases are sporadic without known genetic causes, but sporadic PD cases might suffer from epigenetic modification to PD genes such as LRRK2 later in lives.
To test whether temporal over-expression of the LRRK2 gene with pathogenic mutation, we made inducible LRRK2 transgenic rats expressing G2019S-LRRK2 transgene in adulthood. These transgenic rats did not show a loss of dopaminergic neurons in the midbrain, but did show an impairment of dopaminergic neurotransmission. Our results suggest that impairment of dopaminergic neurotransmission is an initial process toward neurodegeneration.