This document discusses a new rat model developed to study Parkinson's disease. Researchers introduced a mutated version of the LRRK2 gene, which is a common genetic cause of Parkinson's, into the brains of rats. They found this caused progressive loss of dopamine-producing neurons in the substantia nigra, replicating a key feature of Parkinson's. The model provides an efficient way to further study how LRRK2 mutations lead to neuronal degeneration and may help identify neuroprotective strategies.

1. 1
NEW MODEL TO STUDY
PARKINSON'S DISEASE
Elise Villers
Laurent Magnies

2. Introduction
2
An estimated 4 million the number of people affected by Parkinson's disease
Parkinson's disease usually starts between 55 and 65
With the ageing of the world population, the
importance of Parkinson's disease as a public health
issue expected to increase
The number of people with Parkinson's disease worldwide will double in 25 years

3. Parkinson’s disease
3
A degenerative disorder of the central nervous
system. The motor symptoms of Parkinson's
disease result from the progressive loss of
dopamine-generating cells in the substantia nigra,
a region of the midbrain
Clinic symptoms are movement-related:
Shaking
Rigidity
Bradykinesia
Difficulty with walking and gait
In the advanced stages of the disease:
cognitive and behavioural problems
dementia

4. Genetic contribution?
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Purely idiopathic
In 1900, Gowers reported that 15% of patients had a family history
A genetic contribution is suspected for a long time
Genetic factors involved in 10% of cases
Difficult to reproduce the disease in animals due to an
incomplete understanding
Recently, it was found that mutations of the gene coding for
LRRK2, brain enzyme, was the prevalent genetic cause of PD

5. LRRK2: Leucine Rich Repeat Kinase 2
gene
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Chromosome 12
51 exons  encode a 2,527 AA protein
Belong to ROCO (Ras-GTPase) protein family
wich is involved in diverse cellular processes:
- Regulation of cell polarity
- Chemotaxis
- Cytokinesis
- Cytoskeletal rearrangements
- Programmed cell death
Avner Thaler. The LRRK2 G2019S mutation as the cause of Parkinson’s disease in Ashkenazi Jews. J Neural Transm (2009)
116:1473–1482.
Suzanne Lesage, LRRK2, gène majeurde la maladie de Parkinson dans les pays du Maghreb. M/S : médecine sciences, vol. 22, n°

6. What do we know about LRRK2?
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 Contain many domains:
 LRRK2 distribution coincides with brain areas most affected
by PD
 Mutations in LRRK2 are the most common cause of genetic
Parkinsonism
 Dominant mode of inheritance with G2019S
 30 mutations in LRRK2 and 5 pathogens
Avner Thaler. The LRRK2 G2019S mutation as the cause of Parkinson’s disease in Ashkenazi Jews. J Neural Transm (2009) 116:1473
1482

7. 7

8. Focus on G2019S: the most
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common mutation
GLY  SER
amino acid 2,019
MAPKKK domain
To protect the active site To regulate kinase activity
as an anchor for the Mg ion

9. Focus on G2019S: the most
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common mutation
Conformationnal change that:
- Increase Kinase activity
- Enhance autophosphorylation
- Cause neuronal cells’ death=> dopamine
Avner Thaler. The LRRK2 G2019S mutation as the cause of Parkinson’s disease in Ashkenazi Jews. J Neural Transm (2009)

10. Journal of neuroscience : A Rat Model of
Progressive Nigral Neurodegeneration
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To introduce the enzyme
mutated LRRK2 in the cerebral
hemisphere of a rat  To
reproduce the robust nigral
neurodegeneration
To optimize an adenoviral
vector to transport, in the
nigrostriatal system of adult
rats, the DNA encoding the
mutated enzyme
Difficult to design a vector due to the complexity and the size of the LRRK2
Journal of neuroscience : A Rat Model of Progressive Nigral

11. Technics and Results
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Recombinant Ad vectors were injected in the striatum
we observed a widespread distribution of vector around the injection sites,
resulting in efficient transport and good expression in nigral subtance
High-magnification photomicrographs of anti-FLAG immunostainings
Journal of neuroscience : A Rat Model of Progressive Nigral

12. Technics and Results
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TH: dopaminergic marker
No cell loss is detected in rad-WT-
LRRK2-injected groups
Overexpression of LRRK2 G2019S
causes a progressive loss of TH-
positive dopaminergic neurons
Photomicrographs
showing the loss of TH+
Journal of neuroscience : A Rat Model of Progressive Nigral

13. Next, we explored the alterations associated with neuronal
degeneration due to G2019S LRRK2 overexpression
Immunostaining  Abnormal hyperphosphorylation of tau protein
in neurons dystrophies with the mutation G2019S.
Adenoviral vectors provide an efficient answer to the
size constraints of the LRRK2 coding sequence (7.6 kb)
and represent highly flexible tools for the study of
13 mutant LRRK2 pathogenesis PD of adult rats
Journal of neuroscience : A Rat Model of Progressive Nigral

14. Worldwide frequency
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Suzanne Lesage, LRRK2, gène majeurde la maladie de Parkinson dans les pays du Maghreb. M/S : médecine sciences, vol. 22, n°
5, 2006, p. 470-471.

15. A study in Cantabria
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18 probands reported
367 having 1st or 2nd
32 proven carriers degree relative
PD patients
affected by PD
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9 proven carriers
126 Clinically affected
Tested at-risk
relatives
113
47 proven carriers
Clinically unaffected
Marı´a Sierra. High Frequency and Reduced Penetrance of LRRK2 G2019S Mutation Among Parkinson’s Disease Patients in
Cantabria (Spain). Service of Neurology, University Hospital ‘‘Marque´ s de Valdecilla,’’ University of Cantabria (UC). Movement

16. Discussion
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 Homogeneous population coming from a small
geographical area and isolated
=>To extrapolate to the population and providing
an accurate genetic counseling in a local
context
BUT extrapolate to others seem improbable
Marı´a Sierra. High Frequency and Reduced Penetrance of LRRK2 G2019S Mutation Among Parkinson’s Disease Patients in Cantabria
(Spain). Service of Neurology, University Hospital ‘‘Marque´ s de Valdecilla,’’ University of Cantabria (UC). Movement Disorders, Vol. 26

17. LRRK2: to test or not to test?
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Genetic testing for the G2019S mutation might enable early detection and
confirmation of PD :
Improving the accuracy of diagnosis
Rigorous follow- up in patients which may delay or minimize
complications of the disease
To test neuroprotective strategies as they become available
Cause and no consequences
Aiding in the understanding of the pathogenesis and clinics results
But These targets are all still under research
Predictive test of the G2019S mutation is not currently recommended,
partly due to the lack of current neuroprotective therapies.

18. LRRK2 : enzyme
catalytic
Therapeutic target
Therapeutic target for
the treatment of
Parkinson's disease
To identify
neuroprotective
strategies to slow or stop
progression of the
disease
Development of new
pharmaceuticals that inhibit
the hyperactivity of enzyme
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