NEW MODEL TO STUDY

PARKINSON'S DISEASEElise Villers

Laurent Magnies

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Introduction2

An estimated 4 million the number of people affected by Parkinson's disease

The number of people with Parkinson's disease worldwide will double in 25 years

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

Parkinson’s disease3

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

Genetic contribution?

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

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LRRK2: Leucine Rich Repeat Kinase 2

gene5

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°

5, 2006, p. 470-471.

What do we know about LRRK2?6

Contain many domains:

LRRK2 distribution coincides with brain areas most affectedby PD

Mutations in LRRK2 are the most common cause of geneticParkinsonism

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

Focus on G2019S: the most

common mutation8

MAPKKK domain

amino acid 2,019

GLY SER

To protect the active site To regulate kinase activity

as an anchor for the Mg ion

Focus on G2019S: the most

common mutation9

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)

116:1473–1482

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

Neurodegeneration

Technics and Results11

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

Neurodegeneration

Technics and Results12

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

Neurodegeneration

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

mutant LRRK2 pathogenesis PD of adult rats13

Journal of neuroscience : A Rat Model of Progressive Nigral

Neurodegeneration

Worldwide frequency14

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.

A study in Cantabria15

367

PD patients32 proven carriers

18 probands reported having 1st or 2nd

degree relative

affected by PD

126

Tested at-riskrelatives

13

Clinically affected9 proven carriers

113

Clinically unaffected47 proven carriers

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, No. 13, 2011

Discussion

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

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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,

No. 13, 2011

LRRK2: to test or not to test?17

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

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.

Cause and no consequences

LRRK2 : enzyme catalytic

Therapeutic target for the treatment of

Parkinson's disease

To identifyneuroprotective

strategies to slow or stop progression of the

disease

Development of new pharmaceuticals that inhibit the hyperactivity of enzyme

Therapeutic target

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