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Phd student (M/F) : Brain Gene delivery by sonoporation for Fragile X syndrome therapy

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Français - Anglais

Date Limite Candidature : jeudi 4 novembre 2021

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General information

Reference : UPR4301-MARPER-062
Workplace : ORLEANS
Date of publication : Thursday, October 14, 2021
Scientific Responsible name : Dr. Anthony DELALANDE
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 December 2021
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly

Description of the thesis topic

Fragile X Syndrome (FXS) is the most common cause of intellectual disability (ID) hereditary with a prevalence of 1/4000 males and 1/6000 females. This monogenic pathology linked to the X chromosome particularly affects men with a triad of clinical signs such as moderate to severe ID, post-pubertal macro-orchid, as well as facial dysmorphia. In about 40% of cases, FXS is also associated with autism spectrum disorders (Koukoui and Chaudhuri 2007).
At present there is no treatment for this disease, only symptomatic measures to reduce the effects of the disease are proposed. Gene therapy is a promising therapeutic strategy, however, a method of efficient gene transfer and not invasive must be put in place. A study using AAV2/9 viral vectors highlighted evidence an improvement in the phenotype of treated Fmr1-KO mice, these vectors included also a specific promoter of synapsin-1 neurons (Gholizadeh et al. 2014). Despite its cellular tropism, AAV9 is not very efficient to cross the blood-brain barrier. The injections of vectors were carried out by intracranial route, which constitutes a therapeutic brake for translation in human clinic.
The blood-brain barrier (BBB) shields the brain by preventing the access of drugs and blood circulating molecules. The use of ultrasound combined with gas microbubbles a contrast agent routinely used in echography, makes it possible to permeabilize the BBB transiently (Dauba et al. 2020). This method has been established in 1995 and 2001 using pulsed ultrasound on rabbits by Hynynen et al. (Hynynen et al. 2001).
Focused ultrasound applied in presence of intravascular gas microbubbles can be used to elicit transient and focused opening of the BBB by stretching and shrinking the endothelial cells upon microbubble oscillations (Figure 2). This technique, whose clinical translation in on the way with the publication of the results of the phase I study on the feasibility of this technique for Parkinson Disease (Gasca-Salas et al. 2021). This opens new avenues to rethink how the brain can be targeted and the neurovascular unit studied.
Sonoporation is the method that allow a transient permeabilization of cellular membranes for drug and gene delivery. This method has been established for the first time in 1997 in vitro and in 1998 in vivo by Bao et al. (Bao et al. 1997; Bao et al. 1998). Many developments in the technique were made (ultrasound protocol, microbubbles formulations…), leading to efficient protocols for gene delivery in vivo for several applications.
Recently, we developed a gene delivery platform in the brain by focused ultrasound (FUS) using cationic microbubbles for transporting plasmid DNA. Indeed, thanks to the great diversity of molecules that can compose the envelope, it is thus possible to encapsulate drugs or to complex nucleic acids. Our group is working on the development of drug/gene delivery vectors for nanomedicine. We are currently working on cationic microbubbles and nanobubbles allowing an interaction with nucleic acids (Delalande et al. 2017; Manta et al. 2016; Manta et al. 2017; Mignet et al. 2019). We would like to apply our gene delivery strategy for targeted delivery in brain for X fragile syndrome.

FUSBRAIN aims to understand how nucleic acids can be delivered and expressed in the brain after sonoporation and how its regulation can be used to rescue the FXS phenotype.
FUSBRAIN will address the following scientific objectives:
• Assess the sonoporation in the brain in a safe, reproducible and efficient manner
• The analysis of the trafficking of nucleic acid and microbubbles after sonoporation
• The evaluation of the expression levels and kinetics of Fmr1 transgene
• Understand how Fmr1 rescue assay can modify neuron communication and mouse behaviour

Work Context

Within the Molecular Biophysics Center (CBM - UPR4301) located in Orléans on the CNRS campus, the doctoral student will work within the thematic group “Innovative Therapies and Nanomedicine”. The CBM is developing research at the interface of Chemistry, Biology and Physics which is interested in the molecular mechanisms of living organisms and the dysfunctions that lead to the development of certain diseases.
The PhD student will be co-supervised by an assistant professor from this group and by an associate professor from the INEM laboratory (Orléans). The thesis is funded by an ANR program.

Constraints and risks

- Work on rodents
- Possible work in shifted hours and weekend

Additional Information

Candidates must send their CV and cover letter via the emploi.cnrs.fr website.
Only applications received via this CNRS procedure will be considered.

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