Endoplasmic reticulum (ER) is a dynamic, tubular intracellular network implicated in a variety of cellular functions. Although it is known to play a role in neurodegeneration, its organization and precise function in neurons have been neglected. I will use the physiopathology of certain forms of hereditary spastic paraplegia (HSP) as a model to understand why and how alteration of ER dynamics in neurons can lead to neurodegeneration.
I will focus on three genetic entities, SPG11, SPG15 and SPG48, which are clinically and biochemically related, since the proteins encoded by these genes (spatacsin, spastizin and KIAA0415) are all present in a multiprotein complex important for ER function. The project has three objectives:
- Elucidate the role of spatacsin, spastizin and KIAA0415 in the regulation of ER morphology and dynamics;
- Establish the link between abnormal ER function and neurodegeneration;
- Identify new partners of spatacsin, spastizin and KIAA0415 implicated in ER function.
- We will first develop and characterize physiopathological experimental models: (i) an SPG11 knockout mouse; (ii) primary cultures of neurons subjected to RNA interference to downregulate expression of the SPG11, 15 and 48 genes; (iii) neurons differentiated from induced pluripotent stem (iPS) cells derived from fibroblasts of patients with mutations in SPG11, 15 and 48. ER organization and dynamics will be analyzed in these models using electron and fluorescence microscopy (confocal microscopy, super resolution Structured Illumination Microcopy), as well as videomicroscopy on living cultured neurons. The cell culture models will allow us to determine how the functions of ER that are altered in the pathological models in culture are linked to neuronal death. This pioneering work will help understand the functions of neuronal ER in both normal and pathological conditions – HSP, but also other neurodegenerative diseases.
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