Project description:The goal of this project is to study differentially expressed genes in patients affected by Hereditary Spastic Paraplegia (HSP) linked to mutations of the gene encoding spastin an ubiquitously expressed protein that has recently been shown to be involved in microtubule regulation and vesicle trafficking by cell culture studies. Gene profiling was done with Affymetrix U95Av2 GeneChips using the total RNA extracted from muscle biopsies of 3 SPG4-linked HSP patients. Keywords: other
Project description:The goal of this project is to study differentially expressed genes in patients affected by Hereditary Spastic Paraplegia (HSP) linked to mutations of the gene encoding spastin an ubiquitously expressed protein that has recently been shown to be involved in microtubule regulation and vesicle trafficking by cell culture studies. Gene profiling was done with Affymetrix U95Av2 GeneChips using the total RNA extracted from muscle biopsies of 3 SPG4-linked HSP patients.
Project description:Hereditary Spastic Paraplegia (HSP) leads to progressive gait disturbances with lower limb muscle weakness and spasticity. Mutations in SPG4 are a major cause of autosomal-dominant HSP. Spastin, the protein encoded by SPG4, is a microtubule-severing protein and is enriched in the distal axon of corticospinal motor neurons which degenerate in HSP patients. How SPG4 mutations cause axon degeneration in patients is not understood. Multipotent neural stem cells, accessible from patient olfactory mucosa biopsies, provided a new patient-derived cell models for HSP. Olfactory neurosphere-derived cells were obtained from cohorts of HSP patients with, and without, mutations in SPG4 and from healthy controls. Patient cells had extensive changes in expression of cell cycle-related genes and in genes associated with microtubule formation. Despite this, cell proliferation and metabolic functions of the patient cells were similar to controls. Cells with mutated SPG4 had significantly less spastin and acetylated tubulin but significantly more stathmin, a tubulin-depolymerising protein. These cells also significant deficits in the intracellular distribution of peroxisomes and mitochondria, compared to control cells. This model reveals that SPG4-HSP patient-derived neural stem/progenitors compensate for the cell cycle-related effects of reduced spastin levels in the nucleus, in part by large changes in gene expression, but failed to correct deficits in organelle trafficking. The results raise the question of whether these deficits arise directly from the loss of spastin or indirectly from the compensation. Patient-derived olfactory stem cells provide a new model for examining the neural consequences of human genetic mutations in their natural setting: at normal gene dosages against normal genetic backgrounds.
Project description:The HipSci project brings together diverse constituents in genomics, proteomics, cell biology and clinical genetics to create a UK national iPS cell resource and use it to carry out cellular genetic studies. In this sub-study we performed Genotyping analysis using the Infinium HumanExome BeadChip on iPS cells generated from skin biopsies or blood samples from rare disease patients diagnosed with Hereditary Spastic Paraplegia.
Project description:To understand the disease mechanism of SPG7 hereditary spastic paraplegia, we generated and evaluated patient and control induced pluripotent stem cell derived cortical neurons. We then performed gene expression profiling analysis using data obtained from RNA-seq.
Project description:Unbiased phenotypic screens in patient-relevant disease models offer the potential to detect therapeutic targets for rare diseases. In this study, we developed a high-throughput screening assay to identify molecules that correct aberrant protein trafficking in adaptor protein complex 4 (AP-4) deficiency, a rare but prototypical form of childhood-onset hereditary spastic paraplegia, characterized by mislocalization of the autophagy protein ATG9A. Using high-content microscopy and an automated image analysis pipeline, we screened a diversity library of 28,864 small molecules and identified a lead compound, BCH-HSP-C01, that restored ATG9A pathology in multiple disease models, including patient-derived fibroblasts and induced pluripotent stem cell-derived neurons. We used multiparametric orthogonal strategies and integrated transcriptomic and proteomic approaches to delineate potential mechanisms of action of BCH-HSP-C01. Our results define molecular regulators of intracellular ATG9A trafficking and characterize a lead compound for the treatment of AP-4 deficiency, providing important proof-of-concept data for future studies.
Project description:Hereditary Spastic Paraplegia (HSP) is a neurodegenerative disease most commonly caused by autosomal dominant mutations in the SPG4 gene encoding the microtubule severing protein spastin. We hypothesise that SPG4-HSP is attributable to reduced spastin function due to haploinsufficiency, thus therapeutic approaches which elevate levels of the wild type spastin allele may be an effective therapy. However until now, how spastin levels are regulated is largely unknown. Here, we show that the kinase HIPK2 regulates spastin protein levels in proliferating cells, in differentiated neurons and in vivo. Our work reveals that HIPK2-mediated phosphorylation of spastin at S268 inhibits spastin K48-poly-ubiquitination at K554 and prevents its neddylation-dependent proteasomal degradation. In a spastin RNAi neuronal cell model, overexpression of HIPK2, or inhibition of neddylation, restores spastin levels and rescues neurite defects. Notably, we demonstrate that spastin levels can be restored pharmacologically by inhibiting its neddylation-mediated degradation in neurons derived from a spastin mouse model of HSP and in patient derived cells, thus revealing novel therapeutic targets for the treatment of SPG4-HSP. We do not know how S268 phosphorylation prevents spastin ubiquitination at K554; we hypothesised that phosphorylation can protect spastin from polyubiquitination by impairing the recruitment of proteins belonging to ubiquitination pathway or by promoting the interactions with factors that mask spastin region necessary for efficient ubiquitination/degradation. To have insight about these hypotheses, we analysed by mass spectrometry (MS) the interactome of spastin-S268A and -S268D upon overexpression in HeLa cells.