Résumé :
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Infantile spinal muscular atrophy (SMA) is an inherited disorder characterized by the degeneration of spinal motor neurons and progressive muscular atrophy. There is no cure for SMA. The SMA disease is caused by mutations of the survival motor neuron 1 (SMN1) gene. SMN1 gene is duplicated and all patients carry the copy gene SMN2 that modulates the phenotype by a reduced expression of the SMN protein. This ubiquitously expressed protein plays a role in RNA processing, including the assembly and localization of spliceosomal core snRNPs. SMN protein localizes in the cytoplasm and is enriched with snRNPs into nuclear gems/Cajal Bodies (CBs). There is a tight correlation between the levels of SMN protein, the number of gems/CBs and the severity of SMA disease. Moreover, gems/CBs from SMA-derived fibroblast cells show no detectable accumulation of snRNPs. Recent studies have shown that transient overexpression of SMN protein in SMA cells restores the distribution of both SMN and snRNPs in gems/CBs, indicating that up-regulating SMN protein expression might be a potential therapeutics in SMA. Here, we investigated the effects of compounds on the accumulation of SMN in gems/CBs of immortalized fibroblasts from a Type I SMA patient by immunofluorescence microscopy. Three small libraries comprised of 224 chemically active molecules were screened. First, the assay measured the number of 24h-treated cells with gems/CBs compared to the DMSO-treated cells. Then, the effectiveness in the increase of gems/CBs number was measured for treatment under a period of 48 and 72 hr. Nine compounds that increase the number of gems/CBs in a consistent manner after 72 hr were identified. Dose curve analyses were tested on those candidate molecules to determine the minimal concentration at which the compounds still restore the localization in gems/CBs. These findings will be presented.
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