Project description:Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease due to gradual motorneurons (MN) degeneration1. Among the processes associated to ALS pathogenesis, there is the formation of cytoplasmic inclusions produced by mutant protein aggregation, among which the RNA binding protein FUS. In this work we show that such inclusions are significantly reduced in number and dissolve faster when the RNA m6A content is diminished as a consequence of the m6A writer METTL3 knock-down. These effects were obtained observed both in neuronal cell lines and in iPSC-derived human motor neurons expressing mutant FUS. Importantly, stress granules formed in mutant conditionswhen mutant FUS is expressed/ALS condition showed a distinctive transcriptome with respect to control cells; interestingly, after METTL3 downregulation, it reverted to similar to control. Finally, we show that FUS inclusions are reduced also in patient-derived fibroblasts treated with STM-2457, a well characterized inhibitor of METTL3 activity, paving the way for its possible use for counteracting aggregate formation in ALS.
Project description:Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease due to gradual motorneurons (MN) degeneration. Among the processes associated to ALS pathogenesis, there is the formation of cytoplasmic inclusions produced by mutant protein aggregation, among which the RNA binding protein FUS. In this work we show that such inclusions are significantly reduced in number and dissolve faster when the RNA m6A content is diminished as a consequence of the m6A writer METTL3 knock-down. These effects were obtained observed both in neuronal cell lines and in iPSC-derived human motor neurons expressing mutant FUS. Importantly, stress granules formed in mutant conditionswhen mutant FUS is expressed/ALS condition showed a distinctive transcriptome with respect to control cells; interestingly, after METTL3 downregulation, it reverted to similar to control. Finally, we show that FUS inclusions are reduced also in patient-derived fibroblasts treated with STM-2457, a well characterized inhibitor of METTL3 activity, paving the way for its possible use for counteracting aggregate formation in ALS.
Project description:Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease due to gradual motorneurons (MN) degeneration1. Among the processes associated to ALS pathogenesis, there is the formation of cytoplasmic inclusions produced by mutant protein aggregation, among which the RNA binding protein FUS2. In this work we show that such inclusions are significantly reduced in number and dissolve faster when the RNA m6A content is diminished as a consequence of the m6A writer METTL3 knock-down. These effects were obtained observed both in neuronal cell lines and in iPSC-derived human motor neurons expressing mutant FUS. Importantly, stress granules formed in mutant conditionswhen mutant FUS is expressed/ALS condition showed a distinctive transcriptome with respect to control cells; interestingly, after METTL3 downregulation, it reverted to similar to control. Finally, we show that FUS inclusions are reduced also in patient-derived fibroblasts treated with STM-2457, a well characterized inhibitor of METTL3 activity, paving the way for its possible use for counteracting aggregate formation in ALS.
Project description:Stress granules (SG) are part of a cellular protection mechanism where untranslated messenger RNAs and RNA-binding proteins are stored upon conditions of cellular stress. Compositional variations due to qualitative or quantitative protein changes can disrupt their functionality and alter their structure. This is the case of different forms of amyotrophic lateral sclerosis (ALS) where a causative link has been proposed between the cytoplasmic de-localization of mutant proteins, such as FUS (Fused in Sarcoma), and the formation of cytotoxic inclusions. Here, we describe the SG transcriptome in neuroblastoma cells and define several features for RNA recruitment in these condensates. We demonstrate that SG dynamics and RNA content are strongly modified by the incorporation of mutant FUS, switching to a more unstructured, AU-rich SG transcriptome. Moreover, we show that mutant FUS, together with its protein interactors and their target RNAs, are responsible for the reshaping of the mutant SG transcriptome with alterations that can be linked to neurodegeneration. Our data describe the molecular differences between physiological and pathological SG in ALS-FUS conditions, showing how FUS mutations impact the RNA and protein composition of these condensates.
Project description:Mutations in the gene encoding Fused in Sarcoma (FUS) cause amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disorder. FUS is a predominantly nuclear DNA- and RNA-binding protein that is involved in RNA processing. Large FUS-immunoreactive inclusions fill the perikaryon of surviving motor neurons of ALS patients carrying mutations at post-mortem. This sequestration of FUS is predicted to disrupt RNA processing and initiate neurodegeneration. Here, we demonstrate that C-terminal ALS mutations disrupt the nuclear localizing signal (NLS) of FUS resulting in cytoplasmic accumulation in transfected cells and patient fibroblasts. FUS mislocalization is rescued by the addition of the wild-type FUS NLS to mutant proteins. We also show that oxidative stress recruits mutant FUS to cytoplasmic stress granules where it is able to bind and sequester wild-type FUS. While FUS interacts with itself directly by protein-protein interaction, the recruitment of FUS to stress granules and interaction with PABP are RNA dependent. These findings support a two-hit hypothesis, whereby cytoplasmic mislocalization of FUS protein, followed by cellular stress, contributes to the formation of cytoplasmic aggregates that may sequester FUS, disrupt RNA processing and initiate motor neuron degeneration.