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Reactive astrocytes in ALS models display dysregulated intron retention

ABSTRACT: Reactive astrocytes are implicated in Amyotrophic Lateral Sclerosis (ALS), although the mechanisms controlling reactive transformation are unknown. We show that decreased intron retention (IR) is common to human induced pluripotent stem cell (hiPSC)-derived astrocytes carrying VCP, C9orf72 and SOD1 ALS-causing mutations as well as astrocytes stimulated to undergo reactive transformation. Notably, transcripts with decreased IR and increased expression are overrepresented in reactivity processes including cell-adhesion, stress-response, and immune-activation. We examined astrocyte translatome sequencing (TRAP-seq) from a SOD1 mouse model, which revealed a significant number of transcripts with reduced IR in ALS are upregulated in translation. Using nucleo-cytoplasmic fractionation of VCP astrocytes coupled with mRNA sequencing and proteomics, we identify that decreased IR in nuclear-detained transcripts is associated with increased cytoplasmic expression of genes and proteins encoding regulators of reactivity - indicating nuclear-to-cytoplasmic translocation and translation of spliced reactivity-related transcripts. These results provide novel insights into the molecular factors controlling the reactive transformation of ALS astrocytes.

ORGANISM(S): Homo sapiens

PROVIDER: GSE160133 | GEO | 2021/10/25

REPOSITORIES: GEO

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Project description:We established iPSCs from healthy donors, SOD1-ALS and TDP43-ALS patients. Using our differentiation protocol originally developed by Reinhardt et al.,2013, we diferentiated these iPSCs toward spinal motor neurons (MNs) and reproduce ALS pathology in a dish. To extend our understanding of finding different molecular mechanisms and pathways related to SOD1- and TDP43 mutations in ALS disease, we have performed a comprehensive gene expression profiling study using RNA-Seq of the iPSC-derived MN models from control individuals and carefully compared with those from SOD1-ALS and TDP43-ALS patients. To generate novel hypotheses of putative underlying molecular mechanisms in ALS, we used human induced pluripotent stem cell (hiPSCs)-derived motor neurons (MNs) from SOD1- and TARDBP (TDP-43 protein)-mutant-ALS patients and healthy controls to perform high-throughput RNA-sequencing (RNA-Seq). An integrated bioinformatics approach was employed to identify differentially expressed genes (DEGs) and key pathways underlying these familial forms of the disease (fALS). In TDP43-ALS, we found dysregulation of transcripts encoding components of the transcriptional machinery and transcripts involved in splicing regulation were particularly affected. In contrast, less is known about the role of SOD1 in RNA metabolism in motor neurons. Here we found that many transcripts relevant for mitochondrial function were specifically altered in SOD1-ALS, indicating transcriptional signatures and expression patterns can vary significantly depending on the causal gene that is mutated. Surprisingly, however, we identified a clear downregulation of genes involved in protein translation in SOD1-ALS suggesting that ALS-causing SOD1 mutations shift cellular RNA abundance profiles to cause neural dysfunction. Altogether, we provided here an extensive profiling of mRNA expression in two ALS models at the cellular level, corroborating the major role of RNA metabolism and protein translation as a common pathomechanism in ALS

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Reactive astrocytes in ALS models display dysregulated intron retention

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