Project description: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.
Project description: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 iPSC-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 translatome sequencing (TRAP-seq) of astrocytes from a SOD1 mouse model, which revealed that transcripts upregulated in translation significantly overlap with transcripts with decreased IR. 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. Our study provides important insights into the molecular regulation of reactive transformation of ALS astrocytes.
Project description:We present an analysis of intron retention under stress from two different drugs and their combinations in yeast Saccharomyces cerevisiae. We previously established isogrowth profiling, a method to abstract the non-specific effects of growth rate inhibition from the specific effect of perturbation by a small molecule: two drugs are used at varied ratios, but at fixed overall growth inhibition. Here, cycloheximide and LiCl were used at seven different ratios along the 50% growth inhibition isobole and the total ribodepleted RNA was sequenced. This allowed us to gauge the changes in intron retention due to the used drugs, while ensuring that the effects are not caused by growth inhibition. We found a prominent increase in intron retention under LiCl treatment that preferentially affects introns contained in the transcripts of ribosomal proteins.
Project description:We recently described aberrant cytoplasmic SFPQ intron-retaining transcripts (IRTs) and concurrent SFPQ protein mislocalization as a new hallmark of amyotrophic lateral sclerosis (ALS). However the generalizability and potential roles of cytoplasmic IRTs in health and disease remain unclear. Here, using time-resolved deep-sequencing of nuclear and cytoplasmic fractions of hiPSCs undergoing motor neurogenesis, we reveal that ALS-causing VCP gene mutations lead to compartment-specific aberrant accumulation of IRTs. Specifically, we identify >100 IRTs with increased cytoplasmic (but not nuclear) abundance in ALS samples. Furthermore, these aberrant cytoplasmic IRTs possess sequence-specific attributes and differential predicted binding affinity to RNA binding proteins (RBPs). Remarkably, TDP-43, SFPQ and FUS - RBPs known for nuclear-to-cytoplasmic mislocalization in ALS - avidly and specifically bind to this aberrant cytoplasmic pool of IRTs, as opposed to any individual IRT. Our data are therefore consistent with a novel role for cytoplasmic IRTs in regulating compartment-specific protein abundance. This study provides new molecular insight into potential pathomechanisms underlying ALS and highlights aberrant cytoplasmic IRTs as potential therapeutic targets.
Project description:We explored intron retention patterns in normal breast epithelial cells (MCF10A) and estrogen receptor positive (ER+) breast cancer cells (MCF7).
Project description:Exposure to certain stresses leads to readthrough transcription downstream of gene ends. Here we found that this phenomenon impacts the expression of genes located downstream to readthrough genes, whereby readthrough transcription proceeds into downstream genes, termed read-in genes. Using polyA-selected RNA-seq data from mouse fibroblasts, we identified widespread read-in in heat shock, oxidative and osmotic stress conditions. Read-in genes share distinctive genomic characteristics; they are extremely short, mainly due to less, shorter, introns, and they are highly GC rich. Furthermore, using ribosome footprint profiling we found that the translation of genes with high degrees of read-in is significantly reduced. Strikingly, read-in genes show extremely high levels of intron retention during stress, mostly in their first intron. While read-in genes share features that are generally associated with increased likelihood of intron retention, such as short introns and high GC content, intron retention in read-in genes during stress exceeds greatly beyond what is expected given their genomic properties. Finally, we found that first introns in read-in genes have weaker 5’ and 3’ splice sites. Our data portray a relationship between read-in and intron retention, suggesting it may have co-evolved to facilitate reduced translation of read-in genes during stress.