Intron retention induced by microsatellite expansions as a disease biomarker.
Ontology highlight
ABSTRACT: Microsatellite expansions often occur in non-coding regions of the genome. In this study, we test their effect on host transcript RNA processing.
Project description:Expansions of simple sequence repeats, or microsatellites, have been linked to ?30 neurological-neuromuscular diseases. While these expansions occur in coding and noncoding regions, microsatellite sequence and repeat length diversity is more prominent in introns with eight different trinucleotide to hexanucleotide repeats, causing hereditary diseases such as myotonic dystrophy type 2 (DM2), Fuchs endothelial corneal dystrophy (FECD), and C9orf72 amyotrophic lateral sclerosis and frontotemporal dementia (C9-ALS/FTD). Here, we test the hypothesis that these GC-rich intronic microsatellite expansions selectively trigger host intron retention (IR). Using DM2, FECD, and C9-ALS/FTD as examples, we demonstrate that retention is readily detectable in affected tissues and peripheral blood lymphocytes and conclude that IR screening constitutes a rapid and inexpensive biomarker for intronic repeat expansion disease.
Project description:Many aged individuals develop monoclonal expansions of CD8 T cells. These expansions are derived from a CD8 memory T cell that outcompetes neighboring CD8 T cells. The molecular alterations within clonal expansions that confer this competitive advantage relative to other CD8 T cells remains unknown. These microarray experiments were designed to identify genes differentially expressed in age-associated expansions of CD8 memory T cells relative to polyclonal CD8 memory T cells found in the same aged mice. Subsequent analysis of these data identified two major types of clonal expansions, distinguished by expression level of integrin a4 mRNA and protein. Based on this classification, Expansion_rep1 belongs to the integrin a4 high subtype of clonal expansions. In contrast, reps 2, 4, and 5 belong to the integrin a4 low subtype of clonal expansions. Given the divergent biological properties of these two subtypes of clonal expansions, we have focused genes differentially expressed between Expansion_rep 2, 4, and 5 and their paired PolyclonalAged samples. Experiment Overall Design: A total of 8 samples were analyzed for gene expression using the Affymetrix mouse genome 430 2.0 microarray platform. The experimental samples of interest were age-associated clonal expansions of CD8 memory T cells. We purified four clonal expansions from four independent, aged mice (indicated as "Expansion" rep1 2, 3, 4). For each clonal expansion of CD8 memory T cells that was purified, there was a paired control in which polyclonal CD8 memory T cells were harvested from the same aged mouse (denoted as "PolyclonalAged" rep1, 2, 3, 4). These paired samples allow one to consider gene expression changes from mice which have undergone the same age-associated changes in biology. The predominant comparison this study focused on was changes in gene expression between age-associated clonal expansions of CD8 memory T cells and their paired, polyclonal CD8 memory T cells. A total of 4 of these pairs were collected.
Project description:Using mRNA-seq, we determined intron retaining genes that were differentially regulated in FACS purified cells at three progressive stages of mouse granulopoiesis; CD34+Kit+Gr-1low promyelocytes, CD34-Kit-Gr-1mid myelocytes and CD34-Kit-Gr-1high granulocytes. We found that IR affects 86 genes, including those specific to granulocyte (Lyz2 and MMP8) and nuclear architecture (Lmnb1 and Lbr). IR was associated with the decrease in protein levels measured by mass spectrometry (P=0.0015, binomial test). There was a significant overlap of IR between human and mouse (P=2.85E-22, hypergeometric test), showing that IR is conserved.Inhibition of NMD in granulocytes resulted in marked accumulation of 39/86 intron retaining mRNAs (P<0.05, RUV procedure with Holm-Bonferroni correction), indicating that IR triggers NMD to downregulate mRNA and protein expression. Sequencing of polyadenylated RNA from three types of myeloid cells (promyelocytes, myelocytes and granulocytes) using Illumina GAIIx
Project description:Using mRNA-seq, we determined intron retaining genes that were differentially regulated in FACS purified cells at three progressive stages of mouse granulopoiesis; CD34+Kit+Gr-1low promyelocytes, CD34-Kit-Gr-1mid myelocytes and CD34-Kit-Gr-1high granulocytes. We found that IR affects 86 genes, including those specific to granulocyte (Lyz2 and MMP8) and nuclear architecture (Lmnb1 and Lbr). IR was associated with the decrease in protein levels measured by mass spectrometry (P=0.0015, binomial test). There was a significant overlap of IR between human and mouse (P=2.85E-22, hypergeometric test), showing that IR is conserved.Inhibition of NMD in granulocytes resulted in marked accumulation of 39/86 intron retaining mRNAs (P<0.05, RUV procedure with Holm-Bonferroni correction), indicating that IR triggers NMD to downregulate mRNA and protein expression.
Project description:Many aged individuals develop monoclonal expansions of CD8 T cells. These expansions are derived from a CD8 memory T cell that outcompetes neighboring CD8 T cells. The molecular alterations within clonal expansions that confer this competitive advantage relative to other CD8 T cells remains unknown. These microarray experiments were designed to identify genes differentially expressed in age-associated expansions of CD8 memory T cells relative to polyclonal CD8 memory T cells found in the same aged mice. Subsequent analysis of these data identified two major types of clonal expansions, distinguished by expression level of integrin a4 mRNA and protein. Based on this classification, Expansion_rep1 belongs to the integrin a4 high subtype of clonal expansions. In contrast, reps 2, 4, and 5 belong to the integrin a4 low subtype of clonal expansions. Given the divergent biological properties of these two subtypes of clonal expansions, we have focused genes differentially expressed between Expansion_rep 2, 4, and 5 and their paired PolyclonalAged samples. Keywords: Cell type comparison of gene expression
Project description:Using mRNA-seq, we determined intron retaining genes that were differentially regulated in FACS purified cells at three progressive stages of mouse granulopoiesis; CD34+Kit+Gr-1low promyelocytes, CD34-Kit-Gr-1mid myelocytes and CD34-Kit-Gr-1high granulocytes. We found that IR affects 86 genes, including those specific to granulocyte (Lyz2 and MMP8) and nuclear architecture (Lmnb1 and Lbr). IR was associated with the decrease in protein levels measured by mass spectrometry (P=0.0015, binomial test). Inhibition of NMD in granulocytes resulted in marked accumulation of 39/86 intron retaining mRNAs (P<0.05, RUV procedure with Holm-Bonferroni correction), indicating that IR triggers NMD to downregulate mRNA and protein expression. We used Affymetrix's Mouse Gene 1.0 ST array to determine accumulation of RNA-transcripts following inhibition of nonsense-mediated decay in primary mouse granulocytes using caffeine.
Project description:Using mRNA-seq, we determined intron retaining genes that were differentially regulated in FACS purified cells at three progressive stages of mouse granulopoiesis; CD34+Kit+Gr-1low promyelocytes, CD34-Kit-Gr-1mid myelocytes and CD34-Kit-Gr-1high granulocytes. We found that IR affects 86 genes, including those specific to granulocyte (Lyz2 and MMP8) and nuclear architecture (Lmnb1 and Lbr). IR was associated with the decrease in protein levels measured by mass spectrometry (P=0.0015, binomial test). Inhibition of NMD in granulocytes resulted in marked accumulation of 39/86 intron retaining mRNAs (P<0.05, RUV procedure with Holm-Bonferroni correction), indicating that IR triggers NMD to downregulate mRNA and protein expression.
Project description:The transition from hunting and gathering to plant and animal domestication was one of the most important cultural and technological revolutions in human history. According to archeologists and paleoanthropologists, this transition triggered major demographic expansions. However, few genetic studies have found traces of Neolithic expansions in the current repartition of genetic polymorphism, pointing rather toward Paleolithic expansions. Here, we used microsatellite autosomal data to investigate the past demographic history of 87 African and Eurasian human populations with contrasted lifestyles (nomadic hunter-gatherers, semi-nomadic herders and sedentary farmers). Likely due to the combination of a higher mutation rate and the possibility to analyze several loci as independent replicates of the coalescent process, the analysis of microsatellite data allowed us to infer more recent expansions than previous genetic studies, potentially resulting from the Neolithic transition. Despite the variability in their location and environment, we found consistent expansions for all sedentary farmers, while we inferred constant population sizes for all hunter-gatherers and most herders, which could result from constraints linked to a nomadic or semi-nomadic lifestyle and/or competition for land between herders and farmers. As an exception, we inferred expansions for Central Asian herders. This might be linked with the arid environment of this area, which may have been more favorable to nomadic herders than to sedentary farmers. Alternatively, current Central Asian herders may descent from populations who have first experienced a transition from hunter-gathering to sedentary agropastoralism, and then a second transition to nomadic herding.
Project description:For some neurological disorders, disease is primarily RNA-mediated due to expression of non-coding microsatellite expansion RNAs (RNAexp). Toxicity is thought to result from enhanced binding of proteins to these expansions and depletion from their normal cellular targets. However, experimental evidence for this sequestration model is lacking. Here, we use HITS-CLIP and pre-mRNA processing analysis of human control versus myotonic dystrophy (DM) brains to provide compelling evidence for this RNA toxicity model. MBNL2 binds directly to DM repeat expansions in the brain resulting in depletion from its normal RNA targets with downstream effects on alternative splicing and polyadenylation. Similar RNA processing defects were detected in Mbnl compound knockout mice, highlighted by dysregulation of Mapt splicing and fetal tau isoform expression in adults. These results demonstrate that MBNL proteins are directly sequestered by RNAexp in the DM brain and introduce a powerful experimental tool to evaluate RNA-mediated toxicity in other expansion diseases.