• Alterations in mRNA 3' UTR Isoform Abundance Accompany Gene Expression Changes in Human Huntington's Disease Brains

      Romo, Lindsay S.; Ashar-Patel, Ami; Pfister, Edith L.; Aronin, Neil (2017-09-26)
      The huntingtin gene has two mRNA isoforms that differ in their 3' UTR length. The relationship of these isoforms with Huntington's disease is not established. We provide evidence that the abundance of huntingtin 3' UTR isoforms differs between patient and control neural stem cells, fibroblasts, motor cortex, and cerebellum. Huntingtin 3' UTR isoforms, including a mid-3' UTR isoform, have different localizations, half-lives, polyA tail lengths, microRNA sites, and RNA-binding protein sites. Isoform shifts in Huntington's disease motor cortex are not limited to huntingtin; 11% of alternatively polyadenylated genes change the abundance of their 3' UTR isoforms. Altered expression of RNA-binding proteins may be associated with aberrant isoform abundance; knockdown of the RNA-binding protein CNOT6 in control fibroblasts leads to huntingtin isoform differences similar to those in disease fibroblasts. These findings demonstrate that mRNA 3' UTR isoform changes are a feature of molecular pathology in the Huntington's disease brain.
    • Alterations in mRNA 3′UTR Isoform Abundance Accompany Gene Expression Changes in Huntington's Disease

      Romo, Lindsay S. (2017-07-10)
      Huntington’s disease is a neurodegenerative disorder caused by expansion of the CAG repeat in huntingtin exon 1. Early studies demonstrated the huntingtin gene is transcribed into two 3′UTR isoforms in normal human tissue. Decades later, researchers identified a truncated huntingtin mRNA isoform in disease but not control human brain. We speculated the amount of huntingtin 3′UTR isoforms might also vary between control and Huntington’s disease brains. We provide evidence that the abundance of huntingtin 3′UTR isoforms, including a novel mid-3′UTR isoform, differs between patient and control neural stem cells, fibroblasts, motor cortex, and cerebellum. Both alleles of huntingtin contribute to isoform changes. We show huntingtin 3′UTR isoforms are metabolized differently. The long and mid isoforms have shorter half-lives, shorter polyA tails, and more microRNA and RNA binding protein sites than the short isoform. 3′UTR Isoform changes are not limited to huntingtin. Isoforms from 11% of genes change abundance in Huntington’s motor cortex. Only 17% of genes with isoform alterations are differentially expressed in disease tissue. However, gene ontology analysis suggests they share common pathways with differentially expressed genes. We demonstrate knockdown of the RNA binding protein CNOT6 in control fibroblasts results in huntingtin isoform changes similar to those in disease fibroblasts. This study further characterizes Huntington’s disease molecular pathology and suggests RNA binding protein expression may influence mRNA isoform expression in the Huntington’s disease brain.
    • CPEB1 regulates the inflammatory immune response, phagocytosis, and alternative polyadenylation in microglia

      Ivshina, Maria P; van 't Spijker, Heleen M; Jung, Suna; Ponny, Sithara Raju; Schafer, Dorothy P; Richter, Joel D (2022-05-30)
      Microglia are myeloid cells of the central nervous system that perform tasks essential for brain development, neural circuit homeostasis, and neural disease. Microglia react to inflammatory stimuli by upregulating inflammatory signaling through several different immune cell receptors such as the Toll-like receptor 4 (TLR4), which signals to several downstream effectors including transforming growth factor beta-activated kinase 1 (TAK1). Here, we show that TAK1 levels are regulated by CPEB1, a sequence-specific RNA binding protein that controls translation as well as RNA splicing and alternative poly(A) site selection in microglia. Lipopolysaccharide (LPS) binds the TLR4 receptor, which in CPEB1-deficient mice leads to elevated expression of ionized calcium binding adaptor molecule 1 (Iba1), a microglial protein that increases with inflammation, and increased levels of the cytokine IL6. This LPS-induced IL6 response is blocked by inhibitors of JNK, p38, ERK, NFκB, and TAK1. In contrast, phagocytosis, which is elevated in CPEB1-deficient microglia, is unaffected by LPS treatment or ERK inhibition, but is blocked by TAK1 inhibition. These data indicate that CPEB1 regulates microglial inflammatory responses and phagocytosis. RNA-seq indicates that these changes in inflammation and phagocytosis are accompanied by changes in RNA levels, splicing, and alternative poly(A) site selection. Thus, CPEB1 regulation of RNA expression plays a role in microglial function.