Trinucleotide expansions cause disease by both protein-and RNAmediated mechanisms. Unexpectedly, we discovered that CAG expansion constructs express homopolymeric polyglutamine, polyalanine, and polyserine proteins in the absence of an ATG start codon. This repeat-associated non-ATG translation (RAN translation) occurs across long, hairpin-forming repeats in transfected cells or when expansion constructs are integrated into the genome in lentiviral-transduced cells and brains. Additionally, we show that RAN translation across human spinocerebellar ataxia type 8 (SCA8) and myotonic dystrophy type 1 (DM1) CAG expansion transcripts results in the accumulation of SCA8 polyalanine and DM1 polyglutamine expansion proteins in previously established SCA8 and DM1 mouse models and human tissue. These results have implications for understanding fundamental mechanisms of gene expression. Moreover, these toxic, unexpected, homopolymeric proteins now should be considered in pathogenic models of microsatellite disorders.T ranslation of mRNA into protein is an exquisitely regulated, almost error-free process. Well-established rules of translational initiation have been used as a cornerstone in biology to understand gene expression and to predict the consequences of disease-causing mutations (1). For microsatellite expansion disorders, mutations within or outside ATG-initiated ORFs are thought to cause disease either by protein gain-of-function, protein loss-of-function, or RNA gain-of-function mechanisms (2, 3).Microsatellite expansion mutations that express polyglutamine (polyGln) expansion proteins include Huntington disease (Huntingtin, HD), spinal bulbar muscular atrophy, and spinocerebellar ataxia types 1, 2, 3, 6, 7, and 17. Since the discovery of these CAG·CTG expansion mutations, efforts to understand disease mechanisms have focused on elucidating the molecular effects of the polyGln proteins expressed from these loci. Although these polyGln expansion proteins bear no similarity to each other apart from the polyGln tract, a hallmark of these diseases is protein accumulation and aggregation in nuclear or cytoplasmic inclusions. Surprisingly, although the polyGln expansion proteins are widely expressed in the CNS and other tissues, only restricted populations of neurons are vulnerable in each disease (3).Myotonic dystrophy type 1 (DM1) and type 2 (DM2) are the best-characterized examples of RNA-mediated expansion disorders (2). The mutation causing DM1 is a CTG-repeat expansion located in the 3′ UTR of the dystrophia myotonica-protein kinase (DMPK) gene. Although DM1 can be clinically more severe than DM2, the discovery of the DM2 mutation and several mouse models provide strong support that many features of these diseases result from RNA gain-of-function effects in which the dysregulation of RNA-binding proteins is mediated by the expression of CUG and CCUG transcripts (4). Additionally, RNA gain-of-function effects have been reported for CGG and CAG expansion RNAs (5, 6).Both RNA and protein mechanisms appear to operate...

The lung, abdominal lymph nodes, and bone are the most common sites of extrahepatic metastatic HCC. Most extrahepatic HCC occurs in patients with advanced intrahepatic tumor stage (stage IVA). Incidental extrahepatic lesions at CT in patients with stage I or II intrahepatic HCC are unlikely to represent metastatic HCC.

Pathological remodeling of the extracellular matrix (ECM) by fibroblasts leads to organ failure. Development of idiopathic pulmonary fibrosis (IPF) is characterized by a progressive fibrotic scarring in the lung that ultimately leads to asphyxiation; however, the cascade of events that promote IPF are not well defined. Here, we examined how the interplay between the ECM and fibroblasts affects both the transcriptome and translatome by culturing primary fibroblasts generated from IPF patient lung tissue or nonfibrotic lung tissue on decellularized lung ECM from either IPF or control patients. Surprisingly, the origin of the ECM had a greater impact on gene expression than did cell origin, and differences in translational control were more prominent than alterations in transcriptional regulation. Strikingly, genes that were translationally activated by IPF-derived ECM were enriched for those encoding ECM proteins detected in IPF tissue. We determined that genes encoding IPF-associated ECM proteins are targets for miR-29, which was downregulated in fibroblasts grown on IPF-derived ECM, and baseline expression of ECM targets could be restored by overexpression of miR-29. Our data support a model in which fibroblasts are activated to pathologically remodel the ECM in IPF via a positive feedback loop between fibroblasts and aberrant ECM. Interrupting this loop may be a strategy for IPF treatment.

Common human malignancies acquire derangements of the translation initiation complex, eIF4F, but their functional significance is unknown. Hypophosphorylated 4E-BP proteins negatively regulate eIF4F assembly by sequestering its mRNA cap binding component eIF4E, whereas hyperphosphorylation abrogates this function. We found that breast carcinoma cells harbor increases in the eIF4F constituent eIF4GI and hyperphosphorylation of 4E-BP1 which are two alterations that activate eIF4F assembly. Ectopic expression of eIF4E in human mammary epithelial cells enabled clonal expansion and anchorage-independent growth. Transfer of 4E-BP1 phosphorylation site mutants into breast carcinoma cells suppressed their tumorigenicity, whereas loss of these 4E-BP1 phosphorylation site mutants accompanied spontaneous reversion to a malignant phenotype. Thus, eIF4F activation is an essential component of the malignant phenotype in breast carcinoma.

Idiopathic pulmonary fibrosis (IPF) is a relentlessly progressive lung disease in which fibroblasts accumulate in the alveolar wall within a type I collagen–rich matrix. Although lung fibroblasts derived from patients with IPF display durable pathological alterations in proliferative function, the molecular mechanisms differentiating IPF fibroblasts from their normal counterparts remain unknown. Polymerized type I collagen normally inhibits fibroblast proliferation, providing a physiological mechanism to limit fibroproliferation after tissue injury. We demonstrate that β1 integrin interaction with polymerized collagen inhibits normal fibroblast proliferation by suppression of the phosphoinositide 3-kinase (PI3K)–Akt–S6K1 signal pathway due to maintenance of high phosphatase activity of the tumor suppressor phosphatase and tensin homologue (PTEN). In contrast, IPF fibroblasts eluded this restraint, displaying a pathological pattern of β1 integrin signaling in response to polymerized collagen that leads to aberrant activation of the PI3K–Akt–S6K1 signal pathway caused by inappropriately low PTEN activity. Mice deficient in PTEN showed a prolonged fibroproliferative response after tissue injury, and immunohistochemical analysis of IPF lung tissue demonstrates activation of Akt in cells within fibrotic foci. These results provide direct evidence for defective negative regulation of the proliferative pathway in IPF fibroblasts and support the theory that the pathogenesis of IPF involves an intrinsic fibroblast defect.

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Idiopathic pulmonary fibrosis (IPF) is a progressive disease of the middle aged and elderly with a prevalence of one million persons worldwide. The fibrosis spreads from affected alveoli into contiguous alveoli, creating a reticular network that leads to death by asphyxiation. Lung fibroblasts from patients with IPF have phenotypic hallmarks, distinguishing them from their normal counterparts: pathologically activated Akt signaling axis, increased collagen and α-smooth muscle actin expression, distinct gene expression profile, and ability to form fibrotic lesions in model organisms. Despite the centrality of these fibroblasts in disease pathogenesis, their origin remains uncertain. Here, we report the identification of cells in the lungs of patients with IPF with the properties of mesenchymal progenitors. In contrast to progenitors isolated from nonfibrotic lungs, IPF mesenchymal progenitor cells produce daughter cells manifesting the full spectrum of IPF hallmarks, including the ability to form fibrotic lesions in zebrafish embryos and mouse lungs, and a transcriptional profile reflecting these properties. Morphological analysis of IPF lung tissue revealed that mesenchymal progenitor cells and cells with the characteristics of their progeny comprised the fibrotic reticulum. These data establish that the lungs of patients with IPF contain pathological mesenchymal progenitor cells that are cells of origin for fibrosis-mediating fibroblasts. These fibrogenic mesenchymal progenitors and their progeny represent an unexplored target for novel therapies to interdict fibrosis.